VEHICLES OF THEM 
 
 A POPULAR EXPOSITION OF 
 MODERN AERONAUTICS 
 WITH WORKING DRAWINGS 
 
 VICTOR M3UGBEED 
 
GIFT OF 
 
Vehicles of the Air 
 
The Bleriot Monoplane, which Crossed the English Channel, Enthroned on the Stand of 
 Honor in the Grand Palais, Paris, October, 1909. Reproduction of Original Montgolfier Balloon 
 in Background. 
 
 View down main hall of Paris Aeronautical Salon, which closed October 15, 1909. 
 The value of the exhibits and accessories, the cost of the decorations, and the attendance 
 was far greater than at any automobile show ever given in the United States or Europe. 
 It was the second annual event of the kind to be held in Paris and a large number of 
 orders for various makes of machines was placed for future delivery 110 being for one 
 well-known monoplane. 
 
VEHICLES OF THE AIR 
 
 A. Popular Exposition of Modern Aeronautics 
 With Working Drawings 
 
 By 
 
 VICTOR LOUGHEED 
 
 Member of the Aeronautic Society, Founder Member of the Society of Auto- 
 mobile Engineers, former editor of Motor, and author of 
 "Some Trends of Modern Automobile Design." 
 
 PUBLISHERS 
 
 THE REILLY AND BRITTON CO. 
 
 CHICAGO 
 

 Entered at Stationers* Hall 
 
 Copyright. 1909. by the Reilly and Britton Co, 
 
 AH Rights Reserved 
 
 PHOTOGRAPHS BY 
 
 M. Branger. E. Filiatre, M. Rol, and J. Theodoresco, of Paris. All illustrations 
 
 herein are fully protected by international copyright. Reproductions 
 
 positively will not be permitted without due credit, and 
 
 written authorization from the publishers. 
 
 Published November 1909 
 
TABLE OF CONTENTS 
 
 INTEODUCTION 
 
 Scope and Prophecy 21 
 
 Skepticism is Ignorance 23 
 
 Three Traversable Media 24 
 
 Types of Air Craft 24 
 
 Aeroplane Most Successful 26 
 
 Speed and Radius 27 
 
 Sizes of Aeroplanes 28 
 
 First and Operating Costs ; 28 
 
 The Moral Aspect 29 
 
 The Physical Hazard 29 
 
 Dangers in All Travel 32 
 
 Fear a Habit of Mind 33 
 
 Commercial Applications 34 
 
 Limitations Expected 35 
 
 Relation to Warfare 36 
 
 An Imaginative Spectacle 37 
 
 Travel over Water 38 
 
 Conclusion 39 
 
 CHAPTEE 1 THE ATMOSPHEEE 
 
 Introduction 43 
 
 EXTENT 43 
 
 PEOPEETIES AND CHAEACTEEISTICS 45 
 
 Weight 45 
 
 Composition 46 
 
 Color and Transparence 48 
 
 AIE AT EEST. 48 
 
 Compressibility 49 
 
 Effect of Temperature 49 
 
 Liquefaction and Solidification 50 
 
 AIE IN MOTION 50 
 
 Inertia 51 
 
 Elasticity 52 
 
 Viscosity 53 
 
 METEOEOLOGY 53 
 
 Temperature 54 
 
 Barometric Pressure , 56 
 
 Humidity 56 
 
 Condensation of Moisture 57 
 
 Winds 57 
 
 Coastal Winds 59 
 
 Trade Winds 60 
 
 - Cyclones, Whirlwinds, and Tornados 61 
 
 Ascending Components 62 
 
 Wind Velocities 62 
 
 Atmospheric Electricity 64 
 
 7 
 
 4645* 
 
 u 
 
8 VEHICLES OF THE AIR 
 
 CHAPTER 2 UGHTER-THAN-AIR MACHINES 
 Introductory 65 
 
 NON-DIRIGIBLE BALLOONS 66 
 
 History 66 
 
 Spherical Types 75 
 
 DIRIGIBLE BALLOONS 76 
 
 History 80 
 
 Spherical Types 88 
 
 Elongated Types 89 
 
 Pointed Ends 89 
 
 Rounded Ends 90 
 
 Sectional Construction 90 
 
 The Effect of Size 90 
 
 Envelope Materials 91 
 
 Sheet Metal 92 
 
 Silk 93 
 
 Cotton 93 
 
 Linen 94 
 
 Miscellaneous Envelope Materials 94 
 
 Coating Materials 95 
 
 Inflation 96 
 
 Heated Air 97 
 
 Hydrogen 98 
 
 Illuminating Gases 101 
 
 Vacuum 101 
 
 Miscellaneous 102 
 
 Nettings 103 
 
 Car Construction 104 
 
 Rattans 105 
 
 Wood 106 
 
 Miscellaneous 106 
 
 Height Control 106 
 
 Non-Lifting Balloons 107 
 
 Escape Valves 107 
 
 Ballast 109 
 
 Compressed Gas 109 
 
 Drag Ropes 110 
 
 Open Necks HO 
 
 Internal Balloons Ill 
 
 Moisture 112 
 
 Temperature 112 
 
 Steering 113 
 
 Lateral Steering 113 
 
 Vertical Steering 114 
 
 Balloon Housing 115 
 
 Sheds 115 
 
 Landing Pits 116 
 
 CHAPTER 3 HEAVIER-THAN-AIR MACHINES 
 Introductory 117 
 
 ORNITHOPTERS 118 
 
 History 118 
 
 Two Chief Classes 124 
 
 Recent Ornithopters 124 
 
 Analogies in Nature 124 
 
 HELICOPTERS 125 
 
 History 126 
 
CONTENTS 9 
 
 Recent "Experiments . 129 
 
 Lateral Progression . 130 
 
 Analogy with Aeroplane 131 
 
 AEROPLANES 131 
 
 AEROPLANE HISTORY 132 
 
 Clement Ader 134 
 
 Louis Bleriot 135 
 
 Octave Chanute 136 
 
 Samuel Pierpont Langley 136 
 
 Otto and Gustav Lilienthal . 137 
 
 John J. Montgomery 138 
 
 A. Penaud 146 
 
 Percy S. Pilcher . 147 
 
 Alberto Santos-Dumont 148 
 
 F. E. Wenham 149 
 
 Wilbur and Orville Wright 149 
 
 Voisin Brothers 153 
 
 Miscellaneous 153 
 
 CHAPTER 4 AEROPLANE DETAILS 
 
 Introductory 158 
 
 ANALOGIES IN NATURE 159 
 
 Flying Fish 161 
 
 Comparison of Flying Animals and Aeroplanes 162 
 
 Flying Lizards 163 
 
 Flying Squirrels 163 
 
 Flying Lemur 163 
 
 Flying Frog 164 
 
 Soaring Birds 164 
 
 Soaring Bats 165 
 
 The Pterodactyl 165 
 
 Flying Insects 166 
 
 MONOPLANES 167 
 
 MULTIPLANES 168 
 
 Biplanes 169 
 
 More Than Two Surfaces 169 
 
 FORMS OF SURFACES 169 
 
 Flat Sections 171 
 
 Curved Sections 1 72 
 
 Arcs of Circles 172 
 
 Parabolic Surfaces 173 
 
 Force and Motion 193 
 
 Momentum 194 
 
 Action and Reaction 194 
 
 Impact of Elastic Bodies 195 
 
 The Impact of Fluids 198 
 
 Application 199 
 
 Flattened Tips 203 
 
 Angles of Chords 204 
 
 Wing Outlines : 204 
 
 Length and Breadth 204 
 
 ARRANGEMENTS OF SURFACES 205 
 
 Advancing and Following Surfaces 205 
 
 Superimposed Surfaces 205 
 
 Staggered Surfaces 205 
 
 Lateral Placings ; 206 
 
 Separated Wings I 206 
 
 Continuous Wings 206 
 
10 VEHICLES OF THE AIR 
 
 Lateral Curvature 207 
 
 Dihedral Angles 207 
 
 VERTICAL SURFACES -. 209 
 
 SUSTENTION OF SURFACES 210 
 
 Effect of Section 210 
 
 Effect of Angle 211 
 
 Effect of Speed 211 
 
 Effect of Outline 212 
 
 Effect of Adjacent Surfaces 212 
 
 Center of Pressure 213 
 
 Head Eesistances 213 
 
 METHODS OF BALANCING 215 
 
 Lateral Balance 215 
 
 Vertical Surfaces 216 
 
 Dihedral Angles 216 
 
 Wing Warping 216 
 
 Tilting Wing Tips 217 
 
 Hinged Wing Tips 217 
 
 Variable Wing Areas 218 
 
 Shifting Weight 218 
 
 Rocking Wings 218 
 
 Swinging Wing Tips 219 
 
 Plural Wing Tips 220 
 
 Longitudinal Balance 220 
 
 By Front Rudders 220 
 
 By Rear Rudders 220 
 
 Box Tails '. 220 
 
 Shifting Weights 221 
 
 Elevators as Carrying Surfaces 221 
 
 Automatic Equilibrium 221 
 
 Arrangement of Surfaces 222 
 
 Electric Devices 222 
 
 The Gyroscope 222 
 
 Compressed Air 223 
 
 The Pendulum, 223 
 
 STEERING 223 
 
 Effects of Balancing 223 
 
 Vertical Eudders 224 
 
 Pivoted Rudders 224 
 
 Flexible Rudders 224 
 
 Horizontal Eudders 225 
 
 Twisting Eudders 225 
 
 CONTROLLING MEANS 226 
 
 Compound Movements .- 227 
 
 Plural Operators 227 
 
 Wheels 228 
 
 Levers 228 
 
 Pedals - 229 
 
 Miscellaneous 229 
 
 Shoulder Forks 229 
 
 Body Cradles 229 
 
 FRAMING 230 
 
 CHAPTER 5 PROPULSION 
 
 Introductory 231 
 
 MISCELLANEOUS PROPELLING DEVICES 231 
 
 Feathering Paddles 
 
 Wave Surfaces 233 
 
CONTENTS 11 
 
 Reciprocating Wings and Oars 234 
 
 SCREW PROPELLERS 236 
 
 Some Comparisons 237 
 
 Essential Characteristics 238 
 
 Effective Surface 241 
 
 Angles of Blades 242 
 
 Slip !'..!..'.! 244 
 
 Forms of Surfaces 244 
 
 Plane Sections 245 
 
 Parabolic Sections 245 
 
 Blade Outlines 246 
 
 Multibladed Propellers 248 
 
 Two-Bladed Propellers 249 
 
 Propeller Diameters 250 
 
 Arrangements of Blades 252 
 
 Right-Angled Propeller Blades 252 
 
 Dihedrally -Arranged Propeller Blades 253 
 
 Propeller Efficiencies 253 
 
 The Effects of Form 255 
 
 The Effects of Rotational Speed 255 
 
 The Effects of Vehicle Speed 256 
 
 The Effects of Skin Friction 257 
 
 Propeller Placings 258 
 
 Single Propellers 259 
 
 Plural Propellers 259 
 
 Location of Propeller Thrust 264 
 
 Propeller Materials 264 
 
 Wood 265 
 
 Steel 268 
 
 Aluminum Alloys 268 
 
 Framing and Fabric 269 
 
 Propeller Hubs 269 
 
 A TYPICAL PROPELLER 270 
 
 CHAPTER 6 POWER PI*ANTS 
 
 Introductory 273 
 
 GASOLINE ENGINES 277 
 
 Multicylinder Designs 277 
 
 Cylinder Arrangements 279 
 
 Vertical Cylinders 279 
 
 V-Shaped Engines "280 
 
 Opposed Cylinders 281 
 
 Revolving Cylinders 282 
 
 Miscellaneous Arrangements 284 
 
 Ignition 284 
 
 Make-and-Break Ignition , 284 
 
 Jump-Spark Ignition 285 
 
 Hot-Tube Ignition 287 
 
 Ignition by Heat of Compression 287 
 
 Catalytic Ignition 288 
 
 Cooling 288 
 
 Water Cooling 289 
 
 Air Cooling 290 
 
 Carluretion 291 
 
 Carbureters 291 
 
 Fuel Pumps 294 
 
12 VEHICLES OF THE AIR 
 
 Muffling 296 
 
 Auxiliary Exhausts 297 
 
 Flywheels 297 
 
 STEAM ENGINES 299 
 
 Available Types 301 
 
 Boilers 301 
 
 Burners 303 
 
 Fuels 303 
 
 Comparison of Fuels 304 
 
 ELECTRICITY 304 
 
 Electric Motors 304 
 
 Current Sources 305 
 
 Storage Batteries , 306 
 
 Primary Batteries 307 
 
 Thermopiles 307 
 
 MISCELLANEOUS 308 
 
 Compressed Air 309 
 
 Carbonic Acid 309 
 
 Vapor Motors 309 
 
 Spring Motors 310 
 
 EocTcet Schemes 310 
 
 TANKS 310 
 
 CHAPTER 7 TRANSMISSION ELEMENTS 
 
 Introductory 313 
 
 CHAINS AND SPROCKETS 314 
 
 Block Chains 316 
 
 Eoller Chains 317 
 
 Miscellaneous 317 
 
 Block Chains 317 
 
 Standard American Roller Chains 318 
 
 Roller Chains 318 
 
 Cable Chains 319 
 
 Reversible Sprockets 319 
 
 Missed Teeth 319 
 
 SHAFTS AND GEARS 320 
 
 Shafts 32 
 
 Spur Gears 321 
 
 Bevel Gears ' 322 
 
 Staggered and Herringbone Teeth 323 
 
 BELTS AND PULLEYS 324 
 
 Pulley Construction 324 
 
 Belt Materials 325 
 
 CLUTCHES 325 
 
 CHAPTER 8 BEARINGS 
 
 Introductory 327 
 
 BALL BEARINGS 328 
 
 Adjustable Ball Bearings 328 
 
 Annular Ball Bearings 330 
 
 Annular Ball-Bearing Sizes, Capacities, and Weights 337 
 
 ROLLER BEARINGS 339 
 
 Cylindrical Eoller Bearings 340 
 
 Flexible Eoller Bearings 340 
 
 Tapered Eoller Bearings 341 
 
 PLAIN BEARINGS 342 
 
 Plain Bearing Materials 342 
 
 Steel . 342 
 
CONTENTS 13 
 
 Oast Iron 343 
 
 Bronzes 343 
 
 Brasses 343 
 
 Babbitt 343 
 
 Graphite 344 
 
 Wood 344 
 
 Vulcanized Fiber 344 
 
 Finish of Plain Bearings 344 
 
 Areas 344 
 
 Scraping 345 
 
 MISCELLANEOUS BEARINGS 346 
 
 CHAPTER 9 LUBRICATION 
 
 Introductory 347 
 
 SPLASH LUBRICATION 347 
 
 Ring and Chain Oilers 348 
 
 GRAVITY LUBRICATION 349 
 
 Oil Cups 349 
 
 Reservoir Systems 350 
 
 FORCED LUBRICATION. 350 
 
 Pressure Feed 350 
 
 Single Pumps 351 
 
 Multiple Pumps 351 
 
 Grease Cups 352 
 
 LUBRICANTS 352 
 
 Mineral Oils 352 
 
 Vaseline 353 
 
 Vegetable Oils 353 
 
 Castor Oil 353 
 
 Olive Oil 353 
 
 Animal Oils 354 
 
 Sperm Oil 354 
 
 Tallow 354 
 
 Miscellaneous Lubricants 354 
 
 Water 354 
 
 Kerosene 355 
 
 CHAPTER 10 STARTING AND ALIGHTING 
 
 Introductory 356 
 
 STARTING DEVICES 357 
 
 Wheels 358 
 
 Rails ; 358 
 
 Floats 359 
 
 Runners 360 
 
 The Starting Impulse 360 
 
 Propeller Thrust 361 
 
 Dropped Weights 362 
 
 Winding Drums 363 
 
 Inclined Surfaces 364 
 
 Launching Vehicles 365 
 
 Automobiles 365 
 
 Railway Cars 365 
 
 Boats 366 
 
 Cleared Areas 366 
 
 Facing the Wind 367 
 
 Launching from Height 368 
 
 ALIGHTING GEARS 369 
 
 Wheels . 369 
 
14 VEHICLES OF THE AIR 
 
 Runners 370 
 
 Floats 370 
 
 Miscellaneous 371 
 
 CHAPTER 11 MATERIALS AND CONSTRUCTION 
 
 Introductory 372 
 
 WOODS 373 
 
 Hardwoods 374 
 
 Applewood 375 
 
 Ash 375 
 
 Bamboo 375 
 
 Birch 376 
 
 Boxwood 376 
 
 Elm 376 
 
 Hemlock 377 
 
 Hickory 377 
 
 Holly 378 
 
 Mahogany 378 
 
 Maple 378 
 
 Oak 378 
 
 Walnut 378 
 
 Softwoods 379 
 
 Pines 379 
 
 Poplar 379 
 
 Spruce 379 
 
 Willow 380 
 
 Veneers and Bendings , 380 
 
 METALS 381 
 
 Iron 382 
 
 Steel 382 
 
 Alloy Steels 383 
 
 Cast Iron 384 
 
 Aluminum Alloys 384 
 
 Aluman 384 
 
 Argentalium 385 
 
 Chromaluminum 385 
 
 Magnalium 385 
 
 Nickel- Aluminum . , 385 
 
 Partinium 385 
 
 Wolframinium 385 
 
 Brasses and Bronzes 386 
 
 Aluminum Bronze ; 386 
 
 Phosphor Bronze 386 
 
 Metal Parts 386 
 
 CORDAGE AND TEXTILES 387 
 
 Linen 388 
 
 Silk 388 
 
 PAINTS AND VARNISHES 388 
 
 Oils 388 
 
 Shellacs 389 
 
 Spar Varnishes 389 
 
 Aluminum Paint 389 
 
 Miscellaneous 389 
 
 MISCELLANEOUS 389 
 
 Catgut 389 
 
 China Grass 390 
 
 Hair 390 
 
 Rawhide 390 
 
CONTENTS 15 
 
 Silk Cord 390 
 
 Silkworm Gut 390 
 
 ASSEMBLING MATERIALS AND METHODS 390 
 
 Nails 390 
 
 Glues and Cements 390 
 
 Screws 391 
 
 Bolts 391 
 
 Clips 391 
 
 Rivets 391 
 
 Electric Welding 391 
 
 Autogeneous Welding 391 
 
 Brazing 391 
 
 Soldering 392 
 
 Tabular Comparisons of Materials 392 
 
 Metals 393 
 
 Miscellaneous Materials 393 
 
 Transverse Strength of Wood Bars 393 
 
 Woods 393 
 
 CHAPTER 12 TYPICAL AEROPLANES 
 
 Introductory 394 
 
 Antoinette Monoplanes 396 
 
 Bleriot Monoplanes 396 
 
 Chanute Gliders 398 
 
 Cody Biplane 399 
 
 Curtiss Biplane 400 
 
 Farman Biplane 404 
 
 Langley Machine 404 
 
 Lilienthal 's Machines 404 
 
 Maxim Multiplane 405 
 
 Montgomery Machine 406 
 
 Pilcher Gliders 407 
 
 E. E. P. Monoplanes 408 
 
 Santos-Dumont Monoplane 408 
 
 Voisin Biplane 409 
 
 Wright Biplane 409 
 
 CHAPTER 13 ACCESSORIES 
 
 Introductory . . . . 410 
 
 LIGHTING SYSTEMS 410 
 
 Electric Lighting 411 
 
 Advantages of Uniform Motor Speed 411 
 
 Arc Lamps 411 
 
 Incandescent Lamps 412 
 
 The Nernst Lamp 413 
 
 Acetylene 413 
 
 Storage Tanks 414 
 
 Acetylene Generators 414 
 
 Acetylene Burners 415 
 
 Oxygen Systems 416 
 
 With Hydrogen * 416 
 
 With Gasoline 416 
 
 With Acetylene 416 
 
 Incandescent Mantles 416 
 
 With Gas 417 
 
 With Liquid Fuels 417 
 
 Oil Lamps 417 
 
 Sperm Oil 417 
 
 Kerosene ,.,...,..,,..,, 418 
 
16 VEHICLES OF TEE AIR 
 
 Reflectors 418 
 
 Arrangement of Lights 419 
 
 SPEED AND DISTANCE MEASUEEMENTS 420 
 
 Anemometers 420 
 
 Miscellaneous 421 
 
 COMPASS 422 
 
 Fixed-Dial Compasses 423 
 
 Floating-Dial Compares 423 
 
 BAROMETERS 424 
 
 Mercurial Barometers 424 
 
 Aneroid Barometers 424 
 
 WIND VANES 425 
 
 MISCELLANEOUS INSTRUMENTS 425 
 
 CHAPTER 14 MISCELLANY 
 Introductory 427 
 
 APPLICATIONS 428 
 
 Warfare 429 
 
 Sport 432 
 
 Mail and Express 433 
 
 News Service 434 
 
 Effects of Low Cost and Maintenance 434 
 
 General Effects 435 
 
 RADII OF ACTION 436 
 
 Influence of Wind 437 
 
 DEMOUNTABILITY 437 
 
 PASSENGER ACCOMMODATION 439 
 
 Seats 440 
 
 Housing 440 
 
 Upholstery 440 
 
 Pneumatic Cushions 440 
 
 Heating 441 
 
 By the Exhaust 441 
 
 PARACHUTES 442 
 
 DESIGNING 443 
 
 TESTING AND LEARNING 444 
 
 Learning from Teacher 444 
 
 Practice Close to the Surface 444 
 
 Practice over Water 445 
 
 Maintaining Headway 445 
 
 Landing 445 
 
 AERIAL NAVIGATION 446 
 
 Flying High 446 
 
 Steadier Air 446 
 
 Choice of Landing 447 
 
 Flying Low 447 
 
 Falling 448 
 
 Striking Obstacles >. 448 
 
 Vortices and Currents 448 
 
 TERRESTRIAL ADJUNCTS 449 
 
 Signals 449 
 
 Fog Horns and Whistles 450 
 
 PATENTS 451 
 
 GLOSSARY OF AERONAUTICAL TERMS 464 
 
 CHAPTER 15 FLIGHT RECORDS 
 
 Introductory 473 
 
 TABULAR HISTORY OF FLIGHTS 476 
 
LIST OF ILLUSTRATIONS 
 
 FIGURE. PAGE. 
 
 Bleriot Monoplane at Paris Aeronautical Salon Frontispiece 
 
 General View of Paris Aeronautical Salon Frontispiece 
 
 1. Bleriot Flying from Etampes to Orleans 43 
 
 2. View in Paris Aeronautical Exhibition October, 1909 65 
 
 3. Layout of Gores for Spherical Balloon 76 
 
 4. Giffard's Dirigible Balloon 80 
 
 5. Tissandier's Dirigible Balloon 81 
 
 6. Renard's and Krebs' Dirigible Balloon 82 
 
 7. Texture of Modern Balloon Fabrics 65 
 
 8. Modern Spherical Balloon 90 
 
 9. Shuttles for Knotting Balloon Nettings, and Some Typical Knots.. 104 
 
 10. Balloon Valve 108 
 
 11. Car of Modern Spherical Balloon 90 
 
 12. Curious Drag Rope of Wellman Dirigible 94 
 
 13. Internal Balloon Ill 
 
 14. Balloon House for Dirigible "Russie" 94 
 
 153. Portable Balloon House Used By the French Army 96 
 
 16. Balloon Houses Nearing Completion 96 
 
 17. Rigid Construction of Zeppelin Dirigible 100 
 
 18. Dirigible Balloon, "Ville de Nancy" 104 
 
 19. Side View of Nacelle of Wellman Dirigible 108 
 
 20. Front View of Nacelle of Wellman Dirigible 108 
 
 21. Malicot Semi-Rigid Dirigible Balloon 104 
 
 22. Nacelle of the French Dirigible, "Zodiac III" 104 
 
 23. Count de Lambert Piloting Wright Biplane 117 
 
 24. Degen's Orthogonal Flier 120 
 
 25. Trouve's Flapping Filer 121 
 
 20. Engine and Wing Mechanism of Hargrave Model No. 18 122 
 
 27. Collomb Ornithopter 126 
 
 28. Toy Helicopter 127 
 
 29. Toy Helicopter 128 
 
 30. Toy Helicopter 128 
 
 31. Bertin Helicopter 126 
 
 32. Cornu Helicopter 140 
 
 33. Bertin Helicopter- Aeroplane 140 
 
 34. Box Kite 133 
 
 35. Henson Aeroplane of 1843 140 
 
 36. Le Bris' Glider 155 
 
 37. Moy's Aerial Steamer 156 
 
 38. Flying Fish 161 
 
 39. Flying Frog 164 
 
 40. Comparison of Pterodactyl and Condor 166 
 
 41. Wing-Case Insect 166 
 
 42. Pressure on Vertical and Inclined Surfaces 171 
 
 43. plane and Arched Surfaces without Angle of Incidence 172 
 
 44 to 67. Geometrical and other Drawings Explaining the Formation 
 
 and Action of Wing Surfaces 176-199 
 
 68. Staggered Biplane. 205 
 
 69. Goupy Biplane 158 
 
 70. Langley's 25-Pound Double Monoplane 208 
 
 71. Internal Framing of Antoinette Monoplane Wing 158 
 
 72. Framing of Antoinette Wing Inverted 158 
 
 73. Framing of Bleriot Monoplane Wing 164 
 
 74. inverted Upper Wing Frame of Wright Biplane 164 
 
 75. Assembling Wright Wing Frames 170 
 
 76. Aileron Control of Lateral Balance in Antoinette Monoplane 170 
 
 77. Aileron Control of Bleriot Monoplane VIII 170 
 
 78. Lejeune Biplane with Double Aileron Control 174 
 
 79. Front View of Pischoff and Koechlin Biplane 174 
 
 80. Side View of Pischoff and Koechlin Biplane 174 
 
 17 
 
18 VEHICLES OF THE AIR 
 
 FIGURE. PAGE. 
 
 81. Aileron Control of Farman Biplane 174 
 
 82. Sliding Wing Ends 218 
 
 83. Swinging Wing Ends 219 
 
 84. Wright Flexible Elevator or Rudder 225 
 
 85. Rear Controls of Antoinette Monoplane 226 
 
 86. Double Control from Single Wheel 226 
 
 87. Shoulder-Fork Control 228 
 
 88. Frame of New Voisin Biplane 230 
 
 89. Fuselage of Bolotoff Monoplane 230 
 
 90. Feathering-Paddle Flying Machine 232 
 
 91. Partially-Housed Paddle Wheel 233 
 
 92. Wave Surface 233 
 
 93. Helices of Propeller Travel 239 
 
 94. Circles of Propeller Travel 239 
 
 95. Diagram of Propeller Pitch 240 
 
 96. Angle of Propeller Blade to Angle of Travel 242 
 
 97. Advancing and Following Surfaces 248 
 
 98. Three-Bladed Propeller 231 
 
 99. Four-Bladed Propeller 231 
 
 100. Chauviere Walnut Propeller 234 
 
 101. Propeller, Engine, and Wing Frame of Antoinette Monoplane.... 234 
 
 102. Engine and Propeller of Santos-Dumont Monoplane 234 
 
 103. Wooden Propeller of Clement Dirigible Balloon 240 
 
 104. All-Metal Propeller Applied to Dirigible Balloon 240 
 
 105. Straight, Dihedral, and Curved Propellers 252 
 
 106. Effect of Gyroscopic Action of Single Propeller on Steering 263 
 
 107. Twin Wood Propellers on Single Shaft 264 
 
 108. Working Drawings of a Wooden Propeller 266 
 
 109. Templets for Securing a Desired Form in a Wooden Propeller. . . 271 
 
 110. Four Cylinder Motor of Wright Biplane 273 
 
 111. Pump-Fed Antoinette Engine 273 
 
 112. Three-Cylinder, 22-Horsepower Anzani Engine 276 
 
 113. Four-Cylinder "Double-Twin" Anzani Motor 278 
 
 114. Renault Eight-Cylinder V-Shaped Motor 278 
 
 115. Fiat and Panhard Aeronautical Motors 280 
 
 116. Darracq and Dutheil-Chalmers Aeronautical Motors 280 
 
 117. Diagram of Revolving-Cylinder Motor 283 
 
 118. Gnome Revolving-Cylinder Motor 284 
 
 119. Ten-Cylinder Motor with Concentric Exhaust and Inlet Valves 276 
 
 120. Magnetic Plug 285 
 
 121. Make-and-Break Ignition 285 
 
 122. Mechanical-Break Jump-Spark Ignition System 286 
 
 123. Jump-Spark Ignition , 286 
 
 124. Hot-Tube Ignition -. 287 
 
 125. Fuel-Injection Aeronautical Engine 290 
 
 126. Carbureter 292 
 
 127. Mietz and Weiss Fuel Pump 295 
 
 128. Silencer 296 
 
 129. Muffler 296 
 
 130. Steam Engine For Aeronautical Use 300 
 
 131. Flue Boiler 302 
 
 132. Water-Tube Boiler for Aeronautical Use 300 
 
 133. Aeroplane Power-Transmission System 313 
 
 134. Aeroplane Power-Transmission System 313 
 
 135. Aeroplane Power-Transmission System 313 
 
 136. Aeroplane Power-Transmission System 313 
 
 137. Block Chain 316 
 
 138. Roller Chain 317 
 
 139. Chain Transmission of Wright Biplane 313 
 
 140. Chain Transmission in Hydroplane, Driven by Aerial Propellers . . . 313 
 
 141. Belt Transmission in Recent Santos-Dumont Monoplane 316 
 
 142. Voisin Biplane Modified into a Triplane 327 
 
 343. Henry Farman's Biplane in Flight 327 
 
 144. Adjustable Ball Bearing 329 
 
 145. Annular Ball Bearing 330 
 
 146. Full Type Annular Ball Bearing 332 
 
 147. Annular Ball Bearing 332 
 
 148. Annular Ball Bearing 333 
 
LIST OF ILLUSTRATIONS 19 
 
 FIGURE. PAGE. 
 
 150. Ball Thrust Bearing 334 
 
 151. Resultants of Load on Ball Bearing 335 
 
 152. Cylindrical Roller Bearing 340 
 
 153. Flexible Roller Bearing 341 
 
 154. Projected Area of Plain Bearing 345 
 
 155. Adjustment of Plain Bearing 346 
 
 149. Annular Ball Bearing Subjected to Thrust 333 
 
 156. Cone Bearing 346 
 
 157. Bleriot XI. in Flight 347 
 
 158. Bleriot XII. in Flight 347 
 
 159. Ring oiler on Crankshaft 349 
 
 160. Force-Feed Lubricator 351 
 
 161. Wright Biplane Starting and in Flight 348 
 
 162. Koechlin Monoplane in Flight 350 
 
 163. Wright Machine on Starting Rail 350 
 
 164. Bleriot Alighting Gear 350 
 
 165. Wright Starting System 358 
 
 166. Wright Machine and Starting Derrick 360 
 
 167. Starting by Rope Attached to Stake and Wound in on Drum.... 364 
 
 168. Rougier's Voisin Rising from Starting Ground 360 
 
 169. Bleriot Starting Device 368 
 
 170. Typical Alighting Gear 370 
 
 171. Details of Bleriot Monoplane 372 
 
 172. Alighting Gear of Paulhan's Voisin 372 
 
 174. Alighting Gear of Farman Machine 374 
 
 175. Boat-Like Body of Antoinette Monoplane 374 
 
 176. Alighting Gear of Antoinette Monoplane 374 
 
 177. Built-Up Bamboo Spar 376 
 
 178. Sections of Wooden Spars 380 
 
 179. Built-Up Hollow Wooden Spar 381 
 
 180. Built-Up Bamboo, Hickory, and Rawhide Wing Bar 381 
 
 181. Methods of Fastening Wire Ends 386 
 
 182. Strut Sockets and Turnbuckles 387 
 
 183. Wire Tightener 387 
 
 184. Texture of Modern Aeroplane Fabrics 372 
 
 185. Scale Drawings of Wright Biplane 392 
 
 186. Side View of Wright Machine 394 
 
 187. Three-Quarters View of Wright Machine 394 
 
 188. Rear View of Wright Machine 398 
 
 189. Paul Tissandier Seated in Wright Biplane 400 
 
 190. Count de Lambert in Wright Biplane 400 
 
 19 1 Wilbur Wright Instructing a Pupil 400 
 
 .,02 Details of Wright Strut Connections 402 
 
 ., 03* gi e view of Wright Runner Construction 402 
 
 194* Wright Runner and Rib Details 402 
 
 195] Rudder Frame of Wright Machine 404 
 
 196. Elevator Frame of Wright Machine 404 
 
 197. Scale Drawings of Bleriot Monoplane Number XI 406 
 
 198. Bleriot Monoplane Number XII 408 
 
 199. Bleriot Monoplane Number XI 408 
 
 200. Front View of Bleriot XI 408 
 
 201. Three-Quarters View of Bleriot XI 408 
 
 202. Scale Drawings of Cody Biplane 412 
 
 203. Latest Model of Voisin Biplane 414 
 
 204. Three-Quarters Rear View of Voisin Biplane 414 
 
 205. Three-Quarters Front View of Voisin Biplane 414 
 
 206. Scale Drawings of Farman Biplane 416 
 
 207. Side View of Farman Biplane 418 
 
 208. Three-Quarters View of Farman Biplane 418 
 
 209. Maurice Farman's Biplane 420 
 
 210. Front View of Maurice Farman's Biplane 420 
 
 211. Farman's Modified Voisin 420 
 
 212. Scale Drawings of Antoinette Monoplane 397 
 
 213. Three-Quarters View of Antoinette III 424 
 
 214. Rear View of Antoinette V 424 
 
 215. Front View of Antoinette VII 424 
 
 216. Rear View of Antoinette VII 426 
 
 217. Side View of Santos-Dumont's Belt-Driven Monoplane 426 
 
 218. Front View of Santos-Dumont's Belt-Driven Monoplane 426 
 
20 VEHICLES OF THE AIR 
 
 FIGURE. PAGE. 
 
 219. Side View of Santos-Dumont's Demoiselle 424 
 
 220. Front View of Santos-Dumont's Demoiselle 426 
 
 221. Scale Drawings of Santos-Dumont Monoplane 428 
 
 222. Side View of R. E. P. Monoplane 430 
 
 223. Three-Quarters View of R. E. P. Monoplane 430 
 
 224. Captain Ferber's Dihedral Biplane 430 
 
 225. Scale Drawings of Montgomery Glider 432 
 
 226. Front View of Montgomery Monoplane Glider 434 
 
 227. View from Beneath of Montgomery Double Monoplane 434 
 
 228. Scale Drawings of Curtiss Biplane 401 
 
 229. Side View of Latest Curtiss Biplane 436 
 
 230. Early Lilienthal Monoplane Glider 405 
 
 231. Lilienthal Monoplane Glider 405 
 
 232. Lilienthal's Biplane 405 
 
 233. Pilcher Glider 407 
 
 234. Pilcher Glider 408 
 
 235. Maxim Multiplane 406 
 
 236. Maxim Multiplane 406 
 
 237. Chanute Biplane Glider. 398 
 
 238. Santos-Dumont's Demoiselle in Flight 410 
 
 239. Paulhan's Voisin in the Douai-to-Arras Flight 410 
 
 240. Suggested Nernst Lamp 413 
 
 241. Lens Mirror 418 
 
 242. Locomotive Headlight 419 
 
 243. Anemometer Speed and Distance Recorder 421 
 
 244. Universal Level 426 
 
 245. Side View of Bleriot XI. with Wings Tied on Frame ... 427 
 
 246. Front View Bleriot XL, Showing Demountable Wings 427 
 
 247. Assembling Bleriot XI 427 
 
 248. Wicker Chair and Foot Control of Ailerons in Farman Biplane 440 
 
 249. Cockpit of Bleriot Monoplane Number XI 440 
 
 250. Seating Arrangement and Control System of Antoinette Monoplane 448 
 
 251. Sling Seat of Captain Ferber's Biplane 448 
 
 252. Cockpit and General Details of R. E. P. Monoplane 450 
 
 253. Latham's Antoinette Monoplane in the English Channel 450 
 
 254. Latham Heading off the Cliffs at Sangatte 452 
 
 255. Suggested Use of Exhaust Gases to Heat Foot Warmer 441 
 
 256. Parachute 442 
 
 257. Effect of Height Upon Choice of Landing 447 
 
 258. United States Weather Signals 450 
 
 259. Wright Patent Drawings 453 
 
 260. Montgomery Patent Drawings 459 
 
 261. Chanute Patent Drawing 462 
 
 262. Mouillard Patent Drawing 463 
 
 263. Lilienthal Patent Drawing 464 
 
 264. Diagrammatic Comparisons of Modern Aeroplanes 473 
 
 265. Flights over English Channel 474 
 
 266. Farman Flights, Chalons to Rheims, and Chalons to Sulppes 474 
 
 267. Bleriot Flights, Toury to Artenay, and Etampes to Orleans 474 
 
 268. Cody's 40-Mile Cross-Country Flight in England 475 
 
 269. Count de Lambert's Flight over Paris 475 
 
 270. Map Showing Principal Zeppelin Flights 475 
 
" * * * the heavens fill with commerce, argosies of magic sails, 
 Pilots of the purple twilight, dropping flown with costly bales." 
 
 TENNYSON. 
 
 INTRODUCTION 
 
 To the preparation of this work, the author has been 
 influenced largely by the lack of any concrete and 
 popular treatise on aerial navigation. 
 
 With the ob;iect of remed y in S this 
 condition in at least some degree it 
 
 has been sought to produce an adequate, up-to-date, 
 and at the same time a comprehensive presentation of 
 what is fast becoming one of the most important and 
 alluring fields of modern engineering. In the accom- 
 plishment of this purpose it has seemed desirable to 
 plan a volume that should appeal to general curiosity 
 as well as to particular interest. This is because the 
 subject is so new that very few can lay any claim to 
 its mastery, though thousands are commencing its 
 study. 
 
 These conceptions of the need, and of the sort of 
 interest to be met by a book of this character, have 
 dictated the inclusion not only of timely and authori- 
 tative data concerning contemporary successes, but 
 also of some material that is chiefly historical often 
 the history of now discredited mechanisms as a help 
 in easily and clearly conveying to the casual reader a 
 logical idea of just what progress has been made and 
 is making in the modern science of aeronautics. It 
 even has appeared reasonable to venture occasional 
 suggestions of the future forecasts intended simply 
 
 21 
 

 22 VEHICLES OF THE AIR 
 
 to stimulate still doubtful imaginations rather than to 
 invalidate themselves by too-complicated or far-fetched 
 premises. Yet in such prophecies it will be readily 
 appreciated by the technically versed that the prophet 
 is sufficiently safe if he don his robe without too reck- 
 less a disregard of his limitations, and confine himself 
 to impressing upon the general attention only such 
 facts as are already evident and obvious to the few 
 specialists who are closely in touch with their subject. 
 
 Necessarily some portion of the matter herein pre- 
 sented is in a way the product of compilation. It being 
 the province of the writer at a task of this sort to 
 record rather than to create, it is not to be expected 
 that much more can be accomplished than a discrimi- 
 nating and consistent addition of new material to old, 
 with the two arranged and related in an orderly and 
 informing manner. No more than this has been 
 attempted ; if no less has been accomplished the author 
 will feel well satisfied. 
 
 The publishers join with the author in the hope 
 that this book may help to stimulate the English- 
 speaking races into some parallel with foreign enthu- 
 siasm in aeronautics. For it seems as true as it is 
 regrettable that the nations that developed the Wright 
 brothers, Montgomery, Chanute, Langley, Herring, 
 Pilcher, Stringfellow, Wenham, Hargrave, Henson, 
 Maxim, McCurdy, Curtiss, and others, and which once 
 were found always in the van of the world 's progress 
 in science and invention, are replacing their one-time 
 zeal for promising innovations and scorn of hampering 
 precedents with an imitative and trailing commer- 
 cialism, of which there already has been at least one 
 other sufficient example. Certainly it is an inescapable 
 fact that the less tradition-trammeled engineers of 
 
INTRODUCTION 23 
 
 continental Europe are the first to perceive the begin- 
 nings of the practical and commercial era in aero- 
 nautics, just as they were the first to perceive it in 
 the case of the automobile. And equally is it a fact 
 that the United States and the British governments, 
 and American and English capitalists, continue con- 
 spicuously tardy in their recognition of the newest and 
 least-limited advance in the history of transportation. 
 
 Nothing but the utmost blindness to existing 
 achievements can continue to belittle what it cannot 
 SKEPTICISM comprehend. Aerial navigation today 
 is IGNORANCE is no more a joke than was the railway 
 eighty years ago, or the steamship 
 seventy years ago, or the automobile ten years ago. 
 On the contrary, it is already the basis of a vast and 
 progressing industry, founding itself surely on the 
 most advanced discoveries of exact science and the 
 finest deductions of trained minds, and possessed of 
 a future that in its sociological as well as in its engi- 
 neering aspects sooner or later must stir the imagina- 
 tions of the dullest skeptics. Inevitably it is a matter 
 of perhaps no more than a few months certainly of 
 no more than a few years after this is written when 
 in every country of the world the flying machine will 
 enter upon an epoch of wide development and appli- 
 cation, the far-reaching reactions of which are certain 
 to carry significances of the profoundest import to 
 every phase of civilization and every activity of the 
 race. 
 
 Man's movements about the planet he inhabits are 
 
24 VEHICLES OF THE AIR 
 
 restricted to a maximum of the three traversable media 
 with which he can come in physical contact. He can 
 
 THREE travel by land, by water and by 
 TEAVEBSABLE air. Of the difficulties of these, he first 
 
 MEDIA overcame the simplest, as was to have 
 been expected; he next fell to devising one kind and 
 another of water craft, and progressed to navigation 
 of the seas; and now, after centuries of ineffective 
 struggle, he is beginning to apply the hard-won les- 
 sons of his slowly-accumulated knowledge to the con- 
 quest of the air. Of the three media, the air alone 
 exists over the earth's entire surface, thus demanding 
 for its utilization neither specially-constructed high- 
 ways nor restriction of journeys such as limit or make 
 costly all efficient transportation on land and water. 
 And, more than all this, there are unknowable forces 
 greater than the mere opinions and activities of men, 
 so it is only consistent with experience of human 
 progress and observation of the eternal logic of things 
 to recognize that sooner or later mankind must 
 conquer this last highway of the world, thus finally 
 asserting the dominion over all things terrestrial that 
 is declared his right by the scriptures. 
 
 Concerning the types of machines that will survive, 
 as most successfully applicable to practical and com- 
 mercial navigation of the air, present 
 knowledge is distinctly informing. It 
 seems rather clearly indicated, for 
 example, that the "lighter-than-air" type, the balloon, 
 can have little future beyond such as is too often 
 founded upon the activities of ignorant inventors or 
 unscrupulous promoters, or upon the thrills it 
 undoubtedly affords as a Gargantuan spectacle. As is 
 hereinafter suggested the balloon is an evasion rather 
 
INTRODUCTION 25 
 
 than a solution of the real problem of aerial naviga- 
 tion. It floats in the air rather than navigates it, and 
 so is no more a flying machine than a cork in the sea 
 is an ocean liner.* 
 
 The helicopter is the type of "heavier-than-air" 
 machine designed to ascend by the action of one or 
 more lifting propellers, rotating on vertical axes. This 
 type must for the time be dismissed as without present 
 status to condemn or approve it. It is enough to say 
 that more than one engineer of unquestioned eminence 
 has faith in it, while there are others of equal standing 
 who as positively disapprove. 
 
 The term ornithopter is given to any type of 
 heavier-than-air machine in which there is attempted 
 imitation of nature's wing motions. The matter of 
 its merit comes down chiefly to the simple question of 
 whether or not a reciprocating-wing system can be 
 made superior in reliability and efficiency to the 
 rotating-wing system that constitutes a propeller. 
 Probably no engineer of practical abilities will con- 
 tend that it can. It is a common argument that birds, 
 which may be considered the flying machines par 
 excellence, fly on this plan. True enough, but it is 
 equally true that most animals walk on legs and 
 most fishes swim with tails and fins, despite which 
 man finds that with wheels and screw propellers he 
 can secure results vastly superior to any that are to 
 be found in attempts to copy nature's mechanisms 
 more closely. It is a point deserving of regard in 
 
 * It being a fact, however, that the dirigible balloon exists, and that 
 its problems are enlisting the activities of able engineers and powerful 
 governments, for these reasons it will herein in all fairness be accorded 
 such attention as seems demanded by its present prominence rathe* than 
 by its future prospects. 
 
26 VEHICLES OF THE AIR 
 
 this connection that the real reason the continuous 
 rotating mechanism is unknown in the animal economy 
 may be the most excellent one that it is not available. 
 A wheel or any similar continuous-rotating element in 
 a machine involves a complete separation of parts, 
 mere contact or juxtaposition being substituted for the 
 complete structural continuity that is rendered impera- 
 tive in the natural machine by nature's self-contained 
 processes of manufacture, growth, and repair proc- 
 esses with which man's mechanisms are not handi- 
 capped, however imperfect they may be in other 
 respects. 
 
 The aeroplane is far and away the most promising 
 of the several types of machines in so far as any 
 
 AEROPLANE present vision can discern. This type 
 MOST of air craft is sustained by the reac- 
 
 SUCCESSFUI* tions of the air rotations and streams 
 under and adjacent to its inclined curved surfaces, 
 and in nature finds its analogy in the soaring bird, 
 and particularly in certain insects. Ordinarily, to fly 
 an aeroplane must keep moving, wherefore it must 
 attain lateral speed before it can rise and must retard 
 to a stop in alighting. Without exception all the suc- 
 cesses recently achieved in the United States and 
 abroad have been with curved-wing* aeroplanes. 
 
 The questions of speed and flying radius are still 
 some way from any sort of settlement. Certainly the 
 speeds ultimately attained will be very high, but, what 
 is more to the point, they will be easily maintained. 
 In this regard aerial navigation is comparable with 
 
 * The modern substitution of curved surfaces for the flat ones of 
 earlier experiments has made the term "aeroplane" a misnomer, but it 
 seems nevertheless to have fixed itself ineradicably upon the language. 
 and so may as well be accepted. 
 
INTRODUCTION 27 
 
 travel on water rather than with travel on land, 
 maximum speeds being also average speeds in the case 
 
 steamsm P> though this is not 
 
 SPEED AND 
 
 RADIUS ^ e case w ^k l an( * locomotion. In 
 addition to its other advantages, 
 high speed of aerial travel may prove the soundest 
 engineering because it admits of sustaining the 
 heaviest loads upon the smallest surfaces. Another 
 and imperative reason for speed will be to overcome 
 adverse winds. To progress against wind, speed 
 higher than the highest speed in which flying is to 
 be attempted may be required. The limit of wind 
 velocity with which it may prove possible to battle 
 will be determined mainly by conditions of starting 
 and landing. 
 
 As for the possible radii of action the maximum 
 distances of travel without return to a base or 
 descent to the earth for additional supplies of fuels, 
 lubricants, etc. it is evident first of all that the 
 greater the radius the greater the utility. Indeed, the 
 ability to combat long-continued adverse winds, appli- 
 cation to polar and other exploration, transoceanic 
 travel, and sustained rapid transit overland may 
 hinge directly upon capacity to accomplish great dis- 
 tances on minimums of supplies and fuel. 
 
 The sizes of the machines that will be built is 
 another matter for the future to determine. It being 
 a law of geometry that the areas of structures increase 
 with the squares of their linear dimensions, while 
 bulks and weights increase with the cubes, it is evident 
 that at some point the gain of the weights over the 
 areas will impose a limit that cannot be passed. 
 Against this, however, is the likelihood that there may 
 not be much use for large craft. Traffic experts agree 
 
28 VEHICLES OF THE AIR 
 
 that the secret of all rapid transit is the maintenance 
 
 of speed, it being the slowings down and the stops that 
 
 chiefly account for the slow average 
 
 AEROPLANES s P ee d s on l anc * despite the wonder- 
 ful spurts that have been made by 
 land vehicles for short distances. More than this, the 
 existence of the expensive large-unit vehicle on land 
 is mainly due to the necessity for highly-specialized, 
 prepared highways, while on water it has been found 
 an essential means to high speeds and maximum 
 safety. In the air conditions will be different. Here 
 the inexpensive and ideal small-unit vehicle, suggested 
 in some degree by the automobile, and likewise eman- 
 cipating its user from other persons' routes, stops, 
 and time schedules, will find an unlimited field for 
 development. Moreover, such development will pro- 
 gres under the stimulus of lower first and maintenance 
 cost than apply to any other system of travel*. 
 
 Flying machines will be inexpensive to build 
 
 because their construction calls for little use of 
 
 FIRST AND complex forms in resistant metals. 
 
 OPERATING Wood, wire, and fabric, of common 
 
 qualities and at low cost, are almost 
 
 the extent of what is necessary, barring the question 
 
 of motors, which will be cheaply manufactured in 
 
 quantities, to standardized designs. And even more 
 
 vital than mere low cost of manufacture will be the 
 
 fact that manufacture will not require the facilities 
 
 of costly factories, but can be undertaken by any one 
 
 possessed of the requisite data and an ordinary sort 
 
 of carpentering ability. 
 
 That flying machines will be inexpensive to operate 
 must reasonably follow from the small power needed 
 for their propulsion and from the fact that they have 
 
INTRODUCTION 29 
 
 no working parts in constant destructive contact with 
 a roadway. Indeed, the transition from the expedient 
 of confining air in automobile tires to the utilization 
 of the unconfined air of the atmosphere as a vehicle 
 support is rather definitely an advance from a lower 
 to a higher order of engineering. 
 
 Nor are these questions of cost in any sense the 
 least important factors in the future of aerial naviga- 
 tion. Modern engineering abounds in 
 examples of things that are possible 
 but not profitable. Indeed, it is just 
 this point, that limited utilities do not warrant unlim- 
 ited expenditures, that so utterly condemns the dirig- 
 ible balloon. With flying machines, sufficing for the 
 safe, inexpensive, and rapid conveyance of one or two 
 persons, cheaper to build than a modern motorcycle, 
 there enter prospects that must ultimately loom larger 
 on the horizon of transportation and the whole struc- 
 ture of modern society than even so great a prospect 
 as the actual accomplishment of aerial navigation 
 itself. Laws, customs, and conventions must fall in 
 the tremendous readjustments that will ensue. Many 
 forms of social trespass will have to be fought by 
 removal of incentives rather than by attempts at pun- 
 ishment, and there will be discovered innumerable 
 outlets for various movements for race improvement, 
 which the iron inflexibility of present-day environment 
 keeps suppressed and silent. 
 
 Questions of safety are ever uppermost in most 
 persons' contemplations of aerial travel. To the 
 
 average individual let there be said 
 
 THE PHYSICAL flying mac hi ne and at once his brain 
 
 must visualize some horrifying con- 
 ception of an unstable craft of vague outlines and 
 
30 VEHICLES OF THE AIR 
 
 terrible hazards, precariously poised in the cloudland 
 at an illimitable height above terra firma. How dis- 
 tinctly such ideas are at variance with the facts has 
 been shown by the Wright brothers, Farman, Bleriot, 
 and others, in flying for mile after mile only four or 
 five feet from the ground.* 
 
 People are prone to appraise casualty by its horror 
 rather than by its statistics, and the thought of one 
 individual tumbling from the skies grips harder on 
 the popular imagination than the slaughter of a few 
 scores in a railway accident or the drowning of a few 
 hundreds in a shipwreck. As a matter of fact, there 
 are many more factors of safety in present and pros- 
 pective aerial travel than at first appear, even to the 
 well-informed. Besides the proved practicability of 
 close-to-the-ground flight, there is in the case of the 
 aeroplane the complete stability of the type as a 
 glider.f This means that the immediate safety at 
 any moment is not contingent upon the operation of a 
 more-or-less complicated motor, the continued func- 
 tioning of which is dependent upon the unfailing 
 operation of an interconnected aggregation of parts 
 rapidly revolving or reciprocating under heavy 
 stresses. On the contrary, a motor is necessary, if 
 
 * In teaching Captain Lucas Gerardville of the French army to 
 operate the Wright flyer, Wilbur Wright required the control of the 
 levers to be returned to him whenever the machine \vas steered lower 
 than two meters (6% feet) or higher than four meters (13 feet) from 
 the ground, thus indicating that he considered inability to keep within 
 this zone, even for a beginner, as definitely incompetent driving as 
 would be steering out of the road with an automobile. Such close-to- 
 the-ground flight is particularly well shown in the photographs repro- 
 duced in Figure 161. 
 
 t The Wright machine was first developed as a glider without a 
 motor, and in its later motor-propelled models has been on more than 
 
INTRODUCTION 31 
 
 at all, only to maintain continued upward or hori- 
 zontal travel, the ability to soar reliably at a flat 
 angle down a slant of air being contingent only upon 
 the continued structural integrity of non-moving ele- 
 ments, or at worst, of elements readily made very 
 strong or even provided in duplicate, and demanding 
 only moderate and occasional control adjustment 
 against very light stresses. As a consequence, the 
 only risk likely to continue ever-present is that of 
 such derangement or the encountering of such adverse 
 weather conditions as may compel landing upon 
 unfavorable areas without immediate but with the 
 prospect of ultimate disaster. Thus, to be compelled 
 by engine failure or adverse weather to descend in a 
 desert or forest, or on rough mountains, would result 
 in a situation fairly comparable to that of a wrecked 
 vessel, or of a 'derailed train, or of a ditched auto- 
 mobile, rather than in one ascribable to any undue 
 and inherent hazard pertaining to the new conveyance 
 regardless of the conditions of its use. These differ- 
 ent considerations will, however, doubtless produce 
 definite effects on the progress that will be made. 
 And, as progress continues and engineering resource 
 
 one occasion driven to considerable altitudes, the engine stopped pur- 
 posely or inadvertently, and a safe soaring descent to the ground ac- 
 complished. The Montgomery machine, built primarily as a glider, can 
 be dropped upside down in the air, even with loads, and such is its 
 automatic stability that it invariably rights itself and comes to the 
 ground as gently as a parachute. The Antoinette, Bleriot, Voisin, 
 Curtiss, E. E. P. and many other successful flyers likewise have proved 
 safe gliders with engines stopped. Particularly significant in this con- 
 nection were Latham's two descents, enforced by engine failure, into 
 the waters of the English Channel once without even wetting his feet I 
 A similar experience, showing that engine failure does not necessarily 
 mean serious disaster, was C. F. Willard's descent upon Lake Ontario, 
 on September 3, 1909. 
 
32 VEHICLES OF THE AIR 
 
 makes of the trackless air an unrestricted highway 
 of ever-increasing stability, those of the sky pilots 
 whose temerity is greatest may be expected to become 
 more and more venturesome and capable, so that the 
 development of the flying machine, from commencing 
 with cautious flights in favorable weather, at moderate 
 speeds and low altitudes, and over surfaces upon 
 which landing is comparatively safe, must in time pro- 
 gress to exceedingly rapid travel at somewhat greater 
 heights, and with less regard to the state of the 
 weather or to the character of the surface beneath. 
 Aerial navigation offers little prospect of ever 
 becoming safe to the extent of relieving those who 
 take it from the common chances of 
 DANGERS IN jif e an( j d eatn , but it does most 
 L TRAVEL emphatically promise that its hazards 
 per passenger carried a given distance will not exceed 
 the corresponding hazards of terrestrial and aquatic 
 transportation. The railroads of the United Stales 
 alone exact an annual toll of 12,000 persons killed and 
 72,000 injured, yet many very timid individuals think 
 nothing of riding for hours at a time, at speeds of 
 forty, sixty, and eighty miles an hour, along the tops 
 of precipitous embankments and over unguarded 
 bridges and trestles, with their safety never for a 
 moment independent of the somewhat precarious hold 
 of thin wheel flanges on the smooth edges of narrow 
 rails. Thus does familiarity breed contempt. Never- 
 theless, compelled to a choice between being plunged 
 to the ground through a distance of, say, fifteen feet 
 in a light, elastic, and protecting structure of wood, 
 wire, and fabric, against the proposition of rolling a 
 similar distance down an embankment, surrounded by 
 
INTRODUCTION 33 
 
 the crushing mass of a railway coach, what sane indi- 
 vidual would prefer the hazards of the latter? 
 
 As progress continues and safety becomes more 
 and more assured under conservative and reasonable 
 conditions, the timid will in increasing 
 num ^ ers venture first trips as pas- 
 sengers and be reassured by their 
 experiences, until the time will arrive when to fear to 
 travel by air will be to class one with the people who 
 today are afraid to dare the risks of rail and water 
 travel. A gradual overcoming of the inertia of the 
 mind appears to be an essential process in reconciling 
 the generality of people to innovations. Even in the 
 cases of many institutions of the longest standing 
 there are persistent inconsistencies in many people's 
 attitudes. For example, the automobile, which com- 
 pared "passenger-mile" against "passenger-mile" is 
 found responsible for far fewer accidents than regu- 
 larly attend the use of horses, still is regarded as a 
 'sort of death-dealing juggernaut by many normally 
 sensible persons. Likewise, it is commonplace to find 
 people thoroughly hardened to travel by the most dan- 
 gerous type of rail vehicle, the street car, who cannot 
 restrain a feeling of terror at the thought of travel 
 by steamship, which is statistically provable to be any 
 number of times safer. At the time this is written the 
 power-driven heavier-than-air flyer has been respon- 
 sible for the death of only three individuals in the 
 whole world, despite an aggregate of experimental 
 flights totalling fully 35,000 miles. 
 
 Undoubtedly the first commercial applications of 
 aerial vehicles will be to classes of service involving 
 minima of human risk with maxima of utility serv- 
 ices such as the conveyance at high speed of special 
 
34 VEHICLES OF THE AIR 
 
 classes of mail and express matter by aeroplanes, each 
 
 requiring for its management only a single operator, 
 
 or the rapid distribution of news- 
 
 COMMEECIAL paper matrices and illustrations under 
 
 APPLICATIONS ., -I-,- -XT 
 
 similar conditions. Next may come 
 the daring spirits who will take desperate chances in 
 the exploration and prospecting of remote and unset- 
 tled regions not to consider the red-blooded few who 
 from the beginning find in navigation of the air a 
 new means of reckless sport and dangerous recreation, 
 chiefly interesting in the improvements that result 
 from their successes and the lessons that are gleaned 
 from their mishaps. 
 
 To any one who has kept abreast of recent progress 
 it is genuinely amazing that there are still so many 
 who question this matter of commercial applica- 
 tions. Many who even concede that the flying machine 
 may find important application in warfare and meet 
 with considerable success in sport, still are disposed 
 to deny that it ever can find extensive use as a common- 
 place, every-day means of transportation. Such per- 
 sons mistake the bounds of their own knowledge for 
 defects in the thing examined, and see in every failure 
 of an experimental mechanism, no matter to what 
 cause due, a conclusive condemnation of a whole propo- 
 sition, and when they find themselves astute enough 
 to glimpse a limitation, no matter how trifling, its sub- 
 traction from the original quality clearly leaves a 
 remainder of zero. Yet an inability to fly at all 
 through not knowing how is a distinctly different 
 thing from a mere cessation of flight from break- 
 down. The first leaves mankind as positively unable 
 to travel in the air as to travel to Mars. The second 
 is with perfect reasonableness comparable with such 
 
INTRODUCTION 35 
 
 negative disabilities as broken flanges, punctured tires, 
 leaking hulls, and the like, which similarly may termi- 
 nate particular trips by particular means in delay and 
 even in death. 
 
 As for limitations, it certainly is to be admitted, 
 
 for example, that the aeroplane appears totally 
 
 unsuited for urban travel. In its 
 
 Z I n J^j ^ S present most successful forms it re- 
 EAFECTED . . 
 
 quires special devices or, at least, con- 
 siderable clear and unobstructed areas for starting 
 and alighting. But for interurban travel, on the other 
 hand, these limitations fail to constitute objections of 
 material magnitude. There is no more reason for 
 expecting the aeroplane to find its utility by developing 
 a facility in maneuvering through mazes of wires and 
 alighting amid street traffic than there would be for 
 condemning Atlantic liners because they have to dock 
 at Hoboken instead of sailing up Broadway. Undoubt- 
 edly the time will come when it will be considered 
 quite as reasonable that the beginnings and endings of 
 aerial voyages should involve the presence of special 
 launching and landing facilities, as it is that railway 
 trains should travel from station to station. No type 
 of transportation is unlimitedly flexible. Bail vehicles 
 are confined to rails, automobiles must keep to roads 
 or good surfaces, water craft cannot leave the water, 
 bicycles require at least a fair path, and not even 
 beasts of burden and men walking can disregard all 
 topographical difficulties. Against these, surely the 
 ability of the air vehicle to progress in an air line at 
 its high and maintained speed from selected start to 
 selected destination, always regardless of what may 
 be beneath, and ever ready should necessity compel to 
 settle under control and without immediate danger 
 
36 VEHICLES OF THE AIR 
 
 upon any fair area of unencumbered land or water 
 space, may be regarded as a form of flexibility suffi- 
 ciently valuable to offset the lack of other sorts. 
 Moreover, there is some reason for expecting that 
 small aeroplanes and helicopters may arrive ultimately 
 at such reliability and perfection of control that it 
 will be feasible to direct them from or upon almost any 
 place that affords space to accommodate them. 
 
 Particularly interesting is the relation of aerial 
 
 navigation to war it appearing more than probable 
 
 that this latest of man's inventions 
 
 RELATION w ^j serve fi rs t in adding to the ter- 
 
 TO WAEFAEE. -. ,, . ,, n . ,, , , . 
 
 rors of and then in the laying of this 
 grim specter of the centuries. For aside from all 
 mere tactical questions of airships versus battleships 
 it is most of all to be considered, as a very few mili- 
 tary authorities have pointed out, that in the develop- 
 ment of the flying machine there is placed for the first 
 time in history, in the hands of weak and strong com- 
 batants alike, a weapon capable of as effective and 
 unpreventable direction against the kings, congresses, 
 presidents, and diplomats who declare war as it is of 
 direction against the fighting men on the faraway 
 battlefronts. Already more than one great military 
 and naval captain has suffered disquieting visions of 
 what will happen when, maneuvering unopposed and 
 unseen in the obscurity of the night, not merely one 
 or a few, but veritable swarms of light aeroplanes, in 
 twenty- thousand lots costing no more than single 
 dreadnoughts, commence trailing assortments of high 
 explosives at the ends of thousand-foot lengths of 
 piano wire, over cities and palaces and through fleets 
 and armies. 
 
 Many authorities are inclined to disparage the 
 
INTRODUCTION 37 
 
 fighting utility of the aeroplane, basing their views on 
 the fact that it has been demonstrated exceedingly 
 difficult to drop bombs with any considerable accuracy 
 from great heights. But from a slow-moving aero- 
 plane flying very low it should be an easy matter to 
 cast generous parcels of picric acid or fulminate of 
 mercury into the twenty-foot diameters of a battle- 
 ship's funnels. The answer that such an attempt 
 might be foiled by the use of searchlights and quick- 
 firing guns is one that contemplates attack by only 
 one or two of the air craft, rather than to the con- 
 certed descent of a whole host of such emissaries of 
 destruction, each manned by a competent and deter- 
 mined crew, realizing that if only one of the wasp-like 
 swarm achieves its purpose the picking off of a few 
 by lucky shots or extraordinary gunnery will be fear- 
 fully avenged. 
 
 Fancy for a moment the disillusionment to come 
 
 when in some great conflict of the future a splendid 
 
 up-to-date battleship fleet of the traditional order, with 
 
 traditional sailors, traditional admiral, and traditional 
 
 tactics, finds itself beset in midseas by a couple of 
 
 great, unarmored, liner-like hulls, engined to admit of 
 
 speeds and steaming radii such as will permit them 
 
 $ to .pursue or run away from any 
 
 IMAGINATIVE armored craft yet built, and designed 
 
 SPECTACLE with dear and leyel deckg for 
 
 aeroplane launching. Conceive them provided with 
 storage room for hundreds of demountable aeroplanes, 
 with fuel, repair facilities, and explosives, and with 
 housing for a regiment or two of expert air navi- 
 gators. Then picture the terribly one-sided engage- 
 ment that will ensue the thousands of tons and 
 millions of dollars' worth of cunningly-fashioned 
 
38 VEHICLES OF THE AIR 
 
 mechanism all but impotent against the unremitted, 
 harrying, and reinforced attacks from aloft, and 
 unable either to escape from or give chase to the 
 enemy's floating bases of supplies, which, ever warned 
 and convoyed by their aerial supports, will unreach- 
 ably maneuver out of gun range, picking up from the 
 water, reprovisioning, remanning, launching and 
 relaunching their winged messengers of death until 
 the cold waters close over the costly armada of some 
 nation that has refused to profit by the lessons of 
 progress. 
 
 The question of aerial travel over water is one of 
 
 particular significances. Water areas, in common with 
 
 the atmosphere, possess a quality 
 
 OVER WATER ^ a ^ ^ oes no ^ pertain to land the 
 quality of uniformity. The conse- 
 quence is that just so soon as means are devised for 
 launching aeroplanes over water, by the use of hydro- 
 plane under surfaces, boat convoys (as suggested in 
 the preceding paragraph), or any other serviceable 
 expedient, the way is at once opened to the establish- 
 ment of transaquatic mail lines utilizing craft pro- 
 vided with hull-like floats and made capable of flying 
 with almost perfect safety just above the wave crests. 
 Indeed, it is quite to be anticipated that the institu- 
 tion of some such service may constitute the first 
 serious commercial exploitation of the aeroplane. A 
 special incentive to experiment in this direction is 
 the low speed of even the fastest present water travel, 
 by contrast affording to the flying machine an advan- 
 tage that it does not yet possess in comparison with the 
 higher speeds of land travel. The still unsettled ques- 
 tions of flying radius and motor reliability can be at 
 the outset tentatively evaded by establishing the firsf 
 
INTRODUCTION 39 
 
 services over the shorter distances, or by stationing 
 
 patrol boats with fuel supplies at necessary intervals. 
 
 It is an irresistible conclusion that the practical 
 
 utility of the flying machine is no longer to be 
 
 CONCLUSION doubted - The onl y questions are 
 those of the exact methods of realiz- 
 ing these utilities, and the extent of their applica- 
 tion when realized. People begin to see that 
 it is absurd to characterize as impossible what 
 has been long accomplished. The bird flies, and there 
 is nothing occult about either the mechanism of the 
 bird or the laws of its operation. Not even the soaring 
 feats of the bird violate any of the laws of aerody- 
 namics or the law of the conservation of energy, how- 
 ever they may scandalize some pedantic conceptions 
 of these laws. Difficulties are no greater than the 
 knowledge required to surmount them, and knowledge 
 is accumulating hour by hour. The time is arriving 
 when it will be no more difficult to maneuver a flying 
 machine than it is to ride a bicycle. Both are dis- 
 tinctly mechanical inventions, both tend unfailingly to 
 develop from inferior to superior forms, and both 
 have had to encounter various skepticisms. 
 
 Here to digress for a moment let the doubter just 
 consider this case of the bicycle, less as an analogy in 
 mechanism than an analogy in mental attitudes. Think 
 of a "trained engineer" or "conservative business 
 man" of a few years ago confronted with a modern 
 "safety", exhibited with the assertion that here was a 
 vehicle of perfectly practical utilities, inexpensive to 
 build and operate, capable of considerable speeds under 
 an ordinarily vigorous rider, and perfectly suit- 
 able for the use of old people and children under ordi- 
 nary traffic conditions. Fancy the derision the criti- 
 
40 VEHICLES OF TEE AIR 
 
 cism that would be leveled at the pneumatic tires, the 
 strictures that would be visited upon the light construc- 
 tion, and, above all, the ridicule that would be heaped 
 upon the proposition of requiring from ordinary people 
 the balancing instict of the acrobat then, perhaps, 
 some appreciation will be had of the way most present- 
 day opinions on aeronautics will fit conditions five 
 years from now. 
 
 And if all this insistence brings the reader to some 
 belief that possibly, after all, this epic development in 
 transportation is upon us, what of the changes it must 
 involve the far-reaching influences it must inevitably 
 exert in all possible fields of human thought and 
 activity? Ponder the romance of it the certainty 
 that it must completely reorganize more than one fun- 
 damental factor of the present social order. And 
 believe as one must unless lost to all optimism and 
 faith that even -present ills work for ultimate good, 
 and inquire what it will mean to live under skies 
 thronged with aerial fleets, to live in a world from 
 which the artificial barriers of national boundaries and 
 the natural barriers of physical characteristics are by 
 advancing intelligence erased past re-establishment. 
 
 What must be the result when, with a means of 
 travel limited neither by difficulties of topography nor 
 by the shores of the seas, lending itself perfectly to 
 individual use but not at all to the uses of monopoly, 
 and not confined to the narrownesses of specially built 
 highways, the greatest freedom the individual can 
 possess the freedom of travel far and wide at will 
 is vastly enhanced by the vehicles of the skies, vehicles 
 that will prove cheaper to own, maintain, and operate 
 than any other vehicles that have ever existed ! 
 
 Travel on land will be reduced to the extent that it 
 
INTRODUCTION 41 
 
 is slow, inefficient, expensive, and inflexible. Travel 
 on water will become a mere adjunct to that of the air. 
 The world will be narrowed by the speeds attained. 
 Tariff and exclusion laws will be annulled through the 
 sheer impossibility of their enforcement. And the 
 skies will be as thronged with the craft of man's devis- 
 ing as they are today with the fowl of the air. 
 
 Throughout the territories of every nation of the 
 earth there will appear the leveled, circular, landing 
 areas, perhaps provided with strange-appearing start- 
 ing devices and probably bordered with low, capacious, 
 shed-like housings. Automobiles will be at hand to 
 afford rapid transportation to the business centers of 
 adjoining communities. 
 
 There will develop a technique and a language of 
 aerial navigation, and experts will become skilled in 
 contending with the perversity of special mechanisms, 
 in starting and landing under difficult circumstances, 
 in battling with fog and rain and storm, in taking 
 advantage of air currents at different levels, and in 
 seeking out the lanes of the atmosphere in which to 
 add to their speed the sweep of the trade winds. 
 
 And over all will soar with the ease of the gull or 
 drive with the speed of the whirlwind, the myriad 
 ships of the air, transforming the face of the heavens. 
 Of many sizes and at many altitudes, midgets and levi- 
 athans, close to the earth and up in the clouds in the 
 days the shadows of their wings will speed over every 
 corner of all the lands and seas, and in the nights of 
 that future time the eye-like gleams of their search- 
 lights will mingle to the uttermost ends of the earth, 
 beacons of science and romance and progress and 
 brotherhood VlCTOR LouGHEED . 
 
 CHICAGO, November, 1909. 
 
a > 
 
CHAPTEE ONE 
 
 THE ATMOSPHERE 
 
 At least a brief consideration of the properties 
 and phenomena of the atmosphere, as the medium 
 through which all aerial vehicles must travel and 
 from which they must derive their support, has a 
 logical place in a work of this character. 
 
 EXTENT 
 
 The extent of the gaseous envelope that sur- 
 rounds the earth is a subject that has been much 
 investigated by physicists. Knowing the weight 
 of the air, the area of the earth's surface, and the 
 approximate mass of the earth, it is not especially 
 difficult to compute the total weight of the atmos- 
 phere, which is found to be about y.inrJ.Tnnr that 
 of the rest of the earth. 
 
 Determination of the height of the atmosphere 
 is a more difficult problem, whether it be attempted 
 by purely mathematical methods or reasoned more 
 or less empirically from such observations as are 
 available. Were the air of uniform density from 
 the earth's surface to its limit of height it can be 
 easily demonstrated that this upper limit (termed 
 by scientists the "height of the homogeneous at- 
 mosphere") would be at an altitude of about 26,166 
 feet lower than the highest mountain tops but 
 
 43 
 
44 VEHICLES OF THE AIR 
 
 since the air decreases in density at an increasing 
 ratio as the pressure due to air above grows less 
 with each increase in height, until the atmosphere 
 attenuates by imperceptible graduations into a 
 perfect vacuum, no known calculated solution of 
 its ultimate height can be closely depended upon. 
 
 The greatest heights above sea level to which 
 man has actually ascended in the atmosphere have 
 been reached with balloons, Glaisher and Coxwell 
 (see Page 74) having attained a probable height 
 of 29,520 feet, while Berson and Sirring (see Page 
 75) undoubtedly reached an altitude of 35,400 feet. 
 
 The atmosphere has been explored to much 
 greater heights by " sounding balloons" (see Page 
 75), the greatest height on record having been 
 reached by a balloon of this type released from 
 Uccle, Belgium, on November 5, 1908. As shown 
 by self-registering instruments attached to this 
 balloon, it rose to a height of 29,040 meters (95,275 
 feet), over eighteen miles. 
 
 Estimates based on the calculated heights of 
 meteors at the times when they commence to be- 
 come luminous from friction with the earth's at- 
 mosphere have been held to indicate that this must 
 extend, in an exceedingly tenuous state, to a height 
 of 200 miles. Other authorities contend that the 
 extreme upper limit cannot be over 100 miles high. 
 In any case, it is an obvious deduction from the 
 barometric pressures recorded at great heights 
 (see Page 56) that | of the whole atmosphere is 
 below 30,000 feet, T V below 43,000 feet, and 
 below 95,275 feet. 
 
THE ATMOSPHERE 45 
 
 PROPERTIES AND CHARACTERISTICS 
 
 The atmosphere being chiefly composed of sev- 
 eral common forms of matter, its principal phys- 
 ical properties and characteristics have been well 
 investigated. 
 
 WEIGHT 
 
 According to Kegnault, air at sea level, freed 
 absolutely from water vapor, carbon dioxid, and 
 ammonia, weighs .0012932 grams to the cubic cen- 
 timeter at zero Centigrade, under a pressure of 
 760 millimeters of mercury in the latitude of Paris 
 (48 50' N.), and at a height of 60 meters above 
 sea level. In English equivalents this is approxi- 
 mately equal to .080681 pound to the cubic foot 
 or 12.384 cubic feet to the pound at sea level in 
 the latitude of Washington, D. C. Ordinarily, not 
 freed from water vapor and other impurities, air 
 at sea level, at 32 F., can be taken to weigh very 
 close to .080728 pound to the cubic foot. 
 
 At any height above sea level a given volume 
 of the atmosphere weighs an amount less than a 
 similar volume at sea level, in exact proportion to 
 the difference in barometric pressure, other con- 
 ditions being equal. Thus, at the 29,000 feet 
 reached in the Coxwell and Grlaisher balloon ascent 
 the weight of the air was only .052171 pound to the 
 cubic foot. 
 
 The weight of the air is an important consid- 
 eration in the design of aerial vehicles, particu- 
 larly in the case of lighter-than-air constructions, 
 
46 VEHICLES OF THE AIR 
 
 since these are enabled to float only by being 
 lighter than the volume of air they displace. With 
 heavier-than-air machines the weight of the appa- 
 ratus is sustained by the quantity of air acted 
 upon, varying with area of surfaces, rapidity of 
 the action, and mass of the air affected. 
 
 COMPOSITION 
 
 Air consists chiefly of oxygen and nitrogen 
 mechanically admixed (not chemically combined) 
 in the proportion of about 21 volumes of oxygen 
 to 79 volumes of nitrogen (by weight the propor- 
 tions are 23.16 units of oxygen to 76.77 of nitro- 
 gen). In addition to these principal ingredients 
 air carries minute quantities of many other con- 
 stituents, some of which appear in the constant 
 proportions indicative of normal components, 
 while others are variable with locality and 
 circumstance. 
 
 Among the more evident of these minor con- 
 stituents of the atmosphere are water vapor, car- 
 bon dioxid, ammonia, nitric acid, argon, helium, 
 neon, krypton, and ozone, besides quantities of 
 dust, germs, and other minute solid particles held 
 in suspension. The water vapor may represent as 
 much as 2-J- parts by weight of saturated warm 
 air, but ordinarily the quantity is much less. The 
 carbon-dioxid content varies from .0043 in the 
 country to as much as .07 or even .1 of the whole 
 weight of the air in cities. This gas, which is pro- 
 duced in the lungs of all animals, from which it is 
 
THE ATMOSPHERE 47 
 
 constantly given off as a waste product of the con- 
 tinuous oxidation of the blood that is essential to 
 life, to the vegetable kingdom bears the relation 
 of a food, thus beautifully disclosing the wonderful 
 adaptation of all natural phenomena to interlink 
 with one another. For in the leaves of all plants 
 there constantly goes on a mysterious absorption 
 and fixation of the carbon from the carbon dioxid 
 of the atmosphere, apparently by some not under- 
 stood action of the green chlorophyl they contain, 
 while the oxygen thus freed from its combination 
 is in this case the waste product. 
 
 Argon constitutes about .01 of air. The total 
 amount of ammonia and other less important 
 gases js probably less than .01 in the lower atmos- 
 phere, though there are reasons for supposing 
 some of these gases to be more abundant above. 
 The ammonia in air is generally stated as amount- 
 ing to about .000006 of the total weight, while neon 
 is present to the extent of about .00001. Both 
 argon and helium have been determined to exist 
 at all heights up to 46,000 feet, but above this 
 height no helium has been detected. Ozone, which 
 is an allotropic form of oxygen, varies from none 
 in cities to .0000015 in the country, and is more 
 abundant in summer, especially during thunder- 
 storms and high winds. The amount of dust in 
 the air is much the greatest in the lower strata of 
 the atmosphere, to which it is so closely confined 
 that balloonists are frequently able to discern 
 definite dust levels at certain heights. 
 
48 VEHICLES OF THE AIR 
 
 COLOE AND TEANSPAEENCE 
 
 Though in small quantities air is without any 
 color that can be perceived, the fact that distant 
 objects seen through it acquire a blue tinge, which 
 also appears as the color of the sky, makes it evi- 
 dent that even the smallest quantity of air must 
 faintly possess this hue. 
 
 While commonly regarded as perfectly trans- 
 parent, air nevertheless offers considerable ob- 
 struction to the passage of light rays and to vision. 
 Indeed, were the atmosphere in undiminishing 
 density to extend to any great height it is a safe 
 conclusion that its presence would prevent our 
 seeing even the brightest of the heavenly bodies. 
 As it is, the whole amount of air above the earth 
 being only equivalent to 26,166 feet of air at sea- 
 level density, it offers more obstruction to vision 
 in a lateral direction than in the vertical a fact 
 that becomes very apparent when it is attempted 
 to make out distant details from a mountain top 
 or balloon, affording an outlook of many miles 
 in a horizontal direction. Weight for weight, air 
 is little more transparent than glass or water, 30 
 feet of the former and 18 feet of the latter being 
 equivalent to the entire height of the atmosphere 
 and offering little more obstruction to vision, espe- 
 cially when compared with air containing much 
 dust or water vapor. 
 
 AIR AT REST 
 
 Air in a state of rest, subjected to any given 
 but unvarying conditions of pressure, temperature, 
 
THE ATMOSPHERE 49 
 
 and composition, presents comparatively few and 
 simple problems. Of its static properties, the 
 most important are its compressibility, those re- 
 lating to the effects of temperature, and those 
 relating to its phenomena of liquefaction and 
 solidification. 
 
 COMPEESSIBILITY 
 
 Air in common with all other gases has the 
 quality of compressibility a quality not measur- 
 ably possessed by most liquids. For this reason its 
 volume is always proportionate to the pressure 
 upon it, it expanding with every reduction in pres- 
 sure and occupying less space with every increase. 
 Through a considerable range of pressures the 
 space occupied is almost directly proportionate to 
 the pressure a doubling of the pressure reducing 
 the volume by one-half, etc. Air cannot be com- 
 pressed without the work expended appearing in 
 the form of a rise in temperature, and, conversely, 
 allowing compressed air to expand always results 
 in a lowering of temperature. 
 
 EFFECT OF TEMFERATUKE 
 
 Heating or cooling of air causes it to expand or 
 contract. Through a considerable range of the com- 
 moner temperatures such expansion or contraction 
 is closely proportionate to the amount of change 
 in temperature. This property is taken advantage 
 of in hot-air balloons, as explained on Page 97. 
 Heating air that is confined results in an increase 
 of pressure, and cooling compressed air results in 
 a decrease of pressure. 
 
50 VEHICLES OF THE AIR 
 
 LIQUEFACTION AND SOLIDIFICATION 
 
 Almost every known form of matter, whether 
 normally appearing as a solid, liquid, or gas, can 
 by sufficient change in the conditions of tempera- 
 ture and pressure be made to assume any of these 
 three conditions. Thus the hardest rocks and the 
 strongest metals can be melted into liquids and 
 volatilized into gases, while practically all known 
 liquids can be solidified as in the familiar case 
 of the freezing of water. Likewise, the lightest 
 gases, when subjected to sufficient cold and pres- 
 sure, assume first a liquid and then a solid form. 
 Air is no exception to this rule, becoming a liquid 
 at 220 Fahrenheit under a pressure of 574 
 pounds to the square inch or less, if the tempera- 
 ture be lower. Further cooling causes it to become 
 solid, though the temperature required to pro- 
 duce this condition is so low that it can be at- 
 tained only with the greatest difficulty. 
 
 Liquid air, because of its compact form as a 
 source of oxygen, and its expansion into the gas- 
 eous form at high pressure upon exposure to or- 
 dinary atmosphere temperatures, often has been 
 proposed as a source of stored energy for motors, 
 but so far no such application has proved suc- 
 cessful. 
 
 AIR IN MOTION 
 
 Air in motion possesses properties that are 
 very little understood, the laws of its dynamic 
 actions and reactions not having been gener- 
 ally investigated or formulated. Particularly with 
 
THE ATMOSPHERE 51 
 
 reference to the operation of heavier-than-air ma- 
 chines is this the case. Indeed, more than one of 
 the world's foremost physicists, even in compara- 
 tively recent years, has positively declared aerial 
 navigation to be impossible, basing his conclusions 
 upon difficulties encountered in reconciling the 
 idea of man flight with established hypotheses 
 of aerodynamics. Air, possessing almost perfect 
 elasticity in addition to its weight, fluidity, and 
 other qualities, cannot be set in any but the most 
 simple movements without occasioning a multi- 
 tude of resultants that are so utterly complex and 
 involved as to defy analysis. The result is 
 that even such comparatively simple phenomena 
 as those of the movement of air in pipes and in 
 jets are only understood in a general way, while 
 the work of most investigators of flight problems 
 has had to be almost purely empirical, or, when 
 mathematical, has been unsuccessful. The one 
 conspicuous exception with which the writer is 
 familiar is found in the investigations and ex- 
 periments of Professor Montgomery, whose con- 
 clusions are outlined in the article printed in 
 Chapter 4. 
 
 Of the dynamic properties of air, the most im- 
 portant from present standpoints are its inertia, 
 elasticity, and viscosity. 
 
 INEETIA 
 
 Air, in common with all other matter having 
 weight, exhibits the various phenomena of inertia, 
 which may be defined as the tendency of a mass to 
 
52 VEHICLES OF THE AIR 
 
 remain at rest, or to continue in uniform motion in 
 a straight line, until acted upon by some disturb- 
 ing or retarding force. Naturally, air being much 
 lighter than solid and liquid forms of matter, its 
 inertia is less marked than in the case of heavier 
 substances. But that under favorable conditions 
 this is a factor to reckon with is abundantly proved 
 throughout a great range of natural phenomena, 
 from the flight of birds to the extraordinary vaga- 
 ries of cyclone action. In fact, as one great in- 
 vestigator has tersely expressed a profound truth 
 in form to be appreciated by the man in the street, 
 "the air is hard enough if it is hit fast enough." 
 
 ELASTICITY 
 
 The property of elasticity is one of the funda- 
 mental qualities that distinguish air and other 
 gases from liquids. Air and other gases are in 
 fact the only perfectly elastic substances known 
 that is, the only substances that will withstand 
 compression to an indefinite extent and for in- 
 definite periods without in the slightest degree 
 losing their ability fully to recover the original 
 volume. Gases compressed under thousands and 
 even hundreds of thousands of pounds to the 
 square inch, for no matter how long a period, in- 
 stantly and unfailingly expand to any extent per- 
 mitted by release of the pressure. 
 
 It is to a great extent this property that, under 
 favorable conditions, makes for the high efficiencies 
 realized with suitably-designed mechanisms for 
 operating on masses of air. 
 
THE ATMOSPHERE 53 
 
 VISCOSITY 
 
 Viscosity is a property of fluids closely com- 
 parable to the cohesion of solids and may be de- 
 fined as the tendency of the molecules to occasion 
 friction when driven against or past one another. 
 The viscosity of air is often stated to be much 
 higher than that of water (not per unit of volume, 
 but per unit of weight), but there is reason for 
 doubting the soundness of this conclusion. How- 
 ever, it is at least true that air possesses viscosity, 
 and that this sets up increasing resistances to 
 movement as the speed of the movement rises. 
 The question of skin friction on aeroplane and 
 propeller surfaces is closely related to that of the 
 viscosity of air. 
 
 METEOROLOGY 
 
 The matters of climatic conditions, storm 
 phenomena, and temperature, and barometric and 
 electrical conditions in the atmosphere must all, 
 in the nature of things, be of the utmost interest 
 to both present and future air navigators. 
 
 Meteorological conditions may be broadly 
 grouped in two classes the first comprised of con- 
 ditions of a primary or static character, and there- 
 fore not directly inconsistent with fair weather, 
 while the second class includes such meteorological 
 phenomena as are directly related to winds and 
 storms. 
 
 Generally speaking, there are three funda- 
 mental or primary changes to be noted in the at- 
 
54 VEHICLES OF THE AIR 
 
 mosphere in a given period in any locality 
 changes in temperature, changes in barometric 
 pressure, and changes in humidity. Secondary ef- 
 fects, usually rather definitely resultant from the 
 foregoing, are the condensation of moisture and its 
 precipitation in the f orfri of rain, snow, or hail 
 and the movement of the air in the form of winds. 
 
 TEMPEEATUEE 
 
 Besides the seasonal variations in temperature, 
 which vary greatly with locality, there is the re- 
 markably uniform lowering of temperature with 
 increase of height, the atmosphere being warmest 
 at or near the surface at sea level and progressive- 
 ly colder at greater altitudes, as is evident in the 
 phenomenon of perpetual snow on high mountains, 
 even in warm climates. 
 
 Observations with sounding balloons have dis- 
 covered temperatures lower than 100 F. at great 
 heights, with 50 commonly prevailing, even in 
 summer. The lowest temperature ever recorded 
 at the earth's surface is 90 F., observed in Si- 
 beria this degree of cold exceeding any that has 
 been recorded elsewhere on the surface, even in 
 polar exploration. At the other end of the range 
 are temperatures of about 140 above zero Fahren- 
 heit, noted in India, the Sahara, the southwestern 
 United States, Australia, and elsewhere in the 
 desert and equatorial regions of the world. 
 
 The following two tables of sounding-balloon 
 records will be of interest: 
 
THE ATMOSPHERE 55 
 
 FROM SAINT LOUIS, MAY 6, 1906 FROM SAINT LOUIS, MAY 10, 1906 
 
 HEIGHT ABOVE HEIGHT ABOVE 
 
 SEA LEVEL TEMPERATURE SEA LEVEL TEMPERATURE 
 
 623 feet 57.2 F. 623 feet 68.0 F. 
 
 3,281 feet 46.4 F. 3,281 feet 59.0 F. 
 
 6,562 feet 31.2 F. 6,562 feet 46.4 F. 
 
 9,843 feet 21.2 F. 9,843 feet 37.2 F. 
 
 13,123 feet 15.8 F. 13,123 feet 21.2 F. 
 
 16,404 feet 17.6 F. 16,404 feet 6.8 P. 
 
 19,685 feet 5.0 F. 19,685 feet 2.2 F. 
 
 32,808 feet 52.6 F. 22,966 feet 26.6 F. 
 
 26247 feet 29.2 F. 26,247 feet 32.8 F. 
 
 29,527 feet 40.0 F. 29,527 feet 45.4 F. 
 
 32,808 feet 52.6 F. 32,808 feet 59.0 F. 
 
 36,089 feet 50.8 F. 36,089 feet 76.0 F. 
 
 39,370 feet 49.0 F. 39,370 feet 70.6 F. 
 
 42,651 feet 54.4" F. 42,651 feet 67.0 F. 
 
 45,932 feet 56.2 F. 45,932 feet 70.6 F. 
 
 49,212 feet 59.0 F. 49,212 feet 72.4 F. 
 
 52,893 feet 68.8 F. 
 
 54,298 feet 67.0 F. 
 
 A remarkable feature well shown in the above 
 is the " permanent inversion layer", or isothermal 
 stratum, of the upper atmosphere, it being noted 
 that at from 33,000 to 49,000 feet beginning just 
 higher than the tops of the highest mountains a 
 minimum temperature is reached, after which there 
 tends to be a slight but fairly regular rise. This 
 change has been discovered to exist all over the 
 world in both the tropical and temperate zones, 
 near the arctic circle, and over the Atlantic ocean. 
 In the record ascent of the sounding balloon from 
 TIccle (see Page 44) the lowest temperature 
 registered was 108.6 F., at 42,323 feet. At 
 95,275 feet, the greatest altitude reached, the tem- 
 perature had risen to 82.12 P. 
 
 In the Berson and Sirring ascent, on December 
 4, 1894, the lowest temperature at 28,750 feet- 
 was _54 F. At the start in Berlin the tempera- 
 ture was 37 F. 
 
56 VEHICLES OF THE AIR 
 
 BABOMETKIC PEESSUEE 
 
 The weight of the atmosphere, as shown by the 
 barometric pressure, varies with height, tempera- 
 ture, and latitude. As is elsewhere explained 
 herein, by far the most considerable variations are 
 those due to height, for which reason a high-grade 
 aneroid barometer constitutes a very accurate 
 means of estimating altitude. 
 
 At sea level, under normal conditions, the baro- 
 metric pressure is almost exactly 14.7 pounds to 
 the square inch. At great heights it is much less, 
 as, for example in the Glaisher and Coxwell ascent 
 (see Page 74). 
 
 The Uccle sounding balloon recorded a pressure 
 of 1.74 pounds to the square inch at 42,240 feet, 
 and of only .2 pounds to the square inch at its 
 greatest height of 95,275 feet. 
 
 HUMIDITY 
 
 Humidity is a general term for the presence of 
 water vapor in air, but in the more restricted and 
 more specific scientific sense it is commonly under- 
 stood to refer to the percentage of saturation that 
 is to say, to the proportion that the amount of 
 moisture actually present in the air bears to the 
 maximum it might contain. The saturation point 
 varies with temperature cold air being capable of 
 holding less and warm air more water vapor. At 
 a temperature of about 90 F. a cubic foot of 
 saturated air will contain about -g-V ounce, or 
 about T V cubic inch, of water. Saturated air 
 
THE ATMOSPHERE 57 
 
 cooled to a lower temperature always precipitates 
 its excess of water. This is the explanation of the 
 condensed moisture that is often precipitated from 
 the air on the outside of a glass of cold water, or 
 upon any other cold surface in warm weather, and 
 it has most important bearings upon the phe- 
 nomena of rain and snow fall. 
 
 The moisture in the air is chiefly derived by 
 evaporation from water areas and land wetted by 
 rains or floods. 
 
 CONDENSATION OF MOISTURE 
 
 This always occurs when the atmosphere is 
 cooled until the amount of water present in it 
 amounts to more than the saturation quantity for 
 the given temperature, and the result is ordinarily 
 a precipitation of rain, snow, or hail though it 
 is established that under certain conditions mois- 
 ture thus precipitated may pass into vapor, or be 
 frozen in exceedingly minute crystals, and so re- 
 tained in suspension in the form of clouds. 
 
 WINDS 
 
 Winds, amounting simply to more or less rapid 
 movement of portions of the atmosphere with re- 
 lation to the earth's surface, present many aspects 
 of interest to the air navigator, and are worthy 
 of his prof oundest consideration. 
 
 Atmospheric movements vary in direction, 
 velocity, and duration, and in the presence of 
 ascending or descending components, and are 
 classified according to their velocity, direction, 
 
58 VEHICLES OF THE AIR 
 
 and duration into the different classes of storms 
 and winds. 
 
 Winds are supposed to be due chiefly to varia- 
 tions in temperature, though they are affected by 
 tidal movements in the atmosphere and influenced 
 by the earth's rotation. The latter, however, can- 
 not be of very great effect because, though the 
 equatorial speed of rotation is over 1,000 miles in 
 hour, everything terrestrial is so subjected to the 
 earth's attraction that it must be moved uniformly 
 along without materially lagging behind, as might 
 be the case were the rotation irregular or inter- 
 mittent. 
 
 Tidal currents in the air, caused by the attrac- 
 tion of the sun and moon, are well established to 
 exist, but because of the comparatively small mass 
 of the air they do not vary the barometric pressure 
 more than -^ ounce at sea level, and therefore 
 cannot be of any considerable effect in establishing 
 or controlling winds. 
 
 Changes in temperature produce effects of 
 much greater magnitude. Air heated through a 
 range of 50 P. is dilated about one tenth of its 
 volume with corresponding lightening of its 
 weight per unit of volume. The result, therefore, 
 of a change of temperature in any portion of the 
 atmosphere is a compression or attenuation that 
 can be relieved only by a flow of air from or to the 
 locality affected, with a violence proportionate to 
 the suddenness and amount of the temperature 
 change and the quantity of air it affects. Also, 
 air being lightened by heating, heated bodies of it 
 
THE ATMOSPHERE 59 
 
 have a tendency to rise, causing an upward com- 
 pression with a radial inflow from all surrounding 
 places to occupy the spaces thus becoming vacated. 
 Again, air thus caused to ascend into the upper 
 regions of the atmosphere, where, as has been ex- 
 plained, conditions of the most intense cold prevail 
 throughout the year, becomes cooled and thus is 
 turned from its vertical into a horizontal and final- 
 ly a descending course. 
 
 The fact that a rapid fall of the barometer 
 indicating a reduction in the weight of the air 
 almost always precedes violent winds, seems proof 
 positive of the soundness of the accepted theories 
 of wind causation. 
 
 There are two principal modes of heating to 
 which the atmosphere is subjected. One is the 
 regular diurnal heating due to the alternation of 
 day and night, a wave of heated air progressing 
 around the world with the sun while a converse 
 cool wave follows the night. The other type of 
 heating is that to which the atmosphere is sub- 
 jected over great areas in contact with the earth 
 a type of heating that becomes particularly mani- 
 fest over great areas of prairie or desert country 
 in summer. 
 
 Coastal Winds are common along almost all 
 seacoasts and even along the shores of large lakes. 
 They seem distinctly due to the effects of tempera- 
 ture, and, commencing with a light breeze from the 
 sea in the morning rise to a stiff wind by midday, 
 subsiding again to a calm by evening. Then, as 
 darkness comes on, a breeze sets in from the land, 
 
60 VEHICLES OF THE AIR 
 
 reaching its maximum velocity sometime in the 
 night, and thereafter dying down towards morn- 
 ing. These winds are rarely felt more than twenty 
 miles out to sea or inland, and investigation with 
 kites and balloons has shown them to be invariably 
 accompanied by an opposite movement of the air 
 at some distance above usually at a very 
 moderate height (500 to 1,000 feet). This, besides 
 proving that the air travels in a complete circuit, 
 goes a long way towards explaining the phe- 
 nomenon, it being reasoned that as the air is 
 warmed over the land by the heat of the day it 
 rises, is replaced by air flowing in from the sea, 
 and then flows seaward at an upper level because 
 of the reduced pressure in that direction. At night 
 the land is more quickly affected by the withdrawal 
 of the sun's rays, so now the ascending current 
 commences over the sea, with a sequence of results 
 exactly the converse of the foregoing. 
 
 Trade Winds, so called because of the de- 
 pendence placed in them by navigators of sailing 
 vessels, are always in the same direction but with 
 seasonal variations in the areas they extend over. 
 They are due to cold currents flowing in from the 
 polar regions to replace the warm air that rises 
 from the equatorial regions of the earth. Normally, 
 they would flow directly north and south to the 
 equator, but the influence of the earth's rotation 
 and the configuration of the land and water areas 
 in the northern hemisphere causes them gradually 
 to veer about, as they progressively reach latitudes 
 where the peripheral speed of the earth's surface 
 
THE ATMOSPHERE 61 
 
 is higher, until they flow almost directly west, but 
 slightly north or south (constituting the "north- 
 east trade" and the "southeast trade"). The 
 trade winds follow the sun very closely in their 
 areal variations. Over the Atlantic, for example, 
 they come farthest south in February and go 
 farthest north in August, the northeast trades 
 blowing between 7 and 30 north latitude and the 
 southeast trades blowing between 3 north latitude 
 and 25 south latitude. Between the two is a 
 region of calms, from 3 to 8 wide, which goes as 
 far north as 11 north latitude in August and as far 
 south as 1 north latitude in February. 
 
 Above the trade winds there are well estab- 
 lished to exist return currents, blowing in the op- 
 posite directions. In high latitudes this return 
 current often comes down to the surface and pro- 
 duces easterly trade winds. 
 
 Cyclones, Whirlwinds, and Tornadoes are 
 local winds of terrific violence and rotary 
 character, which are started by rapid and intense 
 local heating, with consequent rapid rising of 
 locally-heated atmosphere at such a rate that the 
 radial inflow of adjoining air assumes a rotary 
 movement similar to that of water in draining out 
 through a hole in a vessel. The vortex of the storm 
 is at the center of this rotation, where most ter- 
 rible wind velocities are attained if their frightful- 
 ly-destructive effects are any criterion. For- 
 tunately cyclones are usually very small in their 
 areas of maximum violence and are of compara- 
 tively brief duration. 
 
64 VEHICLES OF THE AIR 
 
 ATMOSPHEEIC ELECTEICITY 
 
 The presence of electrical action in the atmos- 
 phere, due to the accumulation of enormous static 
 charges of current generated presumably by fric- 
 tion of the air upon itself, accounts for the various 
 phenomena of lightning and thunderstorms. To 
 the student of aerial navigation the most interest- 
 ing aspect of these phenomena is their danger from 
 the standpoint of the balloonist, it being well 
 established that hydrogen balloons have been set 
 on fire by electrical discharges, often of otherwise 
 quite imperceptible character. 
 
FIGURE 2. A corner of the Aeronautical Exhibition held in the Grand Palais Paris 
 during October, 1909. The small decorated balloon in the background is a reproduction of 
 the original Montgolfier balloon of 1783 the first ever made. 
 
 C. Double (Silk and Cotton) 
 
 G. Double (Silk and Cotton) 
 
 P. Double (Percale). 
 
 Q. Double (Percale). 
 
 FIGUHE 7. Texture of Modern Balloon Fabrics Reproduced Actual Size. Of these, A is 
 a very light fabric ; B is similar but heavier ; C is the material of the Baldwin government 
 balloon ; D, E, and F are heavy fabrics ; G is similar to C, but heavier ; H is a very light 
 fabric for sounding balloons ; I is a very light double fabric, used in the Zeppelin dirigibles ; 
 T and K are double fabrics with the layers crossed to add strength ; L and M are exceedingly 
 heavy double fabrics, for semi-rigid and non-rigid dirigibles ; N is one of the heaviest balloon 
 fabrics used, weighing 14% ounces to the square yard; and O, P, and Q are all high-grade 
 diagonal fabrics with gray rubber to retain the gas and red surfaces to resist sunlight. 
 
CHAPTER TWO 
 
 LIGKETER-THAN-AIR MACHINES 
 
 I 
 
 Though as a vehicle of practical utilities it is 
 fast losing ground in comparison with the develop- 
 ing forms of heavier-than-air fliers, and seems con- 
 demned by insuperable objections inherent in its 
 very principle of operation, the lighter-than-air 
 machine the balloon was nevertheless the first 
 with which man succeededftn sustaining himself in 
 the air for considerable periods of time. 
 
 Since the essential feature of lighter-than-air 
 craft is their ability to float in the air much as a 
 vessel floats in the water, and since the only sub- 
 stances that even approach air in lightness are 
 also gases, it follows that the design of no conceiv- 
 able sort of lighter-than-air machine can escape 
 the necessity for two essential elements space oc- 
 cupied by something lighter than air, and an envel- 
 ope of heavier-than-air material to enclose this 
 S p ace w ith the relations between these two ele- 
 ments so proportioned that the lifting force of 
 the gas is sufficient to overcome the weight of the 
 envelope. In any practical air craft, to the weight 
 of these primary essentials must be added such 
 further weight of structure as may be considered 
 
 65 
 
66 VEHICLES OF THE AIR 
 
 necessary to afford passenger or cargo accommo- 
 dation, and such further quantity of gas as may be 
 required to lift such passengers or cargo as it may 
 be planned to carry. 
 
 NON-DIKIGIBLE BALLOONS 
 
 The most elementary type of balloon is that de- 
 signed for mere ascension and flotation in the air, 
 with no attempt at navigation in a lateral direction 
 except as such lateral travel may result from fa- 
 vorable winds. It was a very early suggestion in 
 the history of the balloon that, inasmuch as the 
 direction of the winds frequently varies with dif- 
 ferences in altitude, upper currents often flowing 
 directly contrary to those near the surface, sys- 
 tematic prospecting through these different cur- 
 rents by control of height might result in control 
 of the direction of travel. Yet in the hundreds of 
 attempts made to work something practical out of 
 this idea, nothing of real value has developed. 
 
 HISTOBY 
 
 If somewhat uninvestigated, but in nowise dis- 
 credited Oriental history is to be believed, the 
 invention of the balloon is properly to be ascribed 
 to that inscrutable people, the Chinese, who, ac- 
 cording to a French missionary writing in 1694, 
 sent up a balloon in celebration of the corona- 
 tion of the emperor Fo-Kien, at Pekin, in 1306. 
 Furthermore, this ascension is stated to have been 
 only the carrying out of an established custom, 
 rather than the first ever made by the Chinese. It 
 
LIGHTER-THAN-AIR MACHINES 67 
 
 is not recorded whether or not any of the Chinese 
 balloons ever carried passengers. 
 
 The first European appreciation of the prin- 
 ciple by which a balloon is made to ascend appears 
 to have been due to a Jesuit, Francis Lana, who in 
 a work published at Brescia, Italy, in 1670, pro- 
 posed an airship sustained by four hollow copper 
 vacuum balls, each twenty-five feet in diameter 
 and ^ inch thick, affording a total ascensional 
 force of about 2,650 pounds, of which some 1,620 
 pounds would be the weight of the copper shells, 
 leaving 1,030 pounds for the weight of the car, pas- 
 sengers, etc. The difficulty of securing sufficient 
 strength to withstand the pressure of the atmos- 
 phere Lana assumed would be met by the domed 
 form of the surface, but in view of the fact that 
 the total pressure on each sphere would figure over 
 4,000,000 pounds, the possibility of resisting it 
 with so thin a shell still remains to be demon- 
 strated. 
 
 In 1766 Cavendish made public his estimations 
 of the weight of hydrogen, immediately following 
 which Dr. Black, of Edinburgh, made a calf-gut 
 balloon which, however, proved to be too heavy for 
 sustention by the hydrogen it could contain. A 
 few years later, Tiberius Cavallo, to whom a simi- 
 lar idea occurred, found bladders to be too heavy 
 and paper too permeable, but he did succeed in 
 inflating soap bubbles with hydrogen in 1782, with 
 the result that they floated upwards until they 
 burst. 
 
 It is a somewhat remarkable coincidence that 
 
68 VEHICLES OF TEE AIR 
 
 just as the modern aeroplane has been most promi- 
 nently associated with the names of two brothers, 
 so to two brothers, Stephen and Joseph Mont- 
 golfier, is generally ascribed the invention of the 
 balloon. Tradition has it that, inspired originally 
 by reading Dr. Priestly 's " Experiments Relating 
 to Different Kinds of Air", the Montgolfiers, who 
 were sons of Peter Montgolfier, a paper manufac- 
 turer of Annonay, France, were next impressed 
 from observation of the clouds with the idea that 
 if they could fill a light bag with "some substance 
 of a cloud-like nature" it would similarly float in 
 the atmosphere. Accordingly with the notion of 
 using smoke as the required "substance" 
 Stephen, who appears to have been the prime 
 mover in the enterprise, started to experiment with 
 large paper bags, of capacities up to 700 cubic feet, 
 under which were burned fires of chopped straw. 
 Though success immediately resulted, it is inter- 
 esting to note that it was some time before the 
 brothers realized that the real source of the lift- 
 ing effect was the heating of the air within the bags 
 and not the smoke with which they sought to fill 
 them. 
 
 Having demonstrated the possibility of making 
 small balloons ascend, the Montgolfiers next built 
 a spherical paper balloon thirty feet in diameter, 
 with a capacity of about 13,000 cubic feet and pos- 
 sessed of a consequent ascensional force, when 
 inflated with heated air, of probably 500 pounds. 
 This balloon was sent up from Annonay, without 
 passengers, on June 5, 1783, in the presence of 
 
L1GHTER-THAN-AIR MACHINES 69 
 
 many spectators. It rose to an estimated height 
 of a mile and a half before the air within it cooled 
 sufficiently to cause its descent, ten minutes after 
 its release. A modern reproduction of one of the 
 first Montgolfier balloons is shown in Figure 2. 
 
 Following this first balloon ascent, on August 
 27, 1783, M. Faujas de Saint-Fond, a naturalist; 
 M. Charles, a professor of natural philosophy in 
 Paris, and two brothers by the name of Robert, 
 sent up a hydrogen balloon from the Champ de 
 Mars, in Paris. This balloon, thirteen feet in diam- 
 eter and weighing less than twenty pounds, was 
 made of thin silk coated with caoutchouc, and 
 required four days for its inflation, the hydrogen 
 being generated by the action of 500 pounds of 
 sulphuric acid on half a ton of iron filings a proc- 
 ess that only very recently shows signs of being 
 superseded (see Page 99). When liberated the 
 balloon rose rapidly to a height of about 3,000 feet, 
 burst, and then landed three-quarters of an hour 
 later in a field near Gonesse, fifteen miles away, 
 where it was destroyed by terrified peasants. 
 
 The next balloon ascent was that of a spherical 
 bag, of linen covered with paper, made by the 
 brothers Montgolfier. This balloon, which was the 
 second of the same material the first having been 
 destroyed by a storm of wind and rain before it 
 could be used had a capacity of 52,000 cubic feet, 
 and was sent up from Versailles, France, on Sep- 
 tember 19, 1783. A small car was attached, in 
 which were placed a sheep, a cock, and a duck, 
 which thus had thrust upon them the distinction 
 
70 VEHICLES OF THE AIR 
 
 of being the first balloonists. The descent occurred 
 eight minutes after the start, and the sheep and 
 duck were uninjured. The cock had not fared so 
 well, and his condition was gravely attributed by 
 the savants present to the effects of the tenuous 
 atmosphere of the upper regions. Calmer subse- 
 quent diagnosis, however, indicated that he had 
 been tramped upon by the sheep. 
 
 The first ascent of a man-carrying balloon was 
 one ventured by Pilatre de Rozier, who entrusted 
 himself to a captive balloon, built by the Mont- 
 golfiers, on October 15, 1783. The balloon was per- 
 mitted to ascend only to a height of less than 100 
 feet, at which elevation it was kept for a period of 
 a little over four minutes by continuous heating 
 of the air inside of it by means of a fire of chopped 
 straw. Following this, on November 21, 1783, de 
 Rozier and a friend, the Marquis d'Arlandes, made 
 the first free balloon ascension, in which the start 
 was from Paris, with the descent safely accom- 
 plished in a field five miles from the French 
 metropolis after about twenty minutes of drifting 
 at not over 500 feet high. 
 
 It is recorded that Benjamin Franklin, who was 
 a witness of this first aerial voyage, was asked by 
 a pessimistic spectator for his opinion of the utility 
 of the new device, to which Franklin is said to have 
 replied, "Of what use is a new-born babef 
 
 Only seven days after the foregoing, on Novem- 
 ber 28, there was made from Philadelphia, under 
 the auspices of the Philosophical Academy of that 
 
LIGHTER-THAN-AIR MACHINES 71 
 
 city, a balloon ascent that has escaped the atten- 
 tion of most of the writers on the subject. The 
 enterprise was in charge of two local scientists, 
 Hopkins and Eittenhouse, who first made experi- 
 ments by sending up animals in a car attached 
 to forty-seven small hydrogen balloons. They then 
 persuaded one James Wilcox, a carpenter, to go 
 aloft, with the result that to this man belongs the 
 honor of having first ascended with a hydrogen 
 balloon. The descent, which barely missed being 
 into the Schuylkill River, was so abrupt that the 
 lone passenger dislocated his wrist. 
 
 The first European ascent with a hydrogen bal- 
 loon was made on December 1, 1783, by Charles 
 and Robert, who safely accomplished a twenty- 
 seven mile trip at about fifteen miles an hour from 
 Paris to Nesle, France, in two hours, reaching a 
 height of 2,000 feet. At Nesle a landing was 
 effected and Robert got out, whereupon Charles 
 made a further journey of two miles in the course 
 of which it is asserted he rose to a height of 10,000 
 feet, at which altitude he suffered severely from 
 cold and the rapid lowering of the atmospheric 
 pressure. The balloon used on this occasion was 
 over twenty-seven feet in diameter, sewed up of 
 varnished silk gores, and on the whole very well 
 designed, being provided with a net and valve. 
 The car was boat-like, eight feet long, and weighed 
 130 pounds. Ballast was used to control and a 
 barometer to measure the height. Indeed, nearly 
 every essential feature was closely similar to the 
 
72 VEHICLES OF THE AIR 
 
 corresponding features in the best modern gas 
 balloons, which therefore date back more defin- 
 itely to the ingenious Charles than to any other 
 investigator. 
 
 During 1784 balloons became common through- 
 out all Europe and many successful ascents were 
 made. The first woman to ascend in a balloon was 
 a Madame Thible, who went up from Lyons, 
 France, during this year. 
 
 On January 7, 1785, a remarkable balloon voy- 
 age was made with a hydrogen balloon by Jean- 
 Pierre Blanchard and an American physician 
 named Jeffries, these two embarking from the cliff 
 near Dover castle and crossing the English Channel 
 to the forest of Guines, in France, the distance 
 being made with a favorable wind in something 
 less than three hours. In an attempt to repeat this 
 feat, on June 15, 1785, at the age of twenty-eight 
 years, Pilatre de Rozier, the first aeronaut, became 
 also the first victim of aerial travel, he and a friend, 
 M. Romaine, both losing their lives through the 
 balloon, which was of the Montgolfier type, catch- 
 ing fire at a considerable height. 
 
 Since the foregoing, which are the more impor- 
 tant and interesting of the early balloon ascensions, 
 thousands of others have been made all over the 
 world. In the course of these some utility has 
 developed in the way of military and meteorolog- 
 ical observation, but in most cases the immediate 
 purposes and the ultimate results have not been 
 more serious than the catering to a somewhat 
 
LIGHTER-THAN-AIR MACHINES 73 
 
 the crowd to pay its money for the spectacle of a 
 parachute jump. However, despite the extreme 
 and often unnecessary risks that have been taken 
 by the ignorant or reckless, an examination of the 
 statistics of ballooning discloses a surprisingly 
 small number of fatalities in proportion to the 
 number of ascensions that have been made. 
 
 The history of ballooning has been from the first 
 closely associated with warfare. Indeed, it is said 
 that one of the avowed purposes of the Montgol- 
 fiers was to render more effective the siege of 
 Gibraltar, by the combined French and Spanish 
 forces, who, however, gave up the fight some time 
 before the Montgolfiers proved the practicability 
 of the balloon. Subsequently a regular " aero- 
 static corps" was attached to the French army, 
 and did service during the French Revolution and 
 Napoleon's Egyptian campaign. Considerable 
 utility was demonstrated during the battle of Fleu- 
 rus, in the course of which two aerial reconnais- 
 sances from a captive balloon contributed mate- 
 rially to the victory of the French over the Aus- 
 trians. But when a balloon sent up in honor of 
 his coronation was wrecked against a statue of 
 Nero, the great Corsican seems to have lost inter- 
 est in the new invention. 
 
 Some use of balloons was made by both sides in 
 the American Civil War, and in the Spanish- Amer- 
 ican war a balloon was successfully employed to 
 discover the presence of Cervera's fleet in Santiago 
 harbor, but by far the most important use ever 
 
74 VEHICLES OF THE AIR 
 
 made of balloons was in the siege of Paris, dur- 
 ing the Franco-Prussian war in 1870. In this 
 remarkable application seventy-three postal bal- 
 loons were built and sent out from the beleaguered 
 city with cargoes of mail and carrier pigeons, which 
 were used to bring back replies to the messages. 
 In this way over 3,000,000 letters were transmitted, 
 those brought back by the pigeons being reduced 
 so small by photography that 5,000 separate 
 missives weighed only nine grains. 
 
 One of the longest balloon voyages on record 
 not exceeded until within comparatively recent 
 years was that of John Wise from St. Louis to 
 Henderson, N. Y., in July 1859. This journey was 
 accomplished in a lively gale, with the result that 
 the distance of 950 miles was covered in nineteen 
 hours. October 9-11, 1900, Count Henry de la 
 Vaulx and Count Castillion de Saint Victor super- 
 seded the Wise record by a journey from Vin- 
 cennes, France, to Korostichev, Russia, a distance 
 of 1,139 miles, in thirty-five hours and forty-five 
 minutes. 
 
 The present balloon duration record is held by 
 Lieutenant-Colonel Schaeck, of the Swiss Aero 
 Club, who in the balloon Helvetia, sent up from 
 Berlin on October 11, 1909, remained in the air sev- 
 enty-two hours, finally landing in the sea off the 
 coast of Norway. 
 
 The balloon altitude record was long credited to 
 Glaisher and Coxwell, who on September 3, 1862, 
 reached a height claimed to have been 36,090 feet. 
 Some discredit has been cast upon the achievement 
 
LIGHTER-THAN-AIR MACHINES 75 
 
 by doubt concerning the possibility of sustaining 
 life at such a height without carrying a supply of 
 artificial oxygen, with the result that the maxi- 
 mum altitude is now believed to have been not 
 over 29,520 feet. On December 4, 1894, Professors 
 Berson and Gross ascended from Berlin and defi- 
 nitely recorded an altitude of 28,750 feet. Subse- 
 quently, on July 31, 1901, Berson and Sirring, of 
 the "Berlin Verein fur Luftschiffahrt", reached a 
 height of 35,400 feet, using oxygen tanks. 
 
 So-called "sounding balloons", for meteorolog- 
 ical investigation, but without passengers and car- 
 rying only self-registering instruments, have 
 reached much greater heights, the record being 
 held by the balloon which was sent up from the 
 Uccle Observatory in Belgium (see Page 44). 
 
 SPHERICAL TYPES 
 
 The simplest and in some respects the most 
 advantageous form of balloon is the spherical, 
 because a given surface of envelope will enclose a 
 greater volume in the form of a sphere than in 
 any other shape. More than this, since a sphere 
 is the form into which any flexible hollow struc- 
 ture tends to distort under the influence of an 
 interior pressure, a sphere is, therefore, the only 
 form not subject to distortion stresses. 
 
 In the construction of spherical balloons, the 
 plan usually followed is to cut the material into 
 narrow, double-tapered gores, laid out as shown 
 in Figure 3. These gores when sewn together 
 along their adjacent edges afford a practically 
 
76 
 
 VEHICLES OF THE AIR 
 
 perfect approximation to the required form, as is 
 indicated at a, &, c, and d, Figure 3. The correct 
 
 shape of the gores is found 
 by laying them out as 
 shown in Figure 3. 
 
 Practically all non-diri- 
 gible balloons are now made 
 spherical sometimes modi- 
 fied into a pear-shape to 
 provide the open neck com- 
 monly used to allow for ex- 
 pansion and contraction of 
 the gas. Except from the 
 standpoint of dirigibility 
 there are few advantages 
 and many positive disad- 
 vantages in all but the 
 spherical form. One of the 
 most serious of these dis- 
 advantages is the necessity 
 for some sort of rigid or 
 semi-rigid construction to 
 protect non-spherical struc- 
 
 FIGURB 3. Layout of 
 Gores for Spherical Balloon. 
 The dimension a e is one-half 
 of the circumference of the 
 balloon and the dimension 
 6 c is the circumference di- 
 vided by the number of gores 
 it is intended to use. These 
 major dimensions settled 
 upon, intermediate points on 
 the gore curve, as at q, will 
 be found as shown at the 
 Junctures of lines projected 
 from similar points on the 
 diameters of the large and 
 small semicircles. 
 
 tures against dangerous distortion. 
 
 DIRIGIBLE BALLOONS 
 
 Naturally in the development of the balloon 
 it was early attempted to navigate definite 
 courses from one point to another, either in calm 
 weather or independent of the direction of the 
 winds. It was soon seen to be manifestly impos- 
 
LIGHT EE-TH AN -AIR MACHINES 77 
 
 sible, though, to derive propulsion from the wind 
 except directly before the wind, anything analo- 
 gous to the tacking of a ship being out of the ques- 
 tion because of the lack of any fulcrum such as is 
 provided by the hull of a ship in the water. This 
 compelled recourse to various systems of internal 
 power development and application, commencing 
 with the hand-manipulated oars and sails of early 
 investigators and coming down to the engines and 
 propellers of modern dirigibles. 
 
 Another obvious line of improvement along 
 which much work has been done consists in the 
 reduction of the head resistances against which it 
 is necessary to propel a balloon, reduction of these 
 resistances being the ideal held in view in the con- 
 struction of the many cylindrical, cigar-shaped, 
 and other elongated and pointed gas bags with 
 which the modern student of this subject is 
 familiar. 
 
 So far, however, all successes achieved with 
 dirigible balloons have been more spectacular than 
 practical, and there is little reason for expecting 
 that results of more serious value are in any pres- 
 ent prospect of attainment. Certainly, admitting 
 the possibility of an exceedingly limited and pre- 
 carious utility for the dirigible in warfare, it is, in 
 the opinion of those best qualified to judge, most 
 unlikely ever to assume the least importance as a 
 means of travel. 
 
 The great difficulties with the balloon are its 
 inescapably enormous volume and its strict limita- 
 
78 VEHICLES OF THE AIR 
 
 tions in weight of structure. To ascend, a balloon 
 must be lighter than the volume of air it displaces 
 and, the weight of a given volume of air being fixed 
 and unchangeable, no possible discovery or inven- 
 tion (unless of some structural materials of alto- 
 gether ultra-terrestrial strength) can open a way 
 of escape from this inexorable factor of the prob- 
 lem. A sphere of air ten feet in diameter weighs 
 almost exactly seventy-six pounds, while a simi- 
 lar sphere of hydrogen weighs something less 
 than six pounds. Consequently, enclosing the 
 hydrogen in an envelope and causing it to occupy 
 the space of an equivalent volume of air manifestly 
 affords a gross lifting capacity within this consid- 
 erable bulk of seventy-six minus six only seventy 
 pounds. Evidently the unlikely discovery of some 
 gas lighter than hydrogen can effect no material 
 benefit, for even should it become feasible to encase 
 a vacuum of the requisite size, as some enthusiasts 
 have hoped, this could help the sustention only to 
 the extent of the eliminated six pounds of hydro- 
 gen. And always within whatever lifting capacity 
 there may be provided must come not only the 
 loads that it is required to convey, but also the 
 weight of the structure and the enveloping mate- 
 rial, which it is highly desirable to have far 
 stronger and rigider than the strongest and rigid- 
 est ever likely to be attainable. 
 
 From all of which it follows that the best of 
 balloons are, and are likely to continue, hopelessly 
 bulky and fearfully flimsy, and of only the very 
 
LIGHTER-THAN-AIR MACHINES 79 
 
 smallest lifting capacities in proportion to their 
 size. Held captive or let drift with the wind, they 
 can be made to afford fair security with very lim- 
 ited utility. Provided with motors and propelling 
 means, they not only oppose the resistance of enor- 
 mous areas to rapid motion, but also prove of such 
 fragility that their structure must inevitably col- 
 lapse under the heavy stresses, should sufficient 
 power within the weight limit ever become avail- 
 able to drive them greatly faster than the maxi- 
 mums of twenty-five or thirty miles an hour that 
 have been so far attained, and which are nowhere 
 near sufficient to combat ordinary adverse winds. 
 The cost of gas alone for each filling of a large 
 balloon at present places it utterly out of the ques- 
 tion for performing commercial service at reason- 
 able cost. About a thousand dollars worth of gas 
 on the basis of the most economical production pos- 
 sible (see Page 99) is required for each inflation of 
 a Zeppelin balloon, 443 feet long and 42 feet in 
 diameter, but possessed of a reserve carrying capa- 
 city of only five and a half tons. Moreover, no bal- 
 loon builder as yet has been able within the weight 
 limitation to devise an envelope capable of retain- 
 ing a filling of gas for more than a limited period 
 not to consider the further loss that occurs in the 
 necessary trimming of the craft to desired heights 
 by alternate discharges of gas and ballast the 
 latter of which, by the way, is a burden to be reck- 
 oned with in all estimates of passenger and cargo- 
 carrying capacities. 
 
80 
 
 VEHICLES OF THE AIR 
 
 HISTORY 
 
 One of the earliest well studied attempts to pro- 
 duce a successful dirigible balloon was made by 
 Henri Giffard, in Prance, in 1852. In Giffard's 
 
 FIGURE 4. Giffard's Dirigible Balloon. Propelled by 3-horsepower 
 steam engine, weighing, with fuel and water for one hour, 462 pounds. 
 Length 144 feet, diameter 39 feet, capacity 88,300 cubic feet. Made 7 miles 
 an hour In 1852. 
 
 machine, illustrated in Figure 4, the gas bag 
 was spindle-shaped, 144 feet long. Though the 
 motor proved very weak it was found possible in 
 very quiet air to steer and to travel in circles, with 
 a maximum speed of scarcely seven miles an hour. 
 In 1870 another French experimenter, Dupuy 
 de Lome, at Vincennes, tried out a machine pro- 
 vided with an enormous two-bladed propeller, 29 
 feet 6 inches in diameter. This propeller was 
 turned slowly by the muscular efforts of the eight 
 passengers and, in a breeze of about twenty-six 
 miles an hour, "a deviation of twelve degrees" 
 
LIGHTER-THAN-AIR MACHINES 81 
 
 from a normal straight drifting course was 
 obtained. 
 
 At Grenelle, France, in 1884, Gaston and Albert 
 Tissandier maneuvered for two and a half hours in 
 ithe dirigible illustrated in Figure 5. This was 
 driven by a one and one-third horsepower Siemens 
 electric motor, weighing 121 pounds and taking 
 current from a bichromate battery weighing 496 
 
 
 FIGURE 5. Tissandier's Dirigible Balloon. Propelled by 1% -horsepower 
 electric motor and primary battery, weighing 616 pounds. Length 92 feet, 
 diameter 30 feet, capacity 37,440 cubic feet. Made 7 miles an hour in 1884. 
 
 pounds. The propeller was two-bladed, nine feet in 
 diameter. In a wind of eight miles an hour and 
 with a horsepower output estimated to have run as 
 high as one and a half, a large semicircle was suc- 
 cessfully described, following which, in a wind of 
 seven miles an hour, headway was made across the 
 wind and various evolutions performed above the 
 Grenelle observatory. 
 
82 VEHICLES OF THE AIR 
 
 Following the Tissandier experiments, Com- 
 mandant Eenard of the balloon corps of the French 
 army, on September 23, 1885, navigated from 
 Chalais-Meudon to Paris against a light wind and 
 returned with little difficulty to the point of depar- 
 
 FIGURB 6.- Renard and Kreb's Dirigible Balloon. Propelled by 9-horse- 
 power electric power plant, weighing 1,174 pounds. Length 165 feet, diam- 
 eter 27 feet, capacity 65,836 cubic feet. Made 14 miles an hour in 1885. 
 
 ture, making several ascents and descents en route. 
 
 Little more of especial interest was accom- 
 plished until in 1901 a young Brazilian, Alberto 
 Santos-Dumont, commenced in France a record- 
 breaking series of performances with a succession 
 of dirigibles. His most notable accomplishment 
 was winning, on the fourth attempt, with his San- 
 tos-Dumont No. 6, the M. Deutsch prize of about 
 $15,000 on October 9, 1901, for traveling from the 
 Pare d' Aerostation at St. Cloud to and around the 
 Eiffel tower and back. His time was about thirty 
 minutes for the distance of nine miles. The bal- 
 loon, which was the sixth dirigible built by Santos- 
 Dumont, was 108 feet long and 20 feet in diameter, 
 and was propelled by a 16-horsepower gasoline 
 automobile engine. Subsequent to this Santos 
 Dumont built at least six more dirigibles. 
 
 The Lebaudy brothers, in 1903, built a dirigible 
 
LIGHTER-THAN-AIR MACHINES 83 
 
 185 feet long and 32 feet in diameter which, with 
 a 40-horsepower gasoline motor, is said to have 
 attained a speed of 24 miles an hour. 
 
 In England the most successful early dirigibles 
 were those of Spencer, Beedle, and Dr. Barton. 
 The first of these was 93 feet long and 24 feet in 
 diameter, with a 24-horsepower motor. The Beedle 
 balloon was of the same proportions, but had only 
 a 12-horsepower motor. Dr. Barton's balloon was 
 170 feet long and 40 feet in diameter and was pro- 
 pelled by two separate 50-horsepower gasoline 
 motors. It was complicated by an excess of aero- 
 plane stabilizing surfaces that undoubtedly sub- 
 tracted from, rather than added to, its utility. 
 
 Recent military dirigible balloons of some suc- 
 cess or prominence are the English "Baby", the 
 French "Liberte", "and "Republique", and the 
 " Ville de Nancy", and the German Gross and Par- 
 seval balloons. The first of these is very small and 
 makes a speed of only 7 miles an hour, but it is 
 exceedingly convenient and portable. The "Lib- 
 erte" and the "Republique" are up-to-date devel- 
 opments of the Lebaudy type, and the "Ville de 
 Nancy", illustrated in Figure 18, is a Clement- 
 Bayard product designed for the Russian army. 
 The latter airship, which is 180 feet long and 33 
 feet in diameter, with a capacity of 180,000 cubic 
 feet, is provided with an internal balloon or bal- 
 lonet, of the type illustrated in Figure 13, by which 
 the main gas bag is kept constantly distended under 
 an internal pressure of a little over seven pounds 
 to a square foot. This balloon made its first ascent 
 
84 VEHICLES OF THE AIR 
 
 on June 27, 1909, and subsequently, on June 28 and 
 July 2, it twice remained five hours in the air. 
 Late in August, 1909, it was badly damaged by an 
 inadvertent descent into the Seine, occasioned by 
 a heavy wind coming up while it was at a height 
 of 4,000 feet. On September 25, 1909, the "Be- 
 publique" exploded at a height of 500 feet, near 
 Paris, and fell to the ground, causing the death 
 of four French army officers. 
 
 The latest Gross dirigible has a capacity of 
 270,000 cubic feet and is propelled by two motors 
 with a total output of 75 horsepower, driving two 
 propellers. Twin ballonets are used to keep the 
 envelope taut, and journeys of over fifteen hours' 
 duration have been accomplished. 
 
 On May 22, 1909, a race was held near Berlin 
 between the " Gross II" and the "Parseval II", 
 which is of similar construction. The contest was 
 a tie, with a time of fifteen minutes for a circuit 
 over the Templehof parade grounds. 
 
 A very curious small dirigible, designed by Isa- 
 buro Yamada, was used by the Japanese army 
 during the siege of Port Arthur. This balloon, 
 which was 110 feet long, differed from all other 
 dirigibles in that the 50-horsepower gasoline motor 
 was in a separate car, much below and in advance 
 of the car proper. 
 
 A dirigible that has been much in the public 
 eye is the " America", designed by Melvin Vani- 
 man and Louis Godard for use in the polar explora- 
 tion project promoted by Walter Wellman. This 
 
LIGHTER-THAN-AIR MACHINES 85 
 
 balloon, details of which are illustrated in Figures 
 12, 19, and 20, is 184 feet long and 52 feet in 
 diameter, with a capacity of 258,500 cubic feet of 
 gas. The total ascensional force at sea level is 
 19,000 pounds, the weight of the envelope 3,600 
 pounds, and that of the car, motors, and full tanks 
 of fuel 4,500 pounds. Propulsion is by two bevel- 
 gear-driven steel propellers, 11 feet in diameter, 
 revolved by a 70-80-horsepower Lorraine-Dietrich 
 motor. An 80-horsepower Antoinette motor with 
 a duplicate pair of propellers is kept in reserve. 
 Despite the expenditure of large sums of money 
 and attempts made season after season, the nearest 
 this balloon has come to reaching the pole has been 
 a thirty-mile flight from its base in Spitzbergen. 
 
 In the United States little has been done toward 
 the development of dirigible balloons, such activity 
 as there has been being confined to the more or 
 less perfect copying of the best foreign construc- 
 tions. Knabenshue, Baldwin, and Stevens have 
 been the most successful among the American 
 dirigible balloon navigators. 
 
 In every way the most interesting and most 
 important devices in this field of aerial navigation 
 are the great dirigibles of Count Zeppelin, which 
 unquestionably are so far in advance of other con- 
 structions of the same general character that their 
 points of merit constitute a fair measure of all 
 dirigible practicability, while their more serious 
 shortcomings are reasonably to be regarded as 
 among the defects of all possible craft of the 
 lighter-than-air type. 
 
86 VEHICLES OF THE AIR 
 
 In his work Zeppelin appears particularly to 
 have sought the attainment of the utmost possible 
 length in proportion to diameter, with a view to 
 keeping down head resistance while at the same 
 time securing lifting capacity. This in turn has 
 compelled recourse to a rigid structure for the gas 
 bag as the only possible means of keeping one of 
 such length in shape. 
 
 Safety has been provided by a multiplication 
 of lifting units, there being seventeen separate 
 and independent balloons enclosed between par- 
 titions in the structure. Great lifting capacity is 
 secured by sheer size, while height control is in 
 large measure attained by the provision of fin and 
 rudder-like stabilizing or balancing surfaces. 
 
 The partially-sectioned illustration in Figure 
 17 affords an excellent idea of the construction of 
 all the Zeppelins, of which several have been built. 
 The first of these were commenced in the late 
 nineties at Friedrichshafen, on Lake Constance, 
 where there was built a mammoth floating balloon 
 house, 500 feet long, 80 feet wide, and 70 feet high, 
 mounted on ninety-five pontoons. This house, 
 being anchored only at its forward end, was free 
 to swing so as always to face the wind, with the 
 result that the balloon could be taken out and 
 housed without danger of collision. 
 
 The first Zeppelin balloon was 410 feet long 
 and 39 feet in diameter, with its framing made up 
 of sixteen twenty-four-sided polygonal rings, sepa- 
 rated by spaces of 26 feet. The rings, stays and 
 even the wire bracing were at first made of "wol- 
 
LIGHTER-THAN-AIR MACHINES 87 
 
 framinium" (see Chapter 11), but in subsequent 
 models it is said that this metal has been by degrees 
 given up, until in balloons now building for the 
 German government it is almost entirely replaced 
 with wood and steel. 
 
 Over the framing and between the chambers 
 ramie netting was liberally applied, reinforcing 
 both structure and fabric. The nose of the bal- 
 loon was capped with a sheet-aluminum bow plate. 
 
 The compartments, which in the first model 
 contained a total of 351,150 cubic feet of hydrogen, 
 affording a total lift of eleven tons, are lined with 
 rather lighter balloon fabric than is necessary for 
 non-rigid dirigibles, and this fabric is proofed with 
 the gray quality of rubber which affords the high- 
 est resistance to the leakage of gas. Over the 
 outside of the framing a non-gasproof fabric is 
 used. A space of about two feet is provided all 
 around the internal balloons, under this external 
 cover, to serve as a protection from the heat of 
 the sun. 
 
 Two boat-like cars, at the ends of a stiffen- 
 ing keel of latticed framework, are provided on 
 the underside of the cylindrical body, and are suffi- 
 cient to float the whole craft on the water. These 
 cars, each 21.32 by 5.96 by 3.28 feet, are connected 
 by a passageway 326 feet long and from one to the 
 other a cable is stretched, along which a sliding 
 weight can be adjusted to trim the craft fore and 
 aft. In the first Zeppelin a 15-horsepower Daim- 
 ler motor at 700 revolutions a minute was 
 
88 VEHICLES OF THE AIR 
 
 located in each car, each motor driving two four- 
 bladed propellers, 3 |feet in diameter. 
 
 The speed of the first Zeppelin was not over 
 seventeen miles an hour and only short journeys 
 were attempted, but in later models in which the 
 sizes have been increased materially and as much 
 as 250 horsepower applied through four three or 
 two-bladed propellers, speeds of as high as twen- 
 ty-five or perhaps thirty miles an hour have been 
 maintained in calm air for distances as great as 
 950 miles. With the wind the speed is, of course, 
 higher, but, conversely, it is correspondingly lower 
 when the wind is adverse. 
 
 Landing with the balloons of the Zeppelin type 
 always has proved precarious, especially when the 
 descent has not been on water. Of the several that 
 have been built, one has been burned and all of the 
 others more or less seriously damaged at different 
 times in coming to the ground. 
 
 Nevertheless, at least the German government 
 continues to interest itself in this phase of aero- 
 nautics, and at the time this is written is reported 
 to be building dirigibles of the Zeppelin type even 
 larger than any that heretofore have been 
 constructed. 
 
 The map in Figure 270 shows the more impor- 
 tant of the Zeppelin journeys. 
 
 SPHEEICAL TYPES 
 
 Very few balloons of the true dirigible type 
 have been built with spherical envelopes, the most 
 noteworthy being one of Blanchard's first bal- 
 
LIGHTER-THAN-AIR MACHINES 89 
 
 loons, which he sought to propel by hand-manipu- 
 lated wings or oars. 
 
 However, all balloons may be said to be in some 
 degree dirigible, even those of ordinary spherical 
 types being capable of a slight degree of control 
 by the manipulation of drag ropes, as is explained 
 on Page 114. 
 
 ELONGATED TYPES 
 
 As has been previously explained, to reduce 
 head resistances and permit of special strengthen- 
 ing of the bow surfaces practically all dirigible 
 balloons are given elongated forms, necessitating 
 structural stiffening beyond what is obtainable 
 by mere strength and guying of the envelope alone. 
 There are two principal means of attaining such 
 stiffness as is to be had one the use of an under- 
 frame or long truss-like car to which the envelope 
 is securely stayed at intervals, and the other the 
 employment of internal strengthening within the 
 gas bag itself. The first of these constructions, 
 which has been termed "semi-rigid" to distin- 
 guish it from the second type, is the one used in 
 practically all dirigible balloons except the Zep- 
 pelin. The latter machine is not only the foremost 
 exponent, but is also practically the sole represent- 
 ative of the "rigid" system, its details being 
 described in Pages 85 to 88, and in Figure 17. 
 
 Pointed Ends to reduce air resistance are util- 
 ized in most elongated dirigible constructions, but 
 probably have little if any advantage in this 
 
90 VEHICLES OF THE AIR 
 
 regard over hemispherical ends; besides which 
 they are heavier and less strong. 
 
 Rounded Ends, of exact hemispherical shape, 
 are geometrically and mechanically the lightest, 
 simplest, and most stable forms to resist the end 
 pressures in cylindrical envelopes, while, as is sug- 
 gested in the previous paragraph, there is no 
 ground for supposing that they noticeably increase 
 head resistances especially at such speeds as 
 have been attained so far. 
 
 Sectional Construction, though not altogether 
 new, has been worked out in more detail and is 
 more practically applied in the Zeppelin than in 
 any previous airship. In the great balloons of this 
 type see Page 96 and Figure 17 the sixteen or 
 seventeen disk-like sections are entirely indepen- 
 dent of one another, so that leakage from any one 
 can not affect the others. 
 
 The Effect of Size on balloon design is a subject 
 concerning which there is much misunderstanding. 
 It is asserted, for example, that doubling the 
 dimensions of a balloon cubes its capacity while 
 only squaring the areas of its surfaces. This is, 
 of course, perfectly true, but the consequent rea- 
 soning that this makes it possible to secure greater 
 proportionate strength with each increase in size 
 seems largely unwarranted. For, to maintain a 
 proportionate strength, it is necessary to double 
 the thickness of the surface material with the 
 doubling in size, with the result that the quan- 
 tity of material used is cubed, after all, just as 
 the capacity is. Even at this, though, the strength 
 
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 ^ m 
 
 <s ^ 
 
 w 
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 C ca *l 
 
 S -ft5 
 
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 fffta 
 
 gft 
 
 S- ^ 8 
 
 s g. a H. 
 
 m rt; 5 i_L 
 
 
LIGHTER-THAN-AIR MACHINES 91 
 
 possible in a balloon would seem to advance in 
 proportion to increase in its lifting capacity, 
 whereas in an aeroplane there is the unavoidable 
 rapid gain of the weights over the areas. Never- 
 theless, it remains a safe general rule applicable 
 to all structures, that the smaller the size the 
 greater the proportionate strength with a given 
 weight of material. One distinct advantage that 
 comes from great size is the gain of the lifting 
 capacity over the projected area the one cubing 
 while the other squares with each increase in size. 
 This feature definitely permits the provision and 
 application of more power per unit of forward 
 resisting surface in large balloons than in small. 
 
 ENVELOPE MATERIALS 
 
 In the design of balloons, much effort has been 
 put forth to develop the lightest, strongest, and 
 most impervious materials that can be had for 
 envelope construction. In the course of these 
 experiments every art and every country has been 
 ransacked to find new fabrics, varnishes, etc. The 
 result of years of investigation and research, how- 
 ever, has been to settle the superiority of silk, cot- 
 ton, and linen among the fabrics, and linseed oil 
 and rubber as gas-proofing materials. In the 
 accompanying illustrations and captions, Figure 7, 
 an idea is given of the appearance and character- 
 istics of some typical modern balloon fabrics, made 
 by several of the more prominent manufacturers 
 of these materials. 
 
 Naturally, much the same materials that are 
 
92 VEHICLES OF THE AIR 
 
 suitable for aeroplane surfaces are suitable for 
 balloon envelopes, though if any distinction exists 
 it is that the balloon envelope requires to be most 
 heavy and impervious, while aeroplane surfaces 
 may be very light and need not be absolutely air- 
 proof (see Figure 184). 
 
 Large balloons generally require heavier envel- 
 opes than small, because of the greater area and 
 consequently greater stresses. An exception to 
 this rule is the case of rigid balloons of the Zep- 
 pelin type, in which, the necessary strength being 
 chiefly afforded by the framing, much lighter cov- 
 ering materials can be used than in the balloons of 
 other types of similar size. 
 
 Sheet Metal as a balloon covering probably was 
 first exploited in Lana's ingenious plan of the cop- 
 per-covered vacuum (see Page 67). Since then it 
 has not progressed notably in practical application 
 to the purpose in view, though it is perennially 
 reinvented on paper by persons whose zeal to 
 achieve is greater than their technical equipment. 
 Excellent rubber-coated balloon fabrics are to be 
 had weighing no more than six ounces to the 
 square yard, and with a tensile strength of 100 
 pounds to each inch of width. Sheet aluminum of 
 the same weight would be only T vVir -inch thick, 
 would have a tensile strength of not over eighty 
 pounds to each inch of width, and would crack 
 and leak with the slightest straining or denting 
 not to consider the impossibility of fastening the 
 sheets to the framing and one another without 
 creating holes and bad joints beyond toleration. 
 
LIGHTER-THAN-AIR MACHINES 93 
 
 Using steel, which is only three times as heavy 
 as aluminum and ten times as strong, the plates 
 would be -n^nj -inch thick and would sustain 200 
 pounds to each inch of width, but the difficul- 
 ties of construction, maintenance, and adequate 
 protection from rust would be all but insuperable. 
 
 Silk possesses the superiority over cotton that 
 it does not rot as readily, while it is materially 
 stronger under direct tensile stresses, though it is 
 not nearly as capable of withstanding repeated 
 flexing. Some of the modern single and multi- 
 coated rubberized silks are most beautiful and 
 serviceable fabrics, and by many are regarded as 
 the highest quality of all balloon materials. The 
 best silk balloon fabrics come twenty-seven inches 
 wide and at present retail for from $2.00 to $3.50 
 a yard. An objection to silk is its electrostatic 
 properties, rendering the possibility of discharges 
 sufficient to ignite the gas much more likely when 
 it is used than is the case with cotton and linen. 
 
 Cotton, in its best qualities (the sea-island and 
 Egyptian), is one of the strongest and most du- 
 rable of all fabrics, as is particularly evidenced in 
 its exclusive use in pneumatic tires, in which the 
 stresses to which it is subjected are literally ter- 
 rific. It is, however, very subject to weakening 
 from the action of moisture, the least rotting affect- 
 ing it most adversely. In the form of muslins and 
 percales it is very strong and inexpensive, but care 
 must be taken to secure the best grades of closely- 
 woven, unsized, and unbleached goods, if superior 
 results are to be secured. Impregnated with suit- 
 
94 VEHICLES OF THE AIR 
 
 able materials, it is readily made fairly impervious 
 to gases and insusceptible to weather. The best 
 rubberized cotton balloon fabrics come from thir- 
 ty-six to forty inches wide, and cost from 90 cents 
 to $1.50 a square yard. 
 
 Linen threads and fabrics are almost as strong 
 as silk and cotton, the long fiber making an 
 ordinary linen thread or cord stronger than any 
 but the finest sea-island cottons. In durability 
 under flexing it is superior to silk, though not 
 as good as the best cotton. In its resistance to 
 deterioration from water, it finds place between 
 cotton and silk, being superior to the former and 
 inferior to the latter. 
 
 Miscellaneous Envelope Materials are used to 
 some extent, but the best of these are combinations 
 of materials already discussed. Thus some high 
 grade balloon fabrics consist of a layer of rubber 
 faced on one side with silk and on the other with 
 cotton, the idea being to combine the advantages 
 of both materials. Several plies of different 
 weights and materials can be superimposed in this 
 manner. Eamie, jute, manila, and other fabric 
 materials do not possess the advantages of 
 commoner goods. 
 
 Paper the jute manilas, banknote, and parch- 
 ment papers, and the tough papers that are used 
 in Japan for clothing has been tried with success 
 in balloon manufacture, as is, indeed, evident in 
 the early work of the Montgolfiers and in modern 
 fire balloons. Paper has the merit of extreme 
 
FIGURE 12. Curious Drag Rope of Wellman Dirigible. 
 
 FIGURE 14. Balloon House for the Dirigible "Russie" in Course of Construction. 
 
LIGHTER-IRAN- AIR MACHINES 95 
 
 cheapness and a considerable imperviousness, but 
 is not durable. 
 
 Goldbeater's skin, from the caecum of the ox, 
 has been used to some extent for model and 
 "sounding" balloons, and is exceedingly light, 
 strong, and impervious. Its great cost, the diffi- 
 culty of strongly joining the many small pieces, 
 and its susceptibility to moisture have prevented 
 its extensive use. 
 
 Coating Materials that are suitable for gas- 
 proofing balloon envelopes are very few in 
 number. 
 
 Vulcanized rubber undoubtedly is the most 
 impervious and is an excellent protection to the 
 fabric, but it oxidizes and cracks with age. Eed 
 rubber coatings offer a maximum resistance to 
 oxidization from the sun's rays, while gray rubber 
 inner linings are found most impervious to gases. 
 
 Linseed oil varnishes are cheap, slightly lighter 
 than rubber, and easily reapplied as leaks appear, 
 but tend to be sticky, especially when newly 
 applied or in warm weather, usually requiring lib- 
 eral dustings of powdered talc, soapstone, or chalk 
 to keep a folded balloon envelope from sticking 
 together. Besides this they are rather susceptible 
 to the action of rain and mist. 
 
 Gutta percha, dissolved in benzine, has merits 
 in the way of lightness and cleanliness but is rather 
 pervious unless heavily applied, besides which it 
 may crack under repeated folding. 
 
 In addition to the foregoing well known mate- 
 rials there are various balloon varnishes the com- 
 
96 VEHICLES OF THE AIR 
 
 positions of which are kept secret by the manu- 
 facturers, but most of which are of very fair qual- 
 ity. Indeed, to so exact a science has the manufac- 
 ture of balloon envelopes been reduced, the best 
 envelope materials on the market are now guar- 
 anteed when new not to permit the escape of gas 
 faster than at some stated rate ten liters to the 
 square meter per twenty-four hours, under thirty 
 millimeters of water pressure, being the guaran- 
 teed maximum for double sheetings of the qual- 
 ities illustrated in Figure 7. Reduced to English 
 equivalents this is not quite -f$ cubic foot of gas 
 per square yard per twenty-four hours, under a 
 pressure of 6f pounds to the square foot. In the 
 case of a dirigible like the largest Zeppelin, with 
 a surface of about 6,300 square yards and a capacity 
 of about 536,000 cubic feet, this means a loss of 
 only 2,000 cubic feet of gas a day. 
 
 In joining rubberized envelope materials, the 
 breadths are lapped an inch or less, given three 
 successive coats of rubber cement, each of which 
 is allowed to dry, and are then rolled tightly 
 together with a metal roller. This done, the seams 
 are sewed and after sewing covered with adhesive 
 strips of joining material, coated with sticky, 
 unvulcanized rubber, which also are rolled down 
 hard with a metal roller. 
 
 INFLATION 
 
 Inflation materials for balloons present little 
 variety and few possibilities of improvement. 
 Obviously the range is limited to stick gases as 
 
FIGURE 15. Portable Balloon House Used by the French Array. This immense structure 
 is built in easily assembled and dismounted units, so that it can be hauled to a desired point 
 by wagon train and quickly set up. Note the arch on the ground, awaiting erection. 
 
 FIGURE 16. Balloon Houses Nearing Completion. 
 
LIGHTER-THAN-AIR MACHINES 97 
 
 are lighter than air, with reasonable preference for 
 the lightest, though considerations of cost, avail- 
 ability, and safety are not ordinarily to be dis- 
 regarded. 
 
 Heated Air, as has been explained, was one 
 of the first substances used for balloon inflation. 
 Air expands about -^^ of its volume for each 
 degree Fahrenheit increase in temperature, so 
 heating from 60 F. to 150 F. for example will 
 increase the volume occupied by one pound from 
 about 13.1 cubic feet to 22.7 cubic feet, making the 
 contents of a balloon subjected to this rise in tem- 
 perature only |4| as heavy as the external air, with 
 the result of securing an ascensional force of ap- 
 proximately -BT pound for each cubic foot of con- 
 tents. Of course, no matter what the initial expan- 
 sion given the air it rapidly cools with removal of 
 the source of heat, so to maintain a hot-air balloon 
 in the air for any period of time requires that there 
 be carried along some means of continued heating 
 see Page 70. Because the balloons built by the 
 Montgolfiers were of the heated-air type, such 
 balloons are often called "montgolfieres." 
 
 In heating the air in practical ballooning it is 
 not now attempted to do this otherwise than on 
 the ground, before the start, as hot-air balloons 
 are chiefly used for brief ascensions exhibitions, 
 parachute jumps, etc. longer balloon voyages 
 generally being made with gas craft. The chief 
 essentials of a heating plant are cheapness or port- 
 ability, and a capacity for producing quick t 
 inflation. 
 
98 VEHICLES OF THE AIR 
 
 The simplest and at the same time most prac- 
 tical and efficient methods for inflating modern 
 heated-air balloons involve little more than digging 
 a trench in the ground, covering this, and then 
 connecting it with the balloon, which is suspended 
 or partially suspended from a pole erected near 
 one end of the trench. A hot fire is maintained 
 in the end of the trench farthest from the bal- 
 loon by repeated supplies of light solid fuels, or 
 by dashes of gasoline thrown with a cup. Suffi- 
 cient draft must be provided to insure flow of the 
 heated-air through the trench and into the neck of 
 the balloon. 
 
 Hydrogen is the lightest of all known sub- 
 stances, one cubic foot of this gas at 32 F. 
 and at atmospheric pressure weighing only 
 .005592 pound, against .080728 pound for an 
 equal volume of air under the same conditions of 
 temperature and pressure. Hydrogen is very com- 
 bustible, burning readily in the presence of air or 
 oxygen, the product of the combustion being 
 water (hydrogen monoxid). Mixed with air in 
 proper proportions it forms violently explosive 
 mixtures. Though one of the most abundant of all 
 the elements, it rarely is found except in combina- 
 tion with other elements. It was first isolated by 
 Cavendish in 1766. 
 
 Hydrogen is readily prepared by the decompo- 
 sition of water or steam, electrolytically or other- 
 wise, and by the action of dilute sulphuric acid 
 upon zinc or iron, the latter reaction being still 
 much used for the production of this gas for the 
 
LIGHTER-THAN-AIR MACHINES 99 
 
 inflation of balloons. It is a chief constituent of 
 all the common fuel and illuminating gases. 
 
 A modern process for producing hydrogen a 
 process that is coming into considerable use for 
 the inflation of military dirigibles in continental 
 Europe is that of Dellwik-Fleischer for rapidly 
 and inexpensively manufacturing very pure hydro- 
 gen by the reactions that ensue when steam is 
 passed through a spongy mass of iron ore, previ- 
 ously partially reduced to metallic iron by the 
 action of water gas. The process virtually may 
 be said to be divided into four stages the first 
 two in alternation having to do with the rapid 
 and economic production of the necessary water 
 gas and the second two in alternation affording 
 the hydrogen. 
 
 Beginning with the manufacture of the water 
 gas a tall cylinder is filled with coke through 
 which heated air is passed for about a minute, 
 causing sufficient combustion to produce a high 
 temperature; then the air is shut off and steam 
 is passed through the coke for about half an hour 
 until the temperature is so lowered that reheat- 
 ing must be effected by the air blast during which 
 time the water gas is produced from decomposi- 
 tion of the steam by the coke and admixture with 
 the resulting hydrogen of a practically equal quan- 
 tity of carbon monoxid formed in the process. 
 Small quantities of carbon dioxid, sulphuretted 
 hydrogen, etc., which also appear, are removed 
 before the final two stages of the process. 
 
 These final stages, which produce the hydrogen, 
 
100 VEHICLES OF THE AIR 
 
 involve the use of a tall retort filled with hematite 
 or magnetic iron ore, or with a mixture of the 
 two, and surrounded by a furnace capable of main- 
 taining the retort at a temperature of about 
 1,470 F. The first stage consists in passing 
 through the retort enough water gas to reduce 
 the ore to spongy iron the action being stopped 
 at a point dictated by experience, and con- 
 siderably short of complete reduction. The final 
 stage consists in stopping the supply of water gas 
 and substituting for it a flow of steam, which the 
 spongy mass of highly-heated metal decomposes 
 into its elements, hydrogen and oxygen, the first 
 being collected and the second forming with the 
 iron a mass of ferric oxid which can be again 
 reduced by the use of water gas. 
 
 Since the raw materials required coke, iron 
 ore, and water all are very cheap, and both the 
 water gas and hydrogen are produced intermit- 
 tently, the process lends itself readily to econom- 
 ical working and to the use of simple and reason- 
 ably portable apparatus, the latter involving little 
 more than the cylinder for the coke, the retort and 
 furnace for the iron ore, a boiler to supply the 
 steam, and a small gasometer to contain the water 
 gas. No special fuel is required for the retort- 
 heating furnace, the water gas coming through 
 the iron ore without a sufficient loss of combustible 
 elements to preclude its use as a source of heat 
 for this purpose. 
 
 The hydrogen produced by this process is ex- 
 ceptionally pure 98^% containing only a small 
 
3 
 
 S 2. 
 
LIGHTER-THAN-AIR MACHINES 101 
 
 admixture of atmospheric nitrogen and trifling 
 quantities of other gases. 
 
 Illuminating Gases of all the common qualities 
 are lighter than air and therefore are of greater or 
 less theoretical utility for balloon inflation. Prac- 
 tically, however, the only ones available are the 
 common coal and water gases and natural gas 
 acetylene and olefiant gas being almost as heavy 
 as air, besides very expensive, while the pure 
 methanes, pentanes, etc., are not only difficult to 
 prepare but when prepared present no advantages 
 over the more complex compounds that are to be 
 had by tapping the widely-available commercial 
 mains. 
 
 Ordinary coal gas weighs about .03536 pound 
 to the cubic foot, while heavy carbureted hydrogen 
 weighs .04462 pound to the cubic foot. Acetylene 
 weighs .0767 pound to the cubic foot, and olefiant 
 gas weighs .0795 pound to the cubic foot. 
 
 Though the majority of commercial illuminat- 
 ing gases are complex and too often very impure 
 compounds, it is a safe generalization that as taken 
 from the mains for balloon use they can be counted 
 upon to afford ascensional forces equal to from 
 nine to seven-sixteenths of the weight of the air 
 displaced. 
 
 Most natural gas is fairly pure methane, and 
 is light enough to serve very well for balloon 
 inflation. 
 
 Vacuum chambers as means of securing ascen- 
 sional force are from time to time resuggested by 
 deluded inventors, but since this principle is pos- 
 
102 VEHICLES OF THE AIR 
 
 sibly the first ever proposed for balloon construc- 
 tion, besides which it is as unavailable as it is 
 ancient, it need be mentioned only to be dismissed. 
 All that there is to be said on the subject is pretty 
 thoroughly analyzed in the consideration of friar 
 Lana's copper-plated vacuum, on Page 67. 
 
 Miscellaneous inflation possibilities undoubt- 
 edly exist in the prospect of new gases to be dis- 
 covered or in the utilization of ones now known but 
 not employed, but whatever the advantages thus 
 left to be secured it is certain that among them 
 there will not be any material increase in lifting 
 capacity, since hydrogen already affords nearly 
 }4 of all the lift there is to be had, this factor be- 
 ing limited, as has been previously emphasized, not 
 by the lightness of gases, but by the weight of air 
 displaced. However, should helium, which is 
 almost as light as hydrogen (110 units of lifting 
 capacity against 120 with hydrogen), ever be 
 commercially produced in quantity it is possible 
 that it would be of advantage to use it because of 
 its chemical inertness, which in general as well as 
 military uses certainly would contrast favorably 
 with the dangerous inflammability of hydrogen. 
 At the present time practically all the isolated 
 helium in the world is the quantity of about 14| 
 cubic feet in the possession of the University of 
 Leyden. Ammonia gas, which is almost as light 
 as some illuminating gases .04758 pound to the 
 cubic foot might appear to have some possible 
 application to the inflation of balloons designed to 
 be proof against incendiary projectiles. Its cost, 
 
LIGHTER-THAN-AIR MACHINES 103 
 
 difficulty of preparation with present portable 
 facilities, its extremely irritating effect when 
 respired, even in very small quantities, and its 
 deleterious action on envelope coatings, are among 
 the greatest objections to it. 
 
 NETTINGS 
 
 Nettings are necessary in all the non-rigid types 
 of balloons to restrain the gas bag to its proper 
 form and to distribute the load of car and cargo 
 uniformly over it. To meet these requirements, 
 cordage of very high strength is usually employed 
 for nettings, knotted into meshes varying with 
 the size of balloon, the weight supported, and the 
 strength of the fabric, but always sufficiently close 
 to insure uniform distribution of the stresses and 
 to prevent serious accident from local breakages. 
 Very often the nets used are of closer mesh over 
 the upper parts of the gas bags than they are lower 
 down, and they are not usually made to come very 
 much lower than the median line of a balloon, as 
 in Figure 8, in which a typical modern spherical 
 balloon is well illustrated, all of the weight being, 
 of course, sustained upon the upper part. In this 
 illustration, a indicates the lower edge of the net- 
 ting, from which a series of straight cords are used 
 to connect it directly with the car. The large 
 number of these and their practical independence 
 of one another is in the ordinary balloon a chief 
 safeguard against structural disaster. 
 
 Balloon nettings are usually knotted exactly 
 the same as common fish nets, preferred forms of 
 
104 VEHICLES OF THE AIR 
 
 knots employed and the wooden shuttles used for 
 making them being illustrated in Figure 9. 
 
 FIQDBE 9. Shuttles for Knotting Balloon Nettings, and some Typical Knots. 
 
 Decidedly unusual, yet not without some 
 merits, was the use of piano wire in the place of 
 cord supports in the Santos-Dumont dirigible "No. 
 6" and in the ill-fated Servero ballon (see Page 
 107) . The merit of wire, besides the great strength 
 and lightness, is its small resistance to movement 
 through the air. 
 
 CAR CONSTRUCTION 
 
 It becomes obvious upon a most casual con- 
 sideration or investigation of the subject that 
 unending variety of designs and systems of 
 construction are possible in the devising of bal- 
 loons and balloon cars. This being the case, no 
 attempt is made herein to describe all possible 
 forms, it being enough to note a few general prin- 
 ciples that must always prevail, together with 
 some comment on the most-used materials. Natu- 
 
FIGURE 18. Dirigible Balloon "Ville de Nancy. 
 
 FIGURE 21. Malicot Serai-Rigid Dirigible Balloon. 
 
 FIGURE 22. Nacelle of the French Dirigible "Zodaic III." 
 
LIGHTER-THAN-AIR MACHINES 105 
 
 rally, the conservative and well informed investi- 
 gator will be largely influenced by even though 
 he may not closely follow the constructions of 
 others who have pioneered this field. Many of 
 these constructions are described or illustrated 
 herein in connection with the descriptions of the 
 balloons to which they pertain. It may be to the 
 point, however, here to call attention to the fact 
 that dirigible balloon cars, besides serving pri- 
 marily for the accommodation of passengers must 
 also often serve as mounting and bracing for motor 
 and propelling means, and, in the case of semi- 
 rigid dirigibles, as stiffening members for preserv- 
 ing the shape of the gas bag. 
 
 Rattans of the kinds commonly employed in 
 wicker and basket work have found extensive use 
 in the manufacture of ordinary balloon cars, to the 
 construction of which they are eminently adapted 
 by reason of their lightness, strength, and ease 
 of working. For the more elaborate cars, or 
 "nacelles", of dirigibles, they prove less suitable, 
 it being difficult to make such elongated structures 
 as this type generally requires without the use of 
 heavier and stiffer materials. 
 
 Wood is the preferred material for building 
 the understructures of modern non-rigid and semi- 
 rigid dirigible balloons, and is coming to be re- 
 garded as superior to metal for the framing of 
 balloons of the rigid type, such as the Zeppelin. 
 Of the different woods, bamboo, spruce, etc., are 
 generally regarded as the most suitable (see 
 Chapter 11). The nacelles of several typical 
 
106 VEHICLES OF THE AIR 
 
 dirigibles are shown in considerable detail in 
 Figures 18, 19, 20, 21, and 22. That of the Well- 
 man balloon is largely of steel, 
 
 As will be noted from an examination of these 
 illustrations, metal joining members and corner 
 pieces are used in most cases, with diagonal 
 staying with wire. 
 
 Miscellaneous schemes and materials of car 
 construction are disclosed from time to time in the 
 design of new dirigibles, and often new details of 
 considerable interest thus appear. Besides the 
 common use of wire diagonals and metal corner 
 members, already referred to, cordage, leather, 
 and rawhide lashings have their special merits 
 and special applications, as is more fully explained 
 in Chapter 11. Covering materials, such as 
 leather, canvas, thin wood, and ordinary balloon- 
 envelope fabrics often are applied to balloon cars 
 to reduce wind resistance, shelter the passengers, 
 or add to appearance. 
 
 HEIGHT CONTEOL 
 
 The control of height is a balloon problem 
 involving a number of well-established factors and 
 admitting of a considerable variety of solutions. 
 The atmosphere varying in its density and conse- 
 quent sustaining quality with every variation in 
 barometric pressure, whether due to variation in 
 altitude or variation in meteorological conditions, 
 it follows that to navigate a balloon either up or 
 down must involve either a change in the quantity 
 of sustaining gas or in the weight to be sustained, 
 
LIGHTER-THAN-AIR MACHINES 107 
 
 or must require the application of power to operate 
 against the normal tendency to float at some cer- 
 tain level determined by the interaction of the 
 various factors of barometric pressure, weight, 
 ascensional force, etc. 
 
 Non-Lifting Balloons, so-called, are ones in 
 which balance of the weight and ascensional force 
 is provided at the ground level, instead of at some 
 greater height, as is virtually the case with ordi- 
 nary balloons. This balance accomplished, it has 
 been sought to travel up and down by the supple- 
 mentary action of one or more propellers revolving 
 in a horizontal plane, the idea being that no matter 
 how slight the propeller thrust it must be sufficient 
 to produce the vertical movement. The fallacy 
 of this reasoning becomes apparent when it is con- 
 sidered that the required initial equilibrium can 
 exist only at some given level and therefore is 
 lost immediately upon ascent or descent to any 
 higher or lower level. As well expect to draw a 
 balloon in equilibrium at a height down to the 
 ground by a propeller as to expect to raise to a 
 height one in equilibrium at the ground. The 
 thing can be done, of course, but its accomplish- 
 ment loses all practical value in the complication 
 and precariousness of the resulting conditions. It 
 was in a balloon of this type that Auguste Servero 
 and his engineer Sachet lost their lives in France, 
 on May 12, 1902. 
 
 Escape Valves of one sort or another, for dis- 
 charging more or less of the gas, are the time- 
 established means of causing a balloon to descend. 
 
108 
 
 VEHICLES OF THE AIR 
 
 Such valves usually are of very large diameter 
 and are located in the highest part of the gas bag, 
 with control by means of a cord running down 
 within reach of the operator's hand. Originally 
 devised by M. Charles (see Page 71), escape valves 
 have changed but little from the form finally 
 decided upon by him as most satisfactory. One 
 of modern construction is illustrated in Figure 10, 
 in which a & is a double wood ring between which 
 the edges of the fabric at the top of the balloon 
 
 are clamped, while 
 c is a cover to the 
 opening in a &, nor- 
 mally held up by 
 the gas pressure 
 and the spring 
 hinges d d d d, but 
 arranged to pull 
 down as shown by 
 the rope e, when it 
 is desired to permit 
 the escape of gas. 
 
 P r a c t i c ally a 
 form of escape 
 valve is the "rip 
 cord," by means of 
 which a seam running all along the side of a bal- 
 loon can be laid open. The "rip cord" finds its 
 use just at the moment of landing, as a means of 
 quickly collapsing the gas bag before it can be 
 blown about by the wind, or caused to reascend by 
 losing the weight of the passengers. 
 
 FIGURE 10. Balloon Valve. The fab- 
 ric at the top of the gas bag is clamped 
 between the rings a "b, and the opening 
 through these rings is kept normally 
 closed by the disk c, held in place by 
 the pressure of the gas and the tension 
 of the spring hinges d d d d, but a pull 
 on the cord e serves to open the valve, 
 permitting the escape of any desired 
 quantity of gas. 
 
FIGURE 19. Side View of Nacelle of Wellman Dirigible. 
 
 FIGURE 20. Front View of Nacelle of the Wellman Dirigible. The driving system is 
 well shown in this illustration, from which it is evident that the transmission is one that 
 might readily be applied to an aeroplane. The motor is set crosswise of the car, its prolonged 
 crankshaft driving the twin propellers oppositely by bevel gears contained in the housings an. 
 
I 
 
 
 
 
 
 LIGHTER-THAN-AIR MACHINES 109 
 
 Ballast, by the discharge of which ascension 
 can be induced, is another early method of height 
 control, and in alternation with discharge of gas 
 still is found a most effectual means of controlling 
 vertical movement. Pine clean sand is generally 
 preferred as ballast, as calculated to cause the least 
 injury to anything upon which it may fall. Such 
 sand as is commonly used will weigh from 90 to 
 117 pounds to the cubic foot. Water, which weighs 
 63.35 pounds to the cubic foot, has been employed, 
 and has the advantage of breaking into impercep- 
 tible mist before it falls very far, but the necessity 
 for cans or tanks to contain it is a great objection, 
 since these cannot be cast overboard as carelessly 
 as may be the sacks used to contain sand. Bags 
 of ballast usually are carried hung around the 
 edges of a balloon car, as at a a, Figure 11. It has 
 been proposed to carry water in canvas bags. 
 
 With a balloon of moderate size the discharge 
 of even a most trifling weight of ballast often pro- 
 duces an astonishing change in height, the drop- 
 ping of a lead pencil having been observed to cause 
 an ascent of a hundred feet. In emergencies, 
 clothing, instruments, etc., often have been cast 
 away as ballast, and there are instances in the 
 history of ballooning in which the basket itself 
 has been cut loose, the passengers clinging to the 
 netting cords. 
 
 Compressed Gas, carried in cylinders and per- 
 mitted to escape into the balloon and there expand, 
 or drawn out and recompressed, serves to control 
 height in a very scientific manner. Not only is 
 
110 VEHICLES OF THE AIR 
 
 the sustaining force reduced by the withdrawal of 
 a portion of the gas from the envelope, but this 
 gas compressed serves the purpose of ballast. The 
 chief objections to this system inhere in the weight 
 of the containers required for the compressed gas 
 and in the power necessary for compression. 
 
 Drag Ropes can be used in certain circum- 
 stances as a sort of recoverable ballast. Thus with 
 a long rope trailing on the ground it is evident that 
 if for any reason the balloon's lifting capacity 
 decreases, as from condensation of moisture upon 
 the envelope, etc., the consequent descent will 
 reduce the weight as more and more of the rope 
 rests upon the ground until a condition of equi- 
 librium is reached. Conversely, should the balloon 
 start to ascend, the increasing weight of rope it 
 picks up must finally stop it. This system works 
 best only with very long or heavy drag ropes and 
 is obviously inapplicable over rough or thickly- 
 populated country. One of the most interesting 
 applications of this principle was that planned for 
 the Wellman dirigible, with which it was planned 
 to seek the North Pole. In this application the 
 drag rope, made of a leather-casing, was filled with 
 provisions and supplies and armored with steel 
 scales to withstand the wear of the continued 
 dragging. The details of its appearance are shown 
 in Figure 12. Unfortunately, it broke on the first 
 attempt to use it, in August, 1909. 
 
 Open Necks, or incomplete inflation of balloon 
 envelopes, are necessary to provide for the expan- 
 sion of the gas that takes place as the balloon 
 
LIGHTER-THAN-AIR MACHINES 111 
 
 ascends from a level of high barometric pressure 
 to one of lower air pressure, or that results from 
 changes in temperature. With a gas bag com- 
 pletely filled and no provision for the gas to escape, 
 this tendency to expand will cause a bursting of 
 the envelope with consequent disaster, as soon as 
 a sufficient pressure is attained. With large 
 dirigible balloons, especially those built on sec- 
 tional plans, incomplete inflation of the gas-con- 
 taining units is preferred to the use of open necks, 
 since the latter permit a gradual but no less free 
 mingling of the gas with the external air. A dan- 
 ger to be guarded against in the design of open- 
 neck balloons is that of placing the car so close to 
 the opening as to expose the passengers to the risk 
 of complete or partial asphyxiation from prolonged 
 escape of gas. 
 
 Internal Balloons, filled with air kept at a con- 
 stant pressure by some sort of continuously-acting 
 
 blower device, have been 
 very successfully used 
 in many modern diri- 
 gibles, notable among 
 them being that with 
 which Santos Dumont 
 
 FIGURE 13. Internal Balloon, . 
 
 won the Deutsch prize 
 
 gas that some must escape in case -IQA-f / O oo "Pao-P 89 ^ 
 
 of expansion. With this construe- in l^Ul ^See -T dge O6J, 
 
 tion, expansion of the gas in a , j-i ^.4.^, ^ n ~l ^^ 
 
 eimply compresses ft, which is kept to keep the CXtemal 6U- 
 tightly inflated by the blower c. , , . . . .., , , t 
 
 velop tight without the 
 
 use of the open-neck scheme and in spite of insuf- 
 ficient inflation. With this construction expansion 
 of the gas simply compresses the internal balloon 
 
112 VEHICLES OF THE AIR 
 
 and expels a portion of the air from it, but with- 
 out altering the pressure that it is sought to main- 
 tain throughout the entire envelope. A diagram 
 of a dirigible built on this design is given in Figure 
 13, in which a is the main gas bag, & is the internal 
 balloon, and c is a blower. 
 
 Moisture condensed upon the surface or ab- 
 sorbed by the material of a balloon envelope has a 
 marked effect in causing it to descend partly 
 because the quantity of water thus condensed is 
 by no means slight, and partly because it only 
 requires a very slight addition of weight to occa- 
 sion a considerable descent. A film of water only 
 2-J--JJ- inch thick over the entire envelope surface 
 of one of the great Zeppelin dirigibles, for example, 
 adds over half a ton to the weight. As for the 
 effect of moisture actually absorbed, one manufac- 
 turing concern, which produces a particularly ex- 
 cellent balloon fabric weighing 9.5 ounces to the 
 square yard, guarantees that the increase in weight 
 from exposure to an atmosphere of maximum 
 humidity will not exceed .38 ounce to the square 
 yard. 
 
 Temperature also has marked effects upon the 
 sustentional capacity of balloons, a very small 
 increase in temperature being sufficient to enhance 
 the lift very materially, while, conversely, cooling 
 of the gas shrinks it enough to make it lose much 
 of its ascensional force. In the use of balloons it 
 often has been noticed that drift into the shadow 
 of a dark cloud will cause a descent perhaps of 
 
'LIGHTER-THAN-AIR MACHINES 113 
 
 hundreds of feet, with a corresponding rise upon 
 coming into the bright sun again. 
 
 STEERING 
 
 Steering a dirigible is easily effected by the 
 manipulation of rudders, provided the speed of the 
 craft through the air is sufficient to set up reac- 
 tions of sufficient magnitude from the air flow. 
 For slow-moving airships larger rudders are re- 
 quired than suffice for fast-moving craft. Refer- 
 ence to Figures 17, 18, 21, and 22 will afford a clear 
 idea of the rudder schemes employed in modern 
 dirigibles. In addition to the pivoted and mov- 
 able rudders a and b in these illustrations, sta- 
 tionary fins c also are much used, to help keep an 
 airship to its course, and to reduce spinning when 
 it is not under way. And in some vessels it has 
 been proposed to effect steering by other than 
 rudder schemes for shifting the whole gas 
 bag around by swinging, skewing, or tilting 
 movements. 
 
 Lateral Steering is so readily effected by prop- 
 erly designed vertical rudders, such as are marked 
 a in Figures 17, 18, 21, and 22, of sizes propor- 
 tioned to the speeds and sizes of the craft they are 
 intended to control, that experiment with more 
 complicated schemes seems scarcely worth while. 
 Nevertheless considerable attention has been given 
 to devices for swinging the main propellers side- 
 wise, and even to designs in which small side pro- 
 pellers are provided for pulling the whole vehicle 
 around. Seemingly ill-advised on their face, such 
 
114 VEHICLES OF THE AIR 
 
 systems of control so far have met with no practical 
 success. 
 
 In planning the steering of a dirigible, it is 
 necessary, if non-rigid or semi-rigid construction 
 be employed, to allow for the flexibility of the 
 structure and also to make sure that the steering 
 effect shall not twist the car away from its fasten- 
 ings to the gas bag. 
 
 In steering an ordinary balloon by a drag rope, 
 the rope is simply moved from time to time as its 
 reattachment revolves the balloon. By this scheme 
 it is possible to produce only a slight angular 
 deviation from a straight drifting course. 
 
 Vertical Steering, by means of horizontal fins 
 or rudders, as shown at & and c in Figures 17, 18, 
 and 21, is used in some dirigibles with consider- 
 able success as means of changing height without 
 recourse to the discharge of gas or ballast. Used 
 for this purpose, the effectiveness of fins and rud- 
 ders is dependent upon the rate of longitudinal 
 progress maintained through the air, as they 
 obviously can be of no effect when the balloon is 
 at rest or merely drifting. Two chief systems of 
 height control on this principle are in use. In one 
 the horizontal surfaces are inclined up or down 
 as direct steering means, while in the other the 
 whole airship is tilted longitudinally by shifting 
 of weight or gas, in which condition fixed fins serve 
 to produce the required change in level under the 
 influence of longitudinal propulsion. 
 
 It is said that one of the Zeppelin airships, 
 during the week of March 7, 1909, ascended to 
 
LIGHTER-THAN-AIR MACHINES 115 
 
 an altitude of 5,643 feet, and descended again " en- 
 tirely with the use of the elevators ", and without 
 discharge of ballast. The secrecy maintained by 
 those concerned in the Zeppelin trials has pre- 
 vented any definite confirmation of this statement, 
 which if correct is of considerable importance 
 in its bearings upon practical maneuvering and 
 conservation of gas supply. 
 
 BALLOON HOUSING 
 
 The problem of properly housing large balloons 
 when they are not in use, so as to protect them 
 from wind and weather, is a very serious one. 
 Because of its great bulk any balloon, no matter 
 how stoutly constructed, is essentially fragile 
 when fastened to the ground and exposed to the 
 buffeting even of moderate gales. In the air, of 
 course, the only effect of wind is to cause a drift 
 relative to the earth's surface but not to the sur- 
 rounding atmosphere. On the ground, however, 
 restrained from drifting by rope or other attach- 
 ments, the effect of even a light wind is to press 
 the gas bag over and pound it upon the ground. 
 These considerations render imperative the pro- 
 vision of proper housing of some sort. And, such 
 housings being necessarily very large and sub- 
 stantial, and preferably inexpensive enough to 
 permit of extensive placing, it is clear that the 
 question of their design is one to tax the best of 
 architectural abilities and structural methods. 
 
 Sheds for housing balloons and aeroplanes 
 the "hangars" of the French aeronauts and avi- 
 
116 VEHICLES OF THE AIR 
 
 ators, who bid fair to fix this term upon the Eng- 
 lish language have been designed in a great vari- 
 ety of forms. The construction of the best of these 
 will be easiest appreciated by reference to Figures 
 14, 15, and 16, of which Figure 14 shows one 
 building for the dirigible "Russie", while Figures 
 16 and 17 show the Clement-Bayard portable 
 balloon house with which the French army is 
 experimenting. 
 
 Landing Pits have been proposed as substitutes 
 for balloon sheds, over which they possess the 
 advantages of lower cost and readier improvisa- 
 tion. In a characteristic balloon pit the essential 
 feature is the simple excavation in the earth, large 
 enough to shelter wholly or partly the air craft it 
 is designed to protect. The scheme has been tried, 
 and possesses many features of merit, of covering 
 shallow excavations with low sheds, thus in 
 a measure combining the virtues of both 
 constructions. 
 
 
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CHAPTER THEEE 
 
 HEAVIER-THAN-AIR MACHINES 
 
 The idea of machines, heavier than air, which 
 should nevertheless sustain themselves in the air 
 by the operation of suitable mechanism is an 
 obvious deduction from the observation of the 
 birds and of flying animals and insects, all of 
 which, quite without exception, are vastly heavier 
 than the tenuous medium that so securely supports 
 them. As a consequence, the earliest conceptions 
 of heavier-than-air flying machines long antedate 
 the discovery of the balloon, even the various 
 myths and apocryphal accounts of flying men, 
 which have come down from ancient times, being 
 invariably founded upon one or another of the 
 obvious modifications of the mechanical-bird idea. 
 
 In later times, and as science and invention 
 have progressed, attempts innumerable have been 
 made to construct successful machines, but with 
 results so uniformly discouraging that the very 
 term " flying machine" had become a synonym for 
 all that was wild and erratic in inventors' brains 
 and mechanical perversity. However, complete 
 failures though all the ideas of the early air navi- 
 gators proved when put to the test, in the revealing 
 light of more recent successes it begins to appear 
 that past failures were due less to insuperable 
 
 117 
 
118 VEHICLES OF THE AIR 
 
 obstacles than to incomplete knowledge to a 
 failure to understand the essential importance of 
 a very few but most fundamental principles. 
 
 The result is that now, as knowledge is accumu- 
 lated and tested and tabulated in ever-increasing 
 increments, and as the great principles are com- 
 mencing to be wrung from the mazes of indiffer- 
 ence and skepticism and ignorance that had so 
 long concealed them, the aerial vehicle is surely 
 and inevitably issuing from the mists of doubt 
 into the realms of the practical. 
 
 Of the many varieties of heavier-than-air 
 machines that have been constructed or con- 
 ceived, nearly all fall into one or another of three 
 basic classifications ornithopters, helicopters, and 
 aeroplanes. 
 
 ORNITHOPTERS 
 
 The term ornithopter embraces, as its name 
 implies, any type of flying machine modeled after 
 the flapping or vibrating action of bird and insect 
 wings. Evidently, the ornithopter being suggested 
 by all common types of birds, it almost certainly 
 preceded all other conceptions in mankind's won- 
 derful and ages-long development of the art of 
 flying. 
 
 HISTORY 
 
 Possibly the earliest plausible suggestion in 
 recorded history of a machine really capable of 
 flying is the Aulus Gellius reference to the flying 
 dove of Archytas, of which it is gravely asserted 
 
HEAVIER-THAN-AIR MACHINES 119 
 
 "It was built along the model of a dove or pigeon 
 formed in wood, and so contrived as by a certain 
 mechanical art and power to fly ; so nicely was it 
 balanced by weights and put in motion by hidden 
 and enclosed air." Prom this, most authorities 
 conclude that Archytas' machine was a more or 
 less successful ornithopter model, but to the writer 
 it seems that there is just a suggestion, in the 
 "balanced by weights and put in motion by hidden 
 and enclosed air", that the ingenious Archytas 
 might conceivably have demonstrated no more 
 than the flotation of some sort of oddly-shaped, 
 and altogether premature toy balloon surely 
 enough, at this, for a man to achieve so long in 
 advance of his time. 
 
 Even antedating the now unappraisable story 
 of Archytas is the seemingly utter myth of Daeda- 
 lus and Icarus, who, Grecian mythology main- 
 tains, undertook to fly over the five hundred odd 
 miles of the Mediterranean that separate Crete 
 from Sicily. If the "wax "-attached wings were 
 made at all and were made to flap, here undoubt- 
 edly was the original ornithopter, but all of the 
 probabilities of the exploit are rather discounted 
 by the mythical form of the story and by the fur- 
 ther fact that it has taken a matter of several 
 thousand years of progress to enable Bleriot and 
 Latham to reenact the respective roles over a much 
 shorter distance. 
 
 Coming down to modern times and passing by 
 without consideration various unauthenticated or 
 less successful ornithopters, with accounts of 
 
120 VEHICLES OF THE AIR 
 
 which mechanical history commencing with the 
 middle ages is not infrequently embellished,* 
 possibly the first ornithopter really to produce 
 measurable sustention was that of Degen, who 
 
 FIGDEE 24. Degen's Orthogonal Flier. 
 
 in 1809 rose to a height of 54 feet by violently 
 flapping the deeply-concave wings illustrated in 
 Figure 24, which totaled 116 square feet in area, 
 and were covered with taffeta bands arranged to 
 afford a valvular action similar to that of the 
 feathers of the bird's wing. Most accounts of the 
 
 * Among the more interesting of these accounts are those concerning 
 the construction proposed by Leonardo da Vinci, the sound reasoning of 
 Borelli, the mishap that befel the tight-rope dancer Allard, the seemingly 
 interesting but now lost mechanism of Besnier, the unfortunate descent 
 of the Marquis de Bacqueville into the washerwomen's barge in the 
 Seine, the failure of the Abbe Desforges, the flying chariot of Blanchard 
 the balloonist, the feathering wings of Bourcart, the figure-eight action 
 of Dandrieux' machine, the Gibson feathering wings, the early explosion 
 engine and the magnified stag beetle of Quartermain, the Cayley 
 umbrella machine, the parachute-and-wing combination in which Letur 
 met his death, the similar device of De Groof that also proved fatal to 
 its inventor, the proposed Meerwein apparatus, the Breant artificial bat, 
 the first attempt of Le Bris, the very wild Gerard project, the unsuccess- 
 ful Artingstall model, the multi-wing craft of Struve and Teleschiff, the 
 Palmer wing action, the Kaufmann ornithopter propulsion, the Jay 
 model, the fairly successful steam toy of the Leipsic optician, the 
 Prigent dragon fly, the important Jobert and Penaud introduction of 
 rubber-band propulsion with the result of producing successful models, 
 the subsequent improvements in flying models by Pichancourt, the De 
 Louvrie fiasco, the Quinby, Lamboley, Murrell, Keith, Green, Baldwin 
 and Wheeler patents, the Sutton, Pettigrew, and Marey observations, the 
 Frost steam bird, the 45-foot Moore bat, the original beating-wing 
 machine of Ader, and the Napier, Smyth, Alexander, De Labouret, Tatin, 
 Eichet, Chanute, and other calculations, all of which are interestingly 
 described, at the cost of much research and labor, in Chanute 's book, 
 "Progress in Flying Machines," published in 1891-1894. 
 
HEAVIER-THAN-AIR MACHINES 121 
 
 Degen apparatus omit to state that it lifted only 
 70 of the 160 pounds of operator and machine, 
 the other 90 pounds being balanced by a small 
 balloon or a counterweight attached to a rope pass- 
 ing over a pulley. Therefore, considerable though 
 Degen 's success really was, it actually proved 
 man's inability rather than any ability to fly by 
 his own muscular efforts applied to an orthogonal 
 mechanism. 
 
 Among those that came after the Degen 
 machine, one of the most interesting was the excep- 
 tionally ingenious Trouve model, illustrated and 
 
 FIGURE 25. Trouve's Flapping Flier. In this machine the two wings, A 
 and B, are connected together by a flattened tube, the "Bourdon" tube of 
 steam gages, etc., the particular property of which is its tendency to 
 straighten out when subjected to the influence of an internal pressure. In 
 this model pressure is intermittently supplied by the successive explosion of 
 cartridges in the revolver barrel shown in the U of the tube which com- 
 municates with the interior. In this way a series of vigorous flaps can be 
 obtained, with flight for as much as 240 feet. 
 
 described in Figure 25. Not the least curious 
 feature of this model was the method of starting 
 it by the use of two strings, successively cut by; 
 a candle and a blowpipe flame.* 
 
 * Described in Chanute's "Progress in Flying Machines." 
 
122 VEHICLES OF THE AIR 
 
 A most ingenious, persistent, unselfish, and 
 well-equipped investigator of flying-machine prob- 
 lems is Laurence Hargrave, of Sydney, Australia, 
 who is known the world over as the inventor of 
 the box kite (see Figure 34). 
 
 In the course of his experiments with ornithop- 
 ter constructions in which flapping wings were 
 
 FIGURE 26. Engine and Wing Mechanism of Hargrave Model No. 18. The 
 boiler of this machine was of the water-tube type, constituted of 21 feet of 
 *4 -inch copper tubing with an internal diameter of .18 inch. The tubing was 
 arranged in three concentric vertical coils, 1.6 inches, 2.6 inches, and 3.6 
 inches in diameter, inclosed in an asbestos jacket. The weight was 37 
 ounces, but Hargrave asserted that it could be lightened to 8 ounces without 
 reducing the capacity and with the retention of ample strength. The engine 
 was single-cylinder, double-acting, of 2 inches bore and 2.52 inches stroke, 
 and with piston valves .3 inch in diameter. The wings were flapped directly, 
 with no conversion of the reciprocating into rotary motion, and the highest 
 speed attained was 342 strokes a minute. The total weight of engine, boiler, 
 and 21 ounces of water and alcohol, enough to feed the boiler and burner for 
 four minutes, was 7 pounds. The indicated horsepower was .653, with a 
 capacity for evaporating 14.7 cubic inches of water, with 4.13 cubic inches 
 of alcohol, in thirty seconds. This figures 8.71 pounds to the horsepower 
 for the power plant with tanks empty, or 5.93 pounds to the horsepower were 
 the expected lightening of the boiler realized. The wings were 36 inches long, 
 with the outer 22 inches covered with paper, 4 inches wide at the inner ends 
 and 9 inches wide at the tips a total of 286 square inches for the two wings. 
 Thrusts of as high as one pound were obtained and machines of similar type 
 flew distances of several hundred feet. The flapping wings were used for 
 propulsion alone, sustention being had from a large aeroplane surface to 
 the rear. 
 
 invariably employed for propulsion, not susten- 
 tion Hargrave built eighteen different machines, 
 
HEAVIER-THAN-AIR MACHINES 123 
 
 commencing 1883 and culminating in 1893, with 
 the machine illustrated and described in Figure 26. 
 Of the eighteen machines, which were built on 
 similar lines but variously propelled by clockwork, 
 rubber bands in torsion and tension, compressed 
 air, and steam, several were built with single and 
 double, and traction and thrust screw propellers, 
 that the action and efficiencies of these might be 
 compared with one another and with the wings. 
 
 A remarkable feature of many of the Hargrave 
 models is the wonderful lightness of the small 
 power plants, which while built inexpensively, 
 rather crudely, and in a decidedly tinkering sort of 
 way, have never been surpassed in the ratio of 
 power to weight except in a very few of most 
 modern gasoline engines. 
 
 With different ones of these models, the best 
 of which weighed from about four to eight pounds, 
 and ranged up to 6 feet in length and width, 
 recorded flight of 343 feet was definitely accom- 
 plished as early, as 1891, with at least one similar 
 model built to carry within its weight limit enough 
 fuel to fly for a mile. The maximum speeds 
 attained were about 17 miles an hour. 
 
 After 1893, when his box or " cellular" kite 
 was developed, Hargrave turned his attention to 
 the development of this type of sustaining surface, 
 which has come to be regarded as the direct proto- 
 type of at least one most successful modern biplane 
 the Voisin. 
 
124 VEHICLES OF THE AIR 
 
 TWO CHIEF CLASSES 
 
 The work of Hargrave particularly emphasizes 
 the fact that the ornithopter principle is capable 
 of application to either of two wholly different 
 classes of machines those sustained in the air 
 solely by the movement of the wings, and others, 
 usually aeroplanes, in which the flapping is used 
 simply for propulsion. For further consideration 
 of ornithopter propulsion see Page 25. 
 
 RECENT OENITHOPTEKS 
 
 At the time this is written the only known suc- 
 cessful machines of the ornithopter type are the 
 very small models of Jobert, Penaud, Pichancourt, 
 Trouve, and Hargrave the latter being really 
 an aeroplane with ornithopter propulsion. Fur- 
 thermore, no materially greater success seems at 
 all probable, for the reasons explained on Page 000 
 reasons that are further upheld by the invariable 
 failure and unmechanical construction of every 
 ornithopter of man-carrying size that has so far 
 appeared. A characteristic example is the machine 
 illustrated in Figure 27, in which the wing struc- 
 tures and actuating elements are nowhere near 
 strong enough to withstand the rate of flapping 
 necessary to effect sustention. Another example 
 was the Farcot machine, exhibited in Paris in Octo- 
 ber, 1909. 
 
 ANALOGIES IN NATURE 
 
 That the flapping-wing machine has not met 
 with the success of its animal prototypes is beyond 
 any question due to the invariable superiority of 
 
HEAVIER-THAN-AIR MACHINES 125 
 
 rotating over reciprocating mechanisms in all 
 mechanical structures man has the means and the 
 knowledge to devise, and in which the one most 
 conspicuous feature is the frequent use of the wheel 
 and its various equivalents, which are unknown in 
 nature apparently not because they are not supe- 
 rior but because they are not available. This view, 
 which is somewhat amplified on Page 26, gives 
 ground for the belief that as man does learn to 
 fly he will do so in many ways better and more 
 efficiently than the birds, just as his water craft 
 excel the inhabitants of the deep and his land 
 vehicles the creatures of the land in speed, sus- 
 tained travel, and loads carried. 
 
 HELICOPTEKS 
 
 Though in almost the same status as the ornith- 
 opter, in so far as any measurable success that 
 has been achieved is concerned, engineers are 
 nevertheless inclined to regard with some measure 
 of respect the helicopter principle, which in many 
 essential respects appears to be sound engineering, 
 and which is vigorously defended by men like 
 Edison, Berliner, Cornu, Breguet, and others. 
 Even the assertion that, no matter what success 
 may be attained with the helicopter, it must always 
 prove unsafe upon failure of the power, is met 
 by plausible and well-backed reasoning to the 
 effect that the propeller areas can be sufficient to 
 prevent abrupt descent, causing the machine 
 simply to act as a parachute in case the power 
 
126 VEHICLES OF THE AIR 
 
 fails. As for an analogy in nature, it is a fact 
 that the delicately-twisted wing of the ash seed, by 
 causing fairly rapid revolution definitely retards 
 the fall. The forms of maple and sycamore seeds, 
 too, produce a similar effect, though these are less 
 screw-propeller-like. In the matter of sustention, 
 while it is true that nature finds the helicopter 
 principle, in the use of flat blade-like wings that 
 humming birds and many insects there is to be 
 found the closest imaginable approximation to this 
 principle, in the use of flat blade like wings that 
 buzz to and fro with rapidly reversing angles of 
 incidence through arcs as great as 250. 
 
 It has been frequently sought to combine the 
 helicopter principle with that of the aeroplane, as 
 in balanced balloons in which it is sought to cause 
 the vessel to ascend or descend by revolving a 
 propeller in a horizontal plane. A recent com- 
 bination of a helicopter with an aeroplane is shown 
 in Figure 33. 
 
 HISTORY 
 
 Leonardo da Vinci, the wonderful Italian 
 genius of the middle ages, who looms so large in 
 so many fields of endeavor, did not overlook the 
 possibilities of the helicopter as a means to man 
 flight, for in one of his note books there is a sketch 
 of a proposed lifting propeller 96 feet in diameter, 
 to be built of iron and bamboo framing, covered 
 with starched linen. The idea was evidently 
 dropped because of the power required, but it is 
 recorded that light paper propellers were experi- 
 
FIGURE 27. Collomb Ornithopter. This machine is of the direct, orthogonal flapping-wing 
 type, provided with valvular flaps at a a a a. The two wings, which pivot at the upper 
 extremities of the links c o c c, are reciprocated by the vertical reciprocation of the arms d d. 
 
 FIGURE 31. Bertin Helicopter. 
 
HEAVIER-THAN-AIR MACHINES 127 
 
 merited with and made to ascend for very brief 
 periods. 
 
 In 1784, only a year after the Montgolfiers' first 
 balloon ascension, Launoy and Bienvenu jointly 
 exhibited before the French Academy of Sciences 
 the little helicopter pictured in Figure 28. This 
 toy, which can be easily made from a couple of 
 corks, a few feathers, a piece of thread, and a 
 splint of bamboo, is an excellent flier, continuing 
 to ascend until the thread is completely unwound. 
 
 Of the totally unsuccessful or merely projected 
 helicopters there has been a great number, few of 
 which merit description except in a work devoted 
 to the historical rather than to the practical in 
 aeronautics. 
 
 The next advance in helicopters after the 
 Launoy and Bienvenu in- 
 vention was made by W. 
 H. Phillips, who in 1842 
 made a 2-pound helicopter, 
 driven by a reaction tur- 
 bine similar to the first en- 
 gine, attributed to Hero, of 
 Alexandria. This model is 
 stated to have flown across 
 two large fields, but was 
 badly broken in landing. 
 
 In 1870 Penaud devised 
 a toy helicopter, driven 
 by a rubber band and exactly similar to that shown 
 in Figure 29, except that in place of the large sur- 
 faces to keep the whole apparatus from turning 
 
 FIGURE 28. Toy Helicopter. 
 The four propeller blades are 
 suitably placed feathers and the 
 power is derived from the bamboo 
 splint a, which In straightening 
 out as suggested by the dotted 
 lines revolves the vertical shaft. 
 
128 
 
 VEHICLES OF THE AIR 
 
 ber band a is tightly twisted, energy 
 enough is stored for a short flight, 
 the large wings resisting the tendency 
 
 oppo " 
 
 a duplicate screw was provided at the bottom, as 
 in Figure 28. Flights of nearly half a minute 
 
 were obtained much 
 longer than had been 
 previously obtained 
 with lifting screws. 
 
 The helicopter shown 
 in Figure 29 was in- 
 vented by Dandrieux, 
 and has been extensively 
 manufactured in France 
 
 FIGURE 29. Toy Helicopter. By j Tnnnn x<s. Q tnv 
 
 turning the propeller until the rub- dlLCl u dJJdll d d tUJ . 
 
 Another common 
 said to have devel- 
 oped from the Penaud 
 helicopter, is that shown in Figure 30. Wenham 
 made exhaustive measurements and calculations 
 with these toys, and 
 estimated that the 
 best of them will lift 
 33 pounds per horse- 
 power well within 
 the capacity of many 
 modern engines, even 
 of large size. 
 
 Subsequent to this 
 Edison, Renard, and 
 Maxim conducted ex- 
 haustive tests of pro- 
 peller thrusts, for lift- 
 ing as well as for propulsion, but their work proved 
 only of scientific, rather than of practical value. 
 
 FIGURE 30. Toy Helicopter. By rap- 
 idly pulling the string the propeller is 
 revolved at such speed as to cause it to 
 rise off the spool and ascend a consid- 
 erable distance in the air. 
 
HEAVIER-THAN-AIR MACHINES 129 
 
 Also, the findings of these early investigators have 
 for the most part been kept secret, leaving the 
 subject still much in need of investigation and 
 elucidation. 
 
 EECENT EXPERIMENTS 
 
 Emil Berliner, the famous telephone inventor, 
 has given considerable attention to the develop- 
 ment of the helicopter principle, and at last 
 accounts had tested in Washington, D. C., a 
 machine expected to weigh, with operator, only 
 a little over 300 pounds. This machine was pro- 
 vided with a 36-horsepower revolving-cylinder 
 Adams-Farwell motor, weighing 100 pounds and 
 running normally at 1400 revolutions a minute, 
 but geared to drive the 17-foot propeller at 150 
 revolutions a minute. At this speed a lift of 
 360 pounds was calculated, but it is not known 
 what results were secured in the actual tests. 
 Berliner is now building a twin-screw machine, 
 expected to weigh 500 pounds and lift 720 pounds. 
 This machine is to be driven by a 55-horsepower 
 Adams-Farwell revolving-cylinder engine, with 
 five 5-inch by 5-inch plain steel cylinders, and a 
 total weight of only 175 pounds. 
 
 An ingenious modern helicopter, seemingly of 
 fairly sound design but not proved successful is 
 that illustrated in Figure 31. 
 
 Another interesting new helicopter is that of 
 Cornu, which is illustrated in Figure 32. In tests 
 this has proved to lift, but has not yet been per- 
 mitted to rise more than 15 inches from the ground, 
 for fear of accident. 
 
132 VEHICLES OF THE AIR 
 
 safeguard against the possibility of accident due to 
 motor failure. Moreover, the aeroplane certainly 
 will prove far cheaper to build and to operate than 
 any conceivable type of ornithopter, and probably 
 cheaper than any helicopter, that will begin to 
 afford equivalent speeds, lifts, or efficiencies. 
 
 AEROPLANE HISTORY 
 
 The history of the aeroplane involves the devel- 
 opment of three more or less separate conceptions 
 the first, the use of gliding surfaces as means of 
 riding down a slant of air from a greater height 
 to a lower; the second, the application of power- 
 operated propelling elements for continuing on a 
 horizontal course or progressing on an upward 
 slant ; and the third, the idea of indefinite soaring 
 without power by the utilization of obscure and 
 little understood, but very evident principles, that 
 are clearly demonstrated to exist in the flight of 
 soaring birds a mode of flight concerning which 
 there has been much speculation and controversy, 
 and the performance of which is variously attrib- 
 uted to the phenomenon of rising currents in the 
 atmosphere, to the presence of constantly varying 
 factors in the horizontal movement of winds, and to 
 the operation of laws not yet generally formulated 
 or recognized. Probably the real explanation lies 
 in some measure of sound reasoning that is to be 
 found in both the first and the third of these 
 explanations. 
 
 Just as the ornithopter is a logical-enough out- 
 
HEAVIER-THAN-AIR MACHINES 133 
 
 growth from observations of the flapping flight of 
 birds, so the aeroplane is an inevitable deduction 
 from the flight of soaring birds. And so absolute 
 has been the ignorance and misunderstanding of 
 the phenomena of soaring flight that even today 
 the most successful aeroplanes are in many in- 
 stances radically incorrect surfaces made to fly not 
 so much by sound design and engineering refine- 
 ment as by being inefficiently dragged through the 
 air by sheer force of the excessive power that has 
 become available in modern light-weight engines. 
 
 Of the many investigators of aeroplane prob- 
 lems, it is a safe assertion that the most important, 
 original, and successful work that has been done 
 is fairly to be ascribed to a comparativedly small 
 number of men preeminent among whom are 
 Ader, Bleriot, Chanute, Langley, the Lilienthals, 
 Montgomery, Penaud, Pilcher, Santos-Dumont, 
 Wenham, the Wrights, and the Voisins. While 
 this list may not at all fit the selections or opinions 
 of other compilers it at least represents a serious 
 and unbiased effort justly to appraise the compara- 
 tive value of the many different contributions to 
 aeronautical progress, and certainly it must be ad- 
 mitted that the men it includes are in any case 
 possessed of a forever unassailable rank in this 
 field of engineering. As for the many important 
 omissions, these are in no sense intended to dis- 
 parage the earnest and valuable researches of a 
 considerable number of able and disinterested stu- 
 dents, who in more than one instance have freely 
 
134 VEHICLES OF THE AIR 
 
 given years of their lives and large sums of money 
 to the always thankless task of contributing to the 
 progress of the race in advance of commercial de- 
 mand and in the face of popular skepticism. But, 
 in the case of each of these omissions, it is the 
 writer's belief that no fair and unprejudiced analy- 
 sis can fail to discover either such lack of orig- 
 inality or of success as must properly reduce to 
 a secondary status the particular experiments 
 affected. 
 
 CLEMENT ADEB 
 
 In 1872 this inventor, well known as one of the 
 European pioneers in the development of the tele- 
 phone, constructed a 53-pound ornithopter appa- 
 ratus in the form of a bird of a 26-foot wing spread, 
 intended to be flown by the strength of the opera- 
 tor's muscles. Failure naturally resulting, the 
 project was dropped and it was not until 1891 that 
 Ader began his areoplane experiments with the 
 construction of a bat-like machine, 54 feet across, 
 weighing 1100 pounds, and drawn through the air 
 by two four-bladed tractor screws, driven by a 
 twenty or thirty horsepower steam power plant. 
 Fully $120,000 was expended in the experiments, 
 and the result was the first flight of a man-carrying 
 power-propelled aeroplane, for a distance of only 
 164 feet, on October 9, 1890. Subsequently, on 
 October 14, 1897, at Satory, France, a semicircular 
 flight of nearly 1000 feet was accomplished with a 
 machine started by a run along the ground on 
 wheels. In both of these trials the machines were 
 wrecked because of deficient equilibrium. 
 
HEAVIER-THAN-AIR MACHINES 135 
 
 LOUIS BLERIOT 
 
 One of the earliest among the successful aero- 
 plane builders of the world is Louis Bleriot, who 
 has long been noted as one of the foremost auto- 
 mobile-lamp manufacturers in Europe, and whose 
 experiments commenced like those of so many 
 others with a flapping- wing machine, built in 1901. 
 Following the failure of this, nothing more was 
 done until during 1905, when some interesting ex- 
 periments were made with a towed biplane glider 
 Bleriot II mounted on hydroplanes. The Bleriot 
 III was a double biplane or box kite form, but with 
 semicircular instead of vertical ends. It was pro- 
 vided with a motor, but no success resulted from 
 attempts to make it rise from the Seine, on the sur- 
 face of which it was floated like its predecessor. 
 Bleriot IV was Bleriot III modified by removal 
 of the semicircular ends from the front cell, but 
 not until experiments on land were substituted for 
 those over water and a double monoplane for the 
 biplane was the first real flight accomplished in 
 July, 1907. After this the monoplane principle 
 was rapidly developed, with numerous successes in 
 1908 and more in 1909, culminating in the wonder- 
 ful cross-country flights in the spring and summer 
 of the latter year, and, finally, in the memorable 
 crossing of the English Channel in one of the 
 smallest, speediest, lowest-powered, and cheapest 
 aeroplanes yet built. 
 
138 VEHICLES OF THE AIR 
 
 two miles an hour. Though originally a firm be- 
 liever in the monoplane (see Figures 230, 231, and 
 263), and in the ultimate attainment of soaring 
 flight, in 1896 he built a 2|-horsepower motor, 
 weighing 88 pounds, and it was in testing the bi- 
 plane sketched in Figure 232, to which he proposed 
 the application of flapping propulsion by the use of 
 this motor, that he met his death by a fall from a 
 height of 50 feet, on August 10, 1896. 
 
 JOHN J. MONTGOMEKY 
 
 On April 29, 1905, in California, there was pub- 
 licly performed a feat which no competent and un- 
 prejudiced person who investigates its details can 
 fail to characterize as the greatest single advance 
 in the history of aerial navigation. For on this day 
 there ascended from the college grounds at Santa 
 Clara, in the presence of thousands of spectators, 
 an ordinary heated air balloon to which was at- 
 tached, not a parachute, but a 45-pound glider de- 
 signed by Professor Montgomery and mounted by 
 an intrepid parachute jumper, Daniel Maloney (see 
 Figures 225, 226, 227, and 260). 
 
 At a height of about 4000 feet the aeroplane was 
 cut loose from the balloon and commenced to glide, 
 under the most absolute control imaginable, to the 
 ground. In the course of the descent the most 
 extraordinary and complex maneuvers were ac- 
 complished spiral and circling turns being exe- 
 cuted with an ease and grace almost beyond descrip- 
 tion, level travel accomplished with the wind and 
 
HEAVIER-THAN-AIR MACHINES 139 
 
 against it, figure-eight evolutions performed with- 
 out difficulty, and hair-raising dives were termi- 
 nated by abrupt checking of the movement by 
 changing the angles of the wing surfaces. At times 
 the speed, as estimated by eye witnesses, was 
 over sixty-eight miles an hour, and yet after a 
 flight of approximately eight miles in twenty min- 
 utes the machine was brought to rest upon a previ- 
 ously designated spot, three-quarters of a mile from 
 where the balloon had been released, so lightly that 
 the aviator was not even jarred, despite the fact 
 that he was compelled to land on his feet, not on 
 a special alighting gear. 
 
 All of the facts of this wonderful flight are well 
 attested. Newspaper men who were present could 
 not find terms extravagant enough adequately to 
 praise what they witnessed. The correspondent of 
 the Scientific American, in the issue of that peri- 
 odical published on May 20, 1905, declared that 
 "An aeroplane has been constructed that in all 
 circumstances will retain its equilibrium and is sub- 
 ject in its gliding flight to the control and guidance 
 of an operator." Octave Chanute characterized 
 the flight as "the most daring feat ever attempted", 
 and Alexander Graham Bell had no hesitation in, 
 asserting that "all subsequent attempts in aviation 
 must begin with the Montgomery machine."* 
 
 * It is a fact of quite unescapable significance that recent activity 
 and present successes in aeronautics do date most definitely from the 
 public flights of the Montgomery machine in 1905. 
 
 In the June issue of Motor of that year in which magazine the 
 writer had been for some time giving space to a column on aeronautics 
 an account of the Montgomery flights and an illustrated description of 
 
140 VEHICLES OF THE AIR 
 
 While it is difficult for a trained engineer, for 
 the first time made acquainted with Montgomery's 
 work, to prevent being overwhelmed by its extent 
 and importance, it is a singular though not inex- 
 plicable fact that the general public has in no 
 measurable degree appreciated what he has accom- 
 plished. Even eye witnesses of the California 
 flights as a rule seemed to imagine that something 
 akin to a parachute jump was in progress, few 
 realizing that the one great problem of aerial navi- 
 gation from the beginning had been that of con- 
 trolled flight and maintained equilibrium, which 
 here, for the first time in history, it was their privi- 
 lege to witness.f 
 
 the Montgomery machine was published. Prior to this publication, and 
 the accounts in the Scientific American already referred to, all attempts 
 at flight, without a solitary exception that is authenticated, had been 
 marked by ever-present uncertainty as to equilibrium, constant hazard 
 to the operator, and frequent accidents ranging from minor mishaps 
 to fearful fatalities. Moreover, the longest flights with man-carrying 
 machines that are definitely substantiated up to this time were the 
 maximums of 1000 feet by Lilienthal and Ader, the 852 feet by the 
 Wrights in 1903, and the 1377-foot flight by the Wrights in 1904, wit- 
 nessed by Octave Chanute. All of these ended in damage to the 
 apparatus. Subsequent to publication and circulation of these accounts, 
 there promptly followed the experiments with motor-propelled machines 
 by Ferber in France during 1905; the fairly successful glides of Arch- 
 deacon, and of Bleriot and the Voisins, over the Seine in June and 
 July, 1905; the remarkable sustained flights of the Wright brothers 
 over Huffman Prairie, Ohio, between September 26 and October 5, 1905, 
 and the flights of Santos-Dumont, at Bagatelle, France, in August and 
 September, 1906. 
 
 From the foregoing it seems perfectly fair to state that it was Mont- 
 gomery 'a successes that gave definite and recorded beginning to the 
 now fast advancing period of man's mastery over the most elusive 
 medium in which he aspires to travel mastery absolutely comparable 
 to that of the bird, fruitlessly envied and copied, and copied and envied, 
 by earth-bound man from the fables of antiquity until March and April, 
 1905. 
 
 t It has been long recognized by all authorities on the subject 
 that the problem of propulsion is a comparatively minor matter, espe- 
 cially now that high-power and light-weight motors have been made 
 available by the development of the automobile. Moreover, Lilienthal, 
 
FIGURE 32.- Cornu Helicopter. This curious-appearing contrivance is the creation of 
 a prominent European engineer who has given years of study to this problem. The two 
 lifting propellers at aa are mounted on bicycle-like wheels and are belt-driven in opposite 
 directions from a vertical shaft. The flat surfaces 66 are for lateral control and steering. 
 
 FIGURE 33. Bertin Helicopter Aeroplane. 
 
 FIGURE 35. Henson Aeroplane of 1843. 
 
HEAVIER-THAN-AIR MACHINES 141 
 
 The history of engineering abounds in examples 
 of the struggling inventor who, having realized the 
 labor of his brain in the form of a concrete mechan- 
 ism of more or less incalculable value, is thereafter 
 accorded neither deserved recognition nor any ade- 
 quate share in the material returns from his work, 
 which is commonly seized and exploited by more 
 assertive egotisms and sturdier greeds.* 
 
 Of even greater importance than his experi- 
 mental demonstrations have been Professor Mont- 
 gomery's profound researches in aerodynamics. f 
 The son of a former assistant attorney-general of 
 the United States, he was graduated in 1879 from 
 St. Ignatius College,^ in San Francisco, with abun- 
 
 D'Esterno, and Mouillard all have expressed their conviction that indefi- 
 nite soaring flight is as positively possible as it is certain that birds 
 perform it ; Langley wrote his paper on ' ' The Internal Work of the 
 Wind" in an effort to explain this phenomenon; Chanute, in his essay 
 on "Soaring Flight", stoutly contends that we are on the verge of its 
 accomplishment; and Wilbur Wright is authority for the statement that 
 ft there is another way of flying which requires no artificial motor" and 
 which "is as well able to support a flying machine as a bird" while 
 even in the Wright patent specifications there is contemplated flight 
 "either by the application of mechanical power or by the utilization of 
 the force of gravity". 
 
 * It is a fact perhaps worthy of remark that much in the spirit and 
 methods of the times make such a condition perfectly to be expected. 
 A large proportion of the lay press and the general public, the one 
 catering to and deriving its support from the other, possess neither the 
 deliberate outlook nor the special knowledge necessary to just apprecia- 
 tion and appraisals of technical merits and values, while the average 
 institutions of higher learning, from which the inculcation of better- 
 balanced opinions might be reasonably expected, are too commonly 
 devoted to following instead of leading scientific progress, and to occupy- 
 ing the developing mind with mnemonic feats of remembering solved 
 problems instead of with the exercise of reasoning out unsolved ones. 
 
 t For details of Montgomery 's investigations and conclusions see 
 Chapter 4. 
 
 J Classmates of Professor Montgomery were James D. Phelan, 
 mayor of San Francisco, 1896-1902, and Rev. E. H. Bell, well known 
 for his researches in wireless telegraphy. 
 
142 VEHICLES OF THE AIR 
 
 dant equipment and opportunities for investiga- 
 tion of his favorite subject, to which he has devoted 
 the larger portion of his life. First attracted to 
 aeronautical problems as a boy in 1860, it was not 
 until 1883 that Montgomery built his first machine, 
 a flapping- wing contrivance of such merits that one 
 experiment was enough to convince its designer 
 that success was not to be found in this direction. 
 So, during 1884-5, he built three gliders* from the 
 first of which a glide of 600 feet was obtained and 
 the lifting value of curved surfaces (copied from 
 a sea-gull's wings) demonstrated; from the second 
 of which the futility of flat surfaces was proved ; 
 and in the third of which the lateral equilibrium 
 was maintained by wings pivoted as in the latest 
 Antoinette machines. 
 
 Besides the flight at Santa Clara, many others 
 were made, some of them presenting most remark- 
 able features and one terminating in a fatal acci- 
 dent. The full details of these are deemed of 
 sufficient importance to warrant reproduction in 
 its entirety of an article contributed by Professor 
 Montgomery to Aeronautics, and published in Jan- 
 uary, 1909. This article follows without alteration 
 except to correct typography, etc. : 
 
 "When I commenced practical demonstration in 
 my work with aeroplanes I had before me three 
 points; First, equilibrium; second, complete control; 
 and third, long continued or soaring flight. In start- 
 ing I constructed and tested three sets of models, each 
 
 * These machines are described on Pages 248 and 249 of Chanute's 
 "Progress in Flying Machines." 
 
HEAVIEE-THAN-AIR MACHINES 143 
 
 in advance of the other in regard to the continuance 
 of their soaring powers, but all equally perfect as to 
 equilibrium and control. These models were tested by 
 dropping them from a cable stretched between two 
 mountain tops, with various loads, adjustments and 
 positions. And it made no difference whether the 
 models were dropped upside down or any other con- 
 ceivable position, they always found their equilibrium 
 immediately and glided safely to earth. 
 
 "Then I constructed a large machine patterned 
 after the first model, and with the assistance of three 
 cowboy friends personally made a number of flights 
 in the steep mountains near San Juan (a hundred 
 miles distant). In making these flights I simply took 
 the aeroplane and made a running jump. These tests 
 were discontinued after I put my foot in a squirrel 
 hole in landing and hurt my leg. 
 
 "The following year I commenced the work on a 
 larger scale, by engaging aeronauts to ride my aero- 
 plane dropped from balloons. During this work I 
 used five hot-air balloons and one gas balloon, five or 
 six aeroplanes, three riders Maloney, Wilkie and De- 
 folco and had sixteen applicants on my list and had 
 a training station to prepare any when I needed them. 
 
 "Exhibitions were given in Santa Cruz, San Jose, 
 Santa Clara, Oakland, and Sacramento. The flights 
 that were made, instead of being haphazard affairs, 
 were in the order of safety and development. In the 
 first flight of an aeronaut the aeroplane was so ar- 
 ranged that the rider had little liberty of action, con- 
 sequently he could make only a limited flight. In 
 some of the first flights, the aeroplane did little more 
 than settle in the air. But as the rider gained experi- 
 ence in each successive flight I changed the adjust- 
 ments, giving him more liberty of action, so he could 
 obtain longer flights and more varied movements in 
 the flights. But in none of the flights did I have the 
 
144 VEHICLES OF THE AIR 
 
 adjustments so that the riders had full liberty, as I 
 did not consider that they had the requisite knowl- 
 edge and experience necessary for their safety; and 
 hence, none of my aeroplanes were launched so ar- 
 ranged that the rider could make adjustments neces- 
 sary for a full flight. 
 
 "This line of action caused a good deal of trouble 
 with aeronauts or riders who had unbounded confi- 
 dence and wanted to make long flights after the first 
 few trials, but I found it necessary as they seemed 
 slow in comprehending the important elements and 
 were too willing to take risks. To give them the full 
 knowledge in these matters I was was formulating 
 plans for a large starting station on the Mount Ham- 
 ilton Eange from which I could launch an aeroplane 
 capable of carrying two, one of my aeronauts and 
 myself, so I could teach him by demonstration. But 
 the disasters consequent on the great earthquake, com- 
 pletely stopped all my work on these lines.* The 
 flights that were given were only the first of the se- 
 ries with aeroplanes patterned after the first model. 
 There were no aeroplanes constructed according to 
 the two other models, as I had not given the full dem- 
 onstration of the workings of the first, though some 
 remarkable and startling work was done. On one 
 occasion, Maloney in trying to make a very short turn 
 during rapid flight pressed very hard on the stirrup 
 which gives a screw shape to the wings and made a 
 side somersault. The course of the machine ivas 
 very much like one turn of a corkscrew. After this 
 movement, the machine continued on its regular 
 course. And afterwards Wilkie, not to be outdone by 
 Maloney, told his friends he would do the same, and 
 in a subsequent flight, made two side somersaults, one 
 
 * At the present writing arrangements are under way and capital 
 is to be interested for the resumption of the Montgomery experiments. 
 
EEAVIER-THAN-AIR MACHINES 145 
 
 in one direction and the other in an opposite,* then 
 made a deep dive and a long glide, and, when about 
 three hundred feet in the air, brought the aeroplane 
 to a sudden stop and settled to the earth. After these 
 antics, I decreased the extent of the possible change 
 in the form of wing surface so as to allow only 
 straight sailing or only long curves in turning. 
 
 "During my work I had a few capping critics that 
 I silenced by this standing offer: If they would de- 
 posit a thousand dollars I would cover it on this prop- 
 osition. I would fasten a 150-pound sack of sand in 
 the rider's seat, make the necessary adjustments, and 
 send up an aeroplane upside down with a balloon, the 
 aeroplane to be liberated by a time fuse. If the aero- 
 plane did not immediately right itself, make a flight, 
 and come safely to the ground, the money was theirs. 
 
 "Now a word in regard to the fatal accident.* 
 The circumstances are these : The ascension was given 
 to entertain a military company in which were many 
 of Maloney's friends, and he had told them he would 
 give the most sensational flight they ever heard of. 
 As the balloon was rising with the aeroplane, a guy 
 rope dropping switched around the right wing and 
 broke the tower that braced the two rear wings and 
 which also gave control over the tail.* We shouted 
 Maloney that the machine was broken but he prob- 
 ably did not hear us, as he was at the same time say- 
 ing ' Hurrah for Montgomery's airship', and as the 
 break was behind him, he may not have detected it. 
 Now did he know of the breakage or not, and if he 
 knew of it did he take a risk so as not to disappoint 
 his friends? At all events, when the machine started 
 
 * These performances were witnessed by thousands of people. The 
 italics are ours. [Ed.] 
 
 tOn July 18, 1905. 
 
 $ Marked m in Figure 225. 
 
146 VEHICLES OF THE AIR 
 
 on its flight the rear wings commenced to flap (thus 
 indicating they were loose), the machine turned on 
 its back, and settled a little faster than a parachute. 
 When we reached Maloney he was unconscious and 
 lived only thirty minutes. The only mark of any kind 
 on him was a scratch from a wire on the side of his 
 neck. The six attending physicians were puzzled at 
 the cause of his death. This is remarkable for a verti- 
 cal descent of over 2,000 feet." 
 
 In view of the extensive appropriation and 
 utilization by others of ideas originated by him, it 
 must be a source of considerable satisfaction to 
 Professor Montgomery that he holds a United 
 States patent (see Figure 260) broadly covering 
 the combination of "wing warping" with curved 
 surfaces* the only sort that have ever flown. 
 
 A. PENAUD 
 
 An uncommonly ingenious inventor of areo- 
 nautical devices was A. Penaud, who began before 
 he was twenty by devising the toy helicopter re- 
 ferred to on Page 127, and subsequently made the 
 successful toy ornithopter mentioned on Page 120. 
 But his most important contribution to the art was 
 a half -ounce model aeroplane, 18 inches wide and 
 20 inches long, closely resembling the modern 
 Bleriot monoplanes and embodying a remarkable 
 
 * In the opinion of several prominent patent attorneys, there is no 
 conflict between this patent and the earlier one issued to the Wright 
 brothers, for the combination of "normally-flat aeroplanes" (see Page 
 000) with a type of "wing warping" substantially proposed by Le Bris, 
 D 'Esterno, and Mouillard, and tested, if at all, in devices that have been 
 proved inoperative. But in all of the Wright machines that have flown, 
 and in most other successful modern machines, there appears the com- 
 bination of curved surfaces with "wing warping" a direct infringe- 
 ment of the Montgomery patent. 
 
HEAVIER-THAN-AIR MACHINES 147 
 
 system of automatic longitudinal stability. Pro- 
 pelled by twisted rubber bands, this model made 
 both straight and circular flights up to a maximum 
 length of 131 feet, at a speed of over 8 miles an 
 hour. Subsequently Penaud was associated with 
 a mechanician named Gauchot in a plan to build 
 a monoplane large enough to carry two men. This 
 machine was to have weighed 2640 pounds and have 
 a sustaining area of 634 square feet. It was esti- 
 mated that with 20 or 30 horsepower applied 
 through twin tractor screws flight could be accom- 
 plished with an angle of incidence of 2, at a speed 
 of 60 miles an hour. It was planned to experiment 
 over water to reduce the danger, but, a motor of 
 the necessary lightness not being found, an'd the 
 inventor being tormented by misrepresentation and 
 an incurable hip disease, from which he died in 
 October, 1880, before he had reached his thirtieth 
 year, nothing came of a project that possessed at 
 least the merit of being planned by one of the most 
 able men who ever gave his attention to the subject. 
 
 PERCY S. PILCHEB 
 
 Another who began experiments in his early 
 youth was the English engineer Pilcher, whose 
 interest in aeronautics dated from 1882, when he 
 was aged 15, and who in 1892 commenced the con- 
 struction of his first glider, closely similar to those 
 of Lilienthal. In all he built five machines, the 
 first of which had such pronouncedly dihedral 
 wings that it promptly proved the futility of seek- 
 ing balance by a low placing of the weight. His 
 
148 VEHICLES OF THE AIR 
 
 final and most successful type, the "Hawk" (see 
 Figures 233 and 234), was provided with small 
 bicycle wheels, had lightly-curved wing surfaces, 
 and was planned to sustain a total weight of about 
 250 pounds including a 2-horsepower oil engine 
 on an area of 188 square feet. With this machine 
 he made one glide of 800 feet across a valley towed 
 at 11 miles an hour by a light cord, which was 
 pulled kitewise by a cord drawn by running boys 
 through a five-fold multiplying gear with a tractive 
 effort that at the machine measured 30 pounds. 
 Drawings for the necessary engine were then made 
 and study of the problem of equilibrium continued 
 until a headlong plunge from a height of not over 
 40 feet, caused by the snapping of rudder guy, 
 resulted in his death on October 1, 1899, in his 
 thirty-third year. 
 
 ALBERTO SANTOS-DUMONT 
 
 To Santos-Dumont, besides much activity in the 
 development of the dirigible balloon (see Page 82), 
 is due the credit for the first public and successful 
 flight in a power-driven aeroplane in Europe, on 
 August 22, 1906. Following this he has been a 
 most daring and indefatigable worker, fortunate 
 in the possession of both considerable ability and 
 abundant means. The result up to the present time 
 has been the evolution of one of the lightest and 
 most successful monoplanes in existence (see Fig- 
 ure 221), which with characteristic unselfishness its 
 designer has placed on the market at cost, and re- 
 frained from protecting its construction by patents. 
 
HEAVIER-THAN-AIR MACHINES 149 
 
 F. H. WENHAM 
 
 Mr. F. H. Wenham, who died so recently as 
 August 11, 1908, was unquestionably the originator 
 of the biplane and other superimposed multisurf ace 
 constructions, which were subsequently developed 
 by Hargrave into the box kite, and which are so 
 conspicuous a feature of many modern aeroplane 
 designs. This construction he patented in England 
 in 1866, in which year he also presented the idea in 
 a paper read at the first meeting of the Aeronau- 
 tical Society of Great Britain.* Despite the merits 
 of the idea, and its subsequent successful utilization 
 by many inventors, no practical application of the 
 construction ever was made by its originator. 
 
 WILBUR AND ORVILLE WEIGHT 
 
 Commencing in 1900, Wilbur and Orville 
 Wright, two bicycle repairmen of Dayton, Ohio, 
 and the sons of Bishop Wright of that city, began 
 devoting a large portion of their time to the serious 
 development of such previous aeronautical knowl- 
 edge as they found available, their first interest in 
 the subject having been awakened by flying toys 
 years before, and a fresh impetus having been 
 given it by the death of Lilienthal, which directed 
 attention to his work, in 1896. Proceeding with 
 
 * In this paper, which has become a classic on the subject, the most 
 interesting portion is as follows: " Having remarked how thin a 
 stratum is displaced beneath the wings of a bird in rapid flight, it fol- 
 lows that, in order to obtain the necessary length of plane for supporting 
 heavy weights, the surfaces may be superposed, or placed in parallel rows, 
 with an interval between them. A dozen pelicans may fly one above the 
 other without material impediment; as if framed together; and it is 
 thus shown how two hundredweight may be supported in a transverse 
 distance of only ten feet.' 7 
 
150 VEHICLES OF THE AIR 
 
 the sound idea that actual pactice in the air was the 
 surest road to success, an idea that had been fully 
 appreciated but little realized by others, the 
 Wrights levied upon every possible source of infor- 
 mation and, frankly commencing with a modifica- 
 tion of Chanute's biplane glider, which they re- 
 garded as the most advanced construction existent 
 at the time, they entered upon a deliberate, unre- 
 mitting, and enthusiastic prosecution of an at first 
 thankless task, which for sturdy perseverance in 
 the face of obstacles and sensible disregard of 
 ignorant opinions, has few parallels in the history 
 of invention. 
 
 Having from the outset more faith in experi- 
 mental than in analytical methods, the Wrights set 
 themselves first to the task of confirming or cor- 
 recting the various formulas of their predecessors 
 concerning wind pressures, the sustaining effects of 
 different inclined surfaces, etc. Progressing from 
 these to the various possible methods of steering, 
 and of maintaining lateral and longitudinal bal- 
 ance, they tirelessly tested a constantly improving 
 series of constructions by hundreds of kite and 
 gliding experiments conducted among the sand 
 dunes near Kitty Hawk, North Carolina. Having 
 thus secured an amount of practice that enabled 
 them to make reasonably safe gliding flights of 
 considerable length in calms and moderate winds, 
 they next undertook the application of a motor, 
 naturally turning to automobile mechanism as the 
 most promising source of a suitable power plant. 
 
HEAVIER-THAN-AIR MACHINES 151 
 
 This resulted, on December 17, 1903, in four flights 
 in calm air with a gasoline engine, the longest of 
 which, however, was of only 852 feet shorter than 
 many of Lilienthal's glides prior to 1896, hardly 
 a fourth as long as the flight of Langley's model 
 on May 6, 1896, and not quite as long as the flight 
 of Ader with his " Avion", on October 14, 1897. 
 On March 23, 1903, a United States patent was 
 applied for on a wing- warping device, in combina- 
 tion with flat sustaining surface, indicating failure 
 at this time to appreciate fully the absolute impor- 
 tance of definitely and correctly curved surfaces. 
 The construction described in the patent specifica- 
 tions (see Figure 259) being obviously inoperative, 
 they were repeatedly objected to and rejected by 
 the patent-office examiners, and it was not until 
 May 22, 1906, that their claims were allowed even 
 then on the basis of an inoperative construction. 
 Throughout 1904 the Wright experiments con- 
 tinued, surrounded by the utmost secrecy, but it 
 is definitely attested by Chanute that during this 
 year they increased the length of their longest 
 flight to 1,377 feet. 
 
 It was not until nearly the end of September, 
 1905, months after Montgomery's flights in the 
 Santa Clara Valley and publication of his con- 
 struction, and some time after his patent was is- 
 sued, that the Wrights commenced to be conspicu- 
 ously successful with parabolically-curved sus- 
 taining surfaces and a system of wing-warping 
 closely resembling that of Montgomery's patent 
 
152 VEHICLES OF THE AIR 
 
 and not at all like that claimed in the Wright 
 patent (see Figure 260). Following these successes, 
 which though well authenticated were kept out of 
 the newspapers and well away from the general 
 public, vigorous but quiet efforts were made during 
 1906 and 1907 to sell to European governments, not 
 patent rights, but ' ' secrets ' ' of construction. Little 
 success resulting, because of the terms and condi- 
 tions that were stipulated, and European aviators 
 having by this time progressed to the point of mak- 
 ing long flights, this policy was abandoned late in 
 1908, and the Wrights came out into the open with 
 their machines Orville Wright in the United 
 States and Wilbur Wright in France with the re- 
 sult that they were quickly able to establish new 
 distance and duration records, which stood for 
 nearly a year. At the present time, however, the 
 Wright machine does not hold a single distance, 
 duration, speed, weight-carrying, cross-country, or 
 altitude record in the world, and has borne out the 
 rather numerous critics of its construction by being 
 responsible for two of the only three fatal accidents 
 that have occurred in the history of power-pro- 
 pelled heavier-than-air machines. 
 
 Probably the greatest credit due the Wrights is 
 for their well-thought-out development of runner 
 alighting gears, and their exceedingly simple, 
 ingenious, and effective means of securing the 
 necessary starting acceleration in the shortest pos- 
 sible distance by means of a dropped weight (see 
 Figure 165). For details of the Wright construc- 
 tions see Chapter 12. 
 
HEAVIER-THAN-AIR MACHINES 153 
 
 VOISIN BROTHERS 
 
 In the course of the early Bleriot and Arch- 
 deacon experiments over the Seine with towed and 
 free gliders during 1904, much of the most success- 
 ful construction and designing work was done- by 
 Gabriel Voisin, a young French engineer who sub- 
 sequently, in association with his brother, of the 
 firm now known as Voisin Freres, and of their 
 engineer, M. Colliex, designed the excellent ma- 
 chines of box-kite type with which Farman and 
 Delagrange electrified the world by their flights in 
 the latter part of 1907 and the forepart of 1908. 
 The Voisin machines, which, 
 while not without serious short- 
 comings, possess a considerable 
 degree of automatic stability, are 
 the prototypes of the highly suc- 
 cessful Farman machine. Ee- 
 cently their standard construc- 
 tion has been rather radically FIGDRE 34 _ Box KIte 
 modified by removal of the for- 
 ward elevator and the substitution of a horizontal 
 rudder in the cellular tail, in conjunction with a 
 discarding of the rear propellor in favor of the 
 more approved tractor propellor in front of the 
 main planes. See Chapter 12 and Figures 172, 
 203, 204, and 205 for details. 
 
 MISCELLANEOUS 
 
 In addition to the foregoing, those among the 
 world's aeroplane designers who are most worthy 
 of mention are Alexander Graham Bell, inventor 
 
154 VEHICLES OF THE AIR 
 
 of the telephone and founder of the Aerial Experi- 
 ment Association, and whose tetrahedral kite is a 
 construction of great originality and interest ; S. F. 
 Cody, designer of one of the most successful man- 
 lifting kites, and whose biplane (see Figure 202) is 
 the largest and one of the most successful aero- 
 planes that has ever flown ; Glenn H. Curtiss, whose 
 flights with the "June Bug" and "Silver Dart" 
 of the Aerial Experiment, and with subsequent 
 machines of his own, entitle him to front rank 
 among aviators; Danjard, who in 1871 designed 
 what was perhaps the first double monoplane, which 
 proved unsuccessful chiefly because of the lack of 
 a suitable motor; Count D'Esterno, who in 1864 
 wrote a remarkable pamphlet in which he suggested 
 a form of wing warping and proposed other de- 
 tails since proved of practical value, though he 
 died in 1883, before the completion of a machine 
 that was then under construction ; Robert Esnault 
 Pelterie, the young French engineer whose first 
 work began some years ago and whose speedy and 
 ingenious monoplane is regarded as one of the 
 most successful and promising of present machines, 
 besides which it has sustained the highest weight 
 per unit of area of any machine yet flown success- 
 fully ; Henry Farman, whose early flights with the 
 Voisin machines and his subsequent development 
 of this type into the first aeroplane employing both 
 wheels and runners in the starting and alighting 
 gear, and the first to fly over 100 miles, have defi- 
 nitely contributed to progress ; Captain Ferdinand 
 
HEAVIER-THAN-AIR MACHINES 155 
 
 Ferber, of the French army, who ranks equally 
 high as a pioneer worker, as an authority on both 
 heavier-than-air and lighter-than-air craft, and as 
 a writer on the subject of aeronautics, and whose 
 tragic death a short time ago is one of the heaviest 
 tolls yet exacted for aeronautical advancement; 
 Laurence Hargrave, whose invention of the box 
 kite and wonderful work with ornithopter propul- 
 sion have in a measure overshadowed his discov- 
 eries concerning the aeroplane proper; Henson, 
 whose immense, 3000-pound aeroplane built in 1842 
 (see Figure 35), embodied a large proportion of 
 the features since proved needful, and turned out 
 a failure more because it was too much in advance 
 of its time than for any other single reason ; A. M. 
 Herring, whose early association with Chanute and 
 present association with 
 Curtiss at least entitles 
 him to recognition; Cap- 
 tain Le Bris, whose re- 
 
 ' FIGURE 36. Le Bris' Glider. 
 
 puted astounding night 
 
 in France with a wing-warped machine in 1867 
 almost staggers belief (the Le Bris glider is illus- 
 trated in Figure 36); M. Levavasseur, whose 
 Antoinette monoplanes are among the finest 
 present-day fliers and are certainly the most 
 graceful, and whose fuel-injection motors have 
 been used to a greater or less extent in nearly 
 every modern European aeroplane of demonstrated 
 quality; Linfield, who in 1878 conceived the in- 
 genious plan of testing the lift of an aeroplane by 
 
156 
 
 VEHICLES OF THE AIR 
 
 hauling it on a railway flat car, and thus caused it 
 to rise clear though without contributing any- 
 thing to the solution of equilibrium ; Michael Loup, 
 who in 1852 had fully developed the wheeled start- 
 ing gear; Hiram S. Maxim, whose exhaustive and 
 expensive experiments in 1894 gave definite solu- 
 tion of the power and lifting problems, though they 
 were of little help to seekers after efficiency and 
 equilibrium; Louis Pierre Mouillard, whose 
 
 FIGURE 37. Moy's Aerial Steamer. Tested on a track in the Crystal 
 Palace, London, in June, 1875. Six-foot propellers. Steam engine, 2%x3-inch 
 cylinder, developing three horsepower at 550 revolutions a minute. Engine 
 weighed 80 pounds, with boiler. Car ran on three small wheels. Speed of 
 12 miles an hour proved insufficient to lift. 
 
 "L 'Empire de PAir", published in 1881, is one of 
 the great classics of aeronautical literature, whose 
 glidings flights in Egypt are not without interest, 
 and whose United States patent (see Figure 262) 
 shows a tolerably clear appreciation of one type of 
 wing warping; Thomas Moy, who in 1875 got 12 
 miles an hour on the ground by the thrust of the 
 
HEAVIER-THAN-AIR MACHINES 157 
 
 propellers of his " aerial steamer" (see Figure 37) ; 
 Horatio Phillips, who in the years from 1884 to 
 1891 by empirical methods went more deeply into 
 the question of correct wing sections than any pre- 
 vious investigator and then produced slat-like 
 multiplane models of extraordinary lifting capaci- 
 ties ; Stringf ellow, who in 1868 built the first tri- 
 plane (a model) and afterwards produced a steam- 
 engine that developed one horsepower within 13 
 pounds of weight, achievements that he was follow- 
 ing up by the construction of a man-carrying ma- 
 chine, which was left unfinished at his death in 
 1883; Victor Tatin, who made in 1879 the first 
 model aeroplane that lifted itself by a run on the 
 ground, and who at a recent date was working on 
 a modern aeroplane for the Clement-Bayard con- 
 cern, in France; and Vuia, who in 1906 designed 
 one of the earliest of the really modern monoplanes, 
 and accomplished a few very short flights towards 
 the end of this year and during 1907. 
 
CHAPTER FOUE 
 
 AEROPLANE DETAILS 
 
 Passing from the contemplation of the broader 
 possibilities and problems of human flight to con- 
 sideration of the means by which such flight is to 
 be accomplished is necessarily a transition from 
 the general to the particular. 
 
 Aeroplanes, for example, are vehicles involving 
 sustaining surfaces of suitable form, provided 
 with means for propulsion, for the maintenance 
 of equilibrium, and for steering in different lateral 
 and vertical directions. Evidently the provision 
 of these different elements can be carried out in 
 a great variety of ways, which being the case it 
 is possible to work towards the more perfect de- 
 signs only by two policies one requiring study 
 of the laws involved in flight and the application 
 of these laws in suitable mechanisms, and the other 
 involving observation and copying of the flying 
 mechanisms of nature. Both of these policies are 
 beset by tremendous difficulties the first because 
 of the exceedingly complex factors of the problem, 
 and the second because there is no bird that 
 approaches in size or weight the smallest man- 
 carrying vehicle. 
 
 158 
 
FIGURE 69. Goupy Biplane. In this the placing of the surface v in advance of the 
 surface w is intended to cause the air-currents to meet the surfaces in such a manner as to 
 secure greater lift from the upper surface than is secured in biplanes in which it is placed 
 farther back. That flatness of the surfaces is quite erroneous, though perhaps not the only 
 reason the machine failed as a flier. 
 
 FIGURE 71. Internal Framing of Antoinette Monoplane Wing. 
 
 
 FIGURE 72. Framing of Antoinette Wing Inverted. The load is supported on the two 
 main girders aa, which are connected by a maze of crossbraces to the transverse ribs and 
 secondary longitudinal members. 
 
AEROPLANE DETAILS 159 
 
 ANALOGIES IN NATUKE 
 
 Besides constituting the most conclusive evi- 
 dence imaginable of the perfect practicability of 
 flight, as well as serving as the original and a con- 
 stant stimulus to man in his efforts to achieve navi- 
 gation of the air, the birds and other animals that 
 fly afford models that naturally merit the most 
 thorough and profound consideration of all 
 students of aerodynamics. Eor in nature's 
 mechanisms of flight must exist answers to all the 
 problems of flying, awaiting for their discovery 
 only the analyses and applications of sufficiently 
 persevering and painstaking investigators. 
 
 From the facts of animal flight there are cer- 
 tain broad deductions to be made at the outset. 
 Perhaps the most impressive of these is the evident 
 fact that there is more than one way and more 
 than one type of mechanism that can be made to 
 serve the purpose. There are the common flap- 
 ping flight, the less-common soaring flight, and 
 the flight of the wing-case insects, while in the 
 way of structural variety it is a broad range from 
 the tissues of insect wings, the furred skin folds 
 of the flying squirrel, and the membranous integu- 
 ments of the flying fishes, bats, etc., to the feath- 
 ered perfection of the wing of a humming bird or 
 condor. 
 
 The size of flying animals also is a point of 
 interest. Perhaps the heaviest of the soaring 
 fliers is the California vulture, similar to but in its 
 largest specimens larger than the largest speci- 
 
160 VEHICLES OF THE AIR 
 
 mens of the Andean condor, and not uncommonly 
 weighing as much as 20 pounds. Turkeys are said 
 sometimes to weigh twice this, while the albatross 
 is occasionally found of a weight of 18 pounds. 
 Still heavier than these may have been the extinct 
 pterodactyl, which it is more than probable, how- 
 ever, weighed no more than 30 pounds. No flying 
 creature that ever existed appears to have been as 
 heavy as the combination of a man with the lightest 
 structure that can be made to support him, and 
 this fact often has been cited as an argument 
 against the possibility of human flight, having been 
 advanced as conclusive by no less an authority 
 than the late Simon Newcomb. But in this con- 
 nection it is a significant fact that the areas and 
 the power required to support a given weight 
 steadily increase in passing from the larger flying 
 animals to the smaller. This point, so favorable 
 in its bearings on the problems of human flight, is 
 not wholly due to any single cause, though prob- 
 ably the main factors are the effect noted on Page 
 184, and the escape of air around the edges of wing 
 surfaces such edges being necessarily longest in 
 proportion to the area in the smaller sizes, it being 
 a geometrical axiom that the length of boundary 
 of any given shape of surface increases in direct 
 ratio with increases in linear dimensions whereas 
 areas increase with the square of these dimensions. 
 Thus a square one by one, equalling one square 
 unit of area, has four linear units of edge one 
 foot to each one-fourth of a square unit of area, 
 whereas a square two by two, affording four square 
 
AEROPLANE DETAILS 161 
 
 units of area, has only eight linear units of edge 
 one to each one-half of a square unit of area. 
 
 The weights, weight supported per unit of wing 
 area, horsepower, pounds supported per unit of 
 area, and pounds supported per horsepower, in 
 the cases of different flying creatures and success- 
 ful aeroplanes, are given in tabular form on the 
 next page. 
 
 FLYING FISH 
 
 Flying fish, which are found in all the warmer 
 seas, are capable of maximum flights of only a few 
 hundred yards usually at a height of not over 
 fifteen feet by a method of progression that is 
 decidedly peculiar and, in some respects, suffi- 
 ciently mysterious to lead to controversy amongst 
 different observers. It is 
 generally supposed that 
 the flight is of the true 
 gliding type, dependent 
 altogether upon the force 
 of the initial impulse of FIGURE as. Flying Fish, 
 the tail in the rush out of 
 
 the water when these creatures are pursued by any 
 of their numerous enemies, but there are not lack- 
 ing those who stoutly assert that there is on occa- 
 sion a true flapping flight. This has been explained 
 by others as a fluttering of the great pectoral fins 
 into successive wave crests, to keep the membranes 
 from drying in long flights. It is also commonly 
 stated that flying fish go much farther against the 
 wind than with it which if true at once involves 
 the difficult and little understood phenomena of 
 
TABULAR COMPARISON OF FLYING ANIMALS AND AEROPLANES. 
 
 
 Weight 
 (in pounds) 
 
 Wing Area 
 (square feet) 
 
 21 
 
 &l 
 
 Pounds to 
 Square Foot 
 
 Pounds per 
 Horsepower | 
 
 *Cabbage Butterfly 
 
 000169 
 
 00942 
 
 
 0179 
 
 
 
 .0000006 
 
 00003 
 
 
 
 0204 
 
 . . . . 
 
 *Maiden Dragon Fly. . 
 
 000423 
 
 01415 
 
 ..... 
 
 0298 
 
 
 
 Swallow-Tailed Butterfly .... 
 
 000718 
 
 01137 
 
 
 0631 
 
 . . . . 
 
 Flat-Bellied Dragon Fly 
 
 .00128 
 
 0135 
 
 ..... 
 
 0948 
 
 * * * 
 
 House Fly 
 
 000021 
 
 000183 
 
 ..... 
 
 1147 
 
 . . 
 
 Small Bat ... 
 
 0078 
 
 0507 
 
 
 153 
 
 . . . . 
 
 
 
 
 
 .195 
 
 
 
 
 
 
 
 
 Sphinx Moth 
 
 00405 
 
 01892 
 
 
 2140 
 
 
 Stag Beetle (male) 
 
 
 
 
 .266 
 
 
 
 
 
 
 318 
 
 
 
 038 
 
 1116 
 
 
 349 
 
 
 Honev Bee . 
 
 000156 
 
 000396 
 
 
 
 3939 
 
 .... 
 
 
 
 
 
 .424 
 
 . . 
 
 Short-Eared Owl 
 
 
 
 
 .446 
 
 
 Swift 
 
 .0708 
 
 1462 
 
 
 484 
 
 
 
 
 
 .... 
 
 535 
 
 . . . . 
 
 Humming Bird . .. . 
 
 015 
 
 9 6 
 
 001 
 
 577 
 
 15 
 
 Langley Double Monoplane. . . . 
 *Laughing Gull 
 
 30. 
 
 52. 
 
 1.5 
 
 .577 
 .62 
 
 20 
 
 
 
 
 
 649 
 
 
 Sparrow ... 
 
 059 
 
 0791 
 
 
 747 
 
 
 Pilcher Glider (the "Gull") 
 
 
 
 
 .75 
 
 ... 
 
 Goshawk 
 
 
 
 
 .763 
 
 
 * Sparrow Hawk 
 
 549 
 
 69 
 
 
 79 
 
 
 Bumble Bee 
 
 00093 
 
 00104 
 
 ...... 
 
 8942 
 
 .... 
 
 *Herring Gull .... 
 
 2 18 
 
 2 41 
 
 ...... 
 
 9 
 
 . . 
 
 Fishhawk 
 
 
 
 
 .926 
 
 .... 
 
 Crow 
 
 1.25 
 
 1 3 
 
 
 96 
 
 
 
 .619 
 
 .617 ' 
 
 
 1 
 
 .... 
 
 
 4 78 
 
 4 57 
 
 
 1 04 
 
 ... 
 
 * Scavenger Vulture 
 
 
 
 ...... 
 
 1.052 
 
 .... 
 
 
 
 
 
 1 052 
 
 
 *White Pelican 
 
 
 
 
 1 052 
 
 
 Montgomery Monoplane Glider. . 
 Thrush 
 
 200. 
 .211 
 
 185. 
 188 
 
 
 
 1.08 
 1 12 
 
 
 Lilienthal Biplane Glider 
 
 200 
 
 170 
 
 .... 
 
 1 18 
 
 
 *Pterodactyl . ... 
 
 30 
 
 25 
 
 036 
 
 1 2 
 
 f833 
 
 Wright Biplane Glider . 
 
 238 
 
 90 
 
 
 1 22 
 
 
 Wright Biplane Glider 
 
 210 
 
 160 
 
 
 
 1 31 
 
 .... 
 
 *Sea Eagle 
 
 10 57 
 
 805 
 
 
 1 31 
 
 
 Pilcher Glider (the "Hawk") . . 
 Pigeon .... 
 
 215. 
 1 
 
 165. 
 
 7 
 
 6i2 
 
 1.33 
 1 429 
 
 ' '83 
 
 *Griffon Vulture .... 
 
 
 
 
 1 456 
 
 
 *Eared Vulture 
 
 
 
 
 1 456 
 
 
 Curtiss Biplane 
 
 550. 
 
 350. 
 
 25. 
 
 1 57 
 
 16 
 
 
 17 
 
 9 85 
 
 043 
 
 1 726 
 
 1 395 
 
 *Flying Fox . ... 
 
 2 91 
 
 1 65 
 
 
 1 76 
 
 
 *Flamingo 
 
 
 
 
 1 818 
 
 
 Voisin Biplane 
 
 1150. 
 
 597. 
 
 50. 
 
 1 93 
 
 23 
 
 Farman Biplane 
 
 800. 
 
 410. 
 
 45. 
 
 1.95 
 
 17 
 
 Partridge 
 
 67 
 
 34 
 
 
 1 97 
 
 
 Wright Biplane . 
 
 1200. 
 
 560 
 
 25 
 
 2 04 
 
 48 
 
 Cody Biplane 
 
 2000. 
 
 950. 
 
 80. 
 
 2 1 
 
 25 
 
 Lilienthal Monoplane Glider. . . 
 
 180. 
 730 
 
 85. 
 324 
 
 50 
 
 2.11 
 2 ^5 
 
 ' is 
 
 Pheasant 
 
 2 11 
 
 .89 
 
 
 2 37 
 
 
 "Wright Biplane 
 
 1200. 
 
 450. 
 
 28. 
 
 2.66 
 
 43 
 
 Voisin Biplane 
 
 1540. 
 
 537. 
 
 50. 
 
 2.86 
 
 31 
 
 Antoinette Monoplane 
 
 1110. 
 
 370. 
 
 50. 
 
 3. 
 
 22 
 
 *Albatross 
 
 25 36 
 
 8 12 
 
 
 3 12 
 
 
 Bustard 
 
 20 29 
 
 6.02 
 
 
 3.36 
 
 
 Wild Goose 
 
 9. 
 
 2.65 
 
 .026 
 
 3.396 
 
 t346 
 
 Santos-Dumont Monoplane .... 
 Bleriot Monoplane No. 11 
 Bleriot Monoplane No 12 
 
 400. 
 715. 
 1100. 
 
 115. 
 150. 
 216. 
 
 35. 
 22. 
 30. 
 
 3.47 
 4.76 
 5.1 
 
 11 
 33 
 36 
 
 R. E. P. Monoolane. . 
 
 933. 
 
 168. 
 
 30. 
 
 5.55 
 
 31 
 
 * Soaring Fliers. fNote the great efficiency of the bird mechanism. 
 
AEROPLANE DETAILS 163 
 
 soaring flight. An exceedingly interesting fact 
 about flying fish is that they present the only 
 examples in nature's fliers of the use of vertical 
 surfaces-*-presumably to afford automatic lateral 
 stability (see Page 209). The largest flying fish 
 are about 18 inches long (see Figure 38). 
 
 FLYING LIZARDS 
 
 The Malayan gecko, or u flying dragon", is a 
 curious creature the habits of which are little 
 known. It is provided with loose membranous 
 expansions along the sides of the body which are 
 supposed to enable it to make long gliding leaps, 
 like those of the flying squirrels. A commoner 
 lizard of East India has loose folds of skin that 
 are distensible by several movable ribs. Neither 
 of these animals attains a length of more than 
 eight inches. 
 
 FLYING SQUIRRELS. 
 
 The common flying squirrel is a very small 
 nocturnal species with a feather-like tail and folds 
 of skin on either side capable of being stretched 
 out and controlled in such manner by the legs that 
 60-foot glides from treetops are made in safety. 
 There are much larger but less known species in 
 California and Alaska that undoubtedly can glide 
 from trees 200 feet high. 
 
 FLYING LEMUR 
 
 The flying lemur, the "colugo" of the East 
 Indies, has a very loose skin with peculiarly sleek 
 fur, enabling it to make long sailing leaps like the 
 
164 
 
 VEHICLES OF THE AIR 
 
 flying squirrel. It is a slender creature 18 inches 
 long, and is much the largest and heaviest of the 
 several animals that glide in this manner. 
 
 FLYING FROG 
 
 An animal of which there has been little if any 
 accurate observation is the flying frog a Malayan 
 
 tree- dwelling frog 
 that is supposed to 
 sail down from the 
 tree tops in long slant- 
 ing flights. Its feet 
 are very large and 
 webbed between the 
 toes (see Figure 39). 
 It is peculiarly inter- 
 esting as a perfect ex- 
 ample of correct meth- 
 o d s of maintaining 
 
 lateral and longitudinal balance by the manipula- 
 tion of a plurality of separated surfaces (see Page 
 000). 
 
 SOARING BIRDS 
 
 The phenomena of soaring flight has long been 
 a mystery to students of the subject, having baf- 
 fled the most eminent physicists in attempts to 
 explain it and defied the most painstaking observ- 
 ers to disprove its existence. For these reasons 
 the effortless travel of the soaring birds, the 
 largest and practically the heaviest of all flying 
 creatures, is regarded as the ultimate achievement 
 in aerial navigation to be attained by man, if at 
 
 FIGURE 39. Flying Frog. Without 
 being confirmed by observation, it never- 
 theless appears obvious that this curious 
 creature can maintain its lateral and 
 longitudinal balance only by differential 
 tilting of the side pairs of feet in the 
 first case and of the front and rear pairs 
 in the second. 
 
FIGURE 73.- Frame of Bleriot Monoplane Wing. In this wing the longitudinal supporting 
 members are five in number, with cross bracing and curved ribs similar to those used in the 
 Antoinette machine. The curvature is given to the ribs simply by straining them into place 
 as the structure is put together, there being no preliminary bending. 
 
 FIGURE 74. Inverted Upper Wing Frame of Wright Biplane. This frame is inverted 
 on supports for the convenience of men working upon it. It is to be noted that each rib is 
 made of two light strips 66, which are spaced apart by the wing bars aa and by the small 
 spacing members dd. The rib in the foreground is made solid because it forms the end of 
 a section of the wing, which attaches to an adjacent section by the small clamping plates 
 on the ends or the wing bars. 
 
AEROPLANE DETAILS 165 
 
 all, only upon a complete and perfect understand- 
 ing of laws that neither fit into nor follow from 
 many of the accepted conceptions of force and 
 motion (see Page 169). In the table on Page 162 
 the soaring birds are designated with stars *. 
 The most conspicuous features to be discerned in 
 a study of soaring-bird forms are the usually ex- 
 treme length and narrowness of the wings, the 
 lower sustention per unit of area than prevails 
 with flapping fliers, and a pronouncedly different 
 type of curvature to the wing sections. 
 
 SOAEING BATS 
 
 Most of the bats are flapping fliers, but the 
 " flying fox", or "kalong", of Java, which is one 
 of the largest of its kind, sometimes measuring 5 
 feet from tip to tip, practises true soaring flight. 
 This fact is of interest chiefly in that it refutes the 
 assertions of the few theorists who contend that 
 soaring flight requires for its accomplishment a 
 supposed imperceptible movement of feathers. 
 
 THE PTEEODACTYL 
 
 This bird-like reptile, which is known only 
 from the discovery of fossil remains in strata of 
 the Cretaceons period (see Figure 40), measures 
 in ordinary specimens about 20 feet from tip to 
 tip. It must have been, however, very light, the 
 wing bones that have been found being mere shell- 
 like tubes of large diameter and extreme thinness. 
 The fact that there once existed a larger flying 
 animal ttian any now extant has been held to prove 
 
166 
 
 VEHICLES OF THE AIR 
 
 FIGURE 40. Comparison of Pterodactyl and Condor. The extinct pterodactyl, 
 a great flying reptile the fossilized remains of which have been found in 
 strata of the Cretaceous period, is the largest flying creature of which we 
 have any knowledge. Its wing spread was 20 feet, but its maximum weight 
 was possibly not over 30 pounds. 
 
 a greater density to the earth's atmosphere in pre- 
 historic times, but this theory is neither necessary 
 as an explanation nor borne out in the evidence. 
 
 FLYING INSECTS 
 
 It is surprising how generally students of flight 
 have overlooked that fact that in certain insects 
 there seems to be an exceedingly close parallel to 
 
 modern aeroplane construc- 
 tions, in which there ap- 
 pears primarily a sustain- 
 ing surface moved through 
 the air at an angle of inci- 
 dence and secondarily a 
 FIGURE 4i.-wing-c as e insect. se p arate prO pelling ele- 
 ment. This combination is peculiar to insects with 
 wing cases," of the order coleoptera, in which 
 
 " 
 
AEROPLANE DETAILS 167 
 
 during flight the wing covers are rigidly extended 
 at right angles to the line of movement, while the 
 under wings are rapidly vibrated to produce pro- 
 pulsion, as is suggested in Figure 41. The largest 
 known insects that use this mode of flight have a 
 wing span of not over 6 inches. 
 
 MONOPLANES 
 
 This general type of supporting surface, being 
 that used by all flying animals, is on this ground 
 reasonably to be regarded as the superior form, 
 besides which it is a safe as-sertion, despite various 
 conspicuous successes that have been achieved 
 with biplanes and occasional triplanes, that at the 
 present time no aerial vehicle ever built has 
 afforded results more promising or significant than 
 those apparent in the remarkable equilibrium and 
 extraordinarily-flat gliding angles of the Mont- 
 gomery machine (see Page 139), and in the high 
 sustention per unit of area in the Bleriot and 
 E. E. P. machines (see Page 162). 
 
 For reasons that are elsewhere explained 
 herein (see Pages 168 and 169), a monoplane will 
 afford more sustention per unit of surface than can 
 be expected from each of two or more similar sur- 
 faces placed one above the other unless an alto- 
 gether impracticable amount of separation be used. 
 
 The chief objection so far urged against the 
 monoplane is the supposed difficulty of staying the 
 wing surfaces properly, the trussed construction 
 of the biplane naturally being not available. Yet 
 one has only to examine the internal trussing of 
 
168 VEHICLES OF THE AIR 
 
 the Antoinette monoplane (see Figures 71 and 72), 
 or the simple staying of the Bleriot and Montgom- 
 ery wing surfaces, to realize that with this con- 
 struction there are ways and means of achieving 
 results quite as successful as any that can be had 
 with others. 
 
 MULTIPLANES 
 
 The first suggestion of the multiplane was made 
 by F. H. Wenham, in his paper read at the first 
 meeting of the Aeronautic Society of Great 
 Britain, in 1868, which is quoted on Page 149. 
 
 It is obvious that any number of superposed 
 planes can conceivably be used, as was suggested 
 in the decidedly freakish "Venetian-blind" con- 
 struction of Phillips (see Page 157), but so far 
 the most successful results have been obtained 
 with not more than two planes, this number afford- 
 ing all the possible advantages of trussed construc- 
 tion with a minimum of its disadvantages. It is 
 a serious though at the present time little regarded 
 objection to multiplanes that they increase the 
 necessity for always maintaining headway to main- 
 tain sustention. Thus, if a biplane starts to drop 
 vertically, in its normal position, it can oppose 
 only half of its total area to resist the fall. Car- 
 ried to its extreme the result must be something 
 like the Phillips slat-like machine, which without 
 forward movement would drop like a brick. On 
 the other hand, the Montgomery monoplane glider 
 can be released in the air wholly without forward 
 movement, in which case it simply settles slowly 
 
AEROPLANE DETAILS 169 
 
 as it commences to glide. Much the same is true 
 of any monoplane, unless the loading per unit of 
 area is carried to extremes. 
 
 BIPLANES 
 
 The biplane is of particular interest as being 
 the type of machine with which Lilienthal was ex- 
 perimenting when killed, the type of glider with 
 which Chanute attained the greatest success, and 
 the form of flying machine which has developed to 
 a high degree in the Wright, Voisin, Curtiss, and 
 Farman constructions not to mention the close 
 and significant analogy it finds in the box kite. 
 
 MOKE THAN TWO SURFACES 
 
 The only multiplanes that ever have accom- 
 plished any really successful flying at the present 
 writing are the Vaniman triplane and the Voisin- 
 Farman triplane, the latter illustrated in Figure 
 211. Both have been, however, discarded for 
 return to the biplane construction. 
 
 FOEMS OF SURFACES 
 
 It is perfectly evident to any one of most ordi- 
 nary engineering attainments that the only pos- 
 sible complete and thoroughly logical method of 
 treating the subject of wing forms and related air 
 reactions is the mathematical, but since aerodyna- 
 mics involve perhaps the most difficult, obscure, 
 and least-investigated and understood of all the 
 phenomena of force and motion, it is out of the 
 question in the present state of the science to offer 
 
170 VEHICLES OF THE AIR 
 
 final and definite explanations of principles in- 
 volved. The most that may be reasonably at- 
 tempted is to marshal connectedly the empirical 
 deductions that have been reached, to state the 
 few generalizations that seem reliable, and to give 
 space to the opinions of the most advanced authori- 
 ties on the subject.* 
 
 Certainly it must become evident upon the 
 most casual investigation upon the least reading 
 of the great mass of speculation and attempted 
 analyses of aerodynamic reactions that nearly all 
 of the workers in this field have been struggling 
 in the dark, and that their conclusions, when not 
 wholly worthless, are as a rule to be accepted only 
 in part or with many reservations. An example 
 of this appears in a recent issue of a well-known 
 aeronautical journal, in which there appears an 
 article by a writer evidently well-versed in modern 
 physical science and related modes of mathemati- 
 cal reasoning. Yet, at the end of a labored disser- 
 tation in which it is attempted to show that the 
 arc of a circle traveling along a line tangent to the 
 advancing edge is the correct section for a wing 
 surface (in the face of the fact that no successful 
 natural or artificial flier uses this curve or setting 
 
 * Since the foregoing was written, the author has been placed in 
 a position to announce that important laws of aerodynamics hare been 
 fully formulated by Professor Montgomery, and have been put to com- 
 plete and most remarkably successful tests in the way of experimental 
 verification and confirmation. These investigations, a part of which 
 are only briefly outlined in Pages 173 to 203, inclusive, will in the 
 near future be submitted to the consideration and criticism of the 
 world. The writer confidently predicts that they will not only amaze 
 by the originality and completeness of the researches and analyses 
 involved, but will also, by application of their profound principles, 
 vastly advance the science of aerial navigation. 
 
FIGURE 75. Assembling Wright Wing Frames. The complete biplane is made in three 
 portions, the center section slightly overhanging the two runners between which stands 
 the man at the left of the view. This section has attached at each end a section like that 
 at w shown at the moment of attachment. Similar sections are leaning against the wall at v. 
 
 FIGURE 76. Aileron Control of Lateral Balance in Antoinette Monoplane by manipulation 
 of the two hinged tips aa. 
 
 FIGURE 77. Bleriot Monoplane VIII. 
 lateral balance by the pivoted ailerons aa. 
 
 The feature of this machine was the control of 
 
AEROPLANE DETAILS 171 
 
 instead of coming to the definite conclusions one 
 would naturally expect as a result of the mathe- 
 matical method the whole question is characteris- 
 tically begged in this wise: "We cannot follow 
 clearly the pressures and motions that take place 
 when a surface travels obliquely through the air 
 because they are very involved", as if there could 
 be any possible occasion for a technical treatment 
 of the subject which should not in some measure 
 dispel the confusion that surrounds it. 
 
 FLAT SECTIONS 
 
 As the most elementary possible conception 
 it is quite natural that many among the earlier and 
 even some more recent aeroplane experiments 
 should have involved the use of flat surfaces. It is 
 
 FIGURE 42. Pressure on Vertical and Inclined Surfaces. In an air 
 current of 25 miles an hour the surface at 90 receives a pressure of 8.24 
 pounds to the square foot, while the surface inclined 15 from the direction 
 of the current receives a pressure of only .33 pounds, and at the same time 
 affords an upward lift of 1.5 pounds. 
 
 now proved, however, that such surfaces are quite 
 ineffective as compared with curved surfaces. 
 
 Though useless for sustention in any prac- 
 ticable aeroplane construction, a flat surface well 
 illustrates the basic principle of sustention by 
 moving an inclined surface through the air, as is 
 shown in Figure 42. 
 
172 VEHICLES OF THE AIR 
 
 CURVED SECTIONS 
 
 The sections of all animal wings being more or 
 less curved it is a fairly direct conclusion that 
 there are important reasons behind the use of such 
 formations a conclusion that becomes stronger 
 the more the subject is studied. 
 
 Arcs of Circles, as affording curved surfaces of 
 comparatively simple character, were the first 
 tried by early dissenters from the idea of flat sur- 
 faces. Their use, while neither as scientific nor as 
 successful as that of other curves will afford 
 fair results under certain conditions, but far more 
 important than any success that has attended their 
 use has been their influence in suggesting further 
 deviations from preconceived opinions. For ex- 
 ample, Lilienthal in comparing flat with curved 
 surfaces discovered that while a flat surface placed 
 with no angle of incidence in a horizontal wind 
 
 K.P. 
 
 FIGURE 43. Comparison of Plane and Arched Surfaces Without Angle of 
 Incidence. Lilienthal found that while the lift of a flat surface placed as 
 above was zero, the arc of a circle gave a lift equal to 52 percent of the 
 pressure upon it when exposed in a vertical position to the same wind. 
 
 afforded no lift, as would be expected, a circular 
 arc placed in the same position gave a lift equal 
 to 52% of the normal pressure on the same surface 
 held vertically in the same wind! This phenome- 
 non, which is illustrated in Figure 43, is to be 
 explained only by there being an effect of the sur- 
 face on the air currents in advance of the surface 
 realization of which is at the basis of all sue- 
 
AEROPLANE DETAILS 173 
 
 cessful work in aeronautics and all correct reason- 
 ing upon its problems. 
 
 Parabolic Surfaces, with minor modifications 
 (to suit certain practical exigencies) into approxi- 
 mations of other of the conic sections and other 
 curves, have been proved experimentally and can 
 be demonstrated mathematically to be the correct 
 curves for wing sections. In an empirical way 
 this was first deduced by Lilienthal and Phillips, 
 while simple examination proves it to be a prin- 
 ciple involved in the curve of birds' wings, but it 
 has remained for Montgomery to discover the laws 
 involved. These are deemed of such importance 
 that the following popular outline of the prin- 
 ciples involved in the formation of wing surfaces 
 is reprinted as the most valuable and practical 
 material available for the student of the subject.* 
 
 "Although the subject of flight has been a constant 
 and universal study, we find that some of the phe- 
 nomena are still involved in mystery, while many 
 others present only unexplained anomalies. This of 
 itself would suggest the question : have the funda- 
 mental principles or laws been formulated? 
 
 "From what I have gleaned from the writings of 
 the various students I believe they have not this for 
 
 * This paper, which was prepared in 1907 for presentation to the 
 International Aeronautical Congress, and subsequently published in 
 "Aeronautics," under the title of " Principles Involved in the Forma- 
 tion of Wing Surfaces and the Phenomenon of Soaring," is on amplifi- 
 cation of an article by Professor Montgomery, entitled "New Prin- 
 ciples in Aerial Flight," which appeared in the Scientific American 
 Supplement of November 25, 1905 some months after the first trials 
 with the Montgomery glider in California. 
 
174 VEHICLES OF THE AIR 
 
 the reason that because of the apparent simplicity of 
 the phenomena we are tempted to take too much for 
 granted and have been misguided in our trend of 
 thought. My own studies and investigations have 
 forced me to the conclusion that in flight we have a 
 special and unique phenomenon, which for its compre- 
 hension requires something more than the simple sug- 
 gestions offered by the study of surfaces acted upon 
 by the moving air, just as the action of the gyroscope 
 presents special phenomena which are in advance of 
 our first ideas of rotation. 
 
 "Having this view of the subject I am forced to 
 present it in its entirety, as I have been unable to find 
 any researches of others to which I could add mine as 
 an amplification, and, while brevity forbids that I 
 should enter into the many points involved, I desire 
 to make use of such as seem to constitute a direct 
 and complete line of demonstration, using some well 
 known phenomena and principles and developing them 
 in the lines peculiar to this problem. 
 
 "At the Aeronautical Congress of 1893, in Chi- 
 cago, it was my privilege to call attention to some 
 phenomena that I had noted, the most significant of 
 which is this : A current of air approaching an inclined 
 surface is deflected far in advance of the surface, and 
 approaching it in a gradually increased curve, reaches 
 it at a very abrupt angle* This phenomenon is the 
 basis of the observations and studies that I desire to 
 present to your Congress. 
 
 "In the idea of deriving support by moving an 
 inclined plane through the air, the first conception is 
 
 * The italics are ours. This exceedingly early recognition by Mont- 
 gomery of this fundamentally-important phenomenon, still little ap- 
 preciated by many modern investigators, is alone enough to establish 
 its discoverer as one of the pioneers of successful modern aeronautics. 
 
FIGURE 78. Lejeune Biplane, with forwardly-extended ailerons at aaaa, for maintaining 
 lateral balance. 
 
 FIGURE 79. Front View of Pischoff and Koecklin Biplane, with aileron controls at aa. 
 
 FIGURE 80. Side View of Pischoff & Koecklin Biplane, showing one of the ailerons very 
 clearly at a. The ingenious system of controlling the forward elevator hh by direct con- 
 nection of the steering rod e to the steering pillar o is of interest. 
 
AEROPLANE DETAILS 175 
 
 the reaction of a mass meeting or impinging upon the 
 inclined surface, in consequence of which the surface 
 and the mass are forced in opposite directions. This 
 idea would be complete and the resulting phenomena 
 simple and reducible to well known formulae if the 
 mass acting on the surface were a solid, but in the 
 present case this is far from being so, as the mass is 
 an almost perfect fluid, and the resulting phenomena 
 are varied and complicated accordingly. The particles 
 of air coming in contact with the surface are deflected 
 as a solid mass would be, but in being driven from 
 their course they are forced against other exterior 
 particles, which while deflecting the course of the first 
 particles are themselves disturbed. 
 
 "The questions presented by these considerations 
 are : first, what is the nature of the movements of the 
 particles due to these deflections and disturbances; 
 second, what form of surface is best suited for pro- 
 ducing the original deflection, and then meeting the 
 new conditions arising from the disturbance in the 
 surrounding air; and, third, what is the mechanical 
 effect of the particles thus disturbed or thrown into 
 motion. In the study of the first two questions, obser- 
 vation of the movements of a fluid is the safest guide. 
 For this observation we may use a gas or a liquid, 
 as both, being fluid, show the same phenomena and 
 reveal the same laws; the only important difference 
 being, that owing to the limited viscosity of a gas, its 
 movements are more perfect and rapid than those of 
 a liquid, whose viscosity hinders the perfectly free 
 movement of the particles. But owing to the ease 
 with which the experiments may be performed and 
 the movements detected, the use of a liquid offers 
 many advantages. For the purpose of study, I used 
 
176 VEHICLES OF THE AIR 
 
 a broad sheet of water (preferably distilled, as a 
 slight surface tension in ordinary water prevents 
 certain delicate movements being revealed) which by 
 suitable means can be set in motion, giving a perfectly 
 even stream whose velocity is regulated at will, to 
 make manifest the various phenomena. 
 
 "The first phenomena to be noted is when the 
 water is at rest. If a tube be placed close to and 
 parallel with the surface, 
 and a quick blast of air f ^\ 
 
 is forced through it, two t . 
 
 opposite whirls are ^< */ ^ 
 
 formed, which advance /* *~x 
 
 over the surface as they * ^ 
 
 increase in size, as in V^ ^ 
 
 Figure 44. These are ^FIGURE 44 
 
 made manifest by very 
 
 light chaff sprinkled on the surface. In passing, I 
 may note the difference between the action in water 
 and in air. If a similar puff be made in air, by which 
 vortex rings are produced, we notice that the elements 
 of rotation forming a section of the ring are much 
 smaller and more rapid than these rotations shown 
 in water. 
 
 "But if a small flat surface b, Figure 45, be placed 
 ,. in the water and a steady 
 
 ' - > ' * * jet forced through the 
 
 tube a y two whirls are pro- 
 duced and maintained in 
 front of the surface and 
 FIGDEE 45 two in the rear, while 
 
 some of the rotating ele- 
 ments of those in the rear conflict and then blend to 
 form a stream c. 
 
 "If the surface be placed at a small angle to the 
 
AEROPLANE DETAILS 177 
 
 jet, as in Figure 46, there is a breaking up of the 
 system of rotations, but that corresponding to d, 
 Figure 45, is developed and predominates. The 
 impulse sent from the jet over the surface simply 
 reveals the tendency to rotation when a stream 
 impinges upon a surface. This tendency may or may 
 not appear as an actual rotation according to circum- 
 stances, as the following 
 will show. If a plane be 
 placed in shallow water, 
 its lower edge resting on 
 the bottom, and moved 
 gently in a direction perpendicular to its surface, then 
 stopped; four rotations, corresponding to those of 
 Figure 45, will appear, which move away in the direc- 
 tions c c c c, Figure 47. Again, ,. 
 if this plane be moved at an 
 angle (about 45 seems best) 
 as in Figure 48, and then 
 stopped, the two rotations cor- d 
 responding to e and g, Figures c ^_ J 
 45 and 47, will have disap- / PIGUBE 47 
 
 peared and those correspond- 
 ing to / and d will remain. It will be noted that these 
 two have the same direction of rotation, while at the 
 same time there is an incipient rotation in the water, 
 
 as indicated by the small ar- 
 rows h. 
 
 "If at the very instant of 
 stoppage the plane be quickly 
 lifted from the water, the 
 two rotations, / and d, will 
 FIGURE 48 immediately blend and form 
 
 themselves into one large 
 rotation, as is very clearly shown in Figure 49. 
 
 VtMElfl 
 
178 
 
 VEHICLES OF THE AIR 
 
 FlGURK 49 
 
 "From these experiments we see that a surface 
 moving a fluid has a tendency to build up rotations, 
 which under certain circumstances will blend into one, 
 this being retrograde as shown in the last experiment, 
 with the ascending element of rotation in advance of 
 
 the surface. Further tests in 
 moving water will reveal this 
 more completely (with other 
 interesting phenomena applic- 
 able to questions of equili- 
 brium). 
 
 "A surface a, Figure 50, is 
 placed in a gentle stream s and immediately whirls will 
 be noted in its rear, which on examination are seen to 
 have a synchronous movement 
 
 whose time is dependent on the 
 
 velocity of the stream and the $ 
 size of the surface. At one 
 instant the whirl d is devel- 
 oped so as to occupy the whole 
 space, while the whirl e is sup- 
 pressed to a minimum. At this instant d moves in the 
 direction c, while e develops, and another d exists as a 
 
 FIGURE l>0 
 
 FIGURE 51 
 
 miniature, as shown in Figure 51. Between these alter- 
 nately escaping whirls there is a wave line, shown at 
 
AEROPLANE DETAILS 179 
 
 w, Figure 51, suggestive of the waving of a flag (the 
 
 latter phenomenon being probably due to the existence 
 
 of such whirls) ; while at the same time, on the surface 
 
 of the water in front of the plane delicate lines appear, 
 
 which swing from side to side with the movements of 
 
 the whirls in the rear. These lines are not ordinary 
 
 wave lines, but sharp distinct lines of division between 
 
 the movements, etc., of the fluid immediately related 
 
 to or influenced by the deflecting surface, and the rest 
 
 of the fluid mass approaching it, while the whirls in 
 
 the rear indicate a similar division. These and other 
 
 phenomena indicate 
 
 that, though there is a 
 
 general movement in 
 
 the fluid produced by a 
 
 deflecting surface, there FIGURE 52 
 
 is a distinction between 
 
 that immediately related to the surface and that which 
 
 is further removed. 
 
 "When the plane a is placed at an angle with the 
 stream, as in Figure 52, the whirls continue to appear 
 and alternately escape, d being more pronounced and 
 powerful than e, while the stream at c rises in front 
 of the plane and that at w descends. If the planes in 
 these two tests are pivoted so as to be capable of a 
 free movement, they take up a slight swinging or 
 rocking motion, responsive to the movements of the 
 whirls. This movement is much more pronounced if 
 similar tests be made by moving corresponding sur- 
 faces through the air. 
 
 "Up to this point we have seen enough to indi- 
 cate : first, that an impulse in a fluid tends to set up a 
 series of rotations ; and second, that a surface inclined 
 to the impulse tends to suppress some of these rota- 
 
180 VEHICLES OF THE AIR 
 
 tions while augmenting others, and finally to blend 
 all into one. An analysis of these points must be 
 omitted for brevity's sake. However, this element of 
 rotation will appear again in speaking of the proper 
 form and adjustment of surfaces. 
 
 "In determining the proper form of surface, the 
 first suggestions are derived from the conception of a 
 body projected in a straight line but deflected from 
 its course by a constant force acting at right angles 
 as a mass projected horizontally and pulled down 
 by gravity, thus describing a semi-parabola, according 
 to well known laws. 
 
 "In Figure 53 let ab represent the direction and 
 distance a mass m, projected horizontally, would pass 
 
 in two instants of time, 
 a e and e b representing 
 equal times. But under 
 the action of gravity, 
 the mass will describe 
 FIGURE 53 ^ ne curve a h d. Drop 
 
 .the perpendicular e h 
 
 to the curve; then the point h will mark its position 
 at the end of the first instant, while d is its position 
 at the end of the second. Then, as the work per- 
 formed by gravity during the two periods of time is 
 equal, that performed on a h equals that on h d. But 
 as the converse of this is true, if a h d be a curve and 
 a mass m is driven along its surface by a force /, 
 parallel with a b, its reaction against the curve will 
 exert pressures perpendicular to a b, which are equal 
 on the two branches a h and h d. While this idea 
 affords an elementary conception, we find it does not 
 fully satisfy the requirements of a moving fluid mass, 
 and applies only to those particles in contact with the 
 
AEROPLANE DETAILS 
 
 181 
 
 surface. Hence we must look to some other analysis 
 for a full conception.* 
 
 "In a study of the parabola, we find it has an 
 intimate relation to the tangent at its vertex and the 
 circumference of an osculatory 
 contiguous circle whose center 
 is at its focus, as shown in Fig- 
 ure 54. In this a b is the di- 
 rectrix, I m the tangent, and c 
 the focus. In the evolution of 
 the parabola, f g = c g, kh = ch, 
 etc. Subtracting the distance 
 a I, between the directrix and 
 the tangent, from / g, kh, etc., 
 and the radii of the circle from 
 c g, ch, etc., the differences are 
 
 equal, that is, the perpendicular distances from the 
 circle are equal to those from the tangent. A further 
 study of this development shows that all these lines, 
 / 9>c g, etc., form equal angles with the tangents to the 
 . curve at the points of inter- 
 
 \c section. From these two con- 
 
 siderations we see that equal 
 impulses from the tangent I m 
 and the circumference of the 
 circle will meet at the curve, 
 producing resultants in the 
 direction of the tangents at these points. And finally, 
 
 FIGURE 54 
 
 \ 
 
 FIGURE 55 
 
 * To students who are able to follow them, the reasoning and the 
 analyses from this point to the end of Professor Montgomery's paper 
 are commended as worthy of the profoundest attention and consideration. 
 The time is certain to come when the clear logic and brilliancy of these 
 remarkable investigations and conclusions, taken in conjunction with 
 their wonderful experimental verification in California in 1905 (see 
 Page 00), will rank their author not merely with present-day aviators, 
 but with the world's greatest physicists and mathematicians. 
 
182 VEHICLES OF THE AIR 
 
 according to a well known property of the curve, all 
 impulses from the center will be reflected from a para- 
 bolic surface in parallel lines (as j j), and, vice versa, 
 all parallel impulses (as j j) reaching the surface will 
 be reflected to the focus c. 
 
 "Before making application of these properties, I 
 must call attention to a phenomenon of jets or streams. 
 If two jets impinge on one another, as shown at a and 
 b, Figure 55, the particles will escape at the point of 
 impact in lateral movements c c. If the streams are 
 equal, the point of impact will remain fixed ; but if they 
 are not, it will be driven towards the weaker jet. 
 
 "The application of these various elements is 
 shown in Figure 56, in which a h d is a parabolic sur- 
 face placed in a fluid and s is a jet fixed in the line a b. 
 When an impulse from this jet impinges on the surface 
 it will develop pressures against the surface as shown 
 in Figure 53, but as it continually moves away from 
 the tangent line a b it produces pressures on the adja- 
 cent fluid, as shown by the arrow /. And, further, as 
 it moves along the curve, meeting the reaction of the 
 fluid as shown at 0, it produces the phenomena shown 
 
 in Figure 55. And as the direc- 
 tion of impact is parallel with 
 the tangent at this point, one 
 element of the resulting lateral 
 pressure, is against and normal 
 to the curve; while the oppo- 
 site element is towards the 
 fluid mass, and in the direction 
 FIGURE 56 the normal m n. But an analy- 
 
 sis of the normal shows it is 
 
 composed of two equal elements, one, m c, pointing to 
 the center c y and the other, mj, perpendicular to the 
 
AEROPLANE DETAILS 183 
 
 line a b. As this impact of the stream and reaction of 
 the disturbed fluid takes place along the entire surface, 
 producing a normal pressure at every point, there is a 
 diversity of pressures in the fluid mass, which diversity 
 is harmonized by the analysis given; all the elements 
 represented by m c going to the center c to build up a 
 center of pressure, while the elements represented by 
 m j develop parallel pressures against the fluid. These 
 pressures being parallel with those represented by / 
 combine with the latter to produce a compound effect 
 first, they impart to the adjacent mass the movements 
 p p p, and this movement sets up a rotation around the 
 center c; and, second, the reaction of the disturbed mass 
 against the impulses / and j is transmitted as an im- 
 pulse back to the surface, and is reflected to the center 
 c, thus increasing the compression at this point. As 
 might be surmised, the reflected impulses to the center 
 c would have a tendency to drive it out of position, but 
 the impulse s (as an element building up this rotation), 
 is an opposing force, keeping it in place. Owing to the 
 concentration of the various lines of force, and the re- 
 straining influences, and because of the rotation, the 
 point c becomes a center of pressure from which there 
 are constant radiating impulses, which reaching the 
 curve are reflected from its surface in lines parallel 
 with the first impulses. But, as a radiating center 
 sends out equal impulses in equal angles, there is a 
 new distribution of pressure on the curve because of 
 these radiated impulses. An inspection of Figure 54 
 will show that the angle i c e = e c d. Hence, the im- 
 pulses falling on I g equal those falling on g d. The 
 point g then becomes the center of pressure on the 
 curve due to the radiated impulses from c, while Ji is 
 that due to the parallel impulses from the first reac- 
 
184 VEHICLES OF THE AIR 
 
 tions, /, Figure 56, of the moving particles against the 
 curve. But between the points g and h there should 
 be another central point of pressures due to the ele- 
 ments m n. The reason for this will appear in the fol- 
 lowing consideration. Suppose we have a number of 
 elastic particles in a straight line, and a constant force 
 act on the first; each particle successively will react 
 against the force, thereby building up a gradually 
 increasing pressure, till the last is set in motion. 
 And owing to these successive increments of reaction 
 against the force, the pressure will be least at the last 
 particle, gradually increasing in an arithmetical pro- 
 gression to the first. From this it would appear, that 
 the elements mn should increase in intensity from d 
 to a, thereby causing the central point of pressure, 
 from these elements, to be located near the front edge 
 (approximately one-third the total distance). 
 
 "Another conclusion from this principle of succes- 
 sive reactions is, the greater the number of particles 
 in series the more intense should be the pressure, and 
 as a general result of this the intensity of pressure on 
 a surface should increase with its dimensions. And in 
 the special application to wing surface in gliding move- 
 ment (where the escape at the ends is cut off by the 
 length of the wings), the intensity should be propor- 
 tional to the width.* 
 
 "This principle seems to receive confirmation in 
 the following experiment. If a plane be placed in a 
 constant stream, perpendicular to its surface, the ele- 
 vation of the water will increase from its edges to its 
 center. But if the plane be doubled in width, the eleva- 
 
 * This is undoubtedly the law underlying the well-recognized increase 
 in proportion of area to weight, as the creatures become smaller, in 
 nature's flying machines. [Ed.] 
 
AEROPLANE DETAILS 
 
 185 
 
 tion at the center will be much greater than in the first 
 instance, and as the elevation may be taken as an 
 indication of the pressure, the conclusion is obvious. 
 "In an experiment illustrated in Figure 57 some 
 of the phenomena mentioned are shown. In this a b 
 and a d are two surfaces, corresponding to a h d, Fig- 
 ure 56, placed in shallow water, and .;' is a jet of air 
 near and parallel with the 
 surface. The jet sets up 
 a stream on the surface, 
 which is cut by the point 
 a and flows along the 
 curves as shown at h and 
 i. In flowing along, these 
 streams, h and i, set up 
 movements, as shown by 
 the small arrows, which 
 pass into rotations around 
 the points c f. Particles of chaff on the surface reveal 
 these movements, while pins fixed at the foci of the 
 parabolic curves, and extending above the surface, 
 
 assist in observation. 
 
 "If the planes shown in 
 the last experiment are 
 placed in a stream s, Fig- 
 ure 58, the same develop- 
 
 FIGURE 57 
 
 ment of pressures takes 
 place but the complete 
 rotations are hidden be- 
 cause of the general move- 
 ment, though they sub- 
 stantially exist in a gen- 
 
 eral wave line. In this system, there are three general 
 elements of action and reaction; first and second are 
 
 58 
 
186 VEHICLES OF THE AIR 
 
 "h and i, which mutually hold one another in balance, 
 and act reciprocally in building up and maintaining 
 the various movements and pressures; and the third, 
 these combined reacting on the exterior stream, ac- 
 cord to the statements in the discussion of Figures 50 
 and 51. Should one of the elements h, for instance, 
 be removed by taking away the curve a d, the develop- 
 ment would be destroyed and there would be an escape 
 from i towards the side h. And in order to re-estab- 
 lish the pressures on the curve a b there must be a 
 readjustment by which the necessary element is de- 
 rived from the stream. An inspection of the figures 
 shows that the rotary tendencies around / press upon 
 those of c and also on the rear of the curve a b. Then 
 if we draw a tangent of this circle / to the point b, and 
 so place the curve that the stream comes from the 
 point m, we find the desired adjustment, though the 
 pressures on the curve are derived from modifications 
 of the ideal movements. 
 
 ' * On placing the curve a b so that the stream ap- 
 proaches in the direction m b, Figure 59, we test the 
 
 adjustment as follows: 
 Fine sand scattered at 
 
 FIGURE 59 a on the bottom, by its 
 
 movements will indicate 
 
 that the approaching stream is cut by the point or edge 
 a. But if this point be lowered, there will be a pressure 
 on the upper surface, causing a whirl /. Whereas, if it 
 be elevated a reverse whirl, c, is produced, as shown in 
 the illustration. 
 
 "In Figure 60 we have a good illustration of the 
 complete system of movements in this adjustment. 
 The stream s gradually rises and is cut by the edge b; 
 the portion flowing below the curve slows up and is 
 
AEROPLANE DETAILS 
 
 187 
 
 more or less ill-defined in its movement. But, pressing 
 against the curve, it causes the water level to rise and 
 passes out as shown by the arrows g. Near the sur- 
 face of the curve there are jerky movements as shown 
 at c c c. Above the surface, the current sweeps around 
 a, leaving a deep depression, but turns and descends 
 
 FIGURE 60 
 
 against the rear upper surface, and, conflicting with 
 the currents coming around the rear point e, produces 
 a violent disturbance. Some of the current around e 
 takes the direction n but terminates in the whirl m. 
 In the rear the various movements combine and form 
 a displaced current, traveling in the direction /, par- 
 allel with the original stream. Owing to the pressure 
 exerted by the descending current on the upper rear 
 surface, the effectiveness of that on the under surface 
 is reduced. An inspection shows the height of water 
 from e to h to be only a little more than that from e 
 
188 VEHICLES OF TEE AIR 
 
 to w, while, owing to the deep depression at a and the 
 elevation from b to h, the greatest effective pressure 
 is located in this region. The general movement of the 
 current forms a wave line, this being a resultant of 
 rotary movements and the rectilinear movement of the 
 stream. 
 
 "But the complete rotation, indicated by the circle 
 of arrows, gives a positive demonstration, and may 
 be produced as follows: 
 
 "Let the velocity of the stream be gradually de- 
 creased till a reverse current takes place on the surface. 
 This reverse current will carry all the floating particles 
 towards upper end of the stream. In this movement, 
 these floating particles serve as an indicator for any 
 general tendencies in the water, and, on reaching the 
 region of the curved surface, take up the indicated 
 rotation, continuing to rotate around the surface with 
 perfect regularity as long as the stream continues; 
 meanwhile the suspended particles of chaff reveal the 
 varied movements within the stream. In passing, I 
 must state it is not easy to produce this surface whirl. 
 The movement of the water must be perfectly regular 
 and under perfect control as to velocity. There must 
 be no irregularities in the channel and the water must 
 be as free as possible from vicosity and any surface 
 film, rain water being the only kind I have succeeded 
 with. 
 
 "While this seems to be the ideal of the form and 
 position of a surface for receiving fluid impulses and 
 developing the proper reactions, there are certain 
 modifications to be introduced in practice as will ap- 
 pear from the following: 
 
 "It will be noticed in these demonstrations that 
 the free movements of the water are referred to the 
 
AEROPLANE DETAILS 189 
 
 front and rear edges, there being no escape around the 
 edges at the bottom or the surface of the stream. But 
 if we take a curved surface narrow enough to be sub- 
 merged, part of the fluid will escape over the upper 
 edge, and the reactions necessary to produce the rising 
 current in advance of the plane are only partially 
 developed. Hence to have the front edge cut the cur- 
 rent, it must be elevated. This required elevation of 
 the front edge increases as the surface is more com- 
 pletely submerged, as the escape of the water over 
 the upper edge is thereby increased. But if portions 
 of the front edge, as shown at a b c d, etc., Figure 61, 
 be cut off, to allow for the 
 deficiency in the rising cur- 
 rent, the front edge of the FIGURE ei 
 curve may be lowered so that 
 
 the remaining portion of the curve may assume its 
 proper position. The application of this is readily 
 apparent in the wings of a soaring bird. Towards the 
 center, near the body, the curvature is at its fullest 
 development. But near the outer extremities, where 
 the air partially escapes around the ends, the sharp 
 front curvature disappears, the wing surface becoming 
 less curved and more narrow a fact that has been 
 noted by many investigators. 
 
 "Here I must call attention to an important ele- 
 ment. In discussing Figures 54, 55, and 56 I pointed out 
 the positions of the centers of pressure, and in Figure 
 62 we find the application. Let e b be the horizontal, and 
 also the direction of movement of the curve a b, in its 
 proper position. From the construction, we see that 
 the center of pressures due to the direct reaction of the 
 moving particles is at / while that due to the pressure 
 emanating from the center c is at g. If we draw a 
 
190 VEHICLES OF THE AIR 
 
 normal from the point /, its inclination is against the 
 direction of motion, e b. But one drawn from g in- 
 clines with it, or for- 
 ward. The resultant of 
 these two pressures is 
 indicated by h, and the 
 normal to the tangent at 
 this point shows a slight 
 forward pressure. Prom 
 the study of Figure 56 
 we find that there is a 
 third element of pres- 
 sure, mn, whose intensity is greatest towards the 
 front. This again changes the location of the center 
 of pressure, placing it in advance of the point h. And 
 as the normal at this point inclines forward, there 
 should be a perceptible forward pressure developed, 
 a phenomenon I have observed when testing my aero- 
 planes, and one which I believe has been observed by 
 others.* 
 
 " These conclusions regarding the location of the 
 center of pressure seem to be confirmed by observa- 
 tions made when I first entered this study. Taking 
 specimens of large birds, eagles, pelicans, buzzards, 
 etc., newly killed, I braced their wings in the normal 
 position of soaring. I then balanced the body by thrust- 
 ing sharp points into it, immediately under the wings, 
 (frequent corrections having been made to adjust the 
 bracing so as not to introduce errors into balancing), 
 and I found the center of gravity under a point in the 
 wing approximately corresponding with the point I 
 have indicated as being the center of pressure. 
 
 * This is the so-called ' ' tangental ' ', noted by Lilienthal, and con- 
 firmed by the Wrights and others. [Ed.] 
 
AEROPLANE DETAILS 191 
 
 " Before leaving this part of the subject I must call 
 attention to two important elements first, from a 
 study of Figures 59 and 60 it is seen that it is the 
 reaction within, or under, the curve that causes the 
 ascending current in advance of the curve, hence, 
 should there be an object within this space, causing a 
 resistance to the fluid movement, it by reaction will 
 further increase this rising current, and as this is in- 
 creased the front edge may be lowered still more, and 
 thereby the element of pressure on the forward sur- 
 face augmented, which will partially compensate for 
 the resistance due to the object; second, in the use of 
 two surfaces, one in advance of the other, the line of 
 development is suggested in Figure 59. Suppose this 
 surface be divided at d and the sections moved apart, 
 the intervening space gives to each part an individual- 
 ity, but their mutual reactions give them an interrela- 
 tion. Hence in the practical use of such surfaces the 
 curvature of that forward should be more pronounced, 
 and its inclination greater than that in the rear. How- 
 ever, without a proper understanding how to deter- 
 mine these elements dangerous mistakes might be 
 made.* 
 
 "Having pointed out what seem to be the funda- 
 mental principles in the formation and adjustment of 
 a gliding or soaring surfac^, I now place the whole 
 idea in a single expression, as a stepping stone to the 
 consideration of mechanical principles relative to the 
 problem of the energy involved. 
 
 * Definite laws have been found to exist in accordance with which 
 the relation between the focal length and the chord length of the 
 parabola varies in accordance with the size of the machine and with 
 the sustention per unit of area. At the present time the writer is 
 not at liberty to make public this data, but hopes to be in a position to 
 do so in the near future. 
 
192 VEHICLES OF THE AIR 
 
 "Conceive a long narrow surface, such as a bird's 
 wings in a horizontal position, having no formed mo- 
 tion, but being pulled down by gravity. In descending 
 through the air this surface sets up two whirls around 
 its edges, and we readily perceive that the work of 
 gravity in pulling the surface down is divided between 
 the descending surface and the whirls escaping around 
 its edges. Now, suppose the surface be given a hori- 
 zontal movement of such velocity that the complete 
 system of movements shown in Figure 60 is built up; 
 then these opposite whirls being blended into one rota- 
 tion, having its ascending element in advance of the 
 surface, the work of gravity impressed upon the air 
 comes back to the surface, giving it an upward impulse. 
 
 "Now let us inquire what is the significance of this 
 operation, relative to the question of energy. This 
 point is well worthy of the sincere st inquiry, for who 
 has not been enchanted and mystified by the beautiful 
 movement of a soaring bird? And who has not asked 
 the question, over and over again, whence does it derive 
 the power to perform such feats, so much at variance 
 with other phenomena and our ideas of motion? 
 
 "Having passed through the ordeal of these per- 
 plexing questions, and been forced to their solution by 
 going back to the inf anc^of mechanics, I am compelled 
 to state that some of the^lementary questions, as they 
 appear in our text books, have not been developed as 
 completely as they should have been, and thus the 
 minds of even the best students have been left with 
 some erroneous conclusions, attributable directly to a 
 too restricted investigation. 
 
 "In entering into this question let me suggest that 
 we abstract our minds as far as possible from all 
 
AEROPLANE DETAILS 193 
 
 knowledge and conclusions on the subject, so as to 
 follow the building up of the demonstrations without 
 prejudicing them by ideas that we possess, or which 
 must in their natural order come later. As may be 
 inferred from the preceding we shall simply go back to 
 the most elementary principles, and expand them, em- 
 phasizing such points as relate to the question. 3 " 
 
 FOKCE AND MOTION 
 
 "A force acting upon a movable mass imparts to 
 it a velocity which is a product of the force multiplied 
 by the time of action ; v = ft. 
 
 * ' The force may be a pure force, as gravity, it may 
 be the pressure of a compressed elastic body, or it may 
 be the impact of a moving mass. Eegarding the forces 
 derived from a moving mass it may be stated that 
 when there is a series of impacts, the element of time 
 is composed of the duration of each impact multiplied 
 by the number. 
 
 "From a confusion of ideas on this subject erro- 
 neous conclusions sometimes arise. A force is simply 
 considered a force in a general way, and must produce 
 so much motion and no more, the element of time and 
 the factors that determine it being entirely lost sight 
 f _p of. Experiments illustrated 
 
 in Figure 63 will be instruc- 
 tive on these points. A and 
 B in this illustration, are two 
 , '' masses fastened to rods and 
 " supported by the pivots //. 
 
 FIGURE 63 Between them is the spring 
 
 c. In the first experiment, 
 
 let A and B be equal. If the compressed spring be re- 
 leased, it will drive the two masses apart, A reaching 
 
194 VEHICLES OF THE AIR 
 
 the point d, but in a second experiment let B be greater 
 than in the first, A remaining the same ; then when the 
 compressed spring is liberated, the mass A is forced 
 to a higher point, e, owing to a greater velocity being 
 developed through the time of action being prolonged 
 by the greater inertia of the larger mass B. A full and 
 clear conception of the formula v ft, and a realiza- 
 tion of the fact that the masses operated upon are im- 
 portant elements in determining the time, are neces- 
 sary to an understanding of the present problem." 
 
 MOMENTUM 
 
 "When a mass is in motion we have not only the 
 question of velocity, but also that of quantity of mo- 
 tion, or momentum, expressed by the formula m v. A 
 unit of force, acting for a unit of time on a unit of 
 mass will develop a unit of velocity, and the unit of a 
 mass, multiplied by the unit of velocity, gives a unit 
 of momentum. Then introducing the element of mass 
 into the formula, v = ft, we have mv ft. Multiplying 
 both sides of the equation by n units, we have n m v = 
 nft, a general expression for the generation of mo- 
 mentum. (In these expressions, t signifies one unit of 
 time, / one unit of force, v one unit of velocity, m one 
 unit of mass, and n a known quantity. )" 
 
 ACTION AND REACTION 
 
 "According to a well established principle of 'ac- 
 tion and reaction/ a force can only impart motion to 
 a mass by the reaction of another mass, the action and 
 reaction being equal and opposite. As a positive de- 
 duction from this it may be stated that if we find a 
 body moving in a given direction there is somewhere 
 an equal and opposite motion. The first and most 
 
AEROPLANE DETAILS 195 
 
 elementary way of expressing this motion is in terms 
 of momentum; and, representing the opposite direc- 
 tions by + and we have as a general expression, 
 
 Let us now develop this formula in a 
 special line, so as to give a rational explanation to what 
 may appear as an absurdity in some processes which 
 follow. 
 
 * l In the last formula let v = Vu + #m ; then substi- 
 tuting these and developing, the formula becomes 
 
 -Wi V-L. For the purpose of using this 
 
 formula to illustrate certain points, let us put it into 
 figures. 
 
 "Let m = l; m 1 = 2;v 11 = l; Vm = 4, then, from 
 the formula, Vi is found to be f. We now place these 
 figures in order and leave them for future use. 
 
 1X1+1X*=2X 
 Momenta = - = li 
 
 1 + 3 
 IMPACT OF ELASTIC BODIES 
 
 "The impact of elastic bodies presents phenom- 
 ena which very few seem to have studied, still fewer 
 understand, and which many are ready to deny on 
 general principles. And because of certain vague 
 ideas regarding motion and the exchange of momenta 
 there seems to be an inability to grasp the truths de- 
 rived from some of the mathematical formulae, or to 
 understand the phenomena of their experimental dem- 
 
196 VEHICLES OF THE AIR 
 
 onstrations. To have a proper conception of these one 
 must have recourse to a little more profound study 
 than is afforded in the ordinary text-books. 
 
 "In the present discussion all that I hope to do is to 
 give a demonstration of the truth of some of the prop- 
 ositions, with general suggestions, as the revolving of 
 the subject in its many phases would be too lengthy. 
 
 "In presenting the formulae of the impact of elastic 
 bodies I shall develop a special case, so as to demon- 
 strate that what appears an absurdity is a rational 
 conclusion in the light of the formula of action-and- 
 reaction just developed. These are general formulae for 
 the purpose of determining the velocities of two elastic 
 bodies after impact, and cover all possible cases. 
 
 "Let A and B represent two elastic bodies, having 
 the respective velocities F and U; and let v and u rep- 
 resent their velocities after impact. 
 
 Then (A + B) v = 2B U+ (A B) V 
 (A + B)u = 2AV(A B)U 
 Let A = l, V = l, B = Z, U = o 
 
 "Substituting these values in the formulae, we find, 
 v = $ ; u = % ; these being the velocities and directions 
 after impact. Multiplying these velocities by the re- 
 spective masses gives the respective momenta, that of 
 A being J, and B, 1J. This latter, to many, is a mani- 
 fest absurdity ; for as the original momentum of A is 
 supposed to be only 1, how can it give 14? 
 
 "Let us analyze the problem, and assume that two 
 equal elastic masses m 1 and MI = 1, are acted upon 
 by a force /, which imparts a velocity 1 to each, as in 
 Figure 64. 
 
 "Let m 1 now impinge on the elastic mass M = 2. 
 
AEROPLANE DETAILS 197 
 
 Then, according to the formulas just presented, mi will 
 rebound from M with a velocity Vu = 4. If this be 
 
 FIGURE 64 
 
 so, we have, on one side, two masses having a velocity 
 and momentum in the direction 
 
 mv = 1, m l v 11 = J. 
 
 "Referring now to the formula of action-and-reac- 
 tion, we see there must be an equal and opposite mo- 
 mentum in the + direction of li, and this we find in 
 M = 2, with F = t. 
 
 "Now let us combine these ideas with those pre- 
 sented under the discussion of Figure 63, and we have 
 a universal expression of the phenomena of action-and- 
 reaction. In Figure 63 it was noted that with a given 
 force the resulting motion of momentum was de- 
 pendent on the masses 
 IMWT of the bodies acted upon. 
 But, it is apparent, this is 
 not final, for a given 
 Vl . force /, Figure 64, acting 
 
 faz) (m^^mtim on m and m u generates 
 PIGUBE65 momenta which are a 
 
 proximate result; but as 
 
 Wi impinges on another mass M the ultimate result of 
 the action of the force is the momentum generated in 
 M. In this case mi may be considered a force acting 
 on M, and the momentum generated is measured by 
 
198 VEHICLES OF THE AIR 
 
 the intensity multiplied by the time, and the time is 
 determined by the inertia of the masses. 
 
 "An inspection of the system presented in Figure 
 
 64 shows that various 
 ideas are presented ac- 
 cording to the view 
 taken. One is that the 
 force acting on m x ulti- 
 MIRi iMfiffT mately causes it to move 
 against the force, an- 
 
 FIGUBE 66 y 
 
 other is that Wi im- 
 presses upon M a momentum equal to its impact and 
 reaction. Further, while we may for the purpose of 
 drawing special deductions fix our attention on the 
 movement of one or another of the masses, we must 
 bear in mind that each is only one of the operating 
 elements in a system, and hence must not be consid- 
 ered by itself, but as an element related to the whole. 
 Finally, whatever motion any of the elements may 
 have, the algebraic sum of all the movements in the 
 system must be zero. 
 
 "In applying the formulae of the impact of elastic 
 bodies to the case of two equal masses m and m^ Fig- 
 ures 65 and 66, if m be moving with a velocity v and 
 w x is at rest, after impact m^ moves with a velocity v, 
 and m is brought to rest. But if the masses be moving 
 against one another, with the respective velocities v 
 and Vi, after impact Wi has the velocity v 9 while m 
 has VL" 
 
 IMPACT OF FLUIDS 
 
 "The elements of a fluid, being elastic, operate in 
 accordance with the laws just stated, but, their free 
 movements being restrained by the reactions of tte 
 
AEROPLANE DETAILS 199 
 
 surrounding fluid, their impulses are propagated as 
 
 compression waves, which in their movements come 
 
 under the same laws, as the well-known experiments 
 
 in sound prove. But 
 
 when there is a path of \ L 
 
 least resistance the 
 
 pressure exerted on a $ 
 
 fluid gives rise to a 
 
 stream, which, while 
 
 not being elastic as a m^~ V^ 
 
 mass, owing to its fluid FIGUBB e? 
 
 nature, produces the 
 
 same set of actions and reactions as if it were. For 
 the first particles which reach a surface impart to ifc 
 the momentum of their impact, and then are forced 
 away by the compression arising from those following, 
 and hence exert another element of pressure by their 
 reaction." 
 
 APPLICATION 
 
 " Having given the elementary principles involved, 
 I now present their application in an ideal case, in 
 Figure 67, in which a and b, in the views to the right, 
 are two equal elastic masses moving horizontally, as 
 indicated at h, with equal velocities, while m m is the 
 elastic surface of an infinite mass. At any instant let 
 an impulsive force / act on a, which will cause it to 
 impinge on b, the two masses exchanging their mo- 
 menta the latter will take the path b c, while a will 
 continue its original direction towards d. But b will 
 rebound from the surface m m, and take the direction 
 c d, and, coming in contact with a, which has reached 
 the point d, will impart to it the vertical component of 
 its motion, causing it to take the direction a e while b, 
 
200 VEHICLES OF THE AIR 
 
 having lost its vertical element of motion, will continue 
 in the direction d g. But suppose that at an instant 
 just previous to this impact, another impulse /, act 
 upon a, then the two masses will exchange their mo- 
 menta, a taking the direction ae, and b the direc- 
 tion b m. 
 
 ' ' Examining this development, we find that the first 
 force / has simply set up a series of actions and re- 
 actions in consequence of which a is left undisturbed 
 while b impresses on 'm m the force of its action and 
 reaction, these, in this theoretical case, being equal to 
 each other and to the original force /. After the second 
 force has acted on a, and the masses have exchanged 
 their momenta, we find as a result of the action of these 
 two forces / /, and the reactions of a and b and m m, 
 that there are two elements of force in m m, and one in 
 the descending mass b, while a has an ascending veloc- 
 ity theoretically equal to the downward movement im- 
 parted by the first impulse /. From this analysis it 
 appears that each downward impulse imparted to a 
 mass may be transmitted to a larger mass, which while 
 absorbing all the original impulse gives back an ele- 
 ment of reaction which in turn may be transmitted to 
 the body first acted upon, giving it a movement op- 
 posite to that given by the first force; and the large 
 mass then has not only the motion due to the action of 
 the force, but also that due to the reaction of the mass 
 moving from it. 
 
 "In these demonstrations we have one element of 
 the actions and reactions taking place in the phenom- 
 enon of soaring a representing the bird, b the air im- 
 mediately surrounding it, m m the great mass of sur- 
 rounding air, and / /, the impulses of gravity. In this 
 demonstration the impulses are represented as distinct 
 and defined, as are also the masses a b and m m, 
 
AEROPLANE DETAILS 201 
 
 whereas in the phenomenon of soaring, the action of 
 gravity and the impacts and reactions of the air are 
 continuous, while the reflecting mass of air is ever 
 present in all positions. But because of losses due to 
 various causes, the final effect is far below the ideal. 
 The formation, adjustment, and forward movement of 
 the wing surface, are only the means by which the air 
 immediately surrounding is thrown into the movements 
 by which these elementary processes are perpetuated. 
 
 ' l To have a complete idea of the process of soaring, 
 suppose that an appropriate surface be held in the 
 proper position, relative to the horizontal, as shown in 
 Figure 59, but having no horizontal motion. Under 
 the influence of gravity it will slowly descend. But sup- 
 pose it receive a gradually-increasing horizontal veloc- 
 ity, then a time will come when the various elements of 
 action and reaction in the air will just balance the im- 
 pulses of gravity, and the surface will travel in a hori- 
 zontal direction; then, if this motion be further in- 
 creased, these actions and reactions over-balancing 
 gravity will cause it to rise, the rapidity of its ascend- 
 ing motion depending on the increase in velocity. It 
 must be noted, that these various changes in the direc- 
 tion of movement, are due to a variation of velocity 
 alone, for the surface is supposed to retain the position 
 indicated in Figure 57, and, further, owing to the de- 
 velopment indicated in Figure 62, the pressure sup- 
 porting it tends to maintain its forward movement, or 
 at least to balance the retarding resistances. 
 
 ' l If it be necessary to acquire an increase of veloc- 
 ity, the surface may be slightly inclined and a new 
 impetus obtained, whose measure is not the distance it 
 descends through space, but that through the rising 
 current of air. 
 
202 VEHICLES OF THE AIR 
 
 "I am aware various objections may be made, based 
 upon the common principles relative to bodies descend- 
 ing and ascending under the influence of gravity. Be- 
 garding these possible objections, I shall state, that 
 there are four general cases involved in these princi- 
 ples first, bodies moving in free space; second, an 
 elastic mass let fall ; third, the movement of a pendu- 
 lum ; and fourth, the movement of a ball over inclined 
 planes. 
 
 "A little thought will reveal the fact that these are 
 only special expressions of the great fundamental law 
 of action-and-reaction, or the exchange of momenta, 
 and hence are not to be used as a standard for passing 
 judgment on more complicated and advanced develop- 
 ments of the same basic principles, 
 
 "In conclusion, the phenomenon of soaring is the 
 practical operation of a principle pointed out in the dis- 
 cussion under Figure 64 that a force may act on a 
 body under such conditions as to cause the body to 
 move against it. One important and practical instance 
 of the operation of this principle is the tacking of a 
 ship against the wind. Of course, this operation has 
 been frequently analyzed and explained, but underly- 
 ing all we find only the working out of this principle. 
 So it is with the analysis relative to soaring, with this 
 important different. In the instance of the tacking 
 of a ship, the force is the moving air, while in soaring 
 it is the pure force of gravity. In the first instance, 
 the ship tacks against the wind, but as an essential ele- 
 ment in the process must move through a more or less 
 lateral course, while in the second the bird tacks 
 against gravity, its horizontal motion through the air 
 being only an element in the process. 
 
 "In our conception of these operations, we should 
 
AEROPLANE DETAILS 203 
 
 not fix our attention too closely on the moving objects, 
 but must consider them as only one of the elements in a 
 system of moving bodies. 
 
 In each of these cases we have four factors : 
 
 First, a force, the wind, acting on, second, the sails; 
 
 Third, the hull, acting on, fourth, the water. 
 
 and 
 
 First, a force, gravity, acting on, second, the mass; 
 
 Third, the wings, acting on, fourth, the air. 
 
 "From this study of the movements of fluids, and 
 the special laws involved, we see that gliding, or soar- 
 ing, flight is not the haphazard dragging of an inclined 
 surface through the air, but a special and unique 
 phenomenon of motion and energy, and holds the same 
 relation to the ordinary phenomena of inclined planes 
 as the operation of the gyroscope does to the simple 
 rotation on a fixed axis. And in the process of soaring, 
 there are not only the form and adjustment of the sur- 
 face, but also the proper speed and manipulation neces- 
 sary to produce that special development of movements 
 and energy, which may be properly termed soaring. 
 
 "In other words, we must recognize that this is one 
 of the operations in nature based upon a set of laws 
 suited to itself; and we must realize that to reach the 
 end to which we aspire we must understand what these 
 laws are and follow them in the designing, construc- 
 tion, and operation of our devices." 
 
 Flattened Tips to wing surfaces, which are the 
 rule with all birds' wings, are not commonly em- 
 ployed in modern aeroplanes, several highly suc- 
 cessful machines being notable offenders in this 
 
204 VEHICLES OF THE AIR 
 
 respect. Fortunately their absence does not ren- 
 der a construction inoperative, but it does set up 
 wholly unnecessary forward resistances, which 
 waste power and impede the progress of the 
 vehicle.* 
 
 Angles of Chords of wing sections are the 
 "angle of incidence" of curved surfaces. For the 
 best results these angles should be very flat to the 
 path of movement much flatter than is common 
 practice, in which the use of inadequate or wrongly 
 curved surfaces is made possible to considerable 
 extents by the employment of excessive angles of 
 incidence. A method of determining proper 
 angles of incidence is explained on Page 186. 
 
 WING OUTLINES 
 
 There is such great variety in the wing out- 
 lines of flying animals as to force the conclusion 
 that within considerable limits the wing plan does 
 not matter, and that various straight, curved, and 
 irregular front and rear edges, and differences in 
 the rounding of wing tips, may be determined more 
 by structural exigencies than by laws of wing ac- 
 tion. 
 
 Length and Breadth do vary systematically, 
 however, the one rule that is evident in the bird 
 mechanism being the provision of long and narrow 
 wings for fast soaring flight and of shorter and 
 broader wings for slower and flapping flight. 
 
 * The points involved in the formation of the ends of wing surfaces 
 are referred to on Page 189, and are also explained in the closing para- 
 graphs of the Montgomery patent specification. 
 
AEROPLANE DETAILS 205 
 
 ARRANGEMENTS OF SURFACES 
 
 Besides in the forms and outlines of the 
 sustaining surfaces of an aeroplane there is also 
 possible great variety in their number and arrange- 
 ment. 
 
 ADVANCING AND FOLLOWING SUEFACES 
 
 The use of two or more surfaces, one preceding 
 another, has a number of merits, one of which is 
 the compacting of the supporting areas in a mini- 
 mum space, and another of which is their utiliza- 
 tion to afford fore and aft balance (see Page 221). 
 
 SUPERIMPOSED SUEFACES 
 
 The use of pluralities of surfaces in vertical 
 series has been already referred to in the discus- 
 sions of multiplanes and biplanes commencing on 
 Page 168. 
 
 STAGGEEED SUEFACES 
 
 Biplanes with the upper surface set ahead of 
 the lower, as in Figure 68, have been built to secure 
 the supposed advantage 
 of locating the two sur- 
 faces directly above 
 one another, not in ap- 
 
 - 1 " FIGURE 68. Staggered Biplane. 
 
 parent aspect, but gt^^wS^** 
 within the actual flow of c t ^ n ll g f es u ^ m ^ owijis air at 
 the air streams, which 
 
 approach with a rising trend as streams indicated 
 by the arrows. A recent biplane if this type, 
 
206 VEHICLES OF THE AIR 
 
 which proved only indifferently successful, is il- 
 lustrated in Figure 69. 
 
 LATEEAL PLACINGS 
 
 In all successful aeroplanes that have been built 
 the sustaining surfaces extend to much greater 
 distances laterally than they do in any other direc- 
 tion. This limits the variety of practicable com- 
 binations. 
 
 Separated Wings, with either an open interval, 
 as in Figure 33, or the body of the machine be- 
 tween them, are the the commonest construction 
 in monoplanes. The arrangement closely resembles 
 that of the animal mechanism, and, similarly, 
 is probably most effective when the body has a 
 smooth under surface and sides against which the 
 wings abut closely enough to prevent any flow of 
 air through the juncture. Several such construc- 
 tions are well illustrated in Figures 171, 216, 222, 
 247, and 249. 
 
 For maintaining lateral balance, widely separ- 
 ated moveable wing surfaces, or " ailerons", are 
 often used, but these are not main sustaining sur- 
 faces (see Page 217). 
 
 Continuous Wings are used in nearly all bi- 
 planes, to which type of machine they are pe- 
 culiarly adapted. In such vehicles the upper sur- 
 face usually is not only continuous but is also free 
 of attachments and obstructions, while the lower 
 surface affords at its center mounting for the en- 
 gine, accomodation for the operator, etc., as is 
 shown in Figures 23, 172, 189, 190, 208, 224 and 248. 
 
AEROPLANE DETAILS 207 
 
 Lateral Curvature is often imparted to wing 
 surfaces for one reason or another usually in not 
 always discriminating though often effective imi- 
 tation of the similar aspect of birds' wings. 
 Probably the best form, if other details are so de- 
 signed as to permit it, that in which the wing ends 
 droop to a pronounced extent, as in the machine 
 illustrated in Figures 225, 226, and 260, which from 
 the front closely resembles the soaring attitude of 
 the gull. Another instance of this wing form was 
 the upper surface of the "June Bug", of the 
 Aerial Experiment Association. In this biplane 
 the lower surface was curved up, so that a very 
 favorable form for structural stiffness was realized 
 in addition to a combination of the merits of the 
 drooped wing with those of the dihedral form. The 
 Wright machines, which appear to be quite 
 straight, are said to fly best when so trussed that 
 there is a slight droop to the wing ends. 
 
 Dihedral Angles at the juncture of wing pairs, 
 as in the Langley model illustrated in Figure 70, 
 in which the angle was 135, have the merit of af- 
 fording considerable automatic stability in calm 
 air, but in disturbed air have just the opposite ef- 
 fect, the low position of the maximum weight caus- 
 ing the invariable trouble that results from thus 
 placing it a pendulum-like oscillation of increas- 
 ing amplitude until the vehicle overturns (see Page 
 216). Birds often soar and maneuver with their 
 wings in the dihedral position, but their ability in- 
 stantly to adopt other positions relieves them from 
 the risks that appear when the angle is permanent. 
 
208 VEHICLES OF THE AIR 
 
 FIGURE 70. Langley's 25-Pound Double Monoplane, With Wings at Dihedral 
 Angle. This model on May 6, 1896, flew for more than half a mile over the 
 Potomac River, at a speed of about 20 miles an hour. Subsequently, on 
 November 28, 1906, with a similar model weighing about 30 pounds, a three- 
 quarter mile flight at about 30 miles an hour was achieved. This was at the 
 end of a three years' period of experimenting that had for its object the 
 ultimate production of a man-carrying machine. The size of the heavier model 
 was a little over 12 feet from tip to tip, with a length of about 16 feet. The 
 whole power plant, which consisted of a 5-pound boiler and a 26-ounce non- 
 condensing steam engine that developed l 1 /^ horsepower, weighed about 7 
 pounds. Propulsion was by bevel-gear driven, two-bladed twin screws, rotating 
 in opposite directions behind the forward surfaces at about 1,200 revolutions 
 a minute. The hull was metal sheathed to protect the burner from the wind, 
 and the vessel between the forward surfaces was a float to keep the machine 
 up when it alighted upon the water. In conjunction with the experiments 
 with a man-carrying machine, which terminated with the unsuccessful launch- 
 ing on December 8, 1903, a model similar to the above, but weighing 58 
 pounds and having 66 square feet of sustaining surface it being a one- 
 fourth size copy of the large machine was successfully lown with its 
 3-horsepower motor. 
 
 The Bleriot, Santos Dumont, and Antoinette 
 monoplanes have the wing surfaces dihedrally 
 placed, as is evident in Figures 200, 215, and 220, 
 but in all successful models of these aeroplanes the 
 angle is very slight and its merit much in doubt. 
 The only biplane of which the writer knows in 
 which dihedral wings were used was the not very 
 successful machine of Ferber's, illustrated in 
 Figure 224. Nearly all modern biplanes are built 
 with straight or almost straight wings. 
 
 Many soaring birds which in flight set their 
 wings at a drooped or flat angle are observed to 
 hold the extreme tips of their wings pronouncedly 
 upturned possibly for the balancing effect of 
 
'AEROPLANE DETAILS 209 
 
 the dihedral position, though this is by no means 
 certain. 
 
 VERTICAL SURFACES 
 
 Surfaces placed vertically, though not present 
 in any flying animal except the varieties of flying 
 fish, are found quite indispensable in man-made 
 flers in which they are made to serve various pur- 
 poses, including the maintenance of lateral bal- 
 ance, and the effecting of lateral steering (see 
 Pages 216 and 224. Properly placed they also 
 tend to keep a machine to a desired course regard- 
 less of disturbing influences, or headed into gusts 
 of wind that if they continued to come from one 
 side might prove very dangerous. To meet these 
 latter purposes most effectively, the vertical sur- 
 faces should be placed to the rear, as in the ma- 
 chine illustrated in Figures 225, 226, 227, and 260, 
 so that the effect of side gusts always must be to 
 swing the machine into the wind. 
 
 The use of large vertical surfaces forward is 
 now found only in the box-kite like Voisin ma- 
 chines, and is probably altogether mistaken design 
 a conclusion that is especially impressed by 
 Farman's disuse of these surfaces in machines of 
 his own design, despite the fact that he is one of the 
 earliest and most experienced Voisin pilots. 
 
 Very small vertical surfaces in the forward 
 elevator, as in the case of the semicircular surfaces 
 jj, Figure 185, in the Wright machines, and the tri- 
 angular surface j, Figure 229, in the Curtiss ma- 
 chines, are not quite so uncommon as are larger 
 
210 VEHICLES OF THE AIR 
 
 vertical surfaces in front, but even so their value is 
 decidedly doubtful unless to offset some other de- 
 fect in design. In the Wright machines these 
 vertical "half moons " are not rigidly fixed but are 
 allowed a few inches of flapping movement, on their 
 diameters as the axis, under the influence of side 
 gusts, presumably with the idea that they thus tend 
 to nose the front of the machine into the wind. 
 
 SUSTENTION OF SUKFACES 
 
 The sustaining capacities of different flat and 
 curved aeroplane surfaces moved through the air 
 at different speeds and at different angles of in- 
 cidence greatly vary with every new combination 
 of the innumerable possible factors. Determina- 
 tion of the most suitable surfaces and the most ad- 
 vantageous conditions therefore has long been one 
 of the greatest difficulties in the way of aeronauti- 
 cal progress. 
 
 EFFECT OF SECTION 
 
 As has been previously suggested (see Page 
 171), there is the greatest imaginable difference in 
 the sustaining effect of different wing sections, flat 
 surfaces being quite inferior to curved, of which 
 the best are more or less exact approximations to 
 parabolic forms. Moreover, with the ideal sur- 
 faces there are very curious and not widely under- 
 stood relations between the lift and drift between 
 the amount of sustention afforded by a given speed 
 of movement and the resistance (other than head 
 resistances and skin friction) to the forward move- 
 
AEROPLANE DETAILS 211 
 
 ment. In fact, with proper design and operation, 
 there is a positive forward inclination to the 
 sustaining force, or lift, which instead of being 
 normal to the chord of the surface or to its di- 
 rection of movement is definitely inclined forward 
 to an extent sufficient, with certain angles and 
 certain curves, wholly to overcome the drift (see 
 Page 190). 
 
 EFFECT OF ANGLE 
 
 Measured as a proportion of the unit resistance 
 met, w r hen a given surface is opposed flatwise or 
 with its chord at right angles to the air, the values 
 of lift and drift with different surfaces can be 
 tabulated in percentages of this " normal" at dif- 
 ferent speeds and different angles. Many such 
 tables have been prepared most successfully by 
 empirical investigations and from these tables it 
 has been attempted to deduce working formulas by 
 which to solve the variety of practical problems 
 that can arise in given cases. Unfortunately these 
 formulas have been found not to work out cor- 
 rectly in practice to any considerable extent, and 
 many inaccuracies are now known to exist in th3 
 most highly regarded tables, such as those of 
 Smeaton and of Lilienthal, the latter of which 
 are widely considered fairly correct though 
 slightly too high at very small angles. 
 
 EFFECT OF SPEED 
 
 The many formulas that are more or less widely 
 used in calculating the effect of speed upon the 
 sustention of different surfaces cannot, in the light 
 
212 VEHICLES OF THE AIR 
 
 of recent developments in the science and practice 
 of aeronautics, be accepted as correct except within 
 very narrow limits or in a very general way. It can 
 be safely asserted only that the sustention in- 
 creases much faster than the speed possibly with 
 its square. 
 
 Particularly interesting in this connection, 
 rather than especially exact, is the glimmer of 
 truth in "Langley's law" according to which the 
 power required for propelling an aeroplane sur- 
 face through the air indefinitely diminishes as the 
 speed increases. 
 
 EFFECT OF OUTLINE 
 
 With all other conditions equal the sustention 
 of a surface is subject to variation with change of 
 outline particularly with difference in width (see 
 Page 184). No adequate explanation of this phe- 
 nomenon is known, unless it be contained in the 
 reference cited. 
 
 EFFECT OF ADJACENT SUKFACES 
 
 A given surface moved through the air under 
 given conditions will invariably afford greater sup- 
 port when alone than when adjacent to other sur- 
 faces. In a biplane the sustention of the upper sur- 
 face is always materially lower than that of the 
 lower surface, especially if the separation of the 
 surfaces is insufficient or the forward speed very 
 low. In the case of following surfaces, as in Figures 
 97 and 225, at least partial correction for the ad- 
 jacent disturbance of the air can be had by making 
 
AEROPLANE DETAILS 213 
 
 the two surfaces of different form and inclination 
 (see Page 248). 
 
 CENTER OF PRESSURE 
 
 The center of pressure of a sustaining surface 
 is .the lateral axis on which the load is balanced 
 (see Page 181 and Figure 62). With wrong sur- 
 faces at wrong angles the center of pressure is a 
 most elusive and variable factor, tending always 
 to uncertain and precarious equilibrium, but with 
 correct surfaces it can be very definitely located 
 and equilibrium maintained by keeping the center 
 of gravity beneath it. 
 
 HEAD RESISTANCES 
 
 Contrary to the popular notion, the forward re- 
 sistances encountered in moving any object 
 through the air, no matter what its form, are 
 closely related to the " projected area", being little 
 influenced by "wind-cutting" shapes, thin edges, 
 and other misguided expedients to reduce this re- 
 sistance. This is experimentally proved in the 
 use of racing automobiles, which at speeds in ex- 
 cess of 100 miles an hour do not measurably differ 
 in their head resistances whether they have flat 
 or elaborately pointed fronts. Projectiles, even, of 
 the common pointed ogival forms do not travel at 
 velocities perceptibly greater than can be attained 
 under otherwise similar conditions with flat- 
 flat or blunt surface there is carried on the front 
 fronted projectiles. The reason for this seemingly 
 anomalous effect appears to be that in case of a 
 
214 VEHICLES OF THE AIR 
 
 of the visible structure an invisible cushion of com- 
 pressed air varying in its length and form in ac- 
 cordance with the speed, but always automatically 
 created to the exact shapes best calculated to pene- 
 trate and part the main body of the atmosphere 
 in most effective manner. 
 
 Against flat surfaces moved through the air, the 
 pressure is usually stated to vary with the square 
 of the velocity, a surface one foot square placed at 
 90, as in Figure 42, receiving pressures as follows, 
 according to one authority:* 
 
 Speed of movement in miles per hour. 7 14 21 41 61 82 92 
 Pressure in pounds per square foot.. .2 .9 1.9 7.5 16.7 30.7 37.9 
 
 At twenty-five miles an hour the surface re- 
 ceives a pressure of 3.24 pounds, while when it is 
 inclined to 15 from the direction of the current 
 this pressure, or drift, is reduced to .33 pounds, 
 with a lift of 1.5 pounds, as is made clear in Figure 
 42. The ratio of lift to thrust greatly increases as 
 the inclination decreases. 
 
 * According to a table compiled for the "Mechanical Engineer's 
 Pocket Book," the pressures on a square foot of flat surface in different 
 winds are as follows: 
 
 MILES PER HOUR CLASSIFICATION OF WIND PRESSURE ON SQUARE FOOT 
 
 1 Hardly perceptible .005 Pounds 
 
 2 Just perceptible .02 
 
 3 Just perceptible .044 
 
 4 Gentle breeze .079 
 
 5 Gentle breeze .123 
 
 10 Pleasant breeze .492 
 
 15 Pleasant breeze 1.107 
 
 20 Brisk gale 1.968 
 
 25 Brisk gale 3.075 
 
 30 High wind 4.428 
 
 35 High wind 6.027 
 
 40 Very high wind 7.872 
 
 45 Very high wind 9.963 
 
 50 Storm 12.300 
 
 60 i Great storm 17.712 
 
 70 Great storm 24.108 
 
 80 Hurricane 31.488 
 
 100.. ..Hurricane 49.2 
 
AEROPLANE DETAILS 215 
 
 Though not especially affected by the form of a 
 surface, head resistance is affected by the extent 
 of surface, being lower per unit of area on small 
 areas than it is on large. This is because the air 
 centrally in front of a large surface must be dis- 
 placed to a greater extent laterally to pass the sur- 
 face than is necessary with a small surface. Also, 
 the rear form of an object is of importance, a blunt 
 front and finely tapered rear outline being that 
 calculated to displace and reform the air streams 
 with the expenditure of the least energy. 
 
 BALANCING 
 
 An aeroplane can only tip over sideways or end- 
 ways, consequently to maintain it right-side up 
 can require provision only for maintaining lateral 
 and longitudinal equilibrium. 
 
 LATERAL BALANCE 
 
 It is now well established, both from observa- 
 tion of flying animals and in the construction of 
 flying machines that there is a considerable number 
 of ways, all more or less effective, of maintaining 
 the lateral balance of an aeroplane. These methods 
 are, moreover, capable of use both independently 
 and in various combinations.* Furthermore, some 
 of them are of a nature to operate automatically 
 against disturbing forces, whereas others require 
 actuation by controlling means. 
 
 * Many birds obviously employ wing warping, tilting and swinging 
 of wing tips, variation of wing areas and angles, and shifting of the 
 weight, in a great variety of combinations. 
 
216 VEHICLES OF THE AIR 
 
 Vertical Surfaces for maintaining balance are 
 analagous to the similar use of such surfaces in box 
 kites, and act in a most effective and wholly auto- 
 matic manner any tilting bringing the side of the 
 vertical surface that is towards the inclination into 
 play as a more or less effective lifting surface (ac- 
 cording to the extent of the tilting) , with the result 
 that the air pressures promptly force it back to its 
 normal position. As has been previously explained 
 (see Page 209), it seems for a number of excellent 
 reasons inadvisable to place vertical surfaces 
 anywhere but at the rear of a machine. 
 
 Dihedral Angles of wings operate similarly to 
 vertical surfaces in maintaining balance, being in 
 their normal position at angles of less than their 
 maximum effectiveness, so that tilting of the 
 vehicle renders the lowered wing more effective 
 and thus automatically corrects itself. The objec- 
 tions to dihedral wings are explained on Page 207. 
 
 Wing Warping as a means of maintaining 
 lateral balance, for which it is used in the modern 
 Wright, Bleriot, Montgomery, and other machines, 
 consists of a simple unsymmetrical twisting of the 
 wing ends by any suitable means so as to transfer 
 the maximum lift from one side of the machine to 
 the other by varying the angles of wing-tip in- 
 clination to the line of travel. This method of 
 balancing, which is perhaps the most effective 
 known, was patented in Prance by D' Esterno, was 
 used by Le Bris, and was first patented in the 
 United States by Mouillard (see Pigure 262). 
 Another early recognition of its merits appears in 
 
AEROPLANE DETAILS 217 
 
 the Scientific American Supplement of June 4, 
 1881, in which, in an article on aeronautics by Tim 
 Choinski, it is remarked that "When a flying bird 
 wants to go sidewise or turn, it slopes backward to 
 an inclined plane but one wing of that side where it 
 wants to go." Despite the numerous early recog- 
 nitions of the value of wing warping it did not ap- 
 pear in combination with otherwise successfully 
 operative mechanisms until within comparatively 
 recent years. Its application to the Wright, Bleriot, 
 and Montgomery machines is shown in Figures 
 185, 197, and 225. An objection to wing warping 
 as it has been commonly applied is that the ab- 
 rupter inclination of that end of the wing causes 
 a greater resistance to and consequent slowing of 
 the side of the vehicle which should go the fastest 
 in executing a turn it being necessary in some 
 aeroplanes to resist this tendency by the simul- 
 taneous manipulation of rudder-like vertical sur- 
 faces. 
 
 Tilting Wing Tips, capable of being thrown up 
 or down into positions less effective than the nor- 
 mal, constitute a possible means of balancing that 
 so far as the writer is aware has not been tried, 
 though it would at least present the advantage of 
 avoiding the variation in forward resistances re- 
 ferred to in the preceding paragraph. 
 
 Hinged Wing Tips, or "ailerons", adjacent to 
 the end or the rear edges of the wing tips proper, 
 or wholly separated from these in the case of 
 several biplanes, are a common and successful 
 means of maintaining lateral balance without re- 
 
218 VEHICLES OF THE AIR 
 
 course to wing warping. Typical aileron arrange- 
 ments are clearly shown at a a a a in Figures 76, 77, 
 78, 79, 80, and 81. 
 
 Variable Wing Areas, while a common maneu- 
 ver with many birds, have not yet been provided 
 for in any successful flying machine. A suggested 
 
 FIGURE 82. Sliding Wing Ends, 
 
 method of varying wing areas is illustrated in 
 Figure 82. It is evidently analogous to shifting the 
 weight, securing practically the same result. 
 
 Shifting Weight as a means of controlling 
 lateral balance was first practically employed by 
 Lilienthal, and subsequently by Pilcher, Chanute, 
 and others. In some of their early experiments 
 the Wrights controlled the wing warping by a 
 movement of the operator's body side wise in a 
 cradle-like control frame, thus securing a combina- 
 tion of warping with weight shifting (see Page 
 229). One very serious objection to shifting 
 weight is that it requires extraordinary acrobatic 
 skill to apply this method successfully. 
 
 Rocking Wings, pivoted at their point of attach- 
 ment to the body of the machine, are a very old 
 idea. A notable application of this principle in a 
 successful modern monoplane is found in the more 
 recent Antoinette machines, in which the lateral 
 balancing is effected solely by dissimilar rocking 
 
AEROPLANE DETAILS 
 
 219 
 
 of the entire wings. One of these machines is il- 
 lustrated in Figures 215 and 216. A most unusual 
 application of rocking wings is that in the Cody 
 biplane (see Figure 202), in which they appear in 
 the forward elevator and serve to control either 
 lateral or longitudinal balance, according to 
 whether they are rocked oppositely or together. 
 
 Swinging Wing Tips are another feature of bird 
 mechanism that offers interesting possibilities of 
 application to aeroplanes. This idea was proposed 
 by Montgomery as early as 1893, and was used with 
 considerable success by Chanute in a somewhat 
 different form shortly after (see Figure 261), in 
 which the movement of the wing tips was effected 
 
 FIGURE 83. Swinging Wing Ends. 
 
 solely by variations in wind pressure. A control- 
 manipulated system of swinging wing tips is sug- 
 gested in Figure 83. It is an idea of the writers' 
 that if in this the wing tips a a a a be given a down 
 curve at their ends, thus approximating a correct 
 wing section in two directions, the result of swing- 
 ing them to the rear will be to increase the susten- 
 tion and the tangental component forward while 
 at the same time reducing head resistance. This 
 would afford an ideal method of steering and close 
 observation is convincing to the effect that it is 
 a method used by many birds. 
 
220 VEHICLES OF THE AIR 
 
 Plural Wing Tips are plainly existent in the 
 finger-like separated tip feathers of the wings of 
 many soaring birds. The exact utility and manipu- 
 lation of this type of wing is a mystery still await- 
 ing satisfactory explanation, and perhaps contain- 
 ing the secret of some most advantageous con- 
 struction. 
 
 LONGITUDINAL BALANCE 
 
 Longitudinal balancing means are necessary for 
 two purposes primarily to prevent forward or 
 backward upsetting of the vehicle and secondarily 
 to provide means of steering on up or down slants 
 of air. As in the case of lateral balance, the prob- 
 lem of longitudinal balance is one that admits of a 
 variety of solutions. 
 
 By Front Rudders, or " elevators", the hori- 
 zontal course of an aeroplane can be effectively 
 kept under control, as is well proved in the case 
 of many modern aeroplanes (see Figures 80, 172, 
 187, 196, 207, 208, 209, 211, and 229) . This elevator 
 placing is more common to biplanes than to mono- 
 planes. 
 
 By Bear Rudders practically the same effects 
 can be had as with front rudders, the placing being 
 therefore a matter of choice or of minor considera- 
 tion. Typical rear-rudder arrangements for con- 
 trolling fore-and-aft balance are shown at h h in 
 Figures 85, 216, 217, 222, and 229, in the latter of 
 which it will be noted that both front and rear 
 elevating surfaces are provided. 
 
 Box Tails as longitudinally stabilizing elements 
 
AEROPLANE DETAILS 221 
 
 are found highly effective and almost automatic. 
 The most important present examples of this con- 
 struction are the Farman and Voisin machines 
 (see Figures 81, 207, and 211). 
 
 Shifting Weights for maintaining longitudinal 
 balance are even less suitable than for lateral bal- 
 ancing (see Page 218). In the Weiss monoplane 
 an unsuccessful attempt was recently made to ap- 
 ply this principle, the weight sliding on wires and 
 being actuated by a lazy-tongs device. 
 
 Plural Carrying Surfaces are commonly pro- 
 vided as important features in the design of many 
 modern aeroplanes. And, indeed, unless definitely 
 made to operate against the air above them as well 
 as that below them, as in the case of the Wright 
 flexible elevator (see Figure 84), it is necessary 
 that elevator surfaces carry some weight if their 
 action is to be effective. This being the case, the 
 proportion of the weight carried on the elevator 
 will be in proportion to the relation of its area to 
 that of its main surfaces. An extreme example 
 of the possibilities in this direction appears in the 
 Montgomery double monoplane (see Figure 225), 
 in which the two main sustaining surfaces, though 
 equal in area, can be variably inclined to each other 
 for the purpose of controlling longitudinal equi- 
 librium (see Page 220). 
 
 AUTOMATIC EQUILIBRIUM 
 
 In its common significance this term has come to 
 be descriptive of means or devices for correcting 
 an aeroplane's deviations from its normal level 
 
222 VEHICLES OF THE AIR 
 
 automatically, independent of the attention of the 
 operator. In the majority of projects for its appli- 
 cation it is designed to affect only the lateral con- 
 trol the fore-and-aft control remaining in the 
 hands of the operator as a necessary means of 
 governing descent and ascent. 
 
 Arrangement of Surfaces is probably the 
 simplest as well as the most effective means of 
 maintaining lateral balance automatically, as is ex- 
 plained on Page 216, where the effect of vertical 
 surfaces is set forth in detail. 
 
 Electrical Devices for securing equilibrium are 
 of a class that automatically correct rather than 
 maintain balance of a machine, and even in their 
 simplest forms are of a complication requiring that 
 hand control be always ready to supplement their 
 action if disaster is not to be deliberately courted. 
 One proposal for an electrical balancing device 
 involves primarily a bent glass tube in which a 
 small quantity of mercury makes and breaks differ- 
 ent contacts as the vehicle tilts in different direc- 
 tions. Through these contacts power is applied 
 to the devices that must be manipulated to rectify 
 the equilibrium. 
 
 The Gyroscope, because of its peculiar property 
 of resisting forces that tend to shift its plane of 
 rotation, can be so mounted as to remain in a given 
 position irrespective of the movements of its sur- 
 roundings. In this way a secondary control can 
 oe maintained over stabilizing surfaces by the auto- 
 matic distribution of power for their manipulation. 
 Another way of utilizing the gyroscope is by 
 
AEROPLANE DETAILS 223 
 
 making it comparatively heavy and mounting it 
 solidly on a vertical axis. The most impractical 
 feature of this plan the weight involved it is 
 proposed to escape by utilizing as gyroscopes parts 
 of the machine that are required in some form in 
 any case, as the flywheels of engines, etc. 
 
 Compressed Air, or " fluid pressure", has been 
 planned for as a means of transmitting balancing 
 manipulations to aileron and elevator surfaces in a 
 patent issued to the Wright brothers in England. 
 In this system, the initial control is effected by the 
 variation of the air pressures on specially provided 
 vanes, or by the swinging of a pendulum. 
 
 The Pendulum, preferably swung in a reservoir 
 of oil or other liquid to suppress violent oscilla- 
 tions, has been often suggested as a possible means 
 to automatic stability, but attempted applications 
 have met with no more success than has attended 
 efforts to make practical use of other systems of 
 automatic balancing. 
 
 STEERING 
 
 The steering of modern aeroplanes is a problem 
 that presents so few difficulties that it has been 
 more or less successfully solved in a considerable 
 variety of constructions, all of which, however, are 
 subject to certain effects and conditions that must 
 be reckoned with by the experimenter. 
 
 EFFECTS OF BALANCING 
 
 In balancing an aeroplane laterally by the 
 means at the present time most preferred, there is 
 
224 VEHICLES OF TEE AIR 
 
 in most constructions a pronounced steering as well 
 as the balancing effect. Thus in wing warping 
 systems the manipulation of the wing ends is a 
 most effective means of steering and in several 
 machines is definitely so used. In such steering, 
 however, it is necessary to counteract the lag of 
 the most inclined tip (see Page 217) either by the 
 side resistance of a large fin or by the manipulation 
 of a smaller rudder. 
 
 VEETICAL EUDDEES 
 
 Vertical rudders, in the proper significance of 
 the term, are rudders used for lateral, or horizontal, 
 steering, wherefore they must be placed vertically. 
 This fact, and a considerable inconsistency in 
 different writers' use of the term, has given rise 
 to no small amount of confusion, which can be dis- 
 pelled only by more general agreement as to what 
 terms are to mean. Perhaps the easiest escape 
 from the difficulty is to be found in the English 
 substitution of " elevator" for horizontal rudder, 
 leaving the " vertical rudder", placed vertically for 
 steering on a horizontal plane, to be known simply 
 as the rudder. 
 
 Pivoted Rudders, as shown at i, Figures 85, 
 198, 209, 216, 224, and 229, and in Figure 195, are 
 the common form, though perhaps not the most 
 meritorious. 
 
 Flexible Rudders, of the type illustrated in 
 Figure 84, which is taken from the drawings of a 
 patent issued to the Wright brothers, have the 
 merit that they always present curved, instead of 
 
FIGURE 85. Rear Controls of Antoinette Monoplane. In this Mi are horizontally-pivoted 
 surfaces for steering up or down; I is a vertically pivoted surface for steering sidewise ; and 
 ;' is a vertical fin used for its stabilizing effect. 
 
 FIGURE 86. Double Control from Single Wheel. As is very apparent from the system 
 shown in this illustration, two distinct movements can be readily produced by manipulation 
 of a single wheel. For example, the cords passing around the pulley at a can be extended 
 to operate wing tips, instead of the vane &., when the wheel is revolved, while the link c can 
 as well be connected to a vertical rudder as to the arrow d. 
 
AEROPLANE DETAILS 
 
 225 
 
 the less effective flat surfaces, to the air they work 
 against. Obviously this principle of construc- 
 
 FIGURE 84. Wright Flexible Elevator or Rudder. When the hand lever is 
 moved into either of the positions shown by the dotted lines the steering sur- 
 faces are corespondingly sprung into curved form, presenting approximately 
 correct surfaces to the air above or below them, as the case may be. This 
 springing is due to the pivotal points of the surfaces being not in line with the 
 pivot of the actuating bar between them. 
 
 tion is applicable to either vertical or horizontal 
 rudders. 
 
 HORIZONTAL RUDDERS 
 
 Horizontal rudders, or elevators, usually con- 
 trol not only the vertical steering but also serve to 
 maintain the longitudinal equilibrium. Conse- 
 quently they serve a secondary function as sustain- 
 ing surfaces, for which reason it has been already 
 necessary to accord them fairly exhaustive con- 
 sideration (see Page 220). 
 
 TWISTING RUDDERS 
 
 Rudders of the type illustrated at h in Figure 
 222 are in a class by themselves. It has been ex- 
 plained (see Page 161) that flying fish are the only 
 ones of nature 's fliers normally provided with ver- 
 tical surfaces, but this statement perhaps disre- 
 gards the fact that most birds, by twisting move- 
 ments of their tails, are able to use these as vertical 
 
226 VEHICLES OF THE AIR 
 
 rudders. In the E. E. P. rudder just referred to 
 it is sought to imitate this action by providing a 
 rudder with a revolving as well as flexing move- 
 ment so that it can be opposed to the air in any 
 possible direction. There is no question of the 
 effectiveness of such an action, but the problem of 
 a suitable controlling mechanism for it is another 
 and more difficult matter. 
 
 CONTEOLLING MEANS 
 
 The number and complexity of controlling 
 movements involved in the operation and piloting 
 of an aeroplane have long constituted one of the 
 greatest bars to progress in this field of engineer- 
 ing, and still present some of the most difficult of 
 its unsolved problems. 
 
 Man being a creature possessed of only two feet 
 and two hands, and flight ordinarily requiring as 
 displayed by the birds a variety of manipulations 
 delicate and vigorous, quick and slow, simple and 
 complicated, which man can scarcely hope to imi- 
 tate, the difficulty of producing them in unfailingly 
 effective coordination must be apparent. 
 
 For there are lateral and longitudinal balance 
 to be maintained, vertical and horizontal steering 
 to be effected, a motor to regulate and adjust, in- 
 struments and devices to be watched, and the 
 special conditions of starting and landing to be 
 encountered from all of which it might appear 
 that the average aviator must at least find sufficient 
 to occupy his attention if none of these functions 
 are performed automatically. 
 
FIGURE ST. Shoulder-Fork Control. This is a characteristic example of the means of 
 control found successful in the Curtiss, Santos Dumont, and other machines. The fork d 
 engages the shoulders of the operator and is so connected that its lateral swing acts upon 
 the balancing mechanisms of the biplane by the natural swing of the operator's body. 
 
AEROPLANE DETAILS 227 
 
 But problems do not exist without roads to 
 their solution, and already in man's advancing 
 mastery of the air much progress has been made 
 in the devising of simple and effective controlling 
 systems, while more simple and more effective 
 systems are quitejn prospect. 
 
 COMPOUND MOVEMENTS 
 
 One of the most effective methods of control is 
 the combination of two or more movements in a 
 device manipulated by a single hand. A charac- 
 teristic example is given in Figure 86, which is 
 substantially that employed in the Voisin and 
 Curtiss machines (see Figures 202 and 228). An- 
 other example is the lever that controls the wing 
 warping and the vertical rudder in the Wright 
 machines (see Figures 185 and 190). 
 
 PLUEAL OPERATOES 
 
 A plurality of operators in steam and sailing 
 vessel navigation is the rule in all but the smallest 
 craft, larger ships being not capable of manage- 
 ment by a single individual. In the largest steam- 
 ships the pilot, upon whom devolves the steering 
 and the general control of the vessel, has no direct 
 means of causing it to change its speed, stop, or 
 go astern these maneuvers being solely in the 
 hands of the engineer, with whom the pilot is in 
 communication by signals. Similarly, in locomo- 
 tive operation, control of the steam pressure and 
 fire falls to the fireman or stoker, while the throttle, 
 brake handles, etc., are left to the engineer or 
 driver. 
 
228 VEHICLES OF THE AIR 
 
 In flying machines, except in the case of diri- 
 gible balloons, the only use of two operators of 
 which the writer knows is ascribed to the Wrights, 
 who are said to have operated their early three- 
 lever machine together. 
 
 In further development of flying machines the 
 chief need for two operators would appear to be 
 most required as a means of maintaining the motor 
 and the machine generally in continuously and 
 safely operative condition. 
 
 WHEELS 
 
 Wheel controls having been found thoroughly 
 satisfactory in years of experience with automo- 
 biles and watercraft naturally have found exten- 
 sive application to flying machines, in which their 
 advantages of compact form with great range of 
 movement prove very valuable. Typical wheel 
 controls are illustrated in Figures 86, 172, 202, 228, 
 229, and 250. 
 
 LEVEES 
 
 Lever controls are almost ideally simple and in 
 some circumstances perhaps afford less chance for 
 an operator to become confused, by their quality 
 of obviously indicating their position. Levers are 
 used to the exclusion of wheels by the Wrights, 
 and have been employed with considerable success 
 by the Voisins, Farman, Pelterie, and others (see 
 Figures 185, 190, 248, and 252). Undoubtedly 
 there is much to be said for their positive action 
 and simple and inexpensive construction. 
 
FIGURE 88. Frame, or "Fuselage," of New Voisin Biplane. The ingenious use of wood, 
 left of larger section at the points of attachment to the cross struts, which set into metal 
 sockets, and the rigid diagonal wire bracing, constitute a peculiarly interesting example of 
 modern high-grade aeroplane construction. 
 
 FIGURE 89. Fuselage of Bolotoff Monoplane. In the finished machine this frame is 
 covered over with fabric while the boarded floor comes beneath the operator's seat, motor, etc. 
 
AEROPLANE DETAILS 229 
 
 PEDALS 
 
 Except for the manipulation of minor devices, 
 pedals have not been extensively favored in aero- 
 plane controlling systems, though Bleriot uses a 
 pedal to control the elevator of his monoplanes 
 (see Figure 197). Other examples of foot or pedal 
 control appear in Figures 225 and 248. 
 
 MISCELLANEOUS 
 
 Besides wheel, lever, and pedal controls, there 
 are several other devices that have been found of 
 more or less practical utility. 
 
 Shoulder Forks, embracing the shoulders of the 
 operator, as at d, Figure 87, are used to some ex- 
 tent to control lateral balance by the natural swing 
 of the pilot's body as the machine cants to one side 
 or the other. The most conspicuously successful 
 example of the use of shoulder forks appears in 
 the Aerial Experiment Association's, and the Cur- 
 tiss machines (see Figures 228 and 229). Prac- 
 tically similar in its results though not in its con- 
 struction is Santos-Dumont's ingenious control of 
 the wing warping of his tiny monoplane (see 
 Figure 221) by a lever engaging with a short piece 
 of tubing sewed into the back of his coat. 
 
 Body Cradles (see Figure 259) were at first 
 employed by the Wrights as a means of wing-tip 
 control for their early glider, but have .since been 
 given up by them and are not known to have been 
 used in any successful flying machine. 
 
230 VEHICLES OF THE AIR 
 
 FRAMING 
 
 The strongest and lightest frame constructions 
 for the wings, bodies and other elements of aero- 
 plane structures have so far followed very closely 
 the general lines suggested in Figures 71, 72, 73, 
 74, 75, 88, 89, 101, 170, 185, 192, 193, 194, 195, 197, 
 225, and 228. For further details concerning this 
 subject see Chapters 11 and 12. 
 
CHAPTER FIVE 
 
 PROPULSION 
 
 Present-day workers in aeronautics have almost 
 without exception achieved their conspicuous suc- 
 cesses with machines definitely driven through the 
 air by suitable propellers, the power for which is 
 supplied by light-weight engines. This is true of 
 both heavier-than-air and lighter-than-air ma- 
 chines though in the case of the aeroplane there is 
 much evidence of mysterious and little-understood 
 laws upsettings of the very fundamentals of 
 established theories of force and motion which in 
 the opinion of at least a few investigators of the 
 highest standing promise that man will ultimately 
 achieve the indefinite gliding flight of the great 
 soaring birds. This question, however, is one that 
 calls for only casual comment here, it being more 
 fully discussed in Chapters 4 and 6 (see Pages 164 
 and 169. It is enough for the present purpose to 
 assume that, present flying machines requiring pro- 
 pulsion, it is of importance to consider and define 
 the best methods of securing such propulsion. 
 
 MISCELLANEOUS PROPELLING DEVICES 
 
 Though the screw propeller is the only device 
 that has come into extensive use or met with any 
 
 231 
 
232 
 
 VEHICLES OF THE AIR 
 
 considerable success in the propulsion of aerial 
 vehicles, it is by no means the only device that 
 can be applied to the purpose. Such other mechan- 
 isms as have been developed, though, are interest- 
 ing more because of the theoretical alternatives 
 they present rather than because of anything prac- 
 tical in either their promise or their performance. 
 Of the miscellaneous propelling devices that 
 are important enough to be considered there are 
 three chief classes reciprocating wings and oars, 
 paddles, and undulating or wave surfaces. 
 
 FEATHERING PADDLES 
 
 Feathering paddles, in a 
 measure like those used for 
 boat propulsion, have been 
 proposed for propelling and 
 lifting flying machines. An 
 example of one for both 
 propelling and lifting is pic- 
 tured in Figure 90. In all 
 devices of this character the 
 principle is that of a 
 plurality of surfaces carried 
 rapidly around in a revolv- 
 ing structure, within which 
 they possess a secondary 
 movement that causes them 
 to travel flatwise when going 
 downwardly or rearwardly 
 and edgewise when traveling 
 upwardly or forwardly. A 
 
 FIGURE 90. Feathe ring- 
 Paddle Flying Machine. By 
 the rotation of e by the belt 
 c it was expected that the 
 paddles aaaa would sustain the 
 weight by beating down on 
 the air, it being noted that 
 they come down flatwise but 
 rise edgewise through the ac- 
 tion of the feathering me- 
 chanism. 
 
PROPULSION 
 
 233 
 
 simplified modification of this idea is the use of an 
 ordinary paddle wheel in a housing, as shown in 
 Figures 91, the idea being that its exposed portion 
 at a, revolving as shown by the 
 small arrow, will produce a for- 
 ward drive in the direction of 
 the large arrow. It is almost 
 needless to assert that all de- 
 vices of this general character 
 so far built are heavy, compli- 
 cated, and inefficient. 
 
 WAVE SURFACES 
 
 FIGURE 91. Partially- 
 Housed Paddle Wheel. 
 Proposed for propelling 
 in direction of large ar- 
 row by effect of exposed 
 blades at a. 
 
 A somewhat-peculiar and very interesting type 
 of propelling or sustaining mechanism is that sug- 
 gested in Figure 92, in 
 which a b is a flexible 
 surface, of length and 
 width enough to pre- 
 sent considerable area, 
 
 FIGURE, 92. wave surface. Proposed made capable of rapid 
 
 undulation by suitable 
 mechanism with the 
 idea of causing it to progress through the water. 
 The almost hopelessly difficult problem of con- 
 triving durable, reliable, and efficient mechanism 
 for effecting the undulation required is probably 
 a far greater bar to a practical result than any de- 
 fect in principle. A flying machine in which this 
 principle was involved was that of F. W. Breary, 
 secretary of the Aeronautical Society of Great 
 Britain in 1879. 
 
 feet travel in the direction of the arrow. 
 
234 VEHICLES OF THE AIR 
 
 KECIPKOCATING WINGS AND OAKS 
 
 Reciprocating wings being the mechanism by 
 which birds, insects and other flying animals secure 
 propulsion, and in many cases sustention, it is only 
 natural that many designers should have expected 
 to derive satisfactory operation from copies of 
 the mechanism of nature. But, more because of 
 the efficiency of properly designed air propellers 
 than because of the inefficiency of alternative con- 
 structions, and because of the greater simplicity 
 and reliablity of the simple rotating device, few 
 engineers of real standing have been able to con- 
 vince themselves of any material advantages to be 
 gained by recourse to the more-complicated and 
 less-promising wing propulsion. Another basis of 
 comparison by which the propeller profits, and 
 which incidentally explains nature's use of a type 
 of mechanism that man finds less suited to his 
 constructing abilities, is discussed on Page 25. 
 
 One of the earliest attempts to produce a dirig- 
 ible balloon involved the use of reciprocating 
 wings, the ascent being that by Blanchard, on 
 March 2, 1784, from Paris (see Page 72). These 
 wings being worked by man power it is almost 
 unnecessary to remark that the attempt ended in 
 complete failure. 
 
 Both before and after the foregoing, hundreds 
 of investigators have sought to secure sustention 
 or propulsion, or both, from the action of recipro- 
 cating wings. Such success as has been secured, 
 however, has been very small, though it is to be 
 admitted that reciprocating wings used merely for 
 

 
PROPULSION 235 
 
 propulsion have usually afforded results much 
 superior to any that have been attained in con- 
 structions intended to lift as well as to propel by 
 the use of this type of mechanism. 
 
 Undoubtedly the most successful use on record 
 of reciprocating wings was their employment as 
 propelling elements in the various model flying 
 machines built and flown by Hargrave (see Page 
 122), which flew well for distances limited only by 
 the ability to carry fuel. The wings used on the 
 most successful of the Hargrave models were nor- 
 mally straight and flat, the curvature and varying 
 angles of action desirable to produce the best effect 
 being had only to the extent that the wings 
 deformed with a feathering action under the pres- 
 sures and the inertia effects involved in the rapid 
 flapping, thus skulling the whole machine along 
 through the air. 
 
 The highest speed of reciprocation secured with 
 the Hargrave machines was 248 double beats a 
 minute with a 36-inch wing, weighing only a few 
 ounces, and moved through an arc of not over 80, 
 corresponding to a tip speed of possibly 1300 feet 
 a minute fully twice that of the wings of any 
 flying animal, which Marey and Lendenf eld have 
 shown move with remarkably little variation at 
 about half this speed, the proportioning of wing 
 length to rate of vibration being invariably so 
 arranged as to produce this result. Thus the bee, 
 with a wing length of about inch, makes 11,400 
 beats a minute; the sparrow, with a wing length 
 of about 4 inches, makes 720 beats a minute ; and 
 
236 VEHICLES OF THE AIR 
 
 the stork, with a wing length of 27 inches, makes 
 105 beats a minute. When it is discovered that 
 1X11,400=2850; 4x720=2880; and 27x105= 
 2835, at least a glimmering of the law is very 
 apparent. 
 
 It is a safe generalization, based upon known 
 facts of engineering, that tip speeds materially 
 higher than those secured by Hargrave are not 
 likely to be attained in any durable reciprocating- 
 wing mechanism. On the other hand, revolving 
 propellers are safely worked at peripheral speeds 
 of 40,000 feet a minute. Even Hargrave has 
 admitted "that the screw and the flapping wings 
 are about equally effective as instruments of pro- 
 pulsion" despite the fact that he, undoubtedly the 
 foremost experimenter with ornithopter propul- 
 sion, tried propellers now known to be exceedingly 
 inefficient. 
 
 SCEEW PROPELLERS 
 
 Clearly, the surfaces of propeller blades are 
 directly analogous in their action upon the air to 
 the action of aeroplanes traveling in helices (when 
 the machine is traveling ; in circles when it is still) 
 of diameter so small that there is more or less 
 material difference in the circumferences of the 
 concentric paths traversed and in the consequent 
 relative speeds of the portions of the blade surfaces 
 traversing them. These considerations therefore 
 indicate that the problems of propeller design must 
 involve all the complex problems of ordinary aero- 
 plane supporting surfaces in addition to other 
 
PROPULSION 237 
 
 intricate factors introduced by the elements of 
 centrifugal force, the screw form necessary to con- 
 form to the peculiar path of travel, and the varying 
 relative speeds of the different portions of the 
 surfaces. 
 
 SOME COMPARISONS 
 
 Much confusion has existed in the past and 
 still exists in the minds of the uninformed who 
 fail to distinguish between the functions of air 
 propellers and the functions of similar but not 
 analogous mechanisms. To clear away this confu- 
 sion, it should be understood that there are three 
 possible devices of the same general appearance 
 but adapted to quite different purposes. First of 
 these is the ordinary windmill wheel, designed to 
 rotate from the reactions occasioned by a cylin- 
 drical stream of air flowing through its circle of 
 rotation ; second is the revolving fan, which is theo- 
 retically and practically the opposite of the wind- 
 mill wheel, it being designed to produce a current 
 by, so to speak, shearing loose a cylinder of air 
 from the surrounding air and forcing this cylinder 
 of air to flow through its circle of rotation; and 
 third is the air propeller, bearing no such close 
 relationship to the other two devices as they sus- 
 tain to each other an air propeller being intended 
 in a strict sense neither to react from disturbed 
 air flowing through it nor to cause a flow of air, 
 its proper function being that of progressing with 
 its attached mechanisms through the air with a 
 minimum disturbance as nearly as possible like 
 
238 VEHICLES OF THE AIR 
 
 a screw in a solid nut. Unavoidably, when first 
 started or when traveling slower than its proper 
 pitch speed, an air propeller must operate as a 
 more or less efficient fan, but under ideal condi- 
 tions of proper functioning its blades will slide 
 through their helices of travel (see Page 239) with 
 no disturbance of air but that due to the compres- 
 sions and neutralizing reactions against their 
 effective surfaces. 
 
 ESSENTIAL CHARACTERISTICS 
 
 The essential characteristic of a screw pro- 
 peller being its perfect adaptation to travel in a 
 helical path it follows that in addition to conform- 
 ing as nearly as may be to other considerations of 
 design it must also partake of the character of a 
 true screw, the elements of which therefore demand 
 examination. 
 
 If the path of a, Figure 93, at the extremity 
 of a revolving and advancing propeller blade, be 
 described in the interior surface of a hollow cyl- 
 inder its appearance will be that of the solid line 
 c, from which it is at once evident that there are 
 for any possible screw several fundamental fac- 
 tors. One of these is the extreme diameter, which 
 determines the diameter of the cylinder of air 
 through which progression is effected; another 
 is the pitch f which is the amount of advance per 
 revolution ; and a third is the angle of Made travel, 
 which clearly bears a direct determining relation to 
 the pitch and therefore can be expressed by the 
 
PROPULSION 
 
 239 
 
 FIGURE 93. Helices of Propeller Travel. 
 The point d takes the course e, and the 
 point a the course c, in advancing through 
 the air. 
 
 percent the pitch is of the circumference. Continu- 
 ing the examination, it develops that a point in a 
 propeller blade, as at d, not at the extremity of the 
 blade and thus com- 
 pelled to travel the 
 smaller dotted helix 
 c, must nevertheless 
 advance the same 
 axial distance per 
 revolution as the 
 point a, because the 
 propeller as a 
 whole, including all 
 points within it, is an inflexible mechanical unit, all 
 parts of which must therefore progress at a uni- 
 form rate along the axis of the invisible cylinder of 
 
 air. But since e is (in the 
 proportions sketched, and 
 considered as a circle) only 
 one-half the diameter and 
 circumference of the helix c 
 the given advance with only 
 half the rotational travel re- 
 quires that the angle of 
 blade travel at d must be 
 twice that at a, while the 
 angles at all other points 
 along the blade lengths must similarly vary in di- 
 rect proportion with the varying helices traveled. 
 This may be more apparent in the end view, Figure 
 94, of the propeller and helices, in which the hel- 
 ical paths of the blades appear as circles as 
 
 FIGURE 94. Circles of 
 Propeller travel. The 
 point d takes the path e, 
 and the point a the path 
 be, when the propeller is 
 restrained from advancing. 
 
240 
 
 VEHICLES OF THE AIR 
 
 indeed they become if the propeller is permitted 
 to revolve while kept from advancing. In this 
 figure the point a travels the course be and the 
 point d travels the course e. Further to simplify 
 the analysis, now let the circles be and e, Figure 
 94, be represented by the solid lines be and e, Fig- 
 ure 95, in which each of these lines starts from a 
 point at a place proportionate to the circumference 
 it represents e being only .7 as long as be while 
 
 i 
 
 FIGURE 95. Diagram of Propeller Pitch. The base line representing the 
 circumference of the propeller circle, the different diagonal lines represent 
 the angles of travel of different blade portions. 
 
 the distance / g equals the pitch of the screw. 
 Obviously now, as has been explained, for the point 
 d in the propeller blade to travel from f to g in 
 the distance eg it must be inclined at twice the angle 
 called for at a to make the distance f g in going 
 the length of be. Intermediate portions of the 
 blades, having to travel along circumferences rep- 
 resented by the infinity of dotted lines suggested 
 at h and i, will correspondingly call for an infinity 
 of angles of travel corresponding to the angles of 
 
FIGURE 103. Wooden Propeller Applied to Car of Clement Dirigible Balloon. 
 
 FIGURE 104. All-Metal Propeller Applied to Dirigible Balloon. This is a somewhat 
 unusual construction, involving hub arms welded to the rarefaction surface of the sheet-metal 
 blades. It constitutes an interesting example of an attempt to secure results with the highest 
 possible grade of material in combination with a most modern method of assembling. 
 
PROPULSION 241 
 
 h i, giving to the theoretically correct blade a grad- 
 ual twist of blade travel, increasing from a blade 
 travel parallel with the propeller axis at the exact 
 propeller center j to a surface traveling at the 
 pitch angle at the propeller tip a. 
 
 A very curious development in propeller prac- 
 tise has been the highly-successful use of propellers 
 with "straight pitch" that is, with blade angles 
 not varying from hub to tip, thus defying most 
 theories of propeller construction. It was with 
 such a propeller, of uniform blade width, that 
 Glenn Curtiss flew at Rheims, France, in August, 
 1909, on which occasion it was experimentally 
 determined that a scientifically designed and per- 
 fectly constructed Chauviere propeller, such as 
 was used by Bleriot in crossing the English Chan- 
 nel and by Farman in his 118-mile flight at Rheims, 
 materially slowed Curtiss' biplane. The explana- 
 tion possibly is to be found in some not-understood 
 flows of outer cylinders of air over concentric 
 cylinders of air within them. 
 
 Effective Surface of a propeller is that portion 
 of the circle swept by the blades against which 
 thrust is developed. For two principal reasons 
 there is little advantage in attempting to make 
 effective surface of the whole of the circle. One 
 reason is that the speeds and angles of blade travel 
 towards the center of the circle are too slow and 
 too inclined to produce material thrust with any 
 form of blade surface that it is possible to devise. 
 The other reason is that the areas of circles vary- 
 ing with the squares of their diameters very little 
 
242 VEHICLES OF THE AIR 
 
 area is lost in eliminating from thrust considera- 
 tion considerable portions of the inner ends of 
 the propeller blades. Thus, if one-half of the blade 
 length, from j to d, Figure 94, is eliminated from 
 consideration as thrust surface, three-fourths of 
 the area of the circle a b c is still retained the 
 circle d e, swept by j d, being only one-fourth the 
 area of a b c, three-fourths of which is swept by d a. 
 Angles of Blades in an aerial propeller should 
 not be the same at given points as the correspond- 
 ing angles of blade travel, though it has been a 
 common mistake to assume that they should. The 
 reason of this becomes most apparent by consid- 
 
 FIGURE 96. Angle of Propeller-Blade to Angle of Travel. With the blade 
 moving in the direction of the large arrow, it is obvious that to produce 
 a thrust in the direction of the small arrow the blade a must be inclined to 
 the pitch, or line of travel. 
 
 ering the passage of a blade through the air as 
 though it were an ordinary aeroplane surface mov- 
 ing in a straight line, as in Figure 96, in which a 
 is a section of the blade, 6 is its plane of rotation, 
 c is its pitch or angle of travel, and d is its angle 
 of inclination to its angle of travel. This nec- 
 essary difference between blade angle and angle 
 of blade travel has given rise to a number of com- 
 
PROPULSION 243 
 
 plicated misconceptions, chiefly noticeable in the 
 confusion it has occasioned in estimates of propel- 
 ler pitch and slip (see Page 244). Yet the distinc- 
 tion becomes very apparent when Figure 96 is 
 tilted so that c can be regarded as a horizontal path 
 along which a is traveling in the direction of the 
 large arrow. This point of view gained, it is an 
 obvious absurdity to expect a to exert a pull in the 
 direction of the small arrow unless it is thus 
 inclined to its path of travel. 
 
 The amount of inclination necessary in a pro- 
 peller blade varies just as it does in an aeroplane 
 in accordance with several factors, chief among 
 which are the speed of travel, the width of blade 
 section, and the form of blade section. It con- 
 sequently is a safe generalization for the designer 
 to assume that the inner and therefore slower-mov- 
 ing portions of effective blade surface must present 
 greater inclination above the screw-pitch line than 
 the outer and faster-moving portions of blade sur- 
 face, that wide surfaces probably require less 
 inclination than narrow ones (at given speeds), 
 and that the greater effect of properly-curved sec- 
 tions can be approximated with flat and wrongly 
 curved surfaces only by the use of excessive 
 inclinations, and then only at the cost of wasteful 
 power application. 
 
 Failure to give due regard to the question of 
 blade inclination gives rise to overestimates of slip 
 in all cases when the pitch, or angle of blade travel, 
 is confounded with the angle of blade setting. A 
 propeller designed with the blade angle the same 
 
244 VEHICLES OF THE AIR 
 
 as the supposed angle of blade travel naturally fails 
 to operate at the pitch that is calculated for it, with 
 the result that in subsequent trials this discrepancy 
 beween the real pitch and the supposed pitch is dis- 
 covered, added to such actual slip as does occur, 
 and the total set down as all slip. 
 
 Slip is a phenomenon that presents itself in all 
 mechanisms, of whatever type, in which it is sought 
 to produce positive movements or reactions in 
 fluids liquids or gases by the action of solid 
 parts. An air propeller, for example, caused to 
 travel through an internally-threaded cylinder of 
 metal would in fact as in theory progress without 
 slip making the definite and invariable advance 
 demanded by its pitch for each revolution or part 
 of a revolution accomplished. Working in its 
 proper element, however, a body of yielding air, 
 the amount of the yield causes a lagging behind 
 the theoretical rate of pitch advance, this lagging 
 varying with the design of the propeller and the 
 conditions of its operation. Naturally the mini- 
 mization of slip is an important element in the 
 problems of propeller design. 
 
 The amount of slip varies in different propel- 
 lers, and at different speeds of working, from ten 
 to fifty percent. Ordinarily, about fifteen percent 
 slip is to be regarded as a small figure. 
 
 FOEMS OF SURFACES 
 
 In the study of propeller design, after more 
 fundamental questions are disposed of there at 
 once appear the no less important questions con- 
 
PROPULSION 245 
 
 cerning the details of propeller-blade forms. Evi- 
 dently an infinite variety of sections and outlines 
 are to be had, so it becomes necessary to select on 
 as reasonable grounds as may be reached the par- 
 ticular combinations best adapted to afford 
 required results. At the present time, consid- 
 ering the state of aerodynamic science, it is not 
 possible to define positively and logically, by any 
 true scientific methods, the constructions of the 
 highest value. Consequently, recourse has been 
 had to more generalized and tentative methods of 
 reasoning, supplemented by empirical investigation 
 by experiment. As a result certain important 
 facts are fairly well established though the num- 
 ber of these that are common knowledge is pos- 
 sibly less than is possessed more or less in secret 
 by several advanced investigators. 
 
 Plane Sections, as in the case of aeroplane sur- 
 faces, were the first employed by early designers 
 of air propellers, but as time went by and progress 
 became more and more definite, the same objections 
 that were found to apply to flat aeroplanes (see 
 Page 171) were found also to apply to flat pro- 
 peller blades, which in consequence have been 
 discarded by all but ignorant or uninformed 
 experimenters. 
 
 Parabolic Sections, modified or absolute, having 
 now become the most approved form for aeroplane 
 surfaces (see Page 173) after years of unsuccess- 
 ful experimentation with flat surfaces and with 
 other curves, also are coming to be regarded 
 (though in this particular application perhaps less 
 
246 VEHICLES OF THE AIR 
 
 well established as yet) as the correct ones for 
 propeller blades. This being the case, the same 
 general principles that have been found to apply 
 in the design of sustention surfaces (see Page 188) 
 also are found to apply to the cross sections of pro- 
 peller blades with certain modifications intro- 
 duced by the necessity for traveling in the circular 
 or helical path, which most particularly involves 
 a more extreme application of the principle of cut- 
 ting back the front of the curves at the ends of the 
 surfaces, because the curved path and the centrif- 
 ugal action both tend to augment the escape of air 
 around the ends (see Page 189). 
 
 Air propellers being subjected to considerable 
 loading in the way of their ordinary duty, besides 
 to enormous centrifugal stresses set up by their 
 unavoidable high peripheral speed, it is commonly 
 necessary to construct them with blades very thick 
 in proportion to width. This difficulty, especially 
 marked in the use of strong but bulky materials, 
 such as wood, further increases the importance of 
 discovering and applying correct and efficient 
 sections. 
 
 Blade Outlines are the theme of more dispute 
 and of many more differences of opinion than pre- 
 vail in the case of propeller-blade sections. Deduc- 
 tion from present practise is informing as much 
 in the tendencies it discloses as it is in particular 
 examples. Of these tendencies there is that of 
 reducing at least a third and often the inner half 
 of each blade to a mere arm or stem of the blade 
 surface proper, this stem being made stocky and 
 
PROPULSION 247 
 
 strong, and shaped to go through the air with a 
 minimum resistance, rather than to produce any 
 measurable thrust. The portion of the blade 
 designed to produce the thrust is commonly made 
 widest at its middle, the inner end narrowing into 
 the stem and the outer end narrowing to the tip. 
 The object of narrowing the tip is twofold first 
 because the tip travels at the highest speed, mak- 
 ing a given area at this point perform the greatest 
 work (besides which a wide tip possibly increases 
 the skin friction rather materially) ; and second 
 because wide tips greatly add to the centrifugal 
 stresses without adding at all to the strength of 
 the structure. An increasing minority of designers 
 prefer to make the entire advancing edge of each 
 blade perfectly straight lying along a radius 
 drawn from the center of rotation contending 
 that this form is beneficial in that it causes the 
 edge to meet all air particles at right angles, with- 
 out setting up side flows and eddies in the concen- 
 tric zones or helices of air through which the pro- 
 peller passes. With a straight advancing edge, 
 the following edge of a blade must be irregular, 
 since its contour alone must provide for all 
 required variations in width and area. This con- 
 sideration causes a decreasing majority of design- 
 ers to dissent from the theory of the minority, and 
 divide differences of area more or less equally 
 between the advancing and following edge contours. 
 In the matters of total and effective blade area, the 
 undoubted tendency at present is to increase speeds 
 and correspondingly reduce areas. In a past era of 
 
248 VEHICLES OF THE AIR 
 
 inefficient multibladed propellers it was not uncom- 
 mon for half or more of the area of the circle 
 of rotation to be occupied by blade width, but in 
 modern two-bladed, more-efficient propellers the 
 blade width often is as little as one-tenth or one- 
 twentieth of that of the circle of rotation. 
 
 MUTIBLADED PROPELLERS 
 
 It seems to be established to the satisfaction 
 of most modern engineers that the fewer the blades 
 in an air propeller the nearer ideal its conditions of 
 operation too many blades tending to interfere 
 with one another by their close proximity requir- 
 ing each to work against air previously disturbed 
 by the blade preceding. The condition is similar 
 to the case of an aeroplane with identical advanc- 
 
 FIGURE 97. Advancing and Following Surfaces. Showing the necessity 
 for a different curve and steeper angle in the rear wing, that it may operate 
 effectively through air disturbed by the front wing. 
 
 ing and following surfaces closely spaced in the 
 same plane, as at a b and c d, Figure 97, rendering 
 it necessary for the rearward surface to derive its 
 sustention from air to which a downward move- 
 ment has been imparted by the forward surface. 
 In the case of the aeroplane correction can be 
 effected by making the rearward surface of a dif- 
 ferent curve from that forward and by inclining it 
 at a greater angle, as in Figure 97, but this solution 
 
PROPULSION 249 
 
 obviously is not applicable to the equally-spaced 
 propeller surfaces, all of which are both advancing 
 and following because of their rotary travel. The 
 one other possible solution of the problem pre- 
 sented in Figure 97 is to increase the spacing of 
 the blades, which in a propeller can be done only 
 by increasing their length or reducing their 
 number, or by a combination of these. 
 
 A modern three-bladed propeller is shown in 
 Figure 98 and a four-bladed construction in Fig- 
 ure 99. Though used with some success, neither of 
 these meet the approval of the most successful 
 experimenters. 
 
 TWO-BLADED PROPELLERS 
 
 Two blades in a propeller is the least number 
 compatible with smooth running, as a one-bladed 
 propeller inevitably must be badly out of balance 
 in so far as concerns maintenance of a fixed cen- 
 ter of thrust while gyration of the center of mass 
 could be prevented only at some critical speed by 
 the altogether unwarranted expedient of a counter- 
 weight. For these reasons two blades, oppositely 
 placed in the same plane or other figure of rotation, 
 are the least that can be used, and are generally 
 preferred, though four-bladed propellers have 
 some slight vogue and three-bladed ones are occa- 
 sionally met with. Modern two-bladed propellers 
 of successful forms are illustrated in Figures 100, 
 101, 102, 103, and 104, in which characteristic exam- 
 ples of all the more approved construction are 
 clearly shown. A close scrutiny of these will prove 
 informing to the student of the subject. 
 
250 VEHICLES OF THE AIR 
 
 PEOPELLER DIAMETERS 
 
 Mechanically considered, the limiting factor in 
 propeller speed is peripheral speed rather than 
 rotational speed, since it is primarily upon this 
 that the centrifugal stresses, which are by far the 
 most severe of all involved, depend. The propellers 
 of practically all successful aeroplanes yet built 
 are run at peripheral speeds of from 12,000 to 
 40,000 feet a minute, with occasional instances of 
 speeds of over 50,000 feet a minute, the rotational 
 speeds being so adjusted to the diameters as to 
 produce little variation outside of the range given. 
 At the higher of the speeds mentioned nearly 570 
 miles an hour the centrifugal pull exerted at the 
 blade tip is enough to test the qualities of the finest 
 structural materials available. 
 
 That it is better to gain the permissible periph- 
 eral speeds by the use of large-diameter propellers 
 at low rotational speeds, in preference to small 
 propellers at high rotational speeds, becomes very 
 evident with a little study. Consider, for example, 
 the case of a portion of a propeller surface, one 
 foot long and one foot wide, traveling edgewise 
 around a thirty-foot circumference 600 times a 
 minute it being assumed that a peripheral speed 
 of 18,000 feet a minute is as high as it is consid- 
 ered expedient to use in the given case. With the 
 conditions stated the surface passes any given point 
 ten times a second often enough to produce ma- 
 terial disturbance of the air worked against. Now 
 assume the circumference reduced to fifteen feet 
 
PROPULSION 251 
 
 by a corresponding halving of the propeller di- 
 ameter and immediately it becomes apparent that 
 a doubling of the rotational speed is allowed with- 
 out increasing the peripheral. But with this done 
 the assumed propeller surface passes any given 
 point twenty times a second twice as often as 
 before with correspondingly reduced assurance 
 of finding undisturbed air to work against. More- 
 over, since the blade surface travels the same dis- 
 tance in the same time in both cases, there is no 
 opportunity to reduce its area on the ground of 
 the higher rotational speed in the small propeller. 
 The result is that the blade, which is of a width 
 only one-thirtieth the length of its path in the large 
 propellers is in the small propeller one-fifteenth of 
 its length a condition that operates directly 
 against maximum effectiveness. Of course it 
 is reasonably to be urged that when a propeller 
 is progressing through the air in its normal con- 
 dition of operation, instead of revolving in a circle 
 as when kept from advancing the blades travel 
 separate helical paths, wholly distinct from one 
 another. But these paths are nevertheless closely 
 adjacent, and become more closely adjacent with 
 every increase in the number of blades and every 
 decrease in the pitch. From these considerations 
 it must be evident that large diameters and small 
 blade numbers reduce the frequency of the succes- 
 sive traversals of the adjacent helices, and conse- 
 quently the frequency and adjacency of the air 
 disturbances. A practical limit is set, however, by 
 the space that is occupied by very large propellers. 
 
252 
 
 VEHICLES OF THE AIR 
 
 ARRANGEMENTS OF BLADES. 
 
 In considering the design of aerial propellers 
 it at once becomes evident that there is possible a 
 considerable variety of blade arrangements. Not 
 only may the blades differ in their number, in their 
 outlines, in their cross section, in their pitch, and 
 in their angles of setting ; they may also differ in 
 the angles they make with their plane of rotation, 
 in their longitudinal placing on the propeller shaft, 
 and in the use of longitudinal sections from hub 
 to tip that are straight or curved. 
 
 Eight- Angled Propeller Blades, at right angles 
 to the propeller shaft, as in A, Figure 105, are the 
 commonest form. The advantage of this construc- 
 tion is that the centrifugal stress exerts a direct 
 
 a 
 
 Figure 105. Straight, Dihedral, and Curved Propellers. 
 
 pull from the hub, without any tendency to move 
 the blades longitudinally, parallel with the axis 
 of revolution. A supposed disadvantage is the 
 radial escape of air from the propeller tips, as sug- 
 gested at a a, without helping in propulsion. But 
 since such radially-thrown air is more apparent 
 
PROPULSION 253 
 
 when the propeller is kept from advancing, and is 
 thus worked as a blower, than it is under normal 
 conditions in which the propeller goes through the 
 air instead of the air going through the propeller, 
 it probably is not deserving of serious considera- 
 tion. In fact the air can be thrown radially with 
 this type of blade arrangement only to the extent 
 that it is dragged by skin friction or by incorrect 
 propeller section, the first of which is probably 
 not an effect of great magnitude and the second of 
 which is a subject for improved design. 
 
 Dihedrally-Arranged Propeller Blades, set at 
 an angle as at B, Figure 105, or curved as at C, 
 Figure 105, obviously utilize the radially-thrown 
 air at & & and c c in propulsion, but though they 
 utilize it they must also increase the amount of it 
 by subjecting the air behind the blades to direct 
 centrifugal action as well as to the mere skin fric- 
 tion that applies in A, Figure 105. Moreover, they 
 require very stiff blades, or else stay wires as at 
 d d and e e, to prevent the blades from straighten- 
 ing up under the powerful centrifugal pull. The 
 presence of the wires is an added objection in that 
 these set up material resistance to the rotation, 
 besides which they add the distance g h to the 
 necessary overhang of the propeller from the 
 bearing h. 
 
 PEOPELLEE EFFICIENCIES 
 
 The efficiency of aerial propellers is a factor of 
 the utmost importance in aeronautical engineering 
 because of its relation to power required, which 
 in turn involves the questions of engine weight and 
 
254 VEHICLES OF THE AIR 
 
 fuel quantity, all of which finally decide the pos- 
 sible radius of travel without alighting. The meas- 
 urement of efficiency is theoretically very simple, 
 though practically not without some difficulties, the 
 essentials being the thrust developed and the speed 
 of movement, which, when multiplied, give the foot 
 pounds utilized per unit of time. Comparison of 
 these with the horsepower developed affords a 
 direct measure of the efficiency. Thus it has been 
 stated that in the Wright aeroplanes the propellers 
 produce a thrust of 160 pounds at 40 miles an hour 
 when driven by the 30-horsepower engine. Assum- 
 ing these figures to be correct though that con- 
 cerning the thrust is probably overestimated the 
 speed of 40 miles an hour is equivalent to 3,520 
 feet a minute. This multiplied by the 160 pounds 
 requires 563,000 footpounds a minute, which, com- 
 pared with the engine output of 990,000 foot- 
 pounds a minute, indicates an efficiency at the pro- 
 pellers of about 57%. If the engine develops only 
 25 horsepower, as has been asserted, the efficiency 
 figures nearly 65%. That these figures are in- 
 credibly high will be appreciated when it is con- 
 sidered that they represent not merely the pro- 
 peller efficiency but the combined propeller and 
 transmission efficiency with a type of chain trans- 
 mission quite wasteful of power. 
 
 The explanation probably is that so high a pro- 
 peller thrust as 160 pounds is altogether beyond 
 what would be required to overcome the resistance 
 that should be encountered, and, if developed, its 
 necessity is to be explained only on the theory that 
 
PROPULSION 255 
 
 to the unavoidable head resistances there must be 
 added a considerable avoidable resistance due to 
 the use of inadequate or wrongly-curved sustaining 
 surfaces, made to serve only by being dragged 
 through the air at unduly steep angles of incidence 
 to the path of movement (see Page 133). 
 
 In spite of the difficulties that have been en- 
 countered during the experimental period of aero- 
 dynamic science it has been long established that 
 properly-designed air propellers afford much 
 higher efficiencies than ever have been realized 
 from water propellers, it being a fully demon- 
 strated and rather amazing fact that with a given 
 engine power an aerial propeller on a boat can be 
 made to afford a higher thrust than any known 
 form of water propeller that can be provided. 
 
 The Effects of Form on aerial propeller effi- 
 ciencies are very marked, and, though it cannot be 
 said that the best forms have been finally deter- 
 mined, enough experimenting and testing has been 
 done to disclose the widest possible differences in 
 the efficiencies of the different blade sections, out- 
 lines, pitches, etc., that have been tried. 
 
 The Effects of Rotational Speed on aerial- 
 propeller efficiencies having been discussed at some 
 length on Page 250, it is enough to add here that 
 up to some unknown limit the more rapidly a blade 
 surface travels through the air the more perfect 
 the reaction from the stratum of air behind the 
 blade, and, incidentally, the thinner this reactive 
 stratum a phenomenon that has important bear- 
 ings on the question of interference between a 
 
256 VEHICLES OF TEE AIR 
 
 plurality of blades. The head resistance to the 
 blade edges and the skin friction on their surfaces 
 increase with the speeds the former about with 
 the square of the speed and the latter probably at 
 some much slower rate. 
 
 As a rough general rule it can be stated that 
 the power required to drive a driven propeller 
 cubes with increase in speed, a doubling of the 
 propeller speed doubling the amount of air acted 
 upon, doubling the speed at which it is acted upon, 
 and doubling the rate of progress through the air. 
 
 The Effects of Vehicle Speed upon aerial- 
 propeller efficiencies are especially marked when 
 the relations of pitch, propeller speed, and vehicle 
 speed are such as to compel an abnormal amount 
 of slip. Thus, when the vehicle is kept from 
 moving at all the slip is 100%, and the propeller 
 works as an air blower, driving a cylinder of air 
 to the rear at a rate equivalent to the propeller 
 pitch minus its slip considered as a blower, not as 
 a propeller. If under this condition the resistance 
 of the cylinder of air to being sheared loose, so to 
 speak, from the surrounding air, and compressed 
 against the air to the rear of it, is greater than the 
 head and other resistances of the vehicle at any 
 given speed, the propeller thrust under this con- 
 dition may be much greater than can be reasonably 
 expected under the altogether different conditions 
 that prevail when the propeller is moving through 
 the air instead of the air moving through the 
 propeller. 
 
 In the opinion of some, failure to consider these 
 
PROPULSION 257 
 
 points has been the reason for many unwarrant- 
 edly high estimations of propeller efficiencies, based 
 upon tests made with the propellers restrained 
 from movement in an axial direction and revolved 
 in air possessed of no movement other than that 
 produced by the propellers themselves. However, 
 it is only fair to state that Maxim and others vig- 
 orously oppose the claim that there is enough 
 difference in the conditions to invalidate tests 
 made of propeller thrust with the propeller not 
 advancing. 
 
 The greater thrust that ordinarily can be se- 
 cured from propellers restrained from progressing 
 at their pitch speed is one of the strongest argu- 
 ments that can be adduced in favor of the heli- 
 copter principle, the helicopter being intended to 
 derive sustention from the reactions under one 
 or more horizontally-revolving propellers rising 
 through the air at much lower speeds than would 
 result from a rate of progress equivalent to the 
 pitch (see Page 244). 
 
 The Effects of Skin Friction upon aerial- 
 propeller efficiencies are much less of a factor than 
 they are in water propellers, being probably almost 
 negligible, unless at the most prodigious speeds, 
 though there are a few authorities who hold to a 
 contrary view. Moreover, in further dissimilarity 
 from the conditions that apply to water propellers, 
 skin friction is but little dependent upon extreme 
 smoothness of the propeller surfaces. This is be- 
 cause the cohesion of the air is so low that only a 
 small amount of energy can be expended in sliding 
 
258 VEHICLES OF THE AIR 
 
 one portion of it upon another, even should it be 
 the case that instead of the propeller surfaces slid- 
 ing through the air they carry thin air films with 
 them, dragged along by occasion of more or less 
 imperceptible deviations from the unattainable 
 ideal of perfect smoothness. 
 
 Determinations of skin friction can be best 
 made by revolving at high speeds flat propeller- 
 like surfaces without pitch, though in making tests 
 of this sort it naturally is most important that 
 proper allowance be made for the other resistance 
 factor the head resistance of the edges of the 
 surfaces. 
 
 PROPELLER PLACINGS 
 
 The matter of propeller placing is one that 
 admits of a considerable variety of schemes, with 
 a considerable diversity of opinion as to which 
 scheme is best. Maxim, for example, opposes the 
 front-placed " tractor screw" on the ground that 
 it " fails to take advantage of air set in motion by 
 the machine as a whole, as a means of neutralizing 
 some of the normal slip." Pelterie, on the other 
 hand, contends "that the wake from the slip itself 
 is turned to better account with, a tractor screw 
 because it creates a higher efficient velocity of air 
 under the center of the main wings." To the 
 writer in which opinion he is upheld by others 
 it seems probable that both of the foregoing views 
 are based upon exaggerated estimations of slip, 
 which with modern well-designed propellers prob- 
 ably is very small at normal vehicle speeds. In 
 
PROPULSION 259 
 
 this opinion lie is further borne out by the fact 
 that there are highly-successful modern aeroplanes 
 of both the thrust-screw and the tractor-screw 
 types, though the only examples of the former are 
 the Wright, Curtiss, Cody, and Farman machines, 
 now that the Voisins have gone over to the tractor- 
 screw design. But that Pelterie's theory is not 
 without a measure of plausibility is rather inter- 
 estingly suggested in the starting system recently 
 patented by Bleriot (see Figure 169). 
 
 Single Propellers, being necessarily placed at 
 or near the center of the head and other forward 
 resistances to the progress of an aeroplane, can 
 under no conceivable circumstances drive the ma- 
 chine materially out of its course, as is always 
 dangerously possible with two propellers (unless 
 arranged in tandem on the same axis) should 
 one or the other for any reason become inoperative 
 and so fail to maintain its normal share of the 
 thrust. It was a condition of this sort, arising from 
 the breakage of one of the propellers, which occa- 
 sioned the first fatal accident in the history of 
 power-driven heavier-than-air fliers, in which 
 Lieutenant Selfridge lost his life and Orville 
 Wright was injured. 
 
 Plural Propellers are advocated by a few be- 
 cause against the use of single propellers there is 
 to be urged the objection that a machine is unbal- 
 anced by the gyroscopic and reaction effects, it 
 being evident that these can be readily neutralized 
 by the use of two or more propellers, of the same 
 form and size, symmetrically placed, and revolved 
 
260 VEHICLES OF THE AIR 
 
 in opposite directions. That such effects exist 
 there is, of course, no gainsaying, but the prevail- 
 ing opinion of the generality of engineers at the 
 present time is that their magnitude with propel- 
 lers ranging from five to ten feet in diameter and 
 weighing from three to twenty pounds (with a 
 large proportion of this weight in the hub), is too 
 trifling to be seriously regarded a view that is 
 experimentally upheld in the fast-increasing num- 
 bers of single-propeller machines. Indeed, the 
 Wright and the Cody biplanes (see Figures 188 
 and 202), which have identical propelling systems, 
 are the only successful twin-propeller machines of 
 large size that ever have been designed in accord- 
 ance with this system, which was first seriously 
 applied by Maxim in his great multiplane, and 
 subsequently employed in Langley's flying models. 
 It certainly has at least the appearance of reason- 
 ableness that a thin and narrow propeller blade, 
 from two to five feet long, moving at high speed 
 on one side of an aeroplane, cannot produce any 
 considerable reaction per unit of area against a 
 comparatively broad wing surface on the opposite 
 side, from ten to twenty-five feet long. To analyze 
 a particular case, let there be considered the mono- 
 plane with which Bleriot accomplished the first 
 crossing of the English Channel. In this machine 
 the propeller blades are about 3f feet long and the 
 wing span is over 25 feet. The most effective speed 
 of the propeller is about 1,200 revolutions a min- 
 ute, at which about 25 horsepower is applied. This 
 amount of power is the equivalent of 825,000 foot 
 
PROPULSION 261 
 
 pounds a minute, or 688 foot pounds per propeller 
 revolution, involving that the two propeller blades 
 encounter a maximum possible resistance to their 
 rotation of 688 divided by 21 the approximate 
 circumference in feet of the propeller circle. This 
 is an approximate resistance of 33 pounds figured 
 at the propeller tips. This load, extended to the 
 wing tips, is the equivalent of a trifle over 8 pounds 
 unbalanced load on one wing end, raising the 
 weight supported per square foot of area an aver- 
 age of 1 1 ounces higher on one wing than on the 
 other. Assuming a normal load of 75 ounces to the 
 square foot, which is very close to correct, the addi- 
 tion of this amount unbalances the machine to the 
 extent that the weight is only about 2% higher 
 on one side than on the other. 
 
 Wilbur Wright having asserted that the 
 Wright machine can be flown with fifty pounds of 
 unbalanced weight at the tip of one wing, while 
 Santos-Dumont has flown with a forty-pound 
 weight at one side of the body of his little mono- 
 plane, nothing more than a slightly greater warp- 
 ing of the wing on one side being necessary to cor- 
 rect the balance, the altogether immaterial quality 
 of the unbalanced reaction from a single propeller 
 is as manifest in practise as it is in theory. 
 
 Referring again to the magnitudes of the gyro- 
 scopic action from a single propeller, these are 
 dependent wholly upon the factors of propeller 
 mass and speed. With heavy propellers they 
 undoubtedly might become a serious factor, but 
 with the light wooden propellers most favored they 
 
262 VEHICLES OF THE AIR 
 
 are quite as negligible as the reaction effect. In 
 fact, this seems even to hold true of the heavier 
 propellers of sheet steel, magnalium, and other 
 alloys, that are favored by some builders. 
 
 A very material addition to the gyroscopic 
 effect due to light propellers is that due to com- 
 paratively heavy flywheels, when these are used. 
 Thus in the Wright and Cody machines, in which 
 plural propellers are used to balance the gyroscopic 
 and reactive effects, there must be introduced a 
 weight-adding element of unbalance in the fly- 
 wheel, which cannot readily be eliminated from a 
 power plant in which there is chain, gear, or any 
 other than absolutely direct application of the 
 power. 
 
 Nor can this question be begged by the asser- 
 tion that geared-down propellers which therefore 
 might as well be plural are necessary to secure 
 the higher efficiencies known to be secured with 
 larger diameters working over large areas at low 
 rotational speeds. For the answer is found in 
 the fact that in any given cases of equally sound 
 designing the efficiency thus gained at the propeller 
 is certain to be lost in the transmission not to 
 dwell upon the matters of greater weight and com- 
 plication, smaller reliability, and the entry of 
 otherwise avoided possibilities of derangement or 
 failure of a type so dangerous as to constitute an 
 ever-present menace in the use of machines in 
 which this construction is employed. 
 
 Gyroscopic action is possibly most apparent in 
 its effect upon steering, it tending more or less 
 
PROPULSION 263 
 
 markedly to deviate a machine from a desired 
 course, when it is attempted to steer it. This devia- 
 tion is always in the direction of the rotation. 
 Thus, with a propeller rotating clockwise, as 
 viewed from the rear of the machine, in steering 
 to the right the prow drops and in steering to 
 the left the prow rises. In steering up the prow 
 draws to the right, while in steering down the 
 prow goes to the left. With a propeller rotating 
 counter-clockwise, as viewed from the rear, the 
 movements in all four possible cases are just the 
 opposite. These movements have been elaborately 
 confirmed by Alexander Graham Bell by experi- 
 
 FIGUBE 106. Effect of Gyroscopic Action of a Single Propeller on Steering. 
 With the directions of rotation shown, effort to steer in the direction of the 
 solid arrows results in deviation in the direction of the dotted arrows, to an 
 angular extent varying with the magnitude of the gyroscopic effect. This 
 tendency can, of course, be allowed for by a practised operator. In both views 
 the machine is to be regarded as approaching the observer. 
 
 ments with a small gyroscope in a case. In the 
 practical operation of a machine, this peculiarity 
 causes practically no trouble, the pilot learning 
 to allow for it by always executing steering move- 
 ments of an angularity sufficient always to allow 
 for the directional disturbance. These points will 
 be better appreciated from reference to Figure 106. 
 An example of tandem propellers, which may 
 be either similarly or oppositely rotated about the 
 
264 VEHICLES OF THE AIR 
 
 same axis, is illustrated in Figure 107. The advan- 
 tages are few and the complication considerable. 
 Location of Propeller Thrust, which, of course, 
 centers along the propeller axis with a single pro- 
 peller and is balanced between the propellers when 
 a plurality is used, is properly, to secure sustained 
 flight from the thrust or traction, made coincident 
 with the exact center of the head and other resist- 
 ances and preferably with the axes of rotation 
 parallel with the normals to the plane of resistance. 
 In a correct design it would reasonably seem that 
 the normal center of resistance would be chosen, 
 but it has been demonstrated that neither angular 
 nor other deviation is incompatible with success- 
 ful flight, correction for the loose designing being 
 simply made by maintaining unsymmetrical set- 
 tings or abnormal angles of the wing warping or 
 balancing devices and of the vertical elevators or 
 rudders. 
 
 PKOPELLER MATEEIALS 
 
 Of all the possible elements in a flying machine, 
 an aerial propeller probably most requires correct 
 design, careful construction, and the highest qual- 
 ities of materials to make it stand up under the 
 severe stresses that are imposed on these mechan- 
 isms. In every way, approach to an ideal result 
 is restricted by the severest limitations. Weight, 
 which is one road to strength, is placed quite out 
 of court by the tremendously high peripheral 
 speeds involved, which set up most terrific centrif- 
 ugal loads. Thickness, permitting hollow and 
 
FIGURE 107. Twin Wooden Propellers on Single Shaft, for the propulsion of a dirigible 
 balloon. These propellers are driven by a Gnome engine mounted to revolve in a horizontal 
 plane. The power is transmitted to the propeller shafts through bevel gears in the housing a. 
 
PROPULSION 265 
 
 built-up constructions, and the use of light and 
 strong but bulky material, such as wood, is objec- 
 tionable in that it greatly increases the wasteful 
 resistances to be overcome. Restriction of size has 
 its limits because of the tenuity of the medium 
 acted upon, demanding the sweeping over of large 
 areas as the only possible means of securing a req- 
 uisite thrust in an efficient manner. 
 
 Obviously, the inevitable result has had to be a 
 series of compromises, permitting the use of the 
 best of such materials as are available while 
 minimizing their objections. 
 
 In all propellers, no matter what the material, 
 it is most essential that the opposed blades accu- 
 rately balance, with the center of gravity exactly 
 at the center of rotation. If this is not the case, 
 rotation will occur about the center of gravity, 
 around which the proper center of rotation will 
 gyrate in a planetary path, setting up destructive 
 vibration. In finishing metal and wood propellers 
 the final finish or carving must be done with the 
 utmost delicacy if correct balance is to be had. 
 Even an extra brush stroke in painting will throw a 
 propeller out of balance, and the paint must be cor- 
 respondingly treated in polishing to correct its 
 distribution. 
 
 Wood, being easily worked and in selected qual- 
 ities exceedingly strong and reliable, is the pre- 
 ferred material for most modern aerial propellers. 
 Though of course nowhere near as strong for a 
 given section or bulk as are many metals, for a 
 given weight it is excelled only by the finest steels 
 
266 
 
 VEHICLES OF THE AIR 
 7 
 
 FIQDRD 108. Working Drawings of a Wooden Propeller. 
 
PROPULSION 267 
 
 (see Chapter 11). Because of this, in conjunction 
 with the fact that the only really severe stresses 
 on a propeller are the centrifugal, its mass works 
 out so small in a given structure that it reduces the 
 loads even more materially than it reduces the 
 strength of the sections that must sustain them. 
 This becomes very evident from a consideration of 
 the propeller described on Page 270 and illustrated 
 in Figures 108 and 109. 
 
 The greatest objection to wood as a propeller 
 material is, of course, its bulk, rendering impera- 
 tive the use of blade sections decidedly thicker 
 than are most desirable. 
 
 The preferred constructions of wooden pro- 
 pellers involve first the production of built-up 
 blocks from glued laminae of selected timber, with 
 the grain in the different layers crossed at a slight 
 angle to prevent splitting, after which the desired 
 form is worked out with the use of templets to 
 insure correctness of the different sections. To 
 some extent solid blocks have been used for pro- 
 pellers, and this perhaps is not bad practise with 
 certain woods. In making built-up blocks, the indi- 
 vidual boards should be finished with a tooth plane, 
 to provide a slightly-roughened and interlocking 
 surface that will promote adhesion of the glue. 
 Then the block should be clamped under heavy 
 pressure until thoroughly dried. 
 
 The woods considered most suitable for pro- 
 pellers are hickory, applewood, maple, birch, Cir- 
 cassian or " French" walnut, ash, and spruce. The 
 properties and characteristics of these materials 
 
268 VEHICLES OF THE AIR 
 
 are more fully discussed in Chapter 11, which fully 
 treats of this subject. 
 
 Typical wooden propellers are illustrated in 
 Figures 100, 102, 103, 107, 140, 188, and 246. 
 
 Steel, as the strongest known structural mate- 
 rial, compared weight for weight with others, has 
 definite points of superiority over anything else 
 that can be used, the chief objection to it being 
 the difficulty and expense of producing the 
 necessary qualities in the requisite shapes. 
 
 Two principal methods of steel-propeller con- 
 struction are at present in vogue. In one, single 
 sheets of steel (sometimes cast or sheet metal other 
 than steel) are cut to the desired outlines, stamped 
 or bent to the desired forms, and then autogene- 
 ously welded to steel hub arms that are placed on 
 the backs, or rarefaction surfaces of the blades. 
 Such propellers are shown in Figures 99 and 104. 
 In the other construction, the blades are each made 
 of two sheets with the arm extended between them 
 in the manner of the wing bars a a, in Figures 
 72, 74, 193, and 194. Such propellers are shown 
 in Figures 98 and 101, and are best assembled by 
 autogeneous welding of the hub arms and the blade 
 edges, though riveting and brazing are employed 
 to some extent. The qualities and physical charac- 
 teristics of the steels most suitable for use in pro- 
 pellers are discussed in Chapter 11. 
 
 Aluminum Alloys as propeller materials have 
 met with some success, when used to the exclusion 
 of other metals as well as when employed simply 
 for blades or blade tips, mounted on steel hub 
 
PROPULSION 269 
 
 arms. One of the best of the aluminum alloys is 
 magnalium (see Chapter 11), which is both lighter 
 and stronger than pure aluminum, and which lends 
 itself readily to casting, forging, stamping, and 
 machining. A 4-foot propeller of this material sus- 
 tained the highest peripheral speed of which the 
 writer knows in this field of engineering. This 
 speed, reached in a laboratory test, was 50,265 feet 
 a minute, involving 4,000 revolutions a minute. 
 Though the propeller stood the test without flying 
 to pieces, the blades warped somewhat out of shape 
 at the higher velocities. This may have been due, 
 however, to poor design. Everything considered, 
 ease of manufacture included, there seems more 
 than a fair prospect that magnalium, cast in iron 
 molds, may prove superior to all other propeller 
 materials, not even excepting wood and steel. 
 
 Framing and Fabric the use of tubular steel 
 frames with fabric coverings is a combination 
 construction that has been experimented with in 
 propeller design, notably in the case of the mono- 
 plane illustrated in Figures 141, 217, and 218. 
 Even with ribs and edgings to stiffen the fabric, 
 there is serious doubt as to the ability of this con- 
 struction to maintain correct blade surfaces under 
 the distorting influences of the high speeds 
 required, and in all cases of its trial so far it has 
 subsequently been abandoned. 
 
 PROPELLER HUBS 
 
 Propeller-hub design is a most important detail, 
 since through the hub, necessarily small in size 
 
270 VEHICLES OF THE AIR 
 
 and close to the shaft, where the tendency to break 
 is greatest, must be transmitted the entire power 
 used for propulsion. With wood propellers the 
 usual design involves a steel shaft through a hole 
 in the wood, with one or two flanges through which 
 bolts are passed to transmit the turning effort, as 
 shown in Figures 100 and 102. A less usual design 
 is that shown in Figure 118, in which a steel hub 
 and hub arms are used, to which the wooden blades 
 are riveted. With propellers entirely of steel 
 electric or autogeneous welding offer simple solu- 
 tions of hub problems. Similarly, magnalium 
 propellers, cast in one piece, lend themselves 
 readily to ideal hub design in combination with 
 inexpensive production. 
 
 A very unusual propeller hub is that shown in 
 Figure 98, and another interesting propeller is that 
 illustrated in Figure 171, in which it is seen that 
 the hub, the hub arms, and the blades are all sepa- 
 rately made and subsequently assembled. 
 
 A TYPICAL PKOPELLEK 
 
 Having now discussed all the more important 
 and evident considerations that influence propeller 
 design and construction, it is possible to conclude 
 this chapter with a brief description of a typical 
 propeller, which has been found to come very close 
 to realizing the various ideals and requirements 
 of these mechanisms, in so far as these ideals are 
 correct and the requirements understood. This is 
 the propeller illustrated in Figures 108 and 109, 
 which are reproductions of the mechanical draw- 
 
PROPULSION 271 
 
 ings and templets, respectively, used in its con- 
 struction. This propeller, being designed to afford 
 high efficiency with little power and at a low vehicle 
 speed, was made very large in diameter 
 in proportion to its blade width, and very 
 flat in pitch. It is built up of six layers of 
 [-mch wood and two of |-inch stock 
 totaling 2 inches. The two ^-inch layers, 
 nearest the front surface, which is the 
 one that appears in the drawing, are 
 maple and spruce, respectively the first 
 to face the hub and afford a hard surface 
 against which to clamp a flange plate and 
 the second to combine strength with 
 lightness. For the latter reason the first 
 two |-inch layers are also spruce, but the 
 third |-inch layer is of red birch, which is 
 very resistant to splitting and which, as 
 appears particularly in the side section, 
 extends through the thinner parts of the 
 blades, well towards their tips. Beneath 
 this come two more layers of spruce, to 
 secure extreme lightness in the extreme 
 tip of the blade, and then comes the final 
 layer of maple, chosen partly because of 
 its hardness as a flange backing but 
 chiefly for its quality in holding up in 
 thin and finely carved edges, such as ex- 
 
 109. tend clear along the rear edge of the 
 a or D n u H n I blades and partly around their tips. The 
 wo r o'den in pro* advancing edges are the straight ones, as 
 peller ' are shown in the end sections, and the 
 
272 VEHICLES OF THE AIR 
 
 pitch is 18 inches, with a diameter of 6 feet. The 
 heavy lines and figures on the end sections show 
 the corresponding angles at 3-inch intervals from 
 hub to tip. The chord angles, or angles of blade 
 setting (see Page 242), shown by the dotted lines 
 and the light figures in the end sections, are made 
 steeper to calculated extents than the pitch angles, 
 and then a slight further inclination has been em- 
 pirically allowed in certain of the sections. Close 
 to the hub no attempt is made to secure thrust, the 
 sections here being designed to go through the air 
 with as little resistance as is consistent with suffi- 
 cient material to afford the necessary strength 
 
 The sections of the effective concavities of the 
 blades are approximately parabolic, though not 
 exactly so at right angles to the radii. 
 
 The normal speed of rotation is from 1,800 to 
 2,000 revolutions a minute, and the total weight 
 is about 52 ounces, of which 30 ounces is within six 
 inches of the hub center. This leaves a weight 
 of only 11 ounces for each blade, in each of which 
 fully 4 ounces is between 6 and 12 inches from 
 the center, leaving only 7 ounces in the outer 24 
 inches of each blade. 
 
 The finish is several coats of spar varnish on 
 a priming coat of white shellac, the whole polished 
 to a glass smoothness after being thoroughly dried. 
 

 FIGURE 110. Four-Cylinder Motor of Wright Biplane. Despite the remarkable success 
 made with this motor, gas-engine experts consider it of very crude design, and much behind 
 the best automobile practice. Its considerable weight 190 pounds for 25 horsepower renders 
 it reasonably reliable. 
 
 FIGURE 111. Pump-Fed Antoinette Engine. These wonderful motors, one of which holds 
 the world's record for motor-boat speed, have many aeronautical triumphs to their credit 
 and are in many respects most ingenious and advanced engineering. 
 
CHAPTER SIX 
 
 POWER PLANTS 
 
 The question of power for the propulsion of 
 various kinds of flying machines, both of the 
 heavier-than-air and lighter-than-air types, is one 
 at the present time of the utmost importance. In- 
 deed, it is a safe assertion that recent developments 
 in aeronautics have been made possible largely 
 through the development of light-weight motors 
 that has been involved in the history of the auto- 
 mobile industry. Equally, it is undoubtedly true 
 that a most serious obstacle in the way of immedi- 
 ate further progress is the lack of motors still 
 lighter, more efficient, and more reliable. Most 
 flights so far made, for example, have been brought 
 to their ends by motor failure, though close to this 
 limitation always has been that of fuel radius, 
 which is directly dependent upon the matters of 
 weight and efficiency. 
 
 Of course, it is rather obvious that some of the 
 best flying machines of the present time might be 
 flown with much heavier motors than are used in 
 them with motors such as have been available for 
 even twenty or thirty years. But it has seemed 
 to be necessary to apply the light-weight motor 
 first as a means of working out the general details 
 of the necessary mechanism, the discovery that 
 
 273 
 
274 VEHICLES OF THE AIR 
 
 heavier motors could conceivably have been used 
 being therefore an after development. 
 
 While considering this question of power, it is 
 to be understood that (as has been suggested on 
 Pages 164 and 169) some of the foremost authori- 
 ties on aeronautics men whose theoretical attain- 
 ments are as indisputable as is their practical 
 knowledge stoutly contend that it is going to be 
 possible ultimately to achieve without power 
 something akin to the indefinitely-continued soar- 
 ing flight that is so indubitably established in the 
 case of the larger flying birds. Whether or not 
 these prophets are in any degree carried away by 
 their enthusiasm only time can tell. But certainly 
 it must require some daring to deny, in an age that 
 has seen such upsetting of theories of matter and 
 energy as has been involved in the phenomena 
 of radio-active substances and in other recent in- 
 vestigations, that such flight is possible. It may 
 be, perhaps, that the soaring bird does derive sus- 
 tension from upward currents of air, caused by 
 wind friction over surface contours or by ascending 
 streams of heated air, but these hypotheses do not 
 fit in with the views of many trained observers 
 who are almost unanimous in maintaining that 
 soaring is performed by the birds when such as- 
 sumed conditions do not prevail.* 
 
 * In the mountains back of Santa Barbara, California, the writer 
 has witnessed the soaring flight of the turkey buzzard and the great 
 California vulture under conditions differing from any he has heard 
 credited to any other observer, and more than any others leading to the 
 conviction that soaring flight does not require either ascending or hori- 
 zontal currents of air. In the locality referred to it frequently happens 
 that dense fogs drift in from the sea and lay motionless for hours with 
 
POWER PLANTS 275 
 
 For further discussion of this subject, reference 
 should be had to the article quoted from Prof. 
 Montgomery, in Chapter 4. 
 
 In any case one thing seems certain that 
 present machines are exceedingly wasteful of 
 power, losing either through excessive head resist- 
 ances or inefficient application probably nine- 
 tenths of all that is developed. For example, the 
 latest Wright machine requires one horsepower 
 for the conveyance of each fifty pounds, whereas, 
 according to Langley, the condor carries seventeen 
 pounds with an energy output estimated to be 
 not above ^T horsepower 395 pounds sustained 
 per horsepower. 
 
 Obviously, in providing suitable engines, ex- 
 tremely light weight and high efficiency both must 
 be sought, since both are means to greater utilities 
 in the way of increased reserve-carrying capacity 
 directly by reductions in engine weight and indi- 
 rectly by reduction in fuel quantity necessary for 
 given distances of travel. 
 
 The conditions under which a flying-machine 
 engine must operate differ radically from the con- 
 ditions applying in ordinary automobile propul- 
 sion, being even more severe than those appertain- 
 ing to racing automobile engines. For, as in the 
 case of the latter, an aeronautical engine must be 
 
 so uniform and well-defined an upper level that to an observer who 
 climbs the mountains to above the fog level it appears almost substantial 
 enough to walk out upon. Yet adjacent to the surfaces of these per- 
 fectly quiescent seas of fog, which would be visibly stirred by the 
 faintest breath of air, the characteristic soaring flight with its seem- 
 ingly effortless gaining of altitude, has been repeatedly observed. 
 
276 VEHICLES OF THE AIR 
 
 capable of running for hours upon hours at high 
 speed and high power output, in addition to which 
 it must do this with a minimum of attention. 
 These requirements can be met in the case of the 
 commonly-used internal-combustion motor only by 
 the closest attention to such details as lubrication, 
 cooling, carburetion, and ignition. Moreover, any 
 attempt to provide reliability and durability with 
 insufficient bearing sizes and crude lubrication 
 systems, as is often attempted in automobiles by 
 the expedient of building the engine large enough 
 to give much greater power than is normally 
 demanded from it, defeats its own end by the great 
 weight it involves. 
 
 The one feature of its use that favors the flying- 
 machine engine is found in the fact that little 
 fluctuation is required in the power output and still 
 less fluctuation is demanded in the rotational speed. 
 
 Everything considered, and aside from the 
 matter of weight, the duty of the aeronautical 
 motor is more closely comparable to that of a 
 motor-boat engine than to the engine of an auto- 
 mobile. This comparison, too, affords a much 
 clearer idea of the difficulties to be sur- 
 mounted, for, while there are many automobile 
 engines that will deliver a horsepower for each ten 
 or fifteen pounds of weight, there are very few that 
 will do so for long-continued runs, especially with- 
 out much attention. On the other hand, the motor- 
 boat engines, which are capable of delivering full 
 power for hours without attention, weigh from 
 forty to sixty pounds to the horsepower. And yet 
 
FIGURE 112. Three-Cylinder, 22-Horsepower Anzani Engine. This engine, which closely 
 resembles an ordinary twin motorcycle motor, with the addition of an extra cylinder, is the 
 one with which Bleriot crossed the English Channel. Cooling is by air passing around the 
 drilled-out fins 6 b b. At a a a are auxiliary exhaust ports. 
 
 FIGURE 119. R. E. P. Ten-Cylinder Motor with Concentric Exhaust and Inlet Valves. 
 
POWER PLANTS 277 
 
 it is the capabilities of these engines, rather than 
 those of automobile engines, that constitute the 
 ideal towards which aeronautical motors, weighing 
 from two to seven pounds to the horsepower, must 
 develop. 
 
 The quality of the final achievement must be 
 measured by weight, efficiency, and capacity to 
 keep running without care or adjustment as long 
 as fuel and lubricant are supplied. 
 
 GASOLINE ENGINES 
 
 The gasoline engine in certain of its forms being 
 the lightest prime mover known, and having been 
 developed to high degrees of reliability as an 
 element of motor-boat and automobile mechanism, 
 it is the only one at present finding any consider- 
 able amount of favor or offering much promise for 
 future application to aerial vehicles. Aeronautical 
 engines using gasoline as fuel have been built as 
 light as 1^ pounds to the horsepower, and are 
 made of considerable reliability in weights of 
 from 2-| to 7 pounds to the horsepower the latter 
 figure permitting thoroughly adequate water cool- 
 ing and including the weight of all necessary 
 adjuncts, such as ignition and carbureter equip- 
 ment, flywheel, radiator, etc. 
 
 MULTICYLINDEE DESIGNS 
 
 Multicylinder gasoline engines possess various 
 manifest advantages over single-cylinder construc- 
 tions. In the first place, the more usable four- 
 
278 VEHICLES OF THE AIR 
 
 cycle motor giving only one power stroke in each 
 four, it is rather necessary to duplicate cylinders 
 to secure smooth and uniform rotation without 
 excessive flywheel provision or crank balancing. 
 Another advantage of multicylinder construction 
 is a little less obvious, this being its effect on 
 weight. To explain, assume the case of a given 
 cylinder capable of developing five horsepower at 
 its maximum speed. This speed, as is well under- 
 stood by engineers, is only secondarily a matter of 
 rotational speed, it being primarily a matter of the 
 speed of piston reciprocation. Now to increase to, 
 say, twenty horsepower, the cylinder must be 
 doubled in all of its linear dimensions in both 
 bore and stroke. In accordance with a well-known 
 law of geometry, this cubes the weights and 
 volumes, so would at first appear to cube the 
 power, which would be the case if the speed of 
 rotation were maintained. But, because of the 
 piston speed being the limiting factor, it is neces- 
 sary in the larger engine to reduce the rotational 
 speed one-half to avoid increasing the piston speed. 
 The consequence is that though the weight is eight 
 times as great as that of the smaller cylinder, the 
 power developed is only four times as great, with 
 the result that the weight per given power is 
 doubled. 
 
 On the other hand, if instead of increasing the 
 dimensions of the small original cylinder the policy 
 be adopted of duplicating this small cylinder 
 ranging four of them, for example, along a single 
 crankcase and crankshaft then the power is 
 
POWER PLANTS 279 
 
 quadrupled with only a quadrupling in weight, 
 maintaining the original advantageous proportions 
 between weight and power. 
 
 Another advantage of multicylinder construc- 
 tion, resulting from its use of small cylinders, is 
 that these are more readily cooled than large, 
 especially if it is undertaken to cool them by air. 
 
 Of course, as in the case of everything mechan- 
 ical, any given construction is rather likely to be 
 a compound of advantages and disadvantages. 
 Among the latter, operating against the multicylin- 
 der engine, is the fact that the wall area of the 
 combustion chambers totals a much greater pro- 
 portion to the total combustion chamber volume 
 than is the case with a single cylinder of the same 
 total capacity, causing greater heat losses to the 
 cylinder walls and consequently increased fuel con- 
 sumption with reduced efficiency, other things 
 being equal. 
 
 CYLINDEE ARRANGEMENTS 
 
 In engines in which two or more cylinders are 
 used the problem of cylinder arrangement becomes 
 rather a vital one, because of its many bearings 
 upon weight, accessibility, and mechanical and 
 explosion balance. The arrangements found most 
 suited to aeronautical uses are the vertical, 
 V-shaped, opposed, revolving, etc. 
 
 Vertical Cylinders, constituting engines of a 
 type common in automobile practice, have been to 
 a considerable extent favored by aeronautic engi- 
 neers. Characteristic examples of. this type of 
 
280 VEHICLES OF THE AIR 
 
 construction are the four-cylinder motors of the 
 Wright aeroplane, illustrated in Figure 110, and 
 the Panhard motor illustrated in Figure 115. The 
 latter is one of the most remarkable examples of 
 light-weight motor construction in existence, being 
 adequately water-cooled and developing a full 45 
 horsepower, in spite of the fact that its weight is 
 only 176 pounds. 
 
 The chief objection to vertical cylinders, in 
 their usual arrangement in a single line along a 
 crankcase, is that their use inevitably involves 
 longer and heavier crankcases and crankshafts 
 than are required by some other constructions. 
 
 Though four cylinders are commonly favored in 
 vertical gasoline engines, with six used to a consid- 
 erable extent, there are many little-recognized 
 merits in three, five, and seven-cylinder vertical 
 constructions, the two latter of which, particularly, 
 are in better mechanical balance than the six- 
 cylinder (having five and seven throws to their 
 crankshafts, against only three in the six). At 
 the same time sufficient overlap of the successive 
 explosion strokes is provided to afford exceedingly 
 even torque at such high speeds as even the lowest 
 required in aeronautical work. The greatest 
 objection to engines of these odd cylinder numbers 
 is the expense of manufacturing suitable crank- 
 shafts. 
 
 V-Shaped Engines, like the Antoinette motor 
 illustrated in Figure 111, the Anzani engine illus- 
 trated in Figure 113, the Renault engine illustrated 
 in Figure 114, and the Fiat motor illustrated in 
 
FIGURE 115. Fiat and Panhard Aeronautical Motors. These are remarkable examples of 
 refined construction, the Fiat developing 50 horsepower with a weight of only 110 pounds, and 
 the Panhard weighing 176 pounds for 45 horsepower. 
 
 FIGURE 116. Darracq and Dutbeil-Chalmers Aeronautical Motors. The Darracq in the 
 
 lower view is the engine with which Santos-Dumont achieved his recent successful monoplane 
 
 flights. It weighs 66 pounds and develops 35 horsepower. Of particular interest in the other 
 motor is the flywheel a, with steel rim and wire spokes. 
 
POWER PLANTS 281 
 
 Figure 115, permit the working of two cylinders on 
 each throw of the crankshaft or, briefly, of four- 
 cylinder crankshafts for eight-cylinder engines, 
 etc. With proper angles of cylinder placing and 
 proper numbers of cylinders, engines of this type 
 can be made very light in weight and exceptionally 
 perfect in mechanical and explosion balance. 
 
 Twin-cylinder V-shaped engines, which have 
 been much used for motorcycle propulsion, are in 
 no better mechanical balance than single-cylinder 
 engines, but the greater frequency of explosions 
 gives smoother running and evener power output. 
 
 The three-cylinder, V-shaped Anzani engine, 
 illustrated in Figure 112, is of special interest as 
 the motor with which Bleriot accomplished his 
 epoch-marking flight across the English channel. 
 
 The four-cylinder, water-cooled, V-shaped An- 
 zani engine shown in Figure 113 is of a type with 
 two throws to the crankshaft, with two cylinders 
 on each throw. It has very much less crankcase 
 and crankshaft weight than ordinary four-cylinder 
 engines, is in excellent mechanical balance, and in 
 explosion balance that is irregular only to the 
 rather immaterial extent involved by the slight 
 angular separation of the two cylinder rows. 
 
 The ten-cj^linder R. E. P. engine illustrated in 
 Figure 119 is an extreme but very successful 
 example of modified V-shaped construction. 
 
 Opposed Cylinders, on opposite sides of the 
 crankcase, admit of perfect explosion and mechan- 
 ical balance with less cylinders than will give any- 
 thing like an equivalent result in any other type 
 
282 VEHICLES OF TEE AIR 
 
 of construction. In fact, horizontal-opposed 
 motors of the two-cylinder types illustrated in 
 Figure 116 are in better mechanical balance than 
 vertical and V-shaped engines with more cylin- 
 ders, because the masses of pistons and connecting 
 rods are in balance not only in the opposition of 
 their movements but also in the rates of their 
 opposed movements at any given time, which is 
 not the case with vertical engines, in which the 
 angularity of the connecting rods causes the pis- 
 tons to travel the upper halves of their strokes at 
 speeds materially higher than those at which the 
 lower halves of the strokes are traversed. 
 
 Revolving Cylinders, attached to a crankcase 
 that revolves with them on a stationary crankshaft 
 with one throw, to which all of the connecting rods 
 are attached, have been considered rather freakish 
 but in many respects constitute a most meritorious 
 form of gasoline-engine design. Among the ad- 
 vantages are the securing of a considerable fly- 
 wheel effect without the added weight of the 
 flywheel, effective air cooling due to the rapid pas- 
 sage of the cylinders through the air, positive 
 closing of the valves without the use of springs 
 (by taking advantage of the centrifugal force), 
 greatly reduced crankcase and crankshaft weight, 
 simplification of the ignition system, operation of 
 all valves by one or two cams, and remarkably 
 smooth and vibrationless running, even at high 
 speeds, due to the fact that there is literally no 
 reciprocation of parts in the absolute sense, the 
 apparent reciprocation between pistons and cylin- 
 
POWER PLANTS 
 
 283 
 
 ders being solely a relative reciprocation, since 
 both travel in circular paths, that of the pistons, 
 however, being eccentric by one-half of the stroke 
 length to that of the cylinders. This latter point 
 is made clear at Figure 117, in which a, &, c, d, and 
 e, are the cylinders, /, 
 </, h, i, and j, are the 
 pistons and fc, Z, m, n, 
 and 0, are the connect- 
 ing rods of a five- 
 cylinder engine of this 
 type. The pistons, it 
 will be noted, revolve 
 in the path p around 
 the crankpin q as a 
 center, while the cylin- 
 ders revolve in the 
 path r around the 
 crankshaft s. 
 
 In the ignition sys- 
 tem no separate leads 
 are required for the different spark plugs, each of 
 which wipes past a common contact point as the 
 cylinder passes into firing position. In a similar 
 manner the valve push rods all travel over com- 
 mon non-rotating cams. 
 
 One of the most recent and best worked-out 
 designs of revolving-cylinder engines is the seven- 
 cylinder motor shown in Figures 107 and 118. 
 This motor develops 50 horsepower at 1,300 revo- 
 lutions per minute and weighs only about 175 
 pounds. Its seven cylinders and the crankcase 
 
 FIGURE 117. Diagram of Revolving- 
 Cylinder Motor. Note that the cylin- 
 ders abode revolve in the circle r 
 around the crankshaft s, while the 
 pistons / g h i j and the connecting 
 rods k I m n o revolve in the circle p 
 around the crankpin g. Thus there is 
 only a relative reciprocation none 
 with relation to external objects in 
 this way almost eliminating vibration. 
 
284 VEHICLES OF THE AIR 
 
 ring are machined in one piece from a single 
 casting. 
 
 Miscellaneous Arrangements of cylinders have 
 been devised in great variety, the most noteworthy 
 and successful being various systems of grouping 
 cylinders closely around a small crankcase, as in 
 the engine illustrated in Figures 99 and 119. Such 
 grouping of course reduces crankcase and crank- 
 shaft weight. 
 
 IGNITION 
 
 Of the several systems of internal-combustion- 
 engine ignition that are in more or less general 
 use, those possessed of the most interest from 
 aeronautical standpoints are make-and-break igni- 
 tion, with a working element passing through the 
 cylinder walls; jump-spark ignition, with one or 
 more coils, external break by a timer or commu- 
 tator, and sometimes vibrator devices in the exter- 
 nal circuit; ignition by heat of compression; hot- 
 tube ignition; and, possibly, catalytic ignition. 
 
 Of the foregoing, each has its different merits 
 and demerits, most of which have been pretty well 
 established through long experiment and applica- 
 tion in automobile engines. 
 
 Make-and-Break Ignition systems when abso- 
 lutely well designed are most reliable, and un- 
 doubtedly tend to make a motor work at its maxi- 
 mum power output and efficiency, but with poor 
 construction or careless adjusting make-and- 
 break ignition is exceedingly prone to a variety of 
 troubles, among which are leakages along the 
 bearing surfaces through the cylinder wall, and 
 
FIGURE 118. Gnome Revolving-Cylinder Motor. This remarkable engine, which is one 
 of the lightest and most powerful yet built, develops 50 horsepower at 1,200 revolutions a 
 minute. The seven cylinders and the crankcase ring are one piece of metal, bein.? machined 
 down frcm a heavy casting. The advantage of the revolving-cylinder design is its immunity 
 from vibration, due to tho absence of reciprocating parts (the cylinders travel in a circle 
 around the crankshaft and the pistons in a circle around the crankpin) and the elimination 
 of the flywheel. This motcr at present holds the distance and duration record of 118 miles 
 in 3 hours. The above picture also affords an excellent view of the Bleriot alighting gear. 
 
POWER PLANTS 285 
 
 (with multicylinder engines) a lack of 
 
 synchronism in the ignition times in the 
 
 different cylinders, due to uneven wear 
 
 of the operating mechanisms. The 
 
 most-used current source for make-and- 
 
 break systems is the magneto. An in- 
 
 teresting and very successful make-and- 
 
 break ignition system is illustrated in 
 
 Figure 120, in which the break within the cylinder 
 
 is effected magnetically by the magnetic plug. 
 
 V diagram of a typical ignition system with 
 met mnical break inside the cylinder is presented 
 in Figure 121. 
 
 Jump-Spark Ignition involves no working parts 
 through the cylinder walls and is in its best forms 
 rath r more economical in current consumption 
 than make-and-break devices a point of some 
 valu when battery current is depended upon. 
 Furt ermore, a jump-spark ignition system may 
 be so designed as to involve very 
 few mechanical parts requiring 
 much attention or adjustment. 
 FIGURE m.-Make- Its use of very high tension cur- 
 
 m n o d v'e B m e ent ^tiT aS rent approximating 30,000 volts 
 
 d the point c is caused .11 -i > -i 
 
 to make and break con- in the secondary circuit renders 
 
 tact with the point !,..'....-.., , . -, 
 
 of the insulated plug it decidedly subiect to short cir- 
 
 6, thus producing a r 
 
 S^J^XSrS? Trom cuiting from moisture or undue 
 the battery e. proximity of wires and other ele- 
 
 ments. However, in an aerial vehicle it is easier 
 to guard against short circuiting from moisture 
 than it is in the case of the automobile. Designed 
 with multivibrator coils one coil for each cylin- 
 
286 
 
 VEHICLES OF THE AIR 
 
 Figure 122. Mechanical-Break Jump-Spark Ignition System. In this, the 
 current from the battery e flows through the circuit a I), which is positively 
 broken at suitable intervals' by the "snapper" device g. This induces a high 
 tension surge in the fine winding of the coil ;', at the same moment the sec- 
 ondary current in d c is distributed to the plug h in the cylinder i by the 
 
 haf 
 
 distributor f t which is mounted on the same s 
 anism. 
 
 ift bearing the snapper rnech- 
 
 der it is apt to be heavy, unreliable, uneconomical 
 in current consumption, and subject to serious dis- 
 turbances of synchronism, but with single-coil 
 systems, and especially in those systems in which 
 an exceedingly rapid mechan- 
 ical-break device is substituted 
 for the vibrator, it becomes one 
 of the best of all forms of igni- 
 tion, capable of running a 
 multicylinder engine for many 
 hours upon the small quantity 
 of current that is to be had 
 from such small dry cells as 
 are used in pocket flashlights. 
 Larger dry cells and storage 
 batteries are much used in high-tension ignition 
 systems for automobiles, but a magneto is superior 
 to these current sources in convenience and relia- 
 bility, though probably no magneto system can 
 
 FIGURE 123. Jump- 
 Spark Ignition. Every 
 time the primary circuit 
 is closed by the timer, or 
 commutator, g, current 
 from the battery e ener- 
 gizes the coil f, and at- 
 tracts the blade of the 
 trembler h. The conse- 
 quent sudden rupture of 
 the primary circuit induces 
 a current in the secondary 
 circuit of sufficient inten- 
 sity to make a spark at the 
 gap a of the plug l>. 
 
POWER PLANTS 287 
 
 be made as light as such a system as that illus- 
 trated in Figure 122, in which very small dry cells 
 are used. 
 
 A Jump-Spark Ignition System with vibrator 
 coil is illustrated in Figure 123. 
 
 Hot-Tube Ignition, such as is illustrated in Fig- 
 ure 124, in which a is a hollow tube projecting from 
 the cylinder b, and around which is kept playing 
 the flame c, is one of the earliest forms of internal- 
 combustion engine ignition, having been exten- 
 sively used in the first automobile en- 
 gines. In its best types it is exceedingly 
 reliable, requiring but little fuel to main- 
 tain the external flame, and in- FIGURE 
 
 i . t , i . -, , n I-, Ignition. Compression of 
 
 VOlVing Only the Weight OI the a portion of the charge in 
 
 the cylinder 6 into the 
 
 heating lamps, which can be ^^^^^^ 
 made very light. The difficulty the fuel - 
 of timing hot-tube ignition is in a considerable 
 measure met in aeronautical practice by the small 
 need for timing, most aerial vehicles requiring 
 motors working at practically constant speeds. 
 
 Ignition by Heat of Compression is a thing of 
 the future rather than of the present, though its 
 possibilities are strikingly suggested in the com- 
 mon "preignition" that constitutes so disconcert- 
 ing a disability with overheated automobile engines 
 of present types. Engines have, however, been 
 built and run for long periods on ignition by heat 
 of compression, and with careful designing can be 
 made to function very satisfactorily. The Diesel 
 engine the most efficient internal-combustion en- 
 gine ever built works on practically this plan. 
 
288 VEHICLES OF THE AIR 
 
 The engine illustrated in Figure 125 is made to run 
 with preignition, though in its present forms elec- 
 tric or other ignition is required to start and keep 
 it running until it reaches its normal working tem- 
 perature. Naturally, ignition by heat of compres- 
 sion is scarcely applicable to mixture-fed engines, 
 working best with fuel-injection engines. 
 
 Catalytic Ignition, produced by the action of 
 the hydrocarbon gases of the fuel upon a small par- 
 ticle of platinum black or similar material placed 
 in the cylinder, is a promising suggestion that has 
 hung fire for a number of years in the automobile 
 field. Most alluring in its possibilities, it has so 
 far resisted all serious attempts to reduce it to 
 practice, and the fact that a small particle of plati- 
 num black can be brought to a bright, white-hot 
 glow by the action of hydrogen or any hydrocarbon 
 gas is so far more recognized in the building of 
 pocket cigar lighters and automatic gas jets than 
 it is in the design of internal-combustion engines. 
 
 COOLING. 
 
 The cooling of internal-combustion aeronautical 
 engines is very much of a problem at the present 
 time. Unless a flying-machine engine is designed 
 of a size to afford a considerable excess of power, 
 which unavoidably involves an excess of weight, 
 it must normally and continuously be worked up 
 very close to its maximum capacity, which in turn 
 involves much more severe taxing of the cooling 
 system than is the case with automobile engines, 
 which in ordinary use are worked to their full 
 
POWER PLANTS 289 
 
 capacity only exceptionally. This has made the 
 application of air cooling seem even more difficult 
 than in automobile engineering, in which it is 
 enough of a problem to prevent all but a small 
 minority of manufacturers from attempting it. 
 
 Water Cooling therefore being more or less of a 
 present necessity that must be faced in making 
 long runs, the majority of designers plan to pro- 
 vide it in thoroughly serviceable and efficient form, 
 keeping down weights by well-considered applica- 
 tion of principles long established rather than by 
 innovations. Light and effective centrifugal 
 pumps are used to produce rapid circulation, often 
 in conjunction with considerable thermosyphon 
 action secured by very tall radiators; waterjackets 
 are made of light sheet metal, preferably applied 
 by autogenous welding; and radiators are of the 
 thinnest possible materials, most carefully put 
 together. 
 
 Typical water-cooled engines and cooling sys- 
 tems are the Wright, Panhard, and Antoinette 
 power plants, illustrated in Figures 111, 115, and 
 190 and 191, respectively. The first *f these 
 differs from common practice in that the water is 
 boiled and evaporated into steam in the cylinder 
 jackets, thus requiring a true condenser rather 
 than a radiator for its re-use, and permitting the 
 whole motor apparatus to function at a tempera- 
 ture materially higher than the objectionably low 
 temperature of ordinary water-cooled engines. 
 The Wright engine is kept cool by the tall tubular 
 radiator a, Figures 190 and 191, the water being 
 circulated by the centrifugal pump &. 
 
290 
 
 VEHICLES OF THE AIR 
 
 Air Cooling has the merit over water cooling 
 that it reduces weight, increases reliability, and 
 simplifies construction, the only bar to its uni- 
 versal use being the question of its effectiveness. 
 In a flying machine, too, except in the case of the 
 
 FIGURE 125, A Light- Weight Aeronautical Motor. In the functioning of 
 this engine, which is of the four-cycle, internal-combustion type, pure air 
 is inspired through the poppet valve L, during the suction stroke, directly 
 from the outer atmosphere. At the end of the suction stroke, air com- 
 pressed beneath the piston B is scavenged into the cylinder A by the uncov- 
 ering of the ports P, the valve L remaining open. During the compression 
 stroke the combined volumes of air continue to be scavenged out through L 
 until the piston has made from one-fourth to one-third of its travel, at which 
 point, L closing, compression begins and is carried to a very high point in 
 the comparatively small clearance M. Carburetion is by fuel injected directly 
 into the cylinder near the end of this stroke, and ignition immediately fol- 
 lows, being effected by any suitable means. Also, during the compression 
 stroke, air is inspired beneath the piston through the leather clack valve 
 KK. Well before the end of the explosion stroke, L is opened by the cam 
 mechanism to serve now as an exhaust valve, and the burned gases are dis- 
 charged through it directly into the atmosphere, being aided in their exit 
 by another blast of pure air through the ports P when these are uncovered by 
 the piston. Then, throughout the exhaust stroke, L remains open. The 
 cylinder A is a very thin cast-iron shell, with a reinforcing wrapping of piano 
 wire, and it is clamped between the steel head O and the base F by a circle 
 of bicycle spokes DD. The light sheet-steel connecting rod G is built up by 
 autogenous welding and is on annular ball bearings at the crosshead E and 
 the crankpin I, of the crankshaft H. The disk piston B is built up by 
 autogenous welding of a steel center and a cast-iron bearing portion, and is 
 connected by the hollow steel piston rod C to E, which runs in the guides 
 JJ welded to the frame NN and the base F. The internal scavenging affords 
 high efficiency and thorough cooling, but the engine is, of course, very noisy 
 because of the direct discharge of the exhaust. 
 
 dirigible balloons, there always is a good current 
 of air available (for either air or water cooling) 
 without the necessity for any fan, the impossibility 
 of a slow rate of travel of the vehicle assuring this. 
 Nevertheless, to enhance the effect, in some of the 
 most successful air-cooled aeronautic engines there 
 are employed blower schemes to induce powerful 
 
POWER PLANTS 29i 
 
 air currents of great volume, as in the case of the 
 eight-cylinder, V-shaped, air-cooled Renault en- 
 gine illustrated in Figures 98 and 114. 
 
 A principle that is greater in future promise 
 than in present application, is that of internal air 
 cooling cooling the cylinders of the engine by the 
 scavenging action of considerable quantities of air, 
 in excess of those required for the charge volumes, 
 passed through the interiors of the cylinders in 
 the course of their functioning. Internal air cool- 
 ing is most successfully applied in conjunction 
 with fuel injection as a means of carbureting the 
 charges. 
 
 An internally-cooled, fuel-injection, four-cycle 
 engine patented by the writer is shown in a single- 
 cylinder construction adapted to aeronautical uses 
 in Figure 125. 
 
 CAEBUEETION 
 
 The carburetion of the liquid fuel, usually gaso- 
 line, necessary for the common forms of aero- 
 nautical engines is very much of a problem. The 
 ordinary carbureter is in most respects a non- 
 positive mechanism, in consequence of which its 
 functioning is attended with many uncertainties 
 even in its application to automobiles. These un- 
 certainties become many times more serious in 
 application to aeronautics because of the difficulty 
 of effecting adjustment while at the same time 
 keeping the machine in operation. 
 
 Carbureters for flying-machine engines are 
 closely similar to those fooind best for automobile 
 engines. 
 
292 
 
 VEHICLES OF THE AIR 
 
 In the automobile field the general type of car- 
 bureter most used is that illustrated in Figure 126, 
 in which the flow of fuel from the main fuel tank 
 is controlled by the float a operating on the float 
 valve &, the fuel entering the float chamber c 
 
 through the pipe d. 
 From the float chamber 
 c the fuel is drawn by 
 way of the atomizing 
 nozzle e into a current 
 of air passing through 
 the pipe /, this current 
 being induced by the 
 suction within the cylin- 
 ders. 
 
 Obviously, to secure 
 uniformly-proportioned 
 fuel it is necessary that 
 the fuel level in the atomizing nozzle be maintained 
 fairly constant. Also, for variable-speed engines, 
 it is desirable that the carbureter action be such as 
 not to derange the mixture materially through vari- 
 ation in the suction from different speeds. "With 
 no means of compensation, at higher engine speeds 
 and consequent higher suction the air flowing 
 through / tends to attenuate, or " wiredraw ", while 
 the quantity of fuel passing through the atomizing 
 nozzle increases, thus furnishing a fuel altogether 
 too rich for best results. To offset this effect it 
 is customary to provide means of admitting extra 
 air into /, as through the valve g, which automati- 
 cally opens wider and wider as the suction in- 
 
 FIGURE 126. Carbureter. Fuel 
 from the tank flows through the pipe 
 d until the float chamber c is filled 
 to a level determined by the rising of 
 the float a, which closes the valve 6. 
 From c extends a pipe terminating in 
 the atomizing nozzle e, which is lo- 
 cated in the pipe f, through which 
 air is inspired In the direction of the 
 arrows by the suction of the engine. 
 This suction causes gasoline to spray 
 from e in quantities proportionate to 
 the force of the suction, except that 
 at very high suctions the valve g 
 opens and by thus admitting air be- 
 tween c and the engine prevents the 
 fuel from becoming too rich at high 
 engine speeds. The butterfly valve at 
 h is the throttle. 
 
POWER PLANTS 293 
 
 creases. Other means of arriving at a similar 
 result are admission of air through positively-con- 
 trolled valves interconnected with the usual but- 
 terfly throttle placed as at h, or by devices that 
 reduce the orifice of the atomizing nozzle e. 
 
 In many carbureters designed primarily for 
 automobile use, the floats and float chambers are 
 made concentric in form, surrounding the atomiz- 
 ing nozzle, the purpose of this being to maintain 
 a constant level of fuel in the atomizing nozzle 
 regardless of fore-and-aft or lateral tilting of the 
 vehicle. In a flying machine this seems hardly 
 necessary because longitudinal tilting never under 
 normal conditions can exceed the comparatively 
 flat angles of gilding or ascending, while lateral 
 tilting is compensated for by the centrifugal force 
 set up in turning, which acts upon the liquid within 
 the float chamber as well as upon every other 
 element of the machine. 
 
 Because of the objections to carbureters, the 
 use of positive fuel injection, either into the intake 
 piping or directly into the cylinders, is a practise 
 favored by several foremost designers. Fuel 
 injection, besides being positive, admits of much 
 closer regulation than is possible with a carbureter, 
 and because the injection can be timed permits of 
 high compressions without preignition, the fuel in- 
 jection being delayed until ignition is wanted. 
 
 The chief difficulty in the way of general 
 employment of fuel injection is that of commutat- 
 ing the fuel to the different cylinders without the 
 objectionable scheme of employing a plurality of 
 
294 VEHICLES OF THE AIR 
 
 pumps, one for each cylinder, which besides adding 
 complication will scarcely admit of such adjust- 
 ment as to give exactly uniform results in all the 
 cylinders a difficulty, however, which is no greater 
 than that of equalizing the intake manifold from 
 a carbureter so as to produce uniform feeding. In 
 fact, there is no means of carburetion in existence 
 today for automobile or similar liquid-fuel engines 
 that will insure a power output from a plurality 
 of cylinders varying less than from five to ten 
 percent from cylinder to cylinder, as disclosed 
 directly on the face of manograph diagrams. 
 
 Fuel Pumps of the most satisfactory forms are 
 exceedingly simple, involving little more than a 
 brass pump block, chambered out to receive a steel 
 plunger and provided with ball check valves and 
 the necessary pipe connections. 
 
 An ordinary stuffing box, packed with oil and 
 cotton wicking and operated in an oil bath is 
 enough to prevent leakage even with the use of a 
 fuel such as gasoline, which is a solvent for all com- 
 mon lubricants. Soft soap, however, is in some 
 respects preferable as a packing, and affords very 
 good results. 
 
 The proper fitting of the very small valves 
 required, so that they will seat positively and 
 tightly, takes very close work, but is quite within 
 the abilities of any competent machinist. 
 
 All valves in a fuel-injection system should be 
 placed vertically, and extreme care must be exer- 
 cised in the arrangement of piping and in the 
 design of all cavities to prevent air locks, the pres- 
 
POWER PLANTS 
 
 ence of which will cause most obscure and difficult 
 troubles. 
 
 A typical fuel pump, which has been used with- 
 out change for twelve years on the Mietz and Weiss 
 
 FIGURE 127. Mietz and Weiss Fuel Pump. The gasoline comes from the 
 tank through the pipe v, attached by the coupling u, and enters the cavity 
 in the pump block s through the valve *. Its flow is caused by the plunger 
 I, driven by the eccentric d through the strap g, and retracted by the spring 
 m, and it passes out through the valve q and the pipe p to the engine cylin- 
 der. The stroke of I is regulated by the regulator handle a, mounted on the 
 regulating shaft 6, which forces down the plunger-guide sleeve i and thus re- 
 tracts I from the eccentric. Priming is effected by pushing down on the pump 
 handle j, which is forced up after each stroke by the spring fc. At r is an 
 air cock, to clear the system of possible air locks. A governor weight / on 
 the shaft e is used to control the speed automatically, the whole running in 
 the frame c. 
 
 two-cycle kerosene stationary engines, in one, two, 
 three, and four-cylinder units, is illustrated in 
 Figure 127. 
 
 The best steels for making fuel-pump plungers 
 and other steel pump parts are the high nickel 
 steels much employed in automobile-engine valve 
 
296 VEHICLES OF THE AIR 
 
 construction, and containing from 25% to 35% 
 nickel, which has the effect of making them almost 
 non-corrosive. 
 
 MUFFLING 
 
 Muffling a gasoline engine, while highly desir- 
 able and therefore arranged for in practically all 
 automobile, motorcycle, and motor boat engines to 
 reduce noise, is in a measure objectionable from 
 
 aeronautical stand- 
 points because of its 
 
 FIGURE 128.-Sllencer. The gases adding the Weight of 
 entering at a induce an air flow in.ii_ ^.pfl 
 
 through the holes c c, with the result 1116 muffler, 
 
 that by the time the exhaust reaches , . , , , 
 
 the mouth & it is contracted by cooling P W 6 r bV the back 
 to a comparatively small volume. 
 
 pressure it sets up, and 
 
 tending to overheating by retarding the escape of 
 the hot gases. Still, as progress continues it is 
 likely that sufficient margins of power and weight 
 will admit of at least enough muffling to dispense 
 with the more deafening noise of the exhaust. 
 
 Strictly speaking, a distinction can be made 
 between mufflers and silencers, the former reduc- 
 ing noise by choking back and 
 retarding the exit of the gases 
 by means of baffle plates, pro- FIGURE 129. Muffler. The 
 
 i 111 T gases entering at a flow back 
 
 lections, and chambered con- and forth as indicated by the 
 
 . . _ ._ ._ arrows until they issue from 
 
 structions, while silencers re- the vent 6 - 
 
 duce noise not so much by retarding the exhaust 
 
 as they do by cooling and thus shrinking the gases. 
 
 The latter plan is by all means the most advantage- 
 
 ous in designing for minimums of weight and back 
 
 pressure. 
 
 The lightest form of silencer is a long, fun- 
 
POWER PLANTS 297 
 
 nel-shaped tube, such as is illustrated in Figure 
 128, in which a is the exhaust pipe from the engine, 
 b is the mouth of the silencer, and c c are openings 
 into which air is drawn by the blast at d, this 
 induced air assisting cooling. A typical muffler is 
 illustrated in Figure 129. A modification of this 
 type into a combined muffler and heater is 
 illustrated in Figure 255. 
 
 AUXILIAKY EXHAUSTS 
 
 Auxiliary exhaust ports, as at a a a, Figure 112, 
 arranged to be uncovered by the piston just as it 
 reaches the bottom of its stroke, greatly assist cool- 
 ing, especially of the exhaust valve, and add mate- 
 rially to power by conducing to free escape of the 
 burned charge. The auxiliary exhaust is much 
 used in racing-motorcycle and air-cooled automo- 
 bile engines. 
 
 FLYWHEELS 
 
 Flywheels or some equivalent are necessary in 
 all forms of internal-combustion engines to pro- 
 duce uniform rotation and torque from the inter- 
 mittent impulses in the different cylinders. Con- 
 sequently it is a general rule that the fewer the 
 cylinders the greater the flywheel effect required. 
 
 Since the momentum of a flywheel is a function 
 not only of its mass, but also of the velocity at 
 which this mass moves, increased flywheel effect 
 can be secured either by adding more material 
 or by increasing size. The latter when permissible 
 is much the more advantageous plan, because, for 
 example, doubling the diameter of a flywheel sim- 
 
298 VEHICLES OF THE AIR 
 
 ply redistributing the material quadruples the 
 effect, since the resulting doubling of the circum- 
 ference doubles peripheral speed while at the same 
 time the rim is removed to twice the distance from 
 the center. On the other hand, simply adding lat- 
 erally to a flywheel another of similar size and 
 weight is doubling of the weight with only 
 doubling of the flywheel effect. 
 
 From these considerations it will be understood 
 that the larger a flywheel the better, the only limits 
 being those set up by consideration of space avail- 
 able and the matter of interference with the details 
 of surrounding mechanism. 
 
 It being settled as desirable that as much as 
 possible of the weight of a flywheel be concentrated 
 in its rim, where the speed of movement is highest, 
 the tendency in designing flywheels for aeronaut- 
 ical engines is to reduce the centers of these wheels 
 to their lowest terms. 
 
 A very interesting design is that illustrated at 
 a, Figure 116, in which the rim is seen to be of 
 turned steel, held to its hub by such an arrange- 
 ment of stout wire spokes as is used in an ordinary 
 bicycle wheel. 
 
 As is explained in a previous paragraph (see 
 Page 282), the use of revolving cylinders in an 
 engine eliminates the necessity for a flywheel. 
 Another road to the elimination of the flywheel, 
 with its undesirable added weight, is the use of 
 propellers as a substitute for it a perfectly feas- 
 ible and very usual plan when the design is such 
 that the propeller or propellers can be mounted 
 
( POWER PLANTS 299 
 
 directly on a prolongation of the engine crank- 
 shaft. It will be noted that this construction is 
 employed in seveial of the aeroplanes illustrated 
 herein. 
 
 STEAM ENGINES 
 
 The steam engine, though not extensively 
 applied either to automobile propulsion or to aero- 
 nautics, nevertheless has disclosed very definite 
 merits in so far as it has been applied. Not the 
 least of the advantages of a steam power plant is 
 the ability to use in one and the same plant 
 a great variety of common fuels, readily obtainable 
 anywhere. 
 
 In the matter of weight, one of the lightest 
 engines of any kind ever built was that exhibited 
 by Stringf ellow at the British Aeronautical Exhibi- 
 tion in 1868 (see Page 157), this engine develop- 
 ing one horsepower for each thirteen pounds of 
 weight. 
 
 In 1892 Laurence Hargrave built a steam 
 engine weighing only 5 pounds, 11 ounces, with 
 boiler, and showed how the boiler could be light- 
 ened enough to bring the weight down to only 3 
 pounds, 14 ounces without reducing the output of 
 .653 horsepower. This figures less than 6 pounds 
 per horsepower (see Page 122). 
 
 A larger light engine was that designed by 
 Clement Ader, for use in his early aeroplane expe- 
 riments (see Page 134). This engine, which was 
 in duplicate one for each of the two ^ropellers 
 had two high and two low-pressure cylinders in 
 each unit, placed horizontally, and with the bores 
 
300 VEHICLES OF THE AIR 
 
 2.56 inches and 3.937 inches and the stroke 3.937 
 inches. The boiler was of the multitubular type, 
 alcohol-fired, and delivered steam at a pressure of 
 140 pounds to the square inch. The two motors 
 together, without boiler, weighed slightly over 
 92J pounds and ran at 600 revolutions a minute. 
 
 A particularly remarkable engine was that 
 designed by Hiram Maxim and used in his experi- 
 ments in 1894. This engine, which was in the 
 machine illustrated in Figures 235 and 236, 
 weighed with the boiler but without water about 
 1,800 pounds, and developed 363 horsepower less 
 than five pounds to the horsepower. 
 
 Another very light aeronautical engine was the 
 steam engine used by Professor Langley in his suc- 
 cessful model flying machine, which flew over the 
 Potomac Eiver in 1896 (see Page 136). This 
 power plant, with a total weight of 8 pounds, 
 developed 1J horsepower. 
 
 In the matter of reliability, it is a well known 
 fact that several automobiles with steam power 
 plants, besides being substantially as light as the 
 best gasoline cars of similar capacity are well above 
 the average in reliability and durability, though it 
 often is charged against them that they require 
 unusually expert care and handling, a requirement 
 that for the time being is not an especial objection 
 in the case of the flying machine. 
 
 A steam engine recently designed in France for 
 application to an aeroplane is that illustrated in 
 Figure 130, the boiler for supplying it with steam 
 being shown in Figure 132. 
 
FIGURE 130. Steam Engine for Aeronautical Use. This engine, which is of French 
 design, follows gasoline-engine practice in the V-placing of the cylinders and the use of poppet 
 valves. It is designed for use with the boiler shown below. 
 
 FIGURE 132. Water-Tube Boiler for Aeronautical Use. This boiler closely resembles the 
 steam "generators" used in steam automobiles. Its light weight* efficiency, capacity for the 
 rapid production of steam at extremely high pressure, and its freedom from scaling and 
 corrosion are the chief merits of this construction. 
 
POWER PLANTS 301 
 
 AVAILABLE TYPES 
 
 Of the different types of steam engines those 
 most available for aeronautical service are, unfor- 
 tunately, in most cases the least efficient a diffi- 
 culty that applies in practically similar degree to 
 internal-combustion engines. Thus the elaborate 
 compound, triple, and quadruple expansion types, 
 by which a maximum of the available energy of 
 the fuel is transformed into useful work, involve 
 too great a weight of machinery to permit their use. 
 Instead of these the less-efficient, light, high-speed 
 and high-pressure single-acting and double-acting 
 engines are found best, though the amount of com- 
 pounding that has been found permissible in 
 automobile engines is perhaps worth securing. 
 
 The steam turbine would appear on first con- 
 sideration to be the best possible type of motor 
 for a flying machine, its direct rotary movement 
 permitting a minimum loss in the transmission of 
 the power to the evenly-revolving propellers, but 
 it is an unfortunate fact that at present steam 
 turbines in any but the largest size are woefully 
 inefficient. With future developments in this 
 department of steam engineering, together with 
 probable decrease in the size of flying machines, it 
 seems more than likely that the moderate size steam 
 turbine may here come into its own. 
 
 BOILERS 
 
 Steam boilers are of two principal types ^fire- 
 tube and water-tube. Typical of the former is the 
 common flue boiler illustrated in Figure 131, in 
 
302 
 
 VEHICLES OF THE AIR 
 
 which a a are copper tubes headed into the steel 
 crown sheets & and c, which are further connected. 
 by the steel shell d, wrapped with piano wire to 
 afford the necessary strength with extreme light- 
 ness. This type of boiler has been 
 much used in steam automobiles 
 and is very light and efficient, the 
 hot gases from the fire beneatic it 
 passing through the flues and thusr 
 c coming into contact with very ex- 
 tensive surfaces on the other side 
 of which is the water to be heated. 
 t7pe Flu J The flash "generator", which 
 358*1 c! con' has been found most successful in 
 
 nected by the tubes , . n , . . , 
 
 a a a, through which automobile practise, consists iun- 
 
 the fire is forced. The 
 
 (So? piinS f wfre wrapped damentally of one or more long 
 steel tubes more or less closely 
 coiled through the fire, and provided with means 
 for pumping water into one end, to issrue as steam 
 at the other. A boiler of this type naturally must 
 be made to stand a high temperature withont in- 
 jury, regardless of whether or noti it contains 
 water, the water being pumped in only as steam 
 is required and being " flashed" into steam as it 
 comes in contact with the hot surf ace is. The best 
 examples of this type of boiler are remarkably 
 light and efficient, will withstand wcrking pres- 
 sures up to 1,200 pounds to the square i net, and are 
 immune from the explosion possibilities that al- 
 ways exist in connection with other types, espe- 
 cially if very high pressures are employed'. 
 
 A flash generator designed to supjply strain for 
 
POWER PLANTS 303 
 
 the aeronautical engine shown in Figure 130 is 
 illustrated in Figure 132. 
 
 BURNERS 
 
 Burners for steam power plants vary from the 
 common automobile type gasoline burner to the 
 numerous types of grates and fireboxes required 
 for coal, wood, and other heavy fuels. For aero- 
 nautical steam power plants there would appear to 
 be the widest field for a combination firebox, 
 capable of being readily arranged to consume 
 either liquid or solid fuel. This should not involve 
 any serious weight or complication, while the al- 
 most unvarying .power demand makes possible 
 utilization of solid fuels with much less attention 
 than would be necessary with an automobile. 
 
 FUELS 
 
 Of the fuels available for steam power plants, 
 the most easily fed and controlled are the liquid 
 fuels, such as gasoline, kerosene, benzene, benzine, 
 alcohol, and crude petroleum. 
 
 Of the solid fuels there are coal, coke, briquettes 
 (of coal dust, pitch, and other materials), char- 
 coal, and wood. Coke and charcoal afford very 
 clean and hot fires with little or no smoke. Wood 
 has the merit of universal availability, so that a 
 machine utilizing it could find fuel by descending 
 in almost any locality. Something of the same sort 
 is true in lesser degree of coal. The weights, bulks, 
 and heating value of the more common liquid and 
 solid fuels are given in the following table: 
 
304 
 
 VEHICLES OF THE AIR 
 
 COMPARISON OF FUELS 
 
 Cpercnldcftorcftlkni) 
 
 CALORI ric YALCK 
 
 (In Brit 
 
 Units 
 
 Pond) 
 
 Gasoline 
 
 a 
 
 f. 
 
 II 
 
 31 toll 
 
 * Acetylene liquefied at 68 F. under 597 pounds to the square inch. In 
 this form it is rery dangerous unless its use is attended by proper precau- 
 tions, but it is nevertheless considered by some engineers to posses important 
 posibilities in applications to light-weight high-power engines. 
 
 Of even more importance than its theoretical 
 calorific value is the efficiency with which a fuel 
 can be utilized in a practical engine. Thus alcohol, 
 with a comparatively low thermal value, can be 
 utilized with a high thermal efficiency, in internal- 
 combustion engines giving fully as much power as 
 equivalent weights of gasoline. 
 
 BLECTBIdTT 
 
 Though electrical power for the propulsion of 
 aerial vehicles has too many shortcomings to admit 
 of its present practical utilization, it undoubtedly 
 holds out a few promises that, though vague, make 
 it worthy of some consideration. 
 
 ELECTKIC MOTOBS 
 
 Electric motors, while ideal for aeronautical 
 application to the extent that they permit great 
 speeds and develop their power through directly- 
 rotating elements, are decidedly heavy even with- 
 out considering the question of current source as 
 
POWER PLANTS 305 
 
 compared with most other prime movers. The 
 lightest and highest speed electric motor ever built 
 was that of M. G. Trouve, experimented with in 
 Paris in 1887. This motor had aluminum circuits 
 and weighed only 3.17 ounces, but developed T V 
 horsepower at the rate of 7.53 pounds to the 
 horsepower, a figure that there does not seem to be 
 any particular prospect of reducing in any prac- 
 tical construction. The electric motor used in the 
 Tissandier dirigibles, with which the Tissandier 
 brothers experimented in France in 1884 (see Page 
 81), weighed 121 pounds and developed a maxi- 
 mum of only 1| horsepower. This was a direct- 
 current-motor. Undoubtedly alternating-current 
 motors can be built considerably lighter, though no 
 serious attempts, founded upon the present state of 
 electrical knowledge, have been made or are likely 
 to be made to produce them for aeronautical uses. 
 
 CURRENT SOURCES 
 
 The electric motor, unlike the gasoline engine, 
 is not a prime mover, since it requires a supply 
 of electric current from some source external to 
 itself to keep it going. In its application to the 
 propulsion of street-railway cars this current is 
 developed in stationary power plants and trans- 
 mitted to the moving vehicles by sliding or roll- 
 ing contacts against wires or other conductors. In 
 electric automobiles current is supplied by storage 
 batteries carried in the machine. Obviously the 
 first of these systems is not applicable in any prac- 
 tical way to aerial travel. 
 
306 VEHICLES OF THE AIR 
 
 Storage Batteries, or accumulators, do not 
 really store electric current, but produce it by chem- 
 ical reactions, exactly as is the case with pri- 
 mary batteries. They differ from these, however, 
 in that the chemical elements involved in their 
 operation can be electrolytically recomposed by a 
 passage of electric current through the cells after 
 each period of discharge. This process is termed 
 charging. 
 
 The best modern automobile storage batteries 
 of the lead-plate types are capable of delivering 
 a current of 80 ampere hours, at about 2 volts, from 
 each five pounds of weight. Multiplying the 
 amperes by the volts and dividing the watts thus 
 reached by 746 (746 watts being the electrical 
 equivalent of a horsepower) it is found that about 
 24 pounds of battery are required to maintain 
 an output of one horsepower for one hour, against 
 a fuel consumption of about one-half a pound per 
 horsepower hour in the best gasoline engines. 
 
 Much effort has been expended in attempts to 
 produce storage cells much lighter for a given 
 capacity than those now in use, and, though these 
 cells in some cases give better results than the 
 above figures indicate, these improved results in 
 the matter of capacity per unit of weight usually 
 are attained only by great sacrifices of durability. 
 
 By many engineers the most promising pos- 
 sibility in the way of lighter weight storage bat- 
 teries is considered to be the development of the 
 so-called alkaline type of storage cell, of which 
 the Edison and Jungmann cells are today the prin- 
 
POWER PLANTS 307 
 
 cipal exponents. In these cells the elements are 
 metallic nickel and iron, and nickel and cobalt 
 oxide. 
 
 Of lead storage batteries, there are two prin- 
 cipal types the formed and the pasted. In the 
 former the oxide of lead that constitutes the active 
 material is formed on the surfaces of the electrode 
 by electro-chemical processes of charging and 
 recharging, while in the latter the plates are cast 
 lead grids, made in a great variety of forms, and 
 with the interstices filled with oxide of lead com- 
 pressed in place under high pressure. 
 
 Primary Batteries, though not totally unavail- 
 able as a source of current, are by no means excep- 
 tionally light in any forms now known, besides 
 which they are enormously expensive to operate. 
 The plunge-bichromate type, in which the electro- 
 lyte is bichromate of potash in which are immersed 
 positive and negative electrodes of zinc and carbon, 
 respectively, was that used by the Tissandiers (see 
 Page 81), the total weight of their battery being 
 496 pounds. While it is perfectly conceivable that 
 lighter primary batteries may be produced it is to 
 be regarded as certain that they will be hopelessly 
 expensive, while as in the case of the storage bat- 
 tery they will have to be so very much lighter 
 before they can find any considerable utility in 
 application to aeronautics that the prospect of 
 their appearance seems very remote. 
 
 Thermopiles, by which electricity is produced 
 directly from heat, are today interesting devices 
 of the physical laboratory rather than factors in the 
 
308 VEHICLES OF THE AIR 
 
 world's engineering activities. The laws of ther- 
 mopile action are only imperfectly understood, but, 
 in a general way, it can be explained that the typ- 
 ical apparatus of this kind consists of assemblages 
 of numerous dissimilar metal bars or parts, joined 
 together by their ends in series. When the points 
 of juncture are heated the result is that an electric 
 current, very small in proportion to the weight of 
 the apparatus and the quantity of heat required, 
 is produced. Moreover, the joints tend to come 
 apart with continued use and it is found rather 
 difficult to localize the heat as it should be for the 
 best results. The metals at present found to give 
 the most efficient results are bismuth and antimony 
 in combination. It is a recognized remote pos- 
 sibility, however, that development in thermopiles 
 may some day revolutionize present methods of 
 power development. Possibly the road to such 
 development will be found in the use of refractory 
 metals heretofore little tried for this purpose, such 
 as copper and iron, or metals of the platinum 
 group, put together by electric or autogenous weld- 
 ing, and filamented and air-cooled in their mid- 
 dle portions to maintain localization of the heat. 
 
 MISCELLANEOUS 
 
 Besides the various more-or-less well-estab- 
 lished or well-investigated power sources already 
 considered, there are a few more freakish and 
 less serious possibilities that perhaps call for 
 cursory mention. 
 
POWER PLANTS 309 
 
 COMPKESSED AIE 
 
 Compressed air, or liquid air, stored under high 
 pressure in steel cylinders, has been used with some 
 success in model flying machines particularly in 
 those of Hargrave (see Page 122) experimental 
 automobiles, mine locomotives, etc., the power 
 being developed from it through practically a 
 type of small steam engine, but the advantages of 
 this system are most manifest in almost any direc- 
 tion but that of light weight, so its application to 
 practical aerial navigation is not likely. 
 
 CAEBONIC ACID 
 
 Carbonic acid gas can be used in much the 
 same manner as compressed air, in comparison with 
 which it has minor merits and still more serious 
 shortcomings. 
 
 VAPOE MOTOES 
 
 Vapor motors practically small steam power 
 plants in which some more volatile liquid than 
 water is used to produce the steam, the liquid 
 being recondensed and used over and over have 
 long offered an alluring field for experiment, 
 besides which they found rather extensive appli- 
 cation to motorboats and launches before the days 
 of gasoline engines. 
 
 The most successful type of vapor motor is the 
 common naphtha boat engine. Next to this come 
 various types working with acetone, alcohol, etc., 
 few of which have run outside of experimental 
 workshops, and all of which are heavy and 
 inefficient. 
 
310 VEHICLES OF THE AIR 
 
 SPRING MOTOES 
 
 Spring motors, though out of the question for 
 the propulsion of man-carrying aerial vehicles, 
 have served and continue to serve a considerable 
 purpose in experimenting with models. A twisted 
 rubber band, employed as suggested at a, Figure 
 29, can be made to afford a surprising amount of 
 energy within a very small weight. 
 
 Steel springs are from most standpoints less 
 practical than rubber, but they, too, have found use 
 in models. 
 
 A bent wood, whalebone, or bamboo splint, or 
 a flat steel spring, a, furnishes the power in the 
 well-known form of toy or model helicopter 
 illustrated in Figure 28. 
 
 ROCKET SCHEMES 
 
 Rocket schemes, in which propulsion and ascen- 
 sion are expected to be secured from the reaction 
 of sky-rocket-like discharges of gas from explosion 
 chambers, have been a recurring feature of the 
 theoretical phase of aeronautical development for 
 many years. All such schemes seem condemned by 
 the fact that no known explosive contains anything 
 like as many heat units per pound as a great 
 variety of true fuels, their characteristic feature 
 being not a capacity for great power output, but 
 simply the property of expending their entire 
 energy content in exceedingly brief spaces of time. 
 
 TANKS 
 
 The tanks for transporting the fuel, water, and 
 oil necessary to the operation of the various prac- 
 
POWER PLANTS 311 
 
 tical types of aeronautical power plants, must ful- 
 fill a variety of conditions, chief among which are 
 capacity, strength, light weight, immunity from 
 corrosion, and in many cases a form favorable 
 to the reduction of head resistance. For any given 
 capacity and strength, with a minimum weight, 
 spherical tanks are best. Immunity from corrosion 
 is generally provided by the use of copper or brass, 
 but steel is enough stronger to warrant its use, 
 protected by interior and exterior plating with 
 other metal. The form most favorable to progress 
 through the air with a minimum resistance is the 
 elongated pear-like form, blunt-end foremost, next 
 to which come the great variety of elongated cyl- 
 inders and other possible constructions in which 
 circular sections are a feature. Undue elongation 
 of such forms adds greatly to weight and so reduces 
 carrying capacity as to be inexpedient unless in 
 some special case such as that of the dirigible 
 nacelle, illustrated in Figures 19 and 20, in which 
 the tubular tank also constitutes a stiffening mem- 
 ber in the framing. 
 
 The liquid fuel is most reliably fed to the motor 
 by gravity, but pressure or pump feed are both 
 employed, and can be made very satisfactory with 
 sound designing, as has been well established in 
 various constructions now widely recognized as 
 good practice in automobile engineering. 
 
 A point of particular importance when large 
 quantities of fuel for long flights are carried, is 
 the location of the tank at the center of gravity 
 of the whole machine, so its gradual emptying will 
 
312 VEHICLES OF THE AIR 
 
 not disturb the balance. This point has been very 
 carefully observed in the design of all successful 
 modern aeroplanes, including the Wright, Bleriot, 
 Antoinette, and other machines. The same point 
 applies with equal force to the location of tanks for 
 water and oil, and the seating accommodations for 
 passengers. 
 
FIGURE 139. Chain Transmission of Wright Biplane. Note the crossing of tubular chain- 
 guides at the left also the placing of the fuel tank t at the center of gravity. 
 
 - 
 
 FIGURE 140. Double-Chain Transmission in Hydroplane Driven bv Aerial 
 
CHAPTEE SEVEN 
 
 TRANSMISSION ELEMENTS 
 
 Except in the case of a flying machine in which 
 the propeller can be mounted directly upon the 
 engine crankshaft, it is necessary to have some 
 sort of a transmission to communicate the power 
 from the motor to the propelling element. In a 
 number of the most successful present-day aero- 
 planes the designers have not found it easy to 
 make engine location and engine speed readily 
 coincident with propeller location and propeller 
 speed, so are compelled to utilize transmissions of 
 one type or another for the purposes of trans- 
 mitting the power and changing the relative speeds 
 of rotation. 
 
 Propeller- driving arrangements now common 
 in aeroplane practise are those shown in Figures 
 
 FIGURE 133. FIGURE 134. FIGURE 135. FIGURE 136. 
 
 Comparison of Aeroplane Transmission Systems. 
 
 133, 134, and 136. The first of these permits the 
 propeller to run slower than the engine, as in the 
 monoplanes illustrated in Figures 141, 162, and 
 
 313 
 
314 VEHICLES OF THE AIR 
 
 198 ; the second is the means of driving the oppo- 
 sitely rotating propellers on the Wright and the 
 Cody biplanes, as is more clearly shown in Figure 
 188; while the fourth is the widely-favored plan of 
 mounting the propeller directly on the engine shaft, 
 as is shown in many of the illustrations herein. 
 
 A transmission is imperatively necessary when 
 more than one propeller, not on the engine shaft, 
 is run from a single motor as in the machines 
 illustrated in Figures 20, 32, 33, 78, 79, 107, 134, 
 140, and 188. 
 
 The change-speed gear, so necessary in auto- 
 mobiles and other land vehicles to allow advan- 
 tageous application of the power under greatly 
 varying conditions of operation up and down 
 hills, over soft and hard surfaces, etc. is not 
 required in flying-machine transmissions because 
 the conditions under which aerial vehicles operate 
 present far less variation in so far as the matter of 
 power demand is concerned. 
 
 CHAINS AND SPEOCKETS 
 
 Chains and sprockets, of proper design, are one 
 of the most efficient and at the same time one of 
 the lightest and most flexible of all known means 
 of power transmission, as is evident in their ex- 
 ceedingly extensive application to bicycles, auto- 
 mobiles, etc. This type of transmission has, more- 
 over, given good results in several of the most 
 successful aeroplanes so far constructed. 
 
 In the use of chains it is essential to employ 
 only the highest quality materials and the most 
 
TRANSMISSION ELEMENTS 315 
 
 approved designs. Even with these factors closely 
 looked after there is a certain amount of unavoid- 
 able stretch in a chain, due to the accumulated 
 wear at each link and rivet. Lubrication, too, 
 must be provided for, preferably by occasionally 
 soaking in -a mixture of graphite and melted tal- 
 low, or by dosing liberally from time to time with 
 suitable oils. 
 
 Obviously, the difficulty of keeping a chain 
 clean and properly lubricated is much less on a 
 flying machine than it is on an automobile or 
 bicycle, it being much less exposed to dust. 
 
 Chains that are very long require to be guided 
 by small idlers or sleeves of some sort. An 
 example of the use of tubular steel sleeves to guide 
 long chains is afforded in the transmission of the 
 Wright machine, illustrated in Figure 188, in 
 which it is seen that the chain for the propeller a 
 passes through the two slightly-diverging tubes 
 6 and c, while that for the propeller d goes through 
 the tubes e f, crossed to reverse the motion. This 
 very peculiar arrangement, which has been widely 
 denounced as unmechanical, has for its object the 
 reversal of the rotation of one of the propellers 
 so that the two may turn in opposite directions, 
 as is required to balance the gyroscopic and other 
 reactions. That it has serious objections, and is 
 justified only as an experimental construction, 
 has been suggested in several cases of chain break- 
 age in the use of this particular type of machine. 
 
 In the Cody biplane (see Page 202) chains spe- 
 cially made for this purpose by an English manu- 
 
316 VEHICLES OF THE AIR 
 
 facturer are used, their special feature being the 
 provision of a definite amount of lateral flexibility. 
 
 Seemingly a better plan, certain to afford about 
 the same results, would be to provide the engine 
 camshaft with heavier driving gears and a heavy 
 end bearing, so that one of the propellers could be 
 driven from a sprocket on this shaft, the cam gear- 
 ing reversing the motion as is suggested in Figure 
 135. The two-to-one ratio of drive secured in this 
 way could be readily compensated by making the 
 right propeller sprocket twice as large as the left. 
 
 Another chain transmission, used to drive 
 aerial propellers on a hydroplane boat, is illus- 
 trated in Figure 140. 
 
 With proper designing, chains can be satisfac- 
 torily run at speeds as high as 2,000 feet a minute. 
 Such speeds particularly require ample clearance 
 between tooth and roller. 
 
 BLOCK CHAINS 
 
 Block chains, of the type pictured in Figure 
 137, are distinguished by the use of solid steel 
 blocks for each alternate link. Block chains are 
 much used on bicycles but are 
 objected to on automobiles be- 
 m.-Biock chain, cause they run very hard when 
 not clean an objection that is not a very serious 
 one from the flying-machine standpoint. Their 
 advantages are their greater width of tooth and 
 rivet-bearing surface for a given width of chain, 
 their simpler construction and their materially 
 lower price. 
 
FIGURE 141. Belt Transmission in Recent Santos Dumont Monoplane. This machine, 
 while it was not conspicuously successful, is a notable example of what can be done with 
 belt transmission, the light weight of the pulleys 6 6 and the ordinary construction of the belt 
 a a being particularly interesting. 
 
TRANSMISSION ELEMENTS 
 
 317 
 
 ROLLER CHAINS 
 
 Boiler chains, made entirely of links, rollers, 
 and rivets, as shown in Figure 138, are very smooth 
 running even when very dirty and are capable of 
 running smoothly over smaller 
 sprockets than can be used with 
 block chains. The greater width F^BE iss. Roller chain, 
 of roller chains for given bearing widths on rivets 
 and sprocket teeth is not a serious objection in 
 most cases, since it involves no materially greater 
 weight. 
 
 MISCELLANEOUS 
 
 Silent chains and link belts are made very wide, 
 of great numbers of metal or leather links, and call 
 for special sprockets or pulleys. In the case of 
 some link belts the construction is such that a small 
 toothed sprocket can be used at one end and a 
 large smooth pulley at the other, the belt working 
 satisfactorily over both. 
 
 What are known as " cable chains" not made 
 to run over sprockets are much used in place of 
 sash cords and the like. Their strength and flexi- 
 bility renders them ideal for use in control connec- 
 tions where corners must be turned. 
 
 BLOCK CHAINS 
 
 Pitch 
 
 Inside Width 
 
 Outside Width 
 
 Weight to Foot 
 
 Breaking Load 
 
 inch 
 inch 
 
 J inch 
 I inch 
 
 \ inch 
 
 .073 pound 
 .125 pound 
 
 300 pounds 
 1250 pounds 
 
 inch 
 
 i 3 g inch 
 
 
 187 pound 
 
 1500 pounds 
 
 inch 
 
 i inch 
 
 
 .219 pound 
 
 1600 pounds 
 
 inch 
 
 A inch 
 
 
 312 pound 
 
 1800 pounds 
 
 inch 
 
 1 inch 
 
 
 .344 pound 
 
 1950 pounds 
 
 inch 
 
 \ inch 
 
 
 388 pound 
 
 2128 pounds 
 
 inch 
 inch 
 l^o inches 
 
 A inch 
 i inch 
 & inch 
 
 f inch 
 ift inch 
 
 .5 pound 
 .53 pound 
 281 pound 
 
 2400 pounds 
 2400 pounds 
 
 
 1 inch 
 
 
 .312 pound 
 
 1350 pounds 
 
 I/O 
 
 \ inch 
 
 
 375 pound 
 
 2130 pounds 
 
 lie inches 
 
 i inch 
 
 1 inch 
 
 .76 pound 
 
 4032 pounds 
 
318 
 
 VEHICLES OF TEE AIR 
 
 STANDARD AMERICAN ROLLER CHAINS 
 
 Pitch 
 
 Inside Width 
 
 Diameter of 
 Rolls 
 
 Weight to Foot 
 
 W E2." 
 
 ] 
 
 inch 
 
 A inch 
 
 i! inch 
 
 .625 pound 
 
 4000 pounds 
 
 
 inch 
 
 ft inck 
 
 JS inch 
 
 .625 pound 
 
 5000 pounds 
 
 
 inch 
 
 i inch 
 
 li inch 
 
 .687 pound 
 
 4000 pounds 
 
 
 inch 
 
 g inch 
 
 if inch 
 
 .687 pound 
 
 5000 pounds 
 
 
 inch 
 
 i inch 
 
 if inch 
 
 .875 pound 
 
 6000 pounds 
 
 
 inch 
 
 
 inch 
 
 i& inch 
 
 1.25 pounds 
 
 7500 pounds 
 
 1 
 
 1 inch 
 
 
 inch 
 
 ft inch 
 
 1.125 pounds 
 
 6000 pouuds 
 
 1 
 
 inch 
 
 j 
 
 inch 
 
 3 inch 
 
 .125 pounds 
 
 5000 pounds 
 
 1 inch 
 
 
 inch 
 
 inch 
 
 .25 pounds 
 
 COOO pounds 
 
 ] 
 
 inch 
 
 
 inch 
 
 inch 
 
 .25 pounds 
 
 5000 pounds 
 
 ] 
 
 inch 
 
 
 inch 
 
 
 inch 
 
 .875 pounds 
 
 6000 pounds 
 
 ] 
 
 Iinch 
 
 
 inch 
 
 
 inch 
 
 .5 pounds 
 
 6000 pomnds 
 
 ] 
 
 inch 
 
 
 inch 
 
 
 inch 
 
 pounds 
 
 7500 pounds 
 
 It inches 
 
 
 inch 
 
 
 inch 
 
 .25 pounds 
 
 6000 pounds 
 
 ] 
 
 i inches 
 
 
 inch 
 
 
 inch 
 
 .5 pounds 
 
 6000 pounds 
 
 : 
 
 ! inches 
 
 
 inch 
 
 
 inch 
 
 .875 pounds 
 
 8000 pounds 
 
 : 
 
 i inches 
 
 
 inch 
 
 
 inch 
 
 pounds 
 
 0000 pounds 
 
 : 
 
 \ inches 
 
 
 inch 
 
 
 inch 
 
 .625 pounds 
 
 10000 pounds 
 
 : 
 
 i inches 
 
 
 inch 
 
 
 inch 
 
 .75 pounds 
 
 10000 pounds 
 
 : 
 
 I inches 
 
 
 inch 
 
 
 inch 
 
 .437 pounds 
 
 12000 pounds 
 
 : 
 
 i inches 
 
 
 inch 
 
 
 inch 
 
 .875 pounds 
 
 15000 pounds 
 
 1| inches 
 
 
 inch 
 
 1 inch 
 
 .5 pounds 
 
 30000 pounds 
 
 2 inches 
 
 1J inches 
 
 It inches 
 
 .875 pounds 
 
 35000 pounds 
 
 ROLLER CHAINS 
 
 ] 
 
 Pitch 
 
 1 
 \ 
 
 nside 
 Vidth 
 
 Outside 
 Width 
 
 Diameter 
 of Rolls 
 
 Weight to Foot 
 
 Breaking 
 Load 
 
 i 
 
 > s inch 
 inch 
 
 i 
 
 inch 
 inch 
 
 .295 inch 
 
 .197 inch 
 .303 inch 
 
 .109 pound 
 .172 pound 
 
 700 pounds 
 
 
 inch 
 
 
 b inch 
 
 
 .303 inch 
 
 203 pound 
 
 
 
 inch 
 
 1 
 
 inch 
 
 
 .805 inch 
 
 .211 pound 
 
 
 
 inch 
 inch 
 inch 
 
 
 iuch 
 
 inch 
 inch 
 
 .515 inch 
 .64 inch 
 
 .315 inch 
 .SSO inch 
 .308 inch 
 
 .380 pound 
 .453 pound 
 158 pound 
 
 2010 pounds 
 2240 pomnds 
 
 
 inch 
 
 
 j inch 
 
 
 .303 inch 
 
 .172 pound 
 
 
 
 inch 
 
 
 inch 
 
 
 .308 inch 
 
 266 pound 
 
 
 ; 
 
 inch 
 inch 
 inch 
 inch 
 inch 
 inch 
 
 i 
 
 inch 
 inch 
 kinch 
 
 inck 
 fe inch 
 ^ inch 
 
 .625 inch 
 .64 inch 
 .718 inch 
 .781 inch 
 .77 inch 
 
 .4 inch 
 .4 inch 
 .476 inch 
 .476 inch 
 .476 inch 
 .315 inch 
 
 .487 pound 
 .515 pound 
 .75 pound 
 .78 pound 
 .60 pound 
 219 round 
 
 2feOO pounds 
 2800 pounds 
 5808 pounds 
 3808 pounds 
 3696 pounds 
 
 
 
 inch 
 
 ] 
 
 e inch 
 
 
 315 inch 
 
 
 
 
 
 inch 
 
 
 inch 
 
 
 .315 inch 
 
 .281 pound 
 
 
 
 inch 
 inch 
 inch 
 inch 
 inch 
 inch 
 inch 
 inch 
 inch 
 inch 
 
 
 inch 
 k inch 
 inch 
 inch 
 inch 
 inch 
 inch 
 inch 
 inch 
 inch 
 
 .812 inch 
 .75 inch 
 .812 inch 
 .937 inch 
 .837 inch 
 .812 inch 
 .968 inch 
 .843 inch 
 .968 inch 
 1.093 inches 
 
 .475 inch 
 .5 inch 
 .5 inch 
 .5 inch 
 .551 inch 
 .562 inch 
 .562 inch 
 .625 inch 
 .625 inch 
 .625 inch 
 
 75 pound 
 .81 pound 
 .81 pound 
 1.0 pounds 
 1.10 pounds 
 .89 pounds 
 1.2 pounds 
 1.17 pounds 
 1.29 pounds 
 1.44 pounds 
 
 4816 pounds 
 4811 pounds 
 4811 pounds 
 4816 pounds 
 7056 pounds 
 6048 pounds 
 6048 pounds 
 7056 pounds 
 7056 pounds 
 7056 pounds 
 
 Bicycle Chains. 
 
TRANSMISSION ELEMENTS 
 
 319 
 
 CABLE CHAINS 
 
 ] 
 
 3 itch 
 
 Plates 
 
 Outside 
 Width 
 
 Depth 
 
 Thickness 
 of Plates 
 
 Weight to 
 Yard 
 
 Breaking 
 Load 
 
 t J 
 
 inch 
 
 2 & 1 
 
 .117 inch 
 
 .112 inch 
 
 
 .321 pound 
 
 160 pound 3 
 
 t 
 
 inch 
 
 2 & 2 
 
 152 inch 
 
 112 inch 
 
 
 .433 pound 
 
 225 pounns 
 
 1 ' 
 1 
 
 1 
 
 j inch 
 
 1 & 2 
 
 !223 inch 
 
 .185 inch 
 
 .045 inch 
 
 .175 pound 
 
 440 pounds 
 
 
 I? inch 
 
 2 & 2 
 
 .268 inch 
 
 .185 inch 
 
 .045 inch 
 
 .234 pound 
 
 600 pounds 
 
 1 
 
 b inch 
 
 2 & 3 
 
 .813 inch 
 
 .185 inch 
 
 .045 inch 
 
 .292 pound 
 
 800 pounds 
 
 " 
 
 o inch 
 
 3 & 4 
 
 .403 inch 
 
 .185 inch 
 
 .045 inch 
 
 .409 pound 
 
 1100 pounds 
 
 
 'o inch 
 
 4 & 5 
 
 .4U3 inch 
 
 .185 inch 
 
 .045 inch 
 
 .526 pound 
 
 1300 pounds 
 
 
 a inch 
 
 1 & 2 
 
 .20 inch 
 
 .212 inch 
 
 .035 inch 
 
 .116 pound 
 
 460 pounds 
 
 } 
 
 ^ inch 
 
 2 & 2 
 
 .24 inch 
 
 .212 inch 
 
 .035 inch 
 
 .187 pound 
 
 700 pounds 
 
 ! 
 
 a inch 
 
 2 & 3 
 
 .28 inch 
 
 .212 inch 
 
 .035 inch 
 
 .258 pound 
 
 000 pounds 
 
 J 
 
 inch 
 
 3 & 4 
 
 .36 inch 
 
 .212 inch 
 
 .035 inch 
 
 .337 pound 
 
 1140 pounds 
 
 
 S 8 inch 
 
 4 & 5 
 
 .44 inch 
 
 .212 inch 
 
 .035 inch 
 
 .411 pound 
 
 1740 pounds 
 
 
 inch 
 
 1 & 2 
 
 .20 inch 
 
 .315 inch 
 
 .04 inch 
 
 .312 pound 
 
 800 pounds 
 
 
 inch 
 
 2 & 2 
 
 .24 inch 
 
 .315 inch 
 
 .04 inch 
 
 .375 pound 
 
 1560 pounds 
 
 
 inch 
 
 2&8 
 
 .28 inch 
 
 .315 inch 
 
 .04 inch 
 
 .50 pound 
 
 1900 pounds 
 
 
 inch 
 
 8 & 4 
 
 .36 inch 
 
 .315 inch 
 
 .04 inch 
 
 .75 pound 
 
 2500 pounds 
 
 
 inch 
 
 4 & 5 
 
 .44 inch 
 
 .315 inch 
 
 .04 Uch 
 
 .875 pound 
 
 3500 pounds 
 
 ! 
 
 inch 
 
 1 & 2 
 
 .339 inch 
 
 .267 inch 
 
 067 inch 
 
 .322 pound 
 
 680 pounds 
 
 
 inch 
 
 2 & 2 
 
 .406 inch 
 
 .267 inch 
 
 .067 inch 
 
 .4*2 pound 
 
 990 pounds 
 
 
 inch 
 
 2 & 3 
 
 .473 inch 
 
 .267 inch 
 
 .067 inch 
 
 .562 pound 
 
 1280 pounds 
 
 
 inch 
 
 3 & 4 
 
 .607 inch 
 
 .267 inch 
 
 .067 inch 
 
 .72S pound 
 
 1800 pounds 
 
 
 inch 
 
 4 &5 
 
 .741 inch 
 
 .267 inch 
 
 .067 inch 
 
 .887 pound 
 
 2400 pounds 
 
 t These can be run as block chains over sprockets. 
 
 BEVEKSIBLE SPEOCKETS 
 
 Sprockets made exactly the same on both sides, 
 so that it does not matter which way around they 
 are fixed in place, in some situations constitute a 
 useful provision against wear. By simply turning 
 such a reversible sprocket around entirely new 
 wearing surfaces are presented to the chain. This 
 applies, of course, only to transmissions in which 
 all or most of the work is done in one direction of 
 rotation. 
 
 For best results, sprockets with not more than 
 50 nor less than 14 teeth are advised by the most 
 conservative chain manufacturers. 
 
 MISSED TEETH 
 
 In the design of very large sprockets it often is 
 a useful expedient to use less than a tooth for every 
 link, leaving out every other tooth, for example. 
 This reduces friction, slightly lowers weight, 
 
320 VEHICLES OF THE AIR 
 
 cheapens construction, and is quite unobjection- 
 able, except that it is not applicable to small 
 sprockets. 
 
 SHAFTS AND GEARS 
 
 Shafts and gears for the transmission of power 
 are the soundest of sound engineering, though a 
 given amount of material will not as readily sus- 
 tain a given torsional stress in a shaft as it will a 
 corresponding tensile stress in a chain, and gears 
 lack the flexibility of chain-and-sprocket transmis- 
 sion. Advantages of shaft-and-gear transmission 
 are its ready application to greater distances than 
 can be effectively worked over by chains, the small 
 space it occupies, its silence and smoothness of 
 running, and the facility with which it can be 
 encased and lubricated. 
 
 SHAFTS 
 
 Hollow rod or tubing, of the finest alloy steels, 
 of circular cross section, and of large diameter and 
 with comparatively thin walls, is much the highest 
 grade material the strongest and lightest that 
 can be used for shafting. Solid shafts of course 
 have their uses, as for passing through small holes 
 in situations where more room cannot very readily 
 be provided, but, though affording the greatest 
 strength that can be had in a given space they do 
 not begin to be as strong for a given weight as 
 hollow material. Always when it is possible 
 unbroken shaft lengths should be used in any 
 machine compelled to work under heavy duty, but 
 <7hen there are reasons preventing this, excellent 
 
TRANSMISSION ELEMENTS 321 
 
 joints can be made in shaft materials by brazing, 
 or by autogenous or electric welding. In Chapter 
 11 further data is given concerning stock sizes of 
 shafting and tubing, and methods of assembling. 
 
 SPUR GEAES 
 
 Spur gears for the transmission of power are 
 difficult to render perfectly smooth running be- 
 cause of the slight amount of backlash that results 
 from the necessary slight clearance given between 
 the teeth to prevent binding. Consequently they 
 are used only when cost has to be considered, or 
 in situations in which peculiar conditions apply, 
 such as the necessity for endwise meshing of the 
 teeth in sliding gears for automobiles. Spur gears 
 can transmit power only between parallel shafts, 
 and it is most essential that this requisite parallel- 
 ism be perfectly secured and maintained by stiff 
 construction and suitable bearings. Case-hard- 
 ened steel gears are the only kind suitable for 
 heavy power transmission with light weights. 
 Theoretically with properly cut teeth there is only 
 rolling contact between the teeth of meshed gears, 
 but practically there is enough sliding friction to 
 warrant the provision of the tough shell that is 
 produced by suitable methods of case-hardening. 
 With such case-hardening, the tough interiors of 
 the gear teeth resist breakage, while their hard- 
 ened external shells withstand wear. 
 
 Spur-gear drives have been experimented with 
 in one or two of the Voisin machines (see Chapter 
 
322 VEHICLES OF THE AIR 
 
 12), with a view to running the single propeller 
 slower than the engine. 
 
 Bronze or brass gears meshed with steel, or 
 gears built up laterally of rawhide and metal 
 layers, are very silent running, but lack the req- 
 uisite strength and durability for the continued 
 transmission of much power with small sizes. 
 Gears of these materials are much used for cam- 
 shaft, circulating-pump, lubricator, and magneto 
 driving. 
 
 The teeth of gears are cut on three principal sys- 
 tems the involute, the epicycloid, and the "stub." 
 The pitch line of a gear is the working diameter 
 about the height of a tooth less than the actual 
 diameter. The " pitch line" of a pair of meshed 
 gears can be seen when they are running, appear- 
 ing as a sort of shadow line about midway of the 
 tooth lengths. The * ' pitch ' ' of gears has reference 
 to the number of teeth per inch of diameter " di- 
 ametral pitch" and is the number of teeth in 
 3.1416 inches of the pitch line. The proper pitch 
 for given conditions of speed, loading, etc., as well 
 as the width of gears, always must be determined 
 by exhaustive and competent consideration of the 
 circumstances of the particular case. , 
 
 BEVEL GEAES 
 
 Just as spur gears are suitable for the trans- 
 mission of power between parallel shafts, bevel 
 gears are designed to transmit it "around corners" 
 between shafts at angles to each other. Aside 
 from the correct tooth outlines, which are the same 
 
TRANSMISSION ELEMENTS 323 
 
 for bevel gears as for spur gears, the essential 
 thing in bevel-gear design is that all lines pro- 
 longed from the tooth surfaces must meet at the 
 point where the axes of rotation of the gears would 
 meet if prolonged. To explain this more simply, 
 the requirement is that the gears be adjacent sec- 
 tions of two toothed cones, of the same or different 
 altitudes, but with points together and sides in 
 contact. Miter gears are bevel gears with angles 
 of 45, so that both gears of a pair are alike. Such 
 gears are used at a a and ~b, Figures 20 and 107, 
 respectively. 
 
 STAGGEKED AND HEREINGBONE TEETH 
 
 By placing two similar spur gears side by side, 
 with the teeth of one opposite the space between the 
 teeth in the other, and meshing the staggered-tooth 
 gear thus formed with another of similar construc- 
 tion, backlash and rough operation can be largely 
 eliminated. By the use of more than two gears in 
 each element the operation can be still further im- 
 proved until with an infinity of steps in the gear 
 the action would be almost perfect. Such an in- 
 finity of steps is practically secured in the helical 
 gear, in which each tooth runs at a slant across the 
 gear face. An objection to helical gears is that 
 the slant of their teeth tends to force them out of 
 mesh sidewise, so for all but the lightest power 
 transmission the double-helical, the so-called " her- 
 ringbone" gear, is to be preferred. In this type 
 each tooth has a symmetrical double slant from a 
 point on the center of the gear face to its edges, so 
 
324 VEHICLES OF THE AIR 
 
 that a tendency to work to one side is neutralized 
 by a corresponding tendency to work to the other. 
 The helical and herringbone systems of tooth for- 
 mation are applicable to bevel gears as well as to 
 spur gears, though in the first case they are much 
 more expensive to produce. 
 
 BELTS AND PULLEYS 
 
 For the transmission of large amounts of power, 
 belt-and-pulley combinations tend to work out 
 very heavy or inefficient, for which reason they 
 find little application in light-weight power plants 
 except for driving fans, lubricators, and other light 
 accessory devices. An exception is the case of the 
 motorcycle, in many forms of which belt transmis- 
 sion is used with success. The great advantage of 
 belt-and-pulley transmission is its extreme flexibil- 
 ity and its tendency to cushion and eliminate slight 
 irregularities in driving by its tendency to slip 
 under sudden increase of load. 
 
 PULLEY CONSTKUCTION 
 
 Pulleys are variously constructed of wood and 
 metal, and with flat, grooved, and crowned faces. 
 In seeking extreme light weight with a requisite 
 strength, a rim of wood or sheet steel, with wire 
 spokes to complete it, is undoubtedly the ideal con- 
 struction. For a given size, grooved pulleys, by 
 their binding action upon the round or V-shaped 
 belts employed with them transmit the most power, 
 but also lose the most in friction. For flat belts 
 wide flat pulleys can be used if the belt is perfectly 
 
TRANSMISSION ELEMENTS 325 
 
 uniform and the pulleys are correctly alined, but a 
 preferable construction is the crowned pulley, with 
 center slightly higher than the edge, so that it 
 holds the belt on by the resistance opposed by the 
 edges of the latter to stretching over the high 
 pulley center. 
 
 Metal pulleys often are faced with leather or 
 other material, cemented on to increase belt 
 adhesion. 
 
 Idlers are pulleys arranged to press against belts 
 running over other pulleys that transmit and re- 
 ceive the power, so that the tension and consequent 
 adhesion can be adjusted by variation of the idler 
 pressure. 
 
 BELT MATERIALS 
 
 Belts are mostly made of leather, rawhide, can- 
 vas, and canvas and rubber, and may be flat, round, 
 or V-shaped, to fit corresponding pulleys. Some 
 motorcycle and light automobile belts are made of 
 regular link chains with helical leather wrappings 
 to contact with the pulleys. The advantage of 
 this construction is the elimination of stretch. Belt 
 dressings usually are employed to secure proper 
 adhesion to the pulleys without the use of undue 
 belt tension, which causes enormous friction losses. 
 
 Interesting applications of belt-and-pulley 
 transmission to aeroplanes are shown in Figures 
 141 and 217. 
 
 CLUTCHES 
 
 Up to the present time there has been little use 
 of clutches in aeroplane transmissions, but there is 
 
326 VEHICLES OF THE AIR 
 
 no doubt but what some such disengaging device 
 will become increasingly necessary as gliding flight 
 becomes better understood and therefore more fre- 
 quently practised. Present propellers, rather 
 strongly held against rotation when the motor is 
 stopped, must present much more resistance to 
 forward movement (besides tending to tilt the 
 machine when only one is used) than could be the 
 case if they were, on occasion, allowed to spin freely 
 on their shafts. 
 
 The type of clutch most suitable for this service 
 is, of course, an undetermined question. The vari- 
 ous forms of friction clutches common disk, cone, 
 contracting, and expanding constructions used in 
 automobile practise might have the advantage 
 that at the end of a period of gliding they would 
 permit utilization of the propeller as a sort of 
 windmill wherewith to start the engine, but it is 
 more probable that the positiveness, lightness, and 
 durability of simple jaw clutches will prove to be 
 of more definite merit. 
 
FIGURE 142. Voisin Biplane Modified into a Triplane. 
 
 FIGURE 143. Henry Farman's Biplane in Flight. 
 
CHAPTER EIGHT 
 
 BEAEINGS 
 
 From nearly every vital standpoint a most 
 important element in any mechanism are the bear- 
 ings, since it is upon the integrity of these wear- 
 ing surfaces that continued serviceability depends, 
 besides which a minimization of the friction losses 
 in bearings directly and materially affects the 
 amount of power required to run the machine. In 
 aerial vehicles the importance of durable bearings, 
 capable of long-continued operation without atten- 
 tion or adjustment, and of types to minimize power 
 lost through friction, are of the utmost importance. 
 
 In the history of mechanism an immense vari- 
 ety of bearings has been devised to serve as great 
 a variety of needs, but in present-day engineering 
 sound practise has settled upon a few long-tested 
 forms of ball, roller, and plain bearings as most 
 suitable for all ordinary purposes. Each of the 
 different types in established use has its special 
 merits, and, in most cases, demerits, so a choice is 
 usually dictated by special conditions to be met. It 
 therefore is possible to generalize only to the extent 
 of emphasizing the importance of liberal sizes and 
 best materials, as sure means of affording strength, 
 immunity from heating, and slow wear. 
 
 327 
 
328 VEHICLES OF THE AIR 
 
 BALL BEARINGS 
 
 Ball bearings, substituting rolling for sliding 
 contact as a means of diminishing friction, are 
 very old in their conception, but first came into 
 general practical use with the advent of the bicycle. 
 The principle upon which they operate, as com- 
 pared with the conditions that apply in a plain 
 bearing, can be best appreciated from considering 
 the analogous cases of a flat board laid on a flat 
 surface, to represent the plain bearing, and the 
 same board over the same surface but with a num- 
 ber of marbles beneath it, to represent the ball 
 bearing. The difference in friction in the two 
 cases will be appreciated by any one. 
 
 Ball bearings manifest their superiority in the 
 reduction of friction loads most markedly at the 
 moment the mechanism is started in motion, the 
 starting effort when they are used being practically 
 no greater than the effort necessary to maintain 
 the mechanism in operation. In the best types 
 of plain bearings, in which running friction often 
 is reduced to a very small degree, the friction load 
 at starting always is vastly greater. 
 
 The best types of modern ball bearings, prop- 
 erly applied, can be counted upon to reduce friction 
 losses to as little as from .0012 to .0018 of the total 
 load per bearing. 
 
 ADJUSTABLE BALL BEAEINGS 
 
 The original and still a prevailing type of ball 
 bearing is the so-called "cup-and-cone", r adjust- 
 able bearing, in which the inner race a, Figure 144, 
 
BEARINGS 329 
 
 takes the general form of the frustum of a cone, 
 while the outer race is cup-like, as at b, the ball 
 circle c being placed between the two. Bearings 
 of this type are now extensively used only in 
 bicycles and in other very light ma- 
 chinery, or, to state the case more 
 strictly, in mechanisms in which ex- 
 cessive sizes can be used in proportion 
 to the loads. 
 
 The fundamental theory underly- 
 ing the construction of the cup-and- 
 FIGT cone type of ball bearing is that of its 
 
 Adjustable Baii adjustability a theory, however, that 
 is found to fall very flat upon anal- 
 ysis. Of course, it is evident that means of mov- 
 ing the cone endwise on its shaft, or the cup end- 
 wise in its housing, must bring the two closer 
 together or farther apart, with corresponding vari- 
 ation in the closeness of the fit upon the ball circle. 
 This is all right in setting up a new bearing but 
 as a means of using a worn bearing its merits are 
 less apparent, for it is an indisputable fact that 
 such wear as takes place must take the form of 
 grooves worn in the races, which being admitted, 
 the conclusion is inevitable that this groove is cer- 
 tain to be deeper on the loaded side of the non- 
 rotating race. This being the case, any attempt 
 at adjustment simply results in the appearance of 
 tight and loose positions alternate binding and 
 rattling as the bearing is turned, causing rough 
 operation and rapid breakdown, and thoroughly 
 upholding the contention of the advocates of annu- 
 
330 VEHICLES OF THE AIR 
 
 lar bearings to the effect that any ball bearing worn 
 enough to require adjustment is worn enough to 
 throw away. 
 
 Most high-grade adjustable ball bearings are 
 made with " retainers" to hold the balls assembled 
 in the circle. Such retainers usually are of thin 
 sheet metal, lightly embracing the balls so that they 
 cannot fall apart when handled, but of such shape 
 that they do not come into contact with the races 
 when the bearing is assembled. 
 
 ANNTJLAB BALL BEARINGS 
 
 Annular ball bearings, of the type illustrated 
 in Figure 145, are a decidedly modern and 
 advanced development in engineering, only recently 
 commencing to find extensive application in auto- 
 mobiles and 
 in a few oth- 
 er special ex- 
 amples of ex- 
 ceedingly 
 
 FIGURE 145. Annular Ball Bearing. Plan, Sec- high- grade 
 tional, and Perspective Views. n . 
 
 machinery. 
 
 In the evolution of annular-ball bearings the 
 ideal held in view has been to substitute in place 
 of adjustment a decreasing necessity for adjust- 
 ment, by providing ball and race surfaces of the 
 hardest and strongest materials and the utmost 
 accuracies of fit. How completely this ideal is 
 embodied in some of the best modern annular bear- 
 ings will be appreciated from the fact that these 
 bearings, used in sizes properly proportioned to 
 
BEARINGS 331 
 
 the work to be done, protected from grit and rust, 
 and properly lubricated, may be relied upon to 
 outlast almost any other part of any mechanism in 
 which they can be placed. 
 
 All successful annular bearings consist essen- 
 tially of the inner race a and the outer race &, 
 Figure 145, both ring-like, and symmetrical or 
 approximately symmetrical in their sectional 
 aspect, with the ball circle between them, the balls 
 running in grooves of circular cross section, the 
 arcs of these cross sections being of slightly greater 
 radii than the radii of the balls themselves. This 
 results in two-point contact, with the two points in 
 the same rotational plane and on opposite sides of 
 the balls. 
 
 Many different schemes have been devised for 
 assembling annular ball bearings in a permanent 
 and satisfactory manner, it being obvious that a 
 full circle of balls cannot be placed in races of the 
 type shown at a and b, Figure 145, without some 
 special scheme. One of the best expedients is that 
 shown in this Figure, in which only a half -circle of 
 balls is placed in the bearing, these balls being 
 subsequently spaced out to fill the entire circle by 
 the interposition of the small spacing springs 
 shown at d. 
 
 Another construction is that sketched in Fig- 
 ure 146, in which openings e and f are made in 
 the sides of the races, the balls being forced through 
 these, one at a time, by the application of slight 
 pressure. It is obvious that this scheme weakens 
 the races to some extent, besides which in some 
 
332 
 
 VEHICLES OF THE AIR 
 
 PlQUBE 146. F U 1 1 
 
 Type Annular Ball 
 Bearing. The balls are 
 introduced through the 
 cross slots, e and f. 
 
 forms it has been found to permit escape of the 
 balls under certain conditions, though this is ren- 
 dered less likely to occur by the 
 expedient of crossing the two 
 openings, e and f, so so that a 
 slight relative rotation between 
 the two races is required for the 
 insertion or removal of each ball. 
 Another scheme that utilizes 
 a half -circle of balls, thus avoid- 
 ing cutting the races, is to use spreading retainers 
 of the type shown in Figure 147, instead of the 
 spring separators shown in Figure 
 145. 
 
 A non-adjustable ball bearing 
 with flat instead of grooved outer ball 
 track is shown in section in Figure 
 148, in which it is seen that assem- 
 bling with a full circle of balls is ef- 
 fected simply by placing the races to- 
 gether sidewise. Flat surfaces will 
 not, however, carry as heavy loads with given sizes 
 as can be carried in grooved races. 
 
 Annular ball bearings of 
 the type illustrated in Figure 
 145 are capable of perfectly 
 satisfactory operation at most 
 enormous rotational speeds 
 up to 10,000 and 12,000 revolu- 
 tions a minute will stand such 
 shocks as are imposed on gas- 
 engine crankshafts, and are commonly used in a 
 
 FIGURE 147. 
 A n n u 1 ar Ball 
 Bearing. A sheet 
 metal cage is em- 
 ployed to main- 
 tain the spacing 
 of the balls. 
 
 FIGURE 148. Annular 
 Ball Bearing. 
 
BEARINGS 333 
 
 great range of sizes, from bearings less than one 
 inch in diameter up to the sizes required for heavy 
 hoisting cranes, railway-car axles, turbines, etc. 
 
 It is rather a remarkable fact 
 that annular ball bearings of the 
 type illustrated in Figure 145 prove 
 remarkably well adapted to sustain 
 thrust as well as the radial loads to 
 which they would seem more par- 
 ticularly adapted. The reason for 
 
 FIGURE 149. An 
 Subjected to 
 
 3(ring this seems to be discolsed in some 
 
 Thrust. 
 
 such conditon as is suggested in 
 Figure 149, in which it is seen the crowding the 
 races a and b in the contrary directions indicated 
 by the arrows has the effect of rolling the balls 
 slightly upon the side surfaces of the respective 
 race grooves, thus causing them to receive fairly 
 direct side support against the load, instead of the 
 wedging that would be assumed from a more casual 
 consideration. 
 
 It is considered by the best authorities, how- 
 ever, that combined thrust and radial loading of the 
 same bearing is always objectionable unless the 
 sum total of the loads is materially less than the 
 rated capacity of the size of bearing used. For this 
 reason it is regarded as best practise in such condi- 
 tions to use two bearings placed closely together, 
 one provided with an endwise-sliding fit in its hous- 
 ing so that it can carry radial load only, and the 
 other made radially free so that it can carry thrust 
 load only. 
 
 Special types of ball thrust bearings are made 
 
334 VEHICLES OF THE AIR 
 
 in the form illustrated in Figure 150, in which the 
 load is applied through the flat race a, through the 
 ball circle, and to the race b, which is either ground 
 with a spherical surface, or placed in a spherically- 
 seated holder, so that adjustment will occur auto- 
 matically to slight discrepancies 
 of alignment due either to im- 
 perfect fitting or to movement 
 while running. Thrust bearings 
 of these types, though capable 
 FIGURE 150. Ban of carrying very heavy loads. 
 
 Thrust Bearing. The flat J J J 
 
 Jn p tL T ^Jt, wSJTSJ cannot be run at as high speeds 
 
 s r ph e eric 6 ai S 8Srfac a efp?r s mi* as the radial bearings illustrated 
 
 ting it to adjust itself by -m* ~ AC \ i i^ 
 
 movement as suggested in Figure 142 when used ior 
 
 by the dotted lines. 
 
 thrust. 
 
 All the annular bearings so far shown consti- 
 tute permanently assembled units, requiring no 
 retainers to keep them together. Thrust bearings, 
 however, of the type illustrated in Figure 150, 
 often are made with retainers to hold the ball 
 circles together for convenience in handling. 
 
 In applying annular ball bearings it is nec- 
 essary to turn in the housings and on the shafts 
 simply plain cylindrical seats, that for one race 
 being a light driving fit while that for the other 
 is a close sliding fit. Usually the inner race is 
 given the driving fit. 
 
 A frequent misconception with reference to ball 
 bearings is that which regards them as having a 
 tendency to force apart the balls under load, as 
 would be the case at A, Figure 151, were the shaft 
 a to bear as indicated by the large arrow on the 
 
BEARINGS 335 
 
 two balls & and c, resting on the plane surface, in 
 which case the balls would tend to separate as indi- 
 cated by the small arrows. The 
 actual condition in the ball 
 bearing, however, is that 
 sketched at B, Figure 151, in 
 FIGURE isi.-Reuitants which the curved surface e is 
 5earlng ' substituted for the plane sur- 
 face so that the load represented by the large arrow 
 is squarely met by the tangents f and g, normal to 
 which come the two resultant thrusts indicated by 
 the small arrows. This point once grasped it will 
 be readily appreciated how erroneous are notions 
 to the effect that ball bearings of the full type oper- 
 ate with pressure between adjacent balls (which of 
 course revolve in opposite directions, as shown at g 
 and h, Figure 146) or that the balls exert pressure 
 on spacer springs or retainers used to hold them 
 apart as in Figures 145 and 147. Were the condi- 
 tion illustrated at A, Figure 151, to hold true, ball 
 bearings always would operate with the lost motion 
 between the balls represented by a separation at the 
 bottom, instead of at the top as is actually proved 
 the case by the click which every one has noticed in 
 bicycle ball bearings, and which is due to the balls 
 falling one after another over the highest point in 
 the circle of rotation. 
 
 It is a common idea that ball bearings do not 
 require to be lubricated. This is absolutely wrong, 
 and serious injury can be quickly done to a ball 
 bearing by any failure to lubricate properly. It is 
 a fact though that very infrequent and slight lubri- 
 
336 VEHICLES OF THE AIR 
 
 cation is sufficient for most ball bearings, provided 
 they are properly housed. 
 
 As has been previously suggested, it is of the 
 utmost importance that ball bearings be protected 
 from the entry of grit, and from such rusting as is 
 sure to follow the entry of water or the existence 
 of acid in the lubricant used. 
 
 Ball bearings depend absolutely for durability 
 and efficiency on the almost perfect wearing sur- 
 faces that are provided, it being well established 
 that minute inequalities in these surfaces do not 
 wear smgoth but tend to break down into greater 
 inequalities, from all of which it can be readily 
 inferred that quick deterioration is the logical 
 sequence of dirt or rust. Even graphite used as a 
 lubricant is detrimental in good ball bearings, in 
 which the fits are so close as not to provide suffi- 
 cient clearances for the exceedingly small particles 
 of graphite to pass between adjacent surfaces. 
 
 Most manufacturers of ball bearings specify the 
 types of mountings they consider most suitable for 
 housing and protecting their particular product 
 for keeping out water and grit, and retaining the 
 lubricant. It generally pays, in the designing of 
 most mechanisms, to pay close regard to such sug- 
 gestions. 
 
 The following tables show sizes, rated load 
 capacities, and weights of one of the oldest makes 
 of modern ball bearings, to which most other makes 
 conform exactly in the use of the same metric 
 sizes, and more or less closely in qualities of design 
 and material: 
 
ANNULAR BALL-BEARING SIZES. CAPACITIES, AND WEIGHTS 
 
 LIGHT-WEIGHT SERIES 
 
 BORE 
 
 DIAMETER 
 
 WIDTH 
 
 Load * 
 in 
 
 pounds 
 
 Weight 
 in 
 pounds 
 
 Milli- 
 meters 
 
 Approxi- 
 mate 
 equivalent 
 in inches 
 
 Milli- 
 meters 
 
 Approxi- 
 mate 
 equivalent 
 in inches 
 
 Milli- 
 meters 
 
 Approxi- 
 mate 
 equivalent 
 in inches 
 
 10 
 
 0.3937 
 
 30 
 
 1.1811 
 
 9 
 
 0.3543 
 
 120 
 
 0.09 
 
 12 
 
 0.4724 
 
 32 
 
 1.2598 
 
 10 
 
 0.3937 
 
 140 
 
 0.10 
 
 15 
 
 0.5905 
 
 35 
 
 1.3779 
 
 11 
 
 0.4331 
 
 160 
 
 0.12 
 
 17 
 
 0.6693 
 
 40 
 
 1.5748 
 
 12 
 
 0.4724 
 
 250 
 
 0.18 
 
 20 
 
 0.7874 
 
 47 
 
 1.8503 
 
 14 
 
 0.5512 
 
 320 
 
 0.23 
 
 25 
 
 0.9842 
 
 52 
 
 2.0473 
 
 15 
 
 0.5905 
 
 350 
 
 0.26 
 
 30 
 
 .1811 
 
 62 
 
 2.4410 
 
 16 
 
 0.6299 
 
 550 
 
 0.44 
 
 35 
 
 .3779 
 
 72 
 
 2.8346 
 
 17 
 
 0.6693 
 
 600 
 
 0.66 
 
 40 
 
 .5748 
 
 80 
 
 3.1496 
 
 18 
 
 0.7086 
 
 860 
 
 0.83 
 
 45 
 
 .7716 
 
 85 
 
 3.3464 
 
 19 
 
 0.7480 
 
 950 
 
 0.96 
 
 50 
 
 .9685 
 
 90 
 
 3.5433 
 
 20 
 
 0.7874 
 
 1000 
 
 1.09 
 
 55 
 
 2.1653 
 
 100 
 
 3.9370 
 
 21 
 
 6.8268 
 
 1160 
 
 1.36 
 
 60 
 
 2.3622 
 
 110 
 
 4.3307 
 
 22 
 
 0.8661 
 
 1550 
 
 1.75 
 
 65 
 
 2.5590 
 
 120 
 
 4.7244 
 
 23 
 
 0.9055 
 
 1670 
 
 2.28 
 
 70 
 
 2.7559 
 
 125 
 
 4.9212 
 
 24 
 
 0.9449 
 
 1820 
 
 2.50 
 
 75 
 
 2.9527 
 
 130 
 
 5.1181 
 
 25 
 
 0.9842 
 
 2130 
 
 2.63 
 
 80 
 
 3.1496 
 
 140 
 
 5.5118 
 
 26 
 
 .0236 
 
 2650 
 
 3.22 
 
 85 
 
 3.3464 
 
 150 
 
 5.9055 
 
 28 
 
 .1023 
 
 2850 
 
 3.97 
 
 90 
 
 3.5433 
 
 160 
 
 6.2992 
 
 80 
 
 .1811 
 
 3400 
 
 4.84 
 
 95 
 100 
 
 3.7402 
 3.9370 
 
 170 
 180 
 
 6.6929 
 7.0866 
 
 32 
 84 
 
 .2598 
 .3386 
 
 3750 
 2950 
 
 5.94 
 7.17 
 
 105 
 
 4.1338 
 
 190 
 
 7.4803 
 
 36 
 
 .4173 
 
 4600 
 
 8.48 
 
 110 
 
 4.3307 
 
 200 
 
 7.8740 
 
 38 
 
 .4960 
 
 5000 
 
 10.26 
 
 MEDIUM WEIGHT SERIES 
 
 10 
 
 0.3937 
 
 35 
 
 1.3779 
 
 11 
 
 0.4331 
 
 200 
 
 0.11 
 
 12 
 
 0.4724 
 
 37 
 
 1.4567 
 
 12 
 
 0.4724 
 
 240 
 
 0.14 
 
 15 
 
 0.5905 
 
 42 
 
 1.6535 
 
 13 
 
 0.5118 
 
 280 
 
 0.19 
 
 17 
 
 0.6693 
 
 47 
 
 1.8503 
 
 14 
 
 0.5512 
 
 370 
 
 0.25 
 
 20 
 
 0.7874 
 
 52 
 
 2.0473 
 
 15 
 
 0.5905 
 
 440 
 
 0.33 
 
 25 
 
 0.9842 
 
 62 
 
 2.4410 
 
 17 
 
 0.6693 
 
 620 
 
 0.53 
 
 30 
 
 .1811 
 
 72 
 
 2.8846 
 
 19 
 
 0.7480 
 
 860 
 
 0.77 
 
 35 
 
 .3779 
 
 80 
 
 3.1496 
 
 21 
 
 0.8268 
 
 1100 
 
 0.98 
 
 40 
 
 .5748 
 
 90 
 
 3.5433 
 
 23 
 
 0.9055 
 
 1450 
 
 1.35 
 
 45 
 
 .7716 
 
 100 
 
 3.9370 
 
 25 
 
 0.9842 
 
 1750 
 
 1.79 
 
 50 
 
 .9685 
 
 110 
 
 4.3307 
 
 27 
 
 1.0630 
 
 2100 
 
 2.35 
 
 55 
 
 2.1653 
 
 120 
 
 4.7244 
 
 29 
 
 1.1417 
 
 2400 
 
 2.90 
 
 60 
 
 2.3622 
 
 130 
 
 5.1181 
 
 31 
 
 1.2205 
 
 2800 
 
 3.72 
 
 65 
 
 2.5590 
 
 140 
 
 5.5118 
 
 33 
 
 1.2992 
 
 3300 
 
 4.49 
 
 70 
 
 2.7559 
 
 150 
 
 5.90o5 
 
 35 
 
 1.3779 
 
 4000 
 
 5.46 
 
 75 
 
 2.9527 
 
 160 
 
 6.2992 
 
 37 
 
 1.4567 
 
 4400 
 
 6.58 
 
 80 
 
 3.1496 
 
 170 
 
 6.6929 
 
 39 
 
 1.5354 
 
 5000 
 
 7.89 
 
 85 
 
 3.3464 
 
 180 
 
 7.0868 
 
 41 
 
 1.6142 
 
 5700 
 
 9.27 
 
 90 
 
 .5433 
 
 190 
 
 7.4803 
 
 43 
 
 1.6929 
 
 6400 
 
 10.47 
 
 95 
 
 .7402 
 
 200 
 
 7.8740 
 
 45 
 
 1.7716 
 
 7000 
 
 12.27 
 
 100 
 
 .9370 
 
 215 
 
 8.4645 
 
 47 
 
 1.8504 
 
 7700 
 
 15.23 
 
 105 
 
 .1338 
 
 225 
 
 8.8582 
 
 49 
 
 1.9291 
 
 8400 
 
 1719. 
 
 110 
 
 .3307 
 
 240 
 
 9.4488 
 
 50 
 
 1.9685 
 
 10000 
 
 2029. 
 
 "Under uniform load ; from % to % less undershock. 
 
338 
 
 VEHICLES OF THE AIR 
 
 HEAVY-WEIGHT SERIES 
 
 BORE 
 
 DIAMETER 
 
 WIDTH 
 
 T **M A 
 
 1HT-.* U * 
 
 Milli- 
 
 Approxi- 
 mate 
 
 Milli- 
 
 Approxi- 
 mate 
 
 Milli- 
 
 Approxi- 
 mate 
 
 Load 
 in 
 
 Weight 
 in 
 
 meters 
 
 eauivalent 
 in inches 
 
 meters 
 
 equivalent 
 in inches 
 
 meters 
 
 eauivalent 
 in inches 
 
 pounds 
 
 pounds 
 
 17 
 
 0.6693 
 
 62 
 
 2.4410 
 
 17 
 
 0.6693 
 
 850 
 
 0.56 
 
 20 
 
 0.7874 
 
 72 
 
 2.8346 
 
 19 
 
 0.7480 
 
 1050 
 
 0.85 
 
 25 
 
 0.9842 
 
 80 
 
 3.1496 
 
 21 
 
 0.8268 
 
 1320 
 
 1.14 
 
 30 
 
 .1811 
 
 90 
 
 3.54S3 
 
 23 
 
 0.9055 
 
 1600 
 
 1.56 
 
 35 
 
 .3779 
 
 100 
 
 3.9370 
 
 25 
 
 0.9842 
 
 1900 
 
 2.00 
 
 40 
 
 .5748 
 
 110 
 
 4.3307 
 
 27 
 
 .0630 
 
 2200 
 
 2.58 
 
 45 
 
 .7716 
 
 120 
 
 4.7244 
 
 29 
 
 .1417 
 
 2500 
 
 3.33 
 
 50 
 
 .9685 
 
 130 
 
 5.1181 
 
 31 
 
 .2205 
 
 3400 
 
 4.18 
 
 55 
 
 .1653 
 
 140 
 
 5.5118 
 
 33 
 
 .2992 
 
 3900 
 
 5.07 
 
 60 
 
 2.3622 
 
 150 
 
 5.9055 
 
 35 
 
 .3779 
 
 4400 
 
 6.12 
 
 65 
 
 2.5590 
 
 160 
 
 6.2992 
 
 37 
 
 .4567 
 
 4900 
 
 7.22 
 
 70 
 
 2.7559 
 
 180 
 
 7.0866 
 
 42 
 
 .6535 
 
 6200 
 
 10.54 
 
 80 
 
 3.1496 
 
 200 
 
 7.8740 
 
 48 
 
 .8897 
 
 7300 
 
 14.58 
 
 90 
 
 3.5433 
 
 225 
 
 8.8582 
 
 54 
 
 2.1260 
 
 10000 
 
 20.15 
 
 100 
 
 3.9370 
 
 265 
 
 10.4330 
 
 60 
 
 2.3622 
 
 14000 
 
 33.44 
 
 *Under uniform load; from % to % less undershock. 
 
 By most manufacturers of ball bearings it is 
 considered bad practise to attempt to divide a given 
 load among several closely-spaced bearings, such 
 attempts being almost always attended by difficul- 
 ties unless special provision is made to prevent 
 unequal distribution of the load on the two bear- 
 ings, causing one to support greater loads than are 
 calculated for it, with undue wear as a result. 
 Nevertheless, annular ball bearings are now built 
 with double grooves in single races, with the idea 
 of sustaining a given load in a smaller circumfer- 
 ential space. Bearings of this type are so new 
 that their success is fairly to be considered more 
 or less problematical, though in many initial appli- 
 cations they appear to give excellent service. Obvi- 
 ously, nothing but the most superior accuracy can 
 be considered permissible in a construction of this 
 sort. 
 
BEARINGS 339 
 
 All ball bearings of any quality are constructed 
 of the highest grades of alloy-steels made glass- 
 hard throughout, or at least of high-grade carbon 
 steels, casehardened. Both races and balls should 
 be finished to mirror surfaces, to within -guVo- or 
 Tiroinr of an inch of true size, and the balls must be 
 closely tested and selected for size and sphericity. 
 
 ROLLER BEARINGS 
 
 Boiler bearings are analogous to ball bearings 
 in that they substitute rolling for sliding friction, 
 but instead of employing a point of contact on the 
 surface of a sphere as in the ball bearing, a line 
 contact is employed along the side of the cylinder 
 or conical roller, the analogy given on Page 328 
 fitting this case if for the marbles there be 
 substituted small rollers. 
 
 The difficulty of making rollers and races close 
 enough to the theoretically true surfaces required 
 is the one serious difficulty in the manufacture of 
 roller bearings, since if anything materially short 
 of the utmost possible perfection be tolerated the 
 result is certain to be unequal wear, if not absolute 
 breakage, of the rollers. Also, the idea that a roller 
 bearing is capable of carrying greater loads than a 
 ball bearing of approximately the same size qual- 
 ity of materials and workmanship being equal is 
 probably erroneous, it being founded upon the 
 incorrect theory that rollers afford greater areas 
 of contact than balls. It is evident that, contact 
 with the ball being an infinitely small point and 
 that with the roller an infinitely narrow line, the 
 
340 VEHICLES OF TEE AIR 
 
 area in one case is theoretically no greater than the 
 other, being zero in both cases. Practically, how- 
 ever, definite bearing area is secured in both types 
 of bearings by the slight deformation of the bear- 
 ing surfaces which cannot fail to result, even with 
 the most resistant materials, under load. In the 
 case of ball bearings under this deformation the 
 point becomes a circle, while in the roller bearing 
 the line becomes a rectangle and, with loads and 
 materials similar in both cases, the deformations 
 are found to be approximately so proportioned 
 that the area of the circle in one case is practically 
 as great as the area of the rectangle in the other, 
 thus giving the ball bearing as great wearing sur- 
 face as is secured in the roller bearing not to 
 consider the obvious advantages in ease of manu- 
 facture and perfection of operation in favor of 
 the ball. 
 
 CYLINDEICAL ROLLER BEARINGS 
 
 Cylindrical roller bearings usu- 
 ally are assembled in plain, cylin- 
 drical, ring-like races, as shown in 
 Figure 152. Making the rollers very 
 short tends to minimize any laterial 
 inequalities of loading due to devia- 
 
 FlGURE 152. 
 
 fe^BeaSng Rol ~ ti ns from truly cylindrical form. 
 
 FLEXIBLE ROLLER BEARINGS 
 
 Flexible roller bearings, of the description 
 illustrated in Figure 153, are a type possessing 
 many excellent qualities, and therefore widely used 
 
BEARINGS 341 
 
 in cheaper automobiles and other classes of machin- 
 ery. In these bearings, instead of attempting to 
 
 secure exceedingly accu- 
 rate fits, the necessity 
 for exceedingly accurate 
 fitting is avoided by the 
 scheme of making the 
 
 FIGURE 153. Flexible Roller ,, ft , . . 
 
 Bearing. rollers of steel strips, 
 
 flexible enough to adjust themselves to minor ine- 
 qualities of shaft and housing. The rollers being 
 hollow, as at a, with a helical opening between adja- 
 cent turns of the strips, the oil distribution is excel- 
 lently provided for. The housing 6 is used as a 
 liner for the space within which the bearing is 
 placed. 
 
 TAPEEED ROLLER BEARINGS 
 
 Tapered roller bearings, employing rollers 
 made in the form of the frustum of a cone, have 
 the advantage over other types of roller bearings 
 that they are adjustable for wear by lateral move- 
 ment of the races, but in this case the same objec- 
 tion holds that holds against adjustable ball bear- 
 ings that the loaded side of the non-rotating race 
 wears faster than any other part of the bearing 
 and this causes a flattening of one side of the proper 
 circle of travel. In well designed roller bearings 
 of good material this flattening does not occur at 
 a very rapid rate, so it is not necessarily inconsist- 
 ent with long life, but it does make practically use- 
 less the provision for adjustment except as this is 
 found advantageous in the original assembling. 
 
 Roller bearings, like ball bearings, must be 
 
342 VEHICLES OF THE AIR 
 
 made of high-grade steel preferably alloy steel, 
 though carbon steels often are made to serve the 
 
 purpose. 
 
 PLAIN BEARINGS 
 
 Plain bearings are the earliest of all types and 
 in their best forms still possess important appli- 
 cations, their greatest advantage aside from their 
 cheapness being the requirement of smaller cir- 
 cumferential (though greater lateral) space for a 
 given load than is necessary with ball or roller 
 bearings. 
 
 When made of suitable materials, finished to 
 insure distribution of the load over the entire bear- 
 ing surfaces and provided with sufficient and 
 unfailing lubrication, plain bearings are service- 
 able and long-lived, and capable of operation with- 
 out undue friction loss. 
 
 PLAIN BEAEING MATEEIALS 
 
 A wide range of different metals is suitable for 
 plain bearings, one surface of which usually is that 
 of the shaft itself. In most plain-bearing mechan- 
 isms the combination is a steel shaft running in 
 contact with some other metal. 
 
 Steel as a material for plain-bearing surfaces 
 is much better than is commonly supposed. There 
 is in fact little in the whole range of engineering 
 experience or knowledge to condemn the use of 
 steel against steel, though it is essential that this 
 combination of bearing surfaces be exceptionally 
 well finished and perfectly lubricated if heating, 
 
BEARINGS 343 
 
 with consequent wear and " seizing", are to be 
 avoided. Steel-to-steel permits higher loads to a 
 given area than can be safely carried on any other 
 materials. 
 
 Cast Iron as a material for bearing boxes is like 
 steel a material of superior qualities, though it is 
 little used for this purpose. It is, indeed, subject 
 only to the twin disabilities of requiring excep- 
 tionally accurate finish and thoroughly adequate 
 lubrication. 
 
 Bronzes, of copper and tin, and especially those 
 alloys in which the tin component rises very high, 
 with possibly some admixture of antimony, lead, 
 or other fusible metals, are widely favored as a 
 material for plain bearings. 
 
 Brasses, through a wide range of common 
 alloys, possess much of the same bearing qualities 
 as the bronzes. 
 
 Babbitt, an alloy of tin, lead, and antimony, in 
 proportions that vary somewhat with the ideas of 
 different manufacturers, is perhaps the most ex- 
 tensively-used and generally-serviceable plain- 
 bearing material known. In its best qualities it 
 reduces sliding friction almost to its lowest terms, 
 besides which it possesses the advantage, not pos- 
 sessed by brasses and bronzes, of melting out if 
 the bearing overheats through inadequate lubrica- 
 tion, thus avoiding the injury to the shaft which 
 is certain to ensue when a brass or bronze bearing 
 seizes. Babbitt requires, however, larger areas for 
 given loads than are found sufficient for plain 
 bearings of harder metals. 
 
344 VEHICLES OF THE AIR 
 
 Graphite, in the form of compressed bushings 
 surrounding a shaft, is under reasonable loads 
 much more durable than would be imagined, and 
 has the advantage of operating without lubrica- 
 tion. Bearings of this type are much used for 
 trolley wheels in street-railway practise. 
 
 Wood, especially exceedingly hard wood, such 
 as lignum vitae, boxwood, etc., is not without merit 
 for plain-bearing surfaces in certain situations. 
 The thrust blocks for taking the propeller thrust 
 in motor boats and even in large steam vessels 
 often are made of lignum vitae, lubricated with 
 water, such construction proving a means of escap- 
 ing the problems of rusting and leakage that are 
 likely to appear when it is attempted to use bear- 
 ings of other types and keep them supplied with 
 oil. 
 
 Vulcanized Fiber makes a fair bearing material 
 when provided in sufficient area and properly 
 lubricated. In at least one instance of a supposedly 
 well designed modern automobile fiber thrust 
 bearings are used behind the bevel gears com- 
 municating with the final drive to the rear axle. 
 
 FINISH OF PLAIN BEAEINGS 
 
 Of fundamental importance in the successful 
 use of plain bearings is the accuracy of finish, 
 which is second in importance only to the matters 
 of proper material and sufficient size. 
 
 Areas of plain bearings usually are figured on 
 the basis of the "projected area", as suggested by 
 the dotted rectangle abed, Figure 154, this rec- 
 
BEARINGS 345 
 
 tangle being equivalent to a cross section of the 
 center of the shaft within the bearing. The pro- 
 jected area must be of sufficient 
 surface to carry the load consid- 
 ered permissible with the type of 
 bearing material used. For long- 
 lived babbitt bearings the load 
 
 per square inch of projected area projected Area 'of 
 
 111 . . -,1 -. /, Plain Bearing. 
 
 should not materially exceed zorty 
 pounds. With steel-bushed piston-pin bearings 
 the load may run as high as eight hundred pounds 
 to the square inch, though such loading does not 
 prove conducive to slow wear and long life. 
 Scraping plain bearings is necessary in all cases 
 where babbitt, bronze, brass, or similar materials 
 are used. It is a means of giving a more perfect 
 fit to the shaft than is possible by mere turning or 
 reaming, and in the machine shop is technically 
 known as " spotting in", from the fact that the 
 shaft is tested in the bearing many times in the 
 course of the operation, being coated after each 
 scraping with a light wash of Prussian blue, which 
 rubs off on the high spots in the bearing and thus 
 indicates the places that require to be scraped 
 down. Commencing with a babbitt bearing freshly 
 cast and reamed, and contacting with the shaft at 
 only four or five high spots, a good workman will 
 carry this process of spotting-in a bearing until 
 the test with the Prussian blue coating shows an 
 great number of minute, closely-spaced high spots, 
 indicating so even a distribution of the load over 
 
346 
 
 VEHICLES OF THE AIR 
 
 a 
 
 FIGURE 155. Ad just- 
 ment of Plain Bearing. To 
 tighten the bearing one or 
 more of the thin liners of 
 sheet metal at a a are re- 
 moved. 
 
 the entire bearing surface that wear can be counted 
 upon to result with almost perfect uniformity. 
 
 Adjustment of plain bear- 
 ings is generally effected by 
 placing in or removing from 
 the space a a, Figure 155, be- 
 tween the two bearing cups, 
 "shims" of thin sheet metal. 
 The lubrication of a plain 
 bearing must be well provided for, and is usually 
 facilitated by grooving and drilling the bearing 
 surfaces to spread the lubricant. 
 
 MISCELLANEOUS BEARINGS 
 
 Cone bearings, of the type illustrated in Figure 
 156, are much used in very light 
 machinery generally and in deli- 
 cate instruments, in which they 
 prove light-running, fairly du- 
 rable, and especially meritorious 
 
 ., J _ FIGURE 156. Con* 
 
 in that they permit such close ad- Bearing. 
 
 justment as practically to eliminate all end move- 
 ment from the shaft. 
 

FIGURE 157. Bleriot XI in Flight. This is the monoplane that crossed the English Channel. 
 
 FIGURE 158. Bleriot XII in Flight. This monoplane carries three passengers. 
 
CHAPTER NINE 
 
 LUBRICATION 
 
 For mechanisms that must be quite light and 
 yet subjected to a maximum possible duty, as is 
 the case with practically every element of the 
 power plant of a flying machine, it is a most press- 
 ing necessity that constant and adequate lubrica- 
 tion be automatically provided for every bearing, 
 so that unfailing functioning is reasonably assured 
 with a minimum of attention. 
 
 Haphazard methods of lubrication, which can 
 be made to serve in automobiles and other mechan- 
 isms, should under no circumstances be tolerated 
 in the design of an aeronautical power plant, in 
 which the lubrication must be regarded as one of 
 the most important elements of the whole device 
 and arranged for on a correspondingly adequate 
 basis. 
 
 SPLASH LUBRICATION 
 
 Splash lubrication, in which the oil is contained 
 in a reservoir or pit adjacent to the surfaces to be 
 lubricated, and splashed thereon by the movement 
 of parts, is a common and very successful method 
 of lubricating certain types of machinery, being 
 most particularly applicable to the piston and 
 cylinder walls of internal-combustion engines, 
 enclosed gears, etc. 
 
 347 
 
348 VEHICLES OF THE AIR 
 
 In many well-known types of automobile en- 
 gines the connecting-rod and crankshaft bearings 
 are lubricated by the periodic dip of the big end 
 of the connecting rod into oil maintained at a con- 
 stant level in the bottom of the crankcase, while 
 in at least one well-known make a trough-like 
 groove kept full by the splash from the connecting- 
 rod, and located around the lower end of a cylinder 
 so that the edge of the piston dips into it at the 
 bottom of each stroke, is found to render the lubri- 
 cation of the cylinder walls more positive than 
 when dependence is placed solely upon the splash. 
 
 Spoon-like extensions from the lower ends of 
 connecting rods, communicating with both crank- 
 pin and piston-pin bearings, are in some circum- 
 stances found to distribute the oil better than is 
 the case with most splash systems. 
 
 It is a merit of splash lubrication that it auto- 
 matically stops and starts with stopping and start- 
 ing of the mechanism, and thus is always fairly 
 dependable, but it has the fundamental fault that 
 it is a system of re-using the lubricant, the oil 
 being supplied in measured charges of considerable 
 quantity and utilized through a period of progres- 
 sive deterioration. When it no longer serves its 
 purpose it is replaced or admixed with fresh oil. 
 
 EING AND CHAIN OILEES 
 
 Small rings or chains hanging upon a shaft and 
 dipping into small oil pits placed at suitable points 
 constitute a very reliable means of splashing or 
 
LUBRICATION 
 
 349 
 
 taking up a small but steady flow of oil to find its 
 
 way into the adjacent bearings. 
 
 Another type of ring 
 oiler, much used for the lu- 
 brication of crankpins, is 
 that pictured in Figure 159, 
 in which a is the ring, fas- 
 tened to the shaft & and dip- 
 ping below the oil c, so that 
 oil flowing into the groove d 
 is there held centrifugally 
 until it escapes through the 
 hole e, connecting with the 
 hollow pin /. 
 
 GEAVITY LUBKICATION 
 
 FIGURE 159. Ring Oiler on 
 Crankshaft. The ring a, by 
 dipping into c, picks up a 
 small quantity of oil in its 
 grooved edge d, in which it is 
 held by the rotation of the 
 crankshaft & until it is thrown 
 centrifugally through the hole 
 e to the crankpin bearing, 
 whence it finds its way by 
 the pipe / to the piston-pin 
 bearing. 
 
 Gravity lubrication, in 
 which the flow of oil is main- 
 tained through communicat- 
 ing pipes from a tank located above the bearing or 
 bearings, is exceedingly simple and possesses the 
 virtue of always supplying fresh oil to the wearing 
 surfaces, the oil as fast as it is used draining away, 
 directly to the ground or into a sumpor pan which 
 can be emptied at intervals. 
 
 OIL CUPS 
 
 Oil cups, placed directly over the bearings they 
 feed, are probably the simplest and commonest 
 form of gravity lubrication. They usually are 
 provided with some sort of adjustable drip feed, 
 with a sight glass to inspect the rate of drip. 
 
350 VEHICLES OF THE AIR 
 
 RESERVOIR SYSTEMS 
 
 Keservoir systems, with a single reservoir con- 
 nected by a plurality of leads with the different 
 bearings, are the most elaborate forms of gravity 
 lubrication, and usually are provided with sight 
 feeds and means for regulating the flow of oil 
 through the different pipes. 
 
 Like all forms of gravity lubrication these sys- 
 tems have the objection that the pipes may become 
 clogged and thus cease to feed corresponding bear- 
 ings, with prompt overheating and failure. 
 
 FORCED LUBRICATION 
 
 Forced lubrication, by which the lubricant is 
 sent to the bearings under pressure, is in its best 
 forms the most reliable and meritorious system 
 possible, because, while possessing the reliability 
 of splash lubrication, it is a system of feeding fresh 
 lubricant under conditions that may be so arranged 
 as to avoid the possibility of stopped pipes. 
 
 PRESSURE FEED 
 
 One of the simplest forms of forced lubrication 
 involves the use of a single reservoir with a number 
 of leads, much the same as in the just-described 
 reservoir system for gravity feeding but with this 
 difference that air or exhaust-gas pressure is 
 maintained to deliver the lubricant, so as to afford 
 greater assurance of positive feeding than is had 
 with gravity alone. Nevertheless, stoppage of one 
 of a number of leads is likely to go undetected, the 
 pressure being relieved by a greater flow of oil 
 through other leads. 
 
FIGURE 162. Koechlin Monoplane in Flight. 
 
 FIGURE 163. Wright Machine on Starting Rail. The starting rail is at m, n is the 
 connection of the rope by which the starting impulse is given, f are the runners, h is the 
 elevator, o is the elevator control rod, i is the rudder, and I is one of the steadying planes 
 peculiar to this machine. 
 
 FIGURE 164. Bleriot Alighting Gear. The wheels o 0, upon striking the ground, are 
 cushioned in their upward movement by the rubber springs s s. 
 
LUBRICATION 
 
 351 
 
 SINGLE PUMPS 
 
 Single pumps for forcing a continuous flow of 
 oil over bearings or through systems of leads, the 
 oil usually being pumped from a sump or pit in the 
 crankcase or the like, are found very satisfactory 
 for engine lubrication, though as a special safe- 
 guard against breakdown the circulating system 
 should have a loop with a glass sight feed placed 
 within view of the operator. 
 
 MULTIPLE PUMPS 
 
 One of the most reliable of all lubricating sys- 
 tems is that in which oil is sent from a reservoir 
 through a plurality of leads, one 
 to each bearing, by a corre- 
 sponding plurality of small in- 
 dividual pumps each admitting 
 of adjustment to vary the indi- 
 vidual feed and capable of 
 working against high enough 
 pressure to insure the clearing 
 out of any possible obstruction 
 that may pass into the pipes. 
 Such systems of forced lubrica- 
 tion are extensively used in the 
 power plants of the best automobiles, and for fly- 
 ing-machine power plants prove similarly superior. 
 
 A typical force-feed lubricator is illustrated in 
 Figure 160, in which a is the reservoir, 666 are 
 the leads, c c c are adjustments, and d d d are the 
 individual sight feeds by means of which imperfect 
 operation or failure can be instantly detected and 
 remedied. 
 
 FIGURE 160. Force- 
 Feed Lubricator. The 
 pipes leading to the dif- 
 ferent bearings are at 
 b b b, adjustment of the 
 flow through these pipes 
 Is by the thumbscrews 
 c c c, and the rate of the 
 flow is shown by the 
 sight feeds ddd. 
 
352 VEHICLES OF THE AIR 
 
 GREASE CUPS 
 
 Grease cups, while similar to oil cups, are prop- 
 erly systems of forced lubrication in that they are 
 filled with grease or non-fluid oil capable of being 
 forced out by screwing down the top. Grease cups 
 are very reliable because while designed primarily 
 to have occasional attention they will neverthe- 
 less feed automatically by gravity in the case of 
 an overheated bearing, which thus may take care 
 of itself by melting the contents of the grease cup 
 and so causing them to flow down without forcing. 
 
 LUBRICANTS 
 
 Suitable lubricants for aeronautical power 
 plants embrace a considerable range of liquid and 
 solid substances, a comparatively small number of 
 which, however, are found really superior. 
 
 MINERAL OILS 
 
 Mineral oils, derived from the distillation of 
 petroleum, are almost universally used for the 
 lubrication of the heating surfaces in gas engines, 
 being capable of withstanding temperatures as 
 high as 600 F. and 800 F. without giving off 
 ignitable or combustible vapors. Mineral oils also 
 are suitable for the lubrication of gears, plain 
 bearings, etc. 
 
 Vaseline is a petroleum grease that, with or 
 without admixture, is found exceedingly valuable 
 for lubricating gears, ball bearings, etc. 
 
 Miscellaneous mineral lubricants are used in 
 great number, in a great variety of combinations, 
 
LUBRICATION 353 
 
 and it is unfortunately a fact that the composition 
 of many of these is dictated by commercial rather 
 than by technical requirements, for which reason 
 it behooves the user of a high-grade aeronautical 
 engine ball bearings, or other delicate mechanism, 
 to use the most critical judgment in discriminating 
 between the different preparations marketed for 
 the purpose, altogether too many of which are very 
 far from being of the highest quality. Probably 
 the best policy is to patronize only the most repu- 
 table dealers, whose integrity and commodities are 
 both to be relied upon. 
 
 VEGETABLE OILS 
 
 Some vegetable oils are of excellent quality for 
 the lubrication of some types of bearings. 
 
 Castor Oil, for light spindles and for axles not 
 revolving at too high speeds, is excellent, and this 
 oil has been used with considerable success, with 
 or without an admixture of mineral oil, for the 
 lubrication of the close-fitting pistons in racing 
 automobile engines. Used for this purpose it tends 
 to cause a considerable amount of carbonization, 
 but if fed in sufficient quantities it invariably 
 relieves friction and facilitates smooth operation 
 in a degree almost impossible to attain with even 
 the lightest and best of mineral oils. 
 
 Olive Oil, suitably treated and refined, is almost 
 absolutely non-drying, for which reason it is a 
 preferred ingredient in oils for fine watches and 
 delicate instruments. 
 
354 VEHICLES OF THE AIR 
 
 ANIMAL OILS 
 
 Sperm Oil, from the blubber of the sperm whale, 
 is considered by mechanical experts to be the best 
 of all lubricants for light machinery, such as sew- 
 ing machines, phonographs, etc., and undoubtedly 
 will find more or less application in aeronautical 
 mechanisms. 
 
 Tallow, while an engineer of experience might 
 first be inclined to regard it as totally unsuitable 
 for the lubrication of heated surfaces, is neverthe- 
 less found to be the only satisfactory lubricant for 
 the cylinders and pistons used in type-casting ma- 
 chines for pumping molten type metal. This fact 
 might seem to indicate a possibility for it even in 
 the field of internal-combustion engine lubrication. 
 As a component of various greases for gear and 
 other lubrication, tallow fills a recognized place. 
 Most of the solid compounds used for the lubrica- 
 tion of bicycle and automobile chains are an admix- 
 ture of tallow and graphite, and are best applied 
 by being melted, and the chain soaked in the fluid. 
 
 MISCELLANEOUS LUBEICANTS 
 
 In this category fall such solids as finely- 
 divided graphite, mica, asbestos, and plumbago, 
 all of which tend to reduce friction by filling up 
 the minute inequalities that can be microscopically 
 proved to exist in the most perfectly finished 
 surfaces. Graphite is generally considered far 
 superior to the others. 
 
 Water has been mentioned (see Page 344) as a 
 lubricant for wood thrust bearings. Soapsuds is 
 
LUBRICATION 355 
 
 recognized by engineers to be without a superior 
 for cooling and lubricating certain types of plain 
 bearings under certain peculiar conditions of 
 overheating. 
 
 Kerosene, while not commonly regarded as a 
 lubricant, has considerable lubricating qualities, 
 and for light shafts and spindles can be made to 
 serve the purpose very effectively. Even in gas 
 engines periodic dosings of kerosene, preferably 
 fed through the carbureter, are with automobile 
 experts a recognized means of limbering up the 
 mechanism, serving the double purpose of thin- 
 ning used oil to a better lubricating body and of 
 cutting deposits of carbon. 
 
CHAPTER TEN 
 
 STARTING AND ALIGHTING 
 
 The problems of starting and alighting with 
 flying machines may be considered to apply chiefly 
 to flying machines of the aeroplane type, since bal- 
 loons, helicopters, and ornithopters do not require 
 special starting or alighting appliances. 
 
 But for the aeroplane, which flies by means 
 closely analogous to the means employed by soar- 
 ing birds, the necessity for some sort of starting 
 and alighting gear or device is apparent. Even 
 the birds do not escape this necessity, small birds 
 making their initial rise into the air by one or 
 more hops, and larger birds being compelled to 
 drop from an eminence or to make a considerable 
 run on the ground it being an interesting but well 
 established fact that the condor and the California 
 vulture, the largest flying birds known, can be 
 safely imprisoned in a small pen, open at the top, 
 but with sides sufficiently high to require a rather 
 steep angle of ascent. 
 
 For these reasons, already suggested in the 
 introduction to this work (see Page 35), as the suc- 
 cessful flying machine comes more and more into 
 practical use it will reasonably come to be regarded 
 quite natural for aerial vehicles to require for their 
 utilization the provision of special landing places 
 
 356 
 
STARTING AND ALIGHTING 357 
 
 and starting devices, just as it is commonplace for 
 docks to be provided for water craft and stations 
 for railway trains. Also, as is remarked on Page 
 35, it probably is a wholly erroneous idea of the 
 factors of the situation to suppose that aeroplanes 
 are proposed or will be used for urban travel, such 
 as must require their starting from or alighting in 
 the streets of cities, or even the roofs of buildings 
 though it is rather more probable that the latter 
 may in time come to be utilized to a limited extent. 
 But a more likely provision will be that of large 
 cleared areas in the suburbs of towns, permitting 
 suburban flying between these areas and leaving 
 the problems of strictly urban transportation to 
 other than aerial vehicles. 
 
 STARTING DEVICES 
 
 A very logical though not closely-drawn dis- 
 tinction can be made between starting devices and 
 alighting gears, the first being not necessarily, at 
 any rate in all its elements, a permanent part of an 
 aerial vehicle, whereas an alighting gear is neces- 
 sarily a part of the machine. The distinction is 
 complicated, however, by the fact that in some 
 machines the same wheels or other devices serve 
 both as starting and alighting gears. 
 
 For these reasons it will not be attempted 
 herein to draw the lines between classifications too 
 closely, it being more important to give proper 
 consideration to the different devices that have 
 been found most satisfactory and that appear the 
 
358 VEHICLES OF THE AIR 
 
 most promising for the effective launching and 
 safe landing of practical air craft. 
 
 WHEELS 
 
 The simplest and most widely used starting de- 
 vice is the wheel, the Santos-Dumont, Voisin, Cur- 
 tiss, Farman, E. E. P., Antoinette, Bleriot, and 
 many other successful modern biplanes and mono- 
 planes all being provided with bicycle or motor- 
 cycle wheels, which often are used also as alighting 
 gears to which end they are almost without 
 exception fitted with spring and cushioning devices 
 to take up the shock of an abrupt encounter with 
 the earth. 
 
 BAILS 
 
 The use of rails to provide smooth tracks for 
 launching aeroplanes probably originated with 
 Henson in 1842, at which time he employed them 
 
 FIGURE 165. Wright Starting System. 
 
 in an attempt to launch the machine referred to 
 on Page 155. Rails were then used by Maxim, as a 
 course upon which to start and test his wonderful 
 but unsuccessful machine (described on Page 156), 
 which lifted itself on July 31, 1894. The next use 
 
STARTING AND ALIGHTING 359 
 
 of rails was in the catapult-like launching device 
 employed by Langley in his trials over the Potomac 
 River during the years 1896 to 1903, inclusive. 
 
 The most modern and practically the only suc- 
 cessful use of rail launching devices is in conjunc- 
 tion with the modern Wright machines, which are 
 run an initial distance of from 70 to 125 feet, bal- 
 anced on a tiny two-wheeled truck, on a single 
 crude wooden rail, about eight inches high and 
 faced with strap iron. This arrangement is more 
 fully described on Page 362, and is illustrated in 
 Figures 163, 165, and 166. 
 
 FLOATS 
 
 Floats, in the form of boat-like hulls, have been 
 to some extent used in experimenting with aero- 
 planes over water surfaces, and appear to present 
 possibilities of practical development. The use of 
 light racing shells, which are capable of carrying 
 from five to nine men totaling from 800 to 1,600 
 pounds, and which weigh from thirty to fifty 
 pounds, appears to be the most promising line of 
 development, though waterproof fabric floats can 
 be made exceedingly light for a given sustaining 
 effect. 
 
 Undoubtedly, just so soon as some means is 
 devised of permitting aeroplanes to start from and 
 alight upon water surfaces without exterior aid, 
 trans-aquatic journeys will become practicable 
 with almost absolute safety even with present 
 machines. The hydroplane type of boat hull, 
 which skims over the surface of the water rather 
 
360 VEHICLES OF TEE AIR 
 
 than plowing through it, in many respects appears 
 to be the ideal form of float for water-traversing 
 aeroplanes. 
 
 EUNNEES 
 
 Eunners, besides having been used successfully 
 by the Wrights in starting over wet grass under 
 the thrust of the propellers, also have been used 
 in starting from ice frozen lake surfaces in the 
 work of the Aerial Experiment Association. Their 
 most conspicuous merits, however, are as alighting 
 rather than as starting devices. (See Page 370.) 
 
 THE STAETING IMPULSE 
 
 It being necessary with most modern aero- 
 planes to make a shorter or longer run on the 
 ground or on rails before sufficient sustention is 
 secured to rise in the air, the question of securing 
 the necessary starting impulse becomes one of 
 some moment, and it is evident at the outset that 
 the solution can be reached in any one of a number 
 of different ways. 
 
 To maintain an aeroplane in flight no very 
 great thrust or pull, as the case may be, is required, 
 the amount of this thrust or pull being probably 
 from 100 pounds to 250 pounds in the different 
 machines that have proved most successful so far 
 though there is reason for expecting that much 
 lower tractive forces will suffice as head and aero- 
 dynamic resistances come to be lowered but for 
 securing the rapid rate of acceleration required to 
 reach a sustaining speed with only a short run, a 
 much greater thrust is essential. 
 
FIGURE 166. Wright Machine on Starting Rail, with Starting Derrick in the Background. 
 
 FIGURE 168. Rougier's Voisin Rising from Starting Ground. 
 
STARTING AND ALIGHTING 361 
 
 Propeller Thrust, upon which dependence is 
 placed to maintain modern aeroplanes in motion, 
 also is used in most of those with wheeled starting 
 and alighting gears to produce the initial run on the 
 ground, but in most of the machines to which this 
 method is applied it has not been found possible 
 to get into the air with runs of less than from 200 
 to 400 feet over fairly good ground. This distance 
 can be kept to a minimum by holding the machine 
 until the propeller is at full speed, either by a brake 
 or by the efforts of assistants. Another possible 
 scheme might be the use of a sprag-like claw to 
 catch in the ground, until it were desired to release 
 the machine. In Figure 164 it will be noted that 
 the wheels of the machine are blocked. 
 
 Starting solely by its thrust, the propellers 
 have even been employed successfully for starting 
 with the Wright machine, without the rail, the 
 aeroplane being simply slid on its runners over wet 
 grass, but in this case an initial run of five hun- 
 dred feet was found necessary before the machine 
 altogether left the ground. In this connection, 
 however, it is interesting to reflect that no such 
 duty devolves upon the propeller as would be 
 involved in dragging the full weight of the machine 
 over the ground for the entire distance, with it 
 resting solidly upon its runners. The reason for 
 this is that as soon as any headway whatever is 
 attained, there is a corresponding measure of lift 
 which proportionately reduces the weight resting 
 upon the runners the weight thus supported 
 gradually reducing from the entire weight of the 
 
362 VEHICLES OF THE AIR 
 
 vehicle at the start, to an infinitely small percent- 
 age of this just before lifting from the ground. 
 
 An advantage of the propeller in affording the 
 starting impulse is that its thrust is highest when 
 the vehicle speed is lowest at which time the need 
 for high thrust is greatest. 
 
 Dropped Weights, operated in small starting 
 derricks, the pylons of the French, are in some 
 respects an excellent means of securing the initial 
 impulse, though they are so far employed only 
 with the Wright machines. In the Wright starting 
 device, shown in Figures 165 and 166, the tower is 
 an extremely simple and inexpensive one of pyr- 
 amidal form, built of four main timbers each about 
 twenty-five feet long and two inches square, 
 lightly braced by three horizontal frames and 
 diagonal wire stays. The weight, about fourteen 
 hundred pounds of cast iron disks (a can of earth 
 or stone has been suggested as perfectly suitable 
 for emergency use) is attached to one of two pul- 
 ley blocks, the other of which is suspended in the 
 apex of the tower, the rope passing around the 
 sheaves a sufficient number of times to provide a 
 three-to-one relation between the movement of the 
 weight and the movement of the aeroplane along 
 the starting rail. 
 
 Disregarding friction losses in the sheaves, the 
 rope, which passes down to the bottom of the 
 tower, forward to and around a pulley towards the 
 front end of the rail, and thence back to the aero- 
 plane, exerts a pull of about 450 pounds, with a 
 rate of acceleration about in relation to the law 
 
STARTING AND ALIGHTING 363 
 
 of falling bodies, which of course governs the fall 
 of the weight. To the pull of the weight is added 
 the thrust of the propellers, which are set in 
 motion before the machine is released for its start 
 along the rail. The propellers take up the entire 
 work of propelling the machine when some fifty or 
 sixty feet of the rail are traversed, the weight not 
 accelerating the machine clear to the end of the 
 rail. 
 
 At the limit of the weight-impelled portion of 
 its travel along the rail, the rope automatically 
 unhooks from its attachment to the machine, which 
 promptly thereafter lifts off the truck on which it 
 has been mounted and at once commences free 
 flight. 
 
 Winding Drums, as a substitute for the 
 dropped- weight system of starting, have been pro- 
 posed by a number of experimenters. In a patent 
 issued to Octave Chanute the principle is claimed 
 of locating a power-driven winding drum on a con- 
 veniently placed truck, this drum connecting by 
 a cable with the aeroplane in such manner that the 
 cable connections can be thrown off by the opera- 
 tor just before or after the machine leaves the 
 ground. 
 
 In a starting device invented by the writer the 
 principle is claimed of locating a winding drum on 
 the aeroplane as at a, Figure 167, a light wire cable 
 running from this drum to a stake driven in the 
 ground. By providing the end of the cable with 
 a ball-like or flat end fixture, arranged so that it 
 will disengage automatically from the spherically- 
 
364 VEHICLES OF THE AIR 
 
 cupped or otherwise peculiarly-formed head of the 
 stake as soon as it pulls up at a vertical enough 
 angle from the vehicle passing over the latter, a 
 very effective means of starting is provided. The 
 writer prefers to make the drum of a varying 
 diameter from one end to the other so that the 
 desired acceleration is secured without variation 
 
 FIGURE 167. Starting by Rope Attached to Stake and Wound in on Drum. 
 The drum, which may be friction-driven from the engine, winds in the rope 
 until the machine is nearly over the stake. Provision can be made for auto- 
 matic cessation of the winding at this point, so that the rope frees itself 
 from the stake as the machine passes over it. By making the drum of 
 tapered instead of cylindrical form, proper acceleration is readily provided. 
 
 in engine speed. Also, it is preferred to connect 
 the drum with the shaft by a friction clutch, but 
 many alternative constructions of course are pos- 
 sible. In this scheme of starting it is required to 
 leave a stake in the ground each time a start is 
 made, but, the stakes being made very light, pref- 
 erably of steel tubing, the necessity of carrying 
 along a few is not a serious objection, especially 
 when it is considered that even in a machine regu- 
 larly equipped with such a starting device it would 
 be brought into use only when other methods of 
 starting could not be employed. 
 
 Inclined Surfaces, for starting aeroplanes by 
 the action of gravity, have been used most suc- 
 cessfully by Lilienthal, the Wrights, and some 
 others. They constitute one of the simplest of all 
 possible means of starting and under proper con- 
 ditions are very effective. The utilization of natu- 
 
STARTING AND ALIGHTING 365 
 
 rally sloping ground, either alone or in conjunction 
 with any established starting means, greatly facili- 
 tates starting. The Wrights usually endeavor to 
 lay their starting rail down hill, direction of the 
 wind permitting, and the same is true of the runs 
 made by other experimenters on wheeled-starting 
 devices. 
 
 LAUNCHING VEHICLES 
 
 This term is applied by the writer to a class of 
 starting mechanisms that have been more exten- 
 sively suggested than experimented with. By it 
 it is meant to refer to such possible methods of 
 starting as by mounting an aeroplane on an auto- 
 mobile, rail vehicle, or water craft, and making the 
 initial run with this vehicle, with the idea that the 
 aeroplane will rise into free flight as soon as 
 sufficient speed is reached. 
 
 Automobiles might easily be built in a modified 
 form suitable for the purpose just suggested with 
 a rather simple car, capable of the necessary speed 
 on good ground and provided with a substantial 
 framework, rising above the head of the driver, 
 upon which to rest the aeroplane without any 
 attachment other than the use of such lugs as 
 might be necessary to keep the aeroplane from 
 sliding off backwards. With such a construction 
 it should be an easy matter to start an aeroplane 
 in the air by a short run over any suitable surface. 
 
 Railway Cars of a special type possibly small 
 gasoline or electrically-propelled flat cars might 
 readily be made to serve the same purpose, though 
 in this case the necessity for a track is an objection 
 
366 VEHICLES OF THE AIR 
 
 because it is desirable always to have the aeroplane 
 face the wind when leaving the ground. 
 
 Boats, in several types of motor launches, tor- 
 pedo-boats and torpedo-boat destroyers, and fast 
 cruisers and battleships, possess established speeds 
 well in excess of the minimum flying speeds of 
 several successful modern aeroplanes. Conse- 
 quently such water craft, with a perfectly clear 
 deck forward upon which to mount suitably-de- 
 signed aeroplanes, by running into the wind must 
 constitute quite effective means of launching the 
 aerial vehicles. Subsequent alighting upon the 
 water would be perfectly safe with proper floats as 
 alighting gears, while disappearing cranes would 
 serve excellently to hoist the aeroplanes inboard 
 for reprovisioning or restarting. 
 
 CLEAEED AREAS 
 
 No matter which of the starting and landing 
 methods so far considered is to come into ulti- 
 mate prominence, it seems impossible ever to 
 escape the superior desirability of cleared areas 
 from which to start and upon which to alight. 
 Moreover, such areas will hardly suffice if merely 
 made long and comparatively narrow, as has been 
 often suggested. Apparently they must be cir- 
 cular in form, so that alighting or starting in any 
 direction will allow sufficient distance for neces- 
 sary retarding or accelerating. A maximum of 
 500 feet would seem to be the distance suitable for 
 most present-day machines, this distance in all 
 directions calling for a cleared circular field of 
 
STARTING AND ALIGHTING 367 
 
 about six acres. In case of such an area being bor- 
 dered by trees or high buildings, such as might not 
 be readily passed over at the steepest possible 
 angle of ascent, it would be necessary to extend the 
 space considerably beyond that actually required 
 for the mere run on the ground. The possible limit 
 required would be an area large enough to permit 
 circling flight over it until sufficient height were 
 attained to pass over the highest of adjacent ob- 
 stacles. A Voisin aeroplane starting from such a 
 field is shown in Figure 168. 
 
 PACING THE WIND 
 
 Facing the wind, while perhaps not an absolute 
 necessity, certainly is a most desirable condition of 
 starting with present types of machines. Obvi- 
 ously a sustaining surface requiring a certain 
 speed through the air before it can lift the machine 
 from the ground would when running with the 
 wind afford less actual speed through the air than 
 over the ground, requiring a consequently higher 
 speed over the ground to secure the necessary 
 speed through the air. On the other hand, travel 
 against the wind adds substantially the speed of 
 the wind to the ground speed of the vehicle, with 
 the result of rendering starting in a moderate wind 
 easier than in a calm. The only condition under 
 which starting in the wind might be objectionable 
 would be the existence of a gale greater in speed 
 than the maximum flying speed of the aeroplane. 
 This might cause the vehicle to be thrown back- 
 wards with more or less force against the ground 
 or any neighboring obstacle. 
 
368 VEHICLES OF THE AIR 
 
 A wind from one side is particularly objection- 
 able in starting, as it tends to careen the machine 
 over even before it is in flight, and therefore must 
 inevitably result in disaster. 
 
 Of course, once flying is under way it is a com- 
 paratively simple matter to turn and travel in any 
 direction with the wind, against it, or across it. 
 
 LAUNCHING FROM HEIGHT 
 
 Dropping a machine from a height or launching 
 it over the edge of a cliff or building bears a rather 
 close resemblance to the means of starting em- 
 ployed by many birds, whose powers of flight are 
 such that they unhesitatingly plunge from cliffs, 
 trees, buildings, etc. In artificial constructions, 
 
 d 
 
 FIGURE 169. Bleriot Starting Device. The aeroplane is hooked by the 
 rope & to the pulley c, which runs along the rear edge of the pillar a. 
 By starting the propeller the back draft of air thrown under the wings d d 
 is expected to lift the machine until c runs off the top of a. 
 
 the only instance of the successful use of this 
 scheme was its employment by Professor Mont- 
 gomery in his experiments in California in 1905, 
 in the course of which his wonderful glider was 
 released with safety from balloons sent to heights 
 as great as 4,000 feet. Of unsuccessful attempts 
 at this sort of launching, possibly the most recent 
 
STARTING AND ALIGHTING 369 
 
 was Langley's ill-fated launching of his full size 
 machine from the top of a house boat over the 
 Potomac Eiver on December 8, 1903. Previous to 
 these experiments, history records various at- 
 tempts of individuals whose efforts to navigate the 
 air more than once involved leaps from cliffs and 
 towers, as in the cases mentioned in Chapter 15. 
 Practically all of these resulted in more or less 
 serious mishap. 
 
 In gaging the practical merits of this scheme 
 it always is to be considered that should an aerial 
 vehicle be launched from a roof or tower, and sub- 
 sequently prove to have anything seriously wrong 
 with its sustaining elements, the consequence could 
 scarcely fail to be a serious disaster. On the 
 other hand, in launching from the ground, should 
 the machine prove not to be in proper flying con- 
 dition it would be likely simply to fail to go up. 
 
 ALIGHTING GEARS 
 
 Alighting gears, while in many machines iden- 
 tical with the starting means, are not so in all 
 cases. Nevertheless, in practically all present-day 
 aeroplanes that are started on wheels, the wheels 
 also are used for alighting, being usually mounted 
 on one sort or another of shock absorbers as has 
 been already suggested on Page 358. 
 
 WHEELS 
 
 The alighting device of a typical modern aero- 
 plane is very well illustrated in Figure 170. In 
 this the long helical springs at s s take the shock 
 
370 VEHICLES OF THE AIR 
 
 of alighting, the wheels g g swinging on the 
 linkages. 
 
 The Bleriot alighting gear, shown in Figures 
 118, 164, and 171, is similar to the foregoing except 
 in it pluralities of rubber bands are used in place 
 of the helical springs, being found both lighter in 
 weight and less likely to break for a given cush- 
 ioning effect. 
 
 With wheels used as alighting gears, several 
 experimenters have provided brakes to produce 
 rapid retardation after touching the ground. Such 
 a brake is a feature of the Curtiss machine. (See 
 Figure 228 and Chapter 12.) Another unusual fea- 
 ture of the Curtiss running gear is the total absence 
 of any sort of shock absorber. 
 
 EUNNEES 
 
 Eunners for alighting possess the advantage 
 over wheels that they will span inequalities of 
 surface that must inevitably wreck a wheel, as is 
 shown at A and B, Figure 17C. They also consti- 
 tute an effective brake that comes into perfectly 
 gradual and most effective operation as soon as the 
 weight of the vehicle commences to be sustained 
 
 upon the ground. 
 
 FLOATS 
 
 As has already been suggested on Page 359, the 
 use of floats for machines intended to fly over water 
 possesses some merits. And, of course, any float 
 that will suffice to hold a machine up well enough 
 to make a start from the water must also 
 serve very satisfactorily to alight upon. Wilbur 
 
FIGURE 170.- Typical Alighting Gear. In this the upward swing of the wheels g g on 
 their link connections is cushioned by the helical springs s s. 
 
STARTING AND ALIGHTING 371 
 
 Wright's use of a canvas canoe hull attached to 
 the understructure of his machine during his 
 flights around New York during the Hudson-Ful- 
 ton celebration is significant in this connection. 
 
 MISCELLANEOUS 
 
 Besides the more or less distinctly different 
 types of starting and alighting gears so far tried, 
 there appears to be considerable progress to be had 
 from experiments with various combinations of 
 differing individual elements. 
 
 For example, in Figure 174 there is shown the 
 under construction of the recent Farman machines, 
 in which the wheels gggg are used for the 
 starting run, while in alighting the wheels spring 
 up above the runner level from the shock of con- 
 tact, so that the runners come into play as brakes 
 and protect the wheels from inequalities of surface. 
 
 Superior in many respects to the two foregoing 
 would appear to be some more definite scheme of 
 dropping and locking the runners below the wheel 
 level and of raising them above it, as conditions of 
 alighting or landing, respectively, might require. 
 
 In considering possible combinations of start- 
 ing and alighting elements, it appears probable 
 that in time there may even be developed starting 
 and alighting gears capable of starting from or 
 landing upon any reasonably clear space of land 
 or water, without recourse to special constructions 
 for special conditions. 
 
CHAPTER ELEVEN 
 
 MATERIALS AND CONSTRUCTION 
 
 The questions of structural materials and meth- 
 ods of construction are among the most vital of all 
 that the aeronautical engineer has to face. Every 
 matter of safety and success depends directly upon 
 the quality and reliability of the materials of 
 which the machines are built, and the ways in 
 which these materials are put together. 
 
 Fortunately the problem, while one of great 
 difficulties, is also possessed of important compen- 
 sating advantages. It is becoming more and more 
 established that successful flying machines require 
 the use of comparatively little metal, and especially 
 of little metal of resistant qualities worked into in- 
 tricate shapes. The result is that flying-machine 
 construction, while often requiring considerable 
 painstaking labor does not particularly require 
 expensive facilities, and therefore stands open to 
 a greater number of unhandicapped amateur ex- 
 perimenters than almost any other field of engi- 
 neering research or industrial enterprise. 
 
 Necessarily, other equipment being equal, the 
 engineers most certain to achieve success in pio- 
 neering this new field will be those who prove the 
 most widely informed and resourceful. For these 
 reasons at least a smattering of a great many 
 
 372 
 
FIGURE 171 Details of Bleriot Monoplane. This is one of the earlier machines of the 
 "Bleriot XI" type and is provided with an eight-cylinder, water-cooled motor, with i-adiatoi 
 immediately beneath it. The wheels g g and the rubber springs a s are characteristic of 
 Bleriot alighting gear, but in the case of the latter the multiplication of the movement as 
 shown in this view by passing over rollers has been abandoned. 
 
 FIGURE 172. Alighting Gear of Paulhan's Voisin. The wheel g 
 safeguard against undue forward inclination of the machine in landing. 
 
 on the prow 
 
MATERIALS AND CONSTRUCTION 373 
 
 different trades is likely to be prolific in suggested 
 ways of accomplishing things. 
 
 Because of the great need for a comprehensive 
 view of and assimiliation from all fields of engi- 
 neering, it seems proper here to call attention to 
 various examples of construction that have been 
 either overlooked or have failed to gain the con- 
 sideration their merits demand. Certainly no 
 worker in aeronautics can afford to be unfamiliar 
 with the wonderfully light, strong, and durable 
 sled and boat constructions that the Eskimo 
 achieves with bits of wood, sinew lashings, and skin 
 coverings; or with the almost perfect craftsman- 
 ship displayed in the manufacture of the primitive 
 weapons of many savage races not to forget the 
 more enlightened workmanship of the modern 
 tensile strength in a longitudinal direction. 
 
 WOODS 
 
 Not without a considerable basis of fact it has 
 been asserted that the flying machines of the future 
 will be built in the carpenter shops of the future, 
 for wood is by far the most utilized material in all 
 successful fliers. For wing bars and ribs, runners 
 and running gears, frames, braces, and the like, 
 wood seems as serviceable and indispensable as it 
 is for the rims of bicycle wheels, besides which it is 
 cheap and easily worked. 
 
 It is not generally appreciated, even by many 
 engineers, that certain woods constitute almost the 
 strongest, most reliable, and most durable of all 
 
374 VEHICLES OF THE AIR 
 
 structural materials, the best qualities of selected 
 timber being, weight for weight, close rivals in 
 sheer strength compressive, tensile, shearing, and 
 even torsional with all metals but the very finest 
 alloy steels, while in immunity from flaws and 
 uncertainty in regard to physical properties, woods 
 are even superior to metals, especially when well 
 seasoned. Unseasoned woods beside being heavy 
 are often less than half as strong as the same tim- 
 ber thoroughly dry. 
 
 Chemically and microscopically, wood is a mul- 
 ticellular structure of cellulose with a pronounced 
 longitudinal grain, affording its greatest strength 
 in a longitudinal direction, though some woods are 
 enough tied together with transverse fibers to af- 
 ford great resistance to splitting. This resistance 
 is usually from one-tenth to one-twentieth of the 
 tensile strength in a longitudinal direction. 
 
 Woods are commonly divided loosely into two 
 classes hardwoods and softwoods though there 
 is not really any distinct demarcation between the 
 classes, there being a variety of qualities so great 
 as to shade by imperceptible gradations from the 
 softest to the hardest. 
 
 HARDWOODS 
 
 For a given bulk the best hardwoods are much 
 stronger than most softwoods, besides generally 
 possessing qualities of tenacity and flexibility that 
 contrast favorably with the brittleness of some of 
 the very strongest softwoods, but for a given 
 strength within a given weight rather than within 
 
J 
 
 the runners f f and the wheels fj g. 
 
 4. Alighting Gear of Farman Machine. 
 
 PlGURl 17~>. Boat-like Body of Antoinette Monoplane. This machine, which is equipped 
 with a hundred horsepower motor, will run on the land, in the water, and in the air. 
 
 FIGURE 176. Alighting Gear of Antoinette Monoplane. Most of the weight is carried 
 on the two center wheels fj <j, with the spring-mounted spherical wooden rollers at & & to 
 balance the machine. The runner f is an additional safeguard against shock in landing. 
 
MATERIALS AND CONSTRUCTION 375 
 
 a given size, a few of the softwoods are superior 
 to the strongest hardwoods. 
 
 Applewood is in its best qualities a remarkably 
 fine timber, especially for service in which great 
 resistance to splitting is required. For this reason 
 it is much sought by makers of handles, chisel and 
 other handles made of applewood being almost im- 
 possible to split even under the hardest hammer- 
 ing with a mallet. The difficulty of securing large 
 clean pieces undoubtedly prevents more extensive 
 use of this wood. For flying-machine propellers it 
 would appear to possess particular merits. 
 
 Ash is proved second only to hickory in its use- 
 fulness for carriage shafts, ladders, handles, etc., 
 but though it strongly resists utter breakage it 
 lacks stiffness and therefore is best when pliability 
 is a requisite. The foregoing applies especially to 
 white ash particularly to second-growth timber. 
 Black ash splits easily and is even more flexible, 
 but is very tough. It is much used for barrel hoops, 
 while as a material for bows every archer knows it 
 has few superiors. It is also applied to a consider- 
 able extent in the manufacture of oars and paddles. 
 
 Bamboo, botanically the largest of all grasses, 
 grows up to a foot in diameter and 120 feet high in 
 some of its 200 or more varieties, which are particu- 
 larly plentiful in southern Asia and South America, 
 and its marvelously light, elastic, and hard hollow 
 stems are used the world over for everything from 
 fishing poles to primitive but serviceable bridges. 
 Split bamboo, in which the greater strength of the 
 silicious surface of the canes is most favorably 
 
376 
 
 VEHICLES OF THE AIR 
 
 FIGURE 177. Built-Up Bamboo Spar. 
 At a and c are shown cross-sections of 
 the spar e, glued up from pieces cut as 
 shown at b and d. 
 
 placed to resist stresses, is a favored construction 
 for fishing poles, and should readily find applica- 
 tion to flying ma- 
 chines once the de- 
 mand is created (see 
 Figures 177 and 180). 
 In rather remark- 
 able contradistinction 
 to other woods, bam- 
 boo is a material that 
 becomes less valuable 
 as it is well seasoned, 
 natural bamboo poles 
 as large as two inches 
 in diameter or over almost invariably cracking and 
 splitting longitudinally as they become well dried 
 out with age. 
 
 Birch, either red or black, is among the most 
 resistant of woods to splitting and is very fine 
 grained and strong. In its different varieties birch 
 is used for everything from articles requiring fine 
 carving to ox yokes, saddle trees, etc. The bark 
 of the common birch, used by the Indians for 
 making canoes, baskets, etc., is a very light and 
 strong material that might conceivably find some 
 application in flying-machine construction. 
 
 Boxwood is even more resistant in small cor- 
 ners and edges than maple, for which reason it is 
 much used for wood carving. Its great weight is a 
 serious objection from aeronautical standpoints. 
 Elm has a rather interwoven grain and does not 
 split easily, but though very strong it easily works 
 
MATERIALS AND CONSTRUCTION 377 
 
 out of shape under stress if not well braced. It 
 has particular merits for wing bars and other parts 
 of a structure to which it may be required to tack 
 fabric, because tacks do not split it readily. Elm 
 is one of the lightest of the hardwoods, being of 
 about the same weight as Honduras mahogany, 
 but in its strength and density it really comes into 
 an intermediate position between the hardwoods 
 proper and the softwoods. 
 
 Hemlock is a fairly strong and exceptionally 
 light wood, the ratio between its weight and 
 strength being such as to rate it materially higher 
 as a structural material than other woods popu- 
 larly regarded as much stronger. 
 
 Hickory, especially second growth timber rap- 
 idly produced in the form of new shoots from the 
 stumps of felled trees, is one of the strongest and 
 toughest of all woods. This is strictly true only 
 of the so-called * 'shellbark" and " white" hickories. 
 Water hickory is rather soft and comparatively 
 light, while the wood of the pecan (a variety 
 of hickory) is hard and brittle, but nearly all of 
 the other varieties afford the highest grades of 
 material known to the woodworker. The common 
 uses for which hickory is preferred over all other 
 woods alone speak volumes for its quality axe 
 and pick handles, spokes for vehicle wheels, 
 vehicle shafts, oars, etc., being among the more 
 familiar applications. In flying-machine construc- 
 tion it is particularly suitable for members in 
 which it is desired to combine great strength with- 
 out the bulk necessary in spruce and other soft 
 
378 VEHICLES OF THE AIR 
 
 wood members of similar resistance. For propel- 
 lers it is probably unequalled. Hickory particu- 
 larly resists splitting and transverse fracture, 
 breaking when it does break gradually, with a 
 tearing, fibrous, splintered parting. It decays 
 readily, for which reason structures of hickory 
 must be well protected from the weather by 
 suitable finishes. 
 
 Holly is a hardwood of fairly light weight and 
 superior qualities, and is particularly resistant to 
 splitting, but the difficulty of securing it in suit- 
 able sizes and qualities restricts its use. 
 
 Mahogany, of the common quality from Hon- 
 duras, is perhaps the lightest of all the true hard- 
 woods, and in thin veneers, with crossed grain, 
 has great strength, though ordinarily it is regarded 
 as more remarkable for the quality of finish it 
 will take than it is for purely structural merits. 
 Spanish mahogany, though somewhat stronger, is 
 considerably heavier. 
 
 Maple, though not the strongest of hardwoods, 
 is lighter than most, does not split easily, and is 
 superior to most other timbers in its ability to 
 retain fine edges and corners under exposure 
 to conditions that tend to cause chipping and 
 marring. 
 
 Oak, though widely recognized as one of the 
 strongest of woods, is too heavy to measure up well 
 from flying-machine standpoints. 
 
 Walnut, though rather brittle, is very strong 
 and light, and the best French or Circassian wal- 
 nuts are very successfully used in the manufacture 
 
MATERIALS AND CONSTRUCTION 379 
 
 of wooden propellers, though they seem unsuited 
 to less-specialized uses. 
 
 SOFTWOODS 
 
 The distinguishing quality of the softwoods is 
 their great bulk for a given weight, allowing the 
 highest strength to be secured not per unit of bulk 
 but per unit of weight. 
 
 Pines, of a great range of varieties and quali- 
 ties, are among the strongest of all timbers, though 
 the different kinds vary widely in their properties. 
 The best clear white and red pines, free from 
 pitch, are second only to spruce in their lightness 
 and strength. Both of these are extensively used 
 by boat-builders, besides for innumerable purposes 
 of less critical requirements. 
 
 Poplar the term by which several varieties 
 of whitewood and basswood are commonly known 
 though these are not true poplars at all is very 
 tough and durable, and is lighter than almost any 
 other wood possessing strength qualities meriting 
 consideration. Its weight is often as low as 
 twenty pounds to the cubic foot only five pounds 
 heavier than cork and it rarely rises as high as 
 thirty, even in specimens selected for close grain 
 and density. 
 
 Spruce, which is really a fir, and thus closely 
 related to the pines, is a wood that has first claim 
 on the aeronautical engineer's attention. This is 
 most particularly true of the silver fir, and the 
 Norway and California spruces, all of which are 
 unequalled for the spars of vessels, while the sec- 
 
380 VEHICLES OF THE AIR 
 
 ond is widely employed by musical-instrument 
 makers for sounding boards. Selected, clear, and 
 straight-grained spruce, or "deal" as it is ternled 
 in Europe, rarely weighs over thirty pounds to 
 the cubic foot, and is tremendously strong for its 
 weight. Spruce is very strong and stiff, does not 
 easily warp, and will bend as much as elm without 
 brealdng, but being more elastic tends more 
 strongly to spring back. It splits very easily, for 
 
 FIGURE 178. Sections of Wooden Spars. The ends sought in these differ- 
 ent constructions are light weight, great strength, and a minimum resistance 
 to passage through the air. 
 
 which reason ends should be well wrapped with 
 wire or cord, or run into sockets, while holes for 
 nails, screws, and bolts should be bored full to 
 avoid any wedging effect. 
 
 Willow, the "osier" of Europe, is the con- 
 stituent of common wicker ware and furniture. 
 Its strength in proportion to weight is very great 
 because of its extreme lightness. It is much used 
 for balloon baskets (see Page 105) and would ap- 
 pear to have a field before it in way of seats and 
 housings for passengers in aerial vehicles (see 
 Figure 248). 
 
 VENEERS AND BENDINGS 
 
 Veneered, bent, and built-up wooden struc- 
 tures are usually the strongest, because of the 
 many opportunities they present of eliminating 
 
MATERIALS AND CONSTRUCTION 381 
 
 flaws, of crossing grains to prevent splitting, and 
 of building hollow members to combine the maxi- 
 
 m 
 
 FIGURE 179. Built-Up Hollow Wooden Spar. 
 
 mum of strength with the minimum of weight. 
 
 Examples of built-up wooden structures appear in 
 
 Figures 177, 178, 179, 
 and 180. The hollow- 
 box wing bars of the 
 large Langley machine 
 
 FIGURE 180. Built-up Bamboo, Hick- (see Page 137), pOSSi- 
 ory, and Rawhide Wing Bar. v 
 
 bly were the most 
 
 elaborate wooden structures ever designed, as they 
 were certainly among the lightest and strongest. 
 
 METALS 
 
 Though weight for weight very few of the 
 metals are stronger than the best woods, and these 
 few are less superior than is commonly supposed, 
 within a given volume of structure no materials 
 approach the metals. Particularly in their tensile 
 strengths do the metals excel the woods, for which 
 reason they are much used in the form of wire. 
 
 For stays, strengthening wrappings, and con- 
 trol operation, wire is probably unrivalled. An- 
 other important use for metal is in sheet form, 
 which also is cheap and inexpensive to handle, 
 whether used for adding strength to joints and 
 angles, or for more elaborate purposes. Simple 
 
382 VEHICLES OF THE AIR 
 
 castings, too, of the lighter aluminum and other 
 alloys, can be made to serve many useful purposes. 
 
 IRON 
 
 Iron as a structural material is one that has 
 suffered from comparison of its impure qualities 
 with ordinary steels, but really pure iron is a metal 
 of many merits, chief among which is a resistance 
 to shock loads that few steels equal, while in sheer 
 strength it is at least superior to steels of common 
 qualities or careless manufacture. 
 
 STEEL 
 
 Ordinary steel is a compound of carbon and 
 iron, with the carbon ranging from 10 to 200 ten 
 thousandths, Timnr being known in the steel trade 
 as one " point." Thus, " 30-point" carbon steel 
 is steel containing y^VW of carbon. Steel is dis- 
 tinguished from all other materials by its tre- 
 mendous strength. In its strongest forms, how- 
 ever, it is hard and brittle, for which reason an- 
 nealed varieties of moderate strength are most 
 used in structures in which breakage can become 
 very serious. Different steels weigh from 480 to 
 490 pounds to the cubic foot from 3.5 to 3.7 cubic 
 inches to the pound. The strongest form of car- 
 bon steel is fine wire, such as piano wire and the 
 wire used in bicycle spokes. The latter are com- 
 monly to be had with ultimate tensile strengths as 
 high as 300,000 pounds to the square inch, with an 
 "elastic limit" permissible load without perma- 
 
?r-Faced Silk Used on "Golden Flyer." B. Balloon and Aeroplane Material. 
 
 C. Rubber-Faced Silk Used on "Silver Dart." D. Treated nfl Untreated Balloon Silk. 
 
 E. Continental Rubber-Faced Percale No. 109. ^.Continental Rubber Faced Percale No. Ill 
 
 . "Tanalite." H. Continental Unvulcanized Joining Material. 
 
 J. Continental. K. Continental. 
 
 L. Balloon or Aeroplane Fabric. M. Balloon or Aeroplane Fabric. 
 
 FIGURE 184. Texture of Modern Aeroplane Fabrics Reproduced Actual Size. Of the 
 above, A weighs only 3 ounces to the square yard ; C weighs only 2 ounces to the square yard ; 
 D is a balloon silk, much used for tents, weighing from 3 to 4 ounces a squard yard ; E and F 
 are rubber-faced percales weighing about 3% ounces to the square yard; G is a light tent 
 material of some suitability for aeroplanes ; // is for covering seams ; I, J and K are light 
 linen fabrics, and L and M are suitable for either aeroplanes or light balloons. The strengths 
 range from 45 pounds to the inch of width in C, to 100 pounds in the case of I, J and K. 
 
MATERIALS AND CONSTRUCTION 383 
 
 nent deformation nearly as high as the ultimate 
 strength. 
 
 Alloy Steels are a rather modern development 
 in steel manufacture, being produced by the addi- 
 tion to the carbon and iron of small quantities 
 of certain less common metals notably nickel, 
 chromium, vanadian, uranium, and tungsten. By 
 the use of these it is found that the different quali- 
 ties of ultimate strength, elastic limit, and resist- 
 ance to shock are vastly enhanced, provided that 
 in addition to the proper admixture of the proper 
 ingredients the metal is subjected to proper heat 
 treatment in its manufacture. 
 
 In the best grades of chrome-nickel steel elastic 
 limits of 110,000 and 120,000 pounds to the square 
 inch are not uncommon in unannealed qualities of 
 metal, so far from brittle that with sufficient force 
 they can be bent 180 degrees without fracture, 
 while the same steels hardened often test fully 
 twice as high. 
 
 It is one of the interesting problems of modern 
 metallurgy and engineering to discover just what 
 may be the greatest strengths possible to secure 
 with combinations of different metals in which 
 combinations it is to be noted that there appears 
 to be little likelihood of any advantageous elimi- 
 nation of iron and carbon. 
 
 It has been stated on good authority that 
 Krupps, of Germany, has produced test bars of a 
 secret tungsten-containing steel with which tensile 
 strengths of over 600,000 pounds to the square inch 
 have been achieved. No such steel is at present 
 
384 VEHICLES OF THE AIR 
 
 on the market in commercial shapes, nor are the 
 torsional and other qualities of these extraordinary 
 fibrous and tough steels supposed to be very high. 
 It is a difficulty in the utilization of all steels 
 that much of their strength depends upon their 
 proper heat treatment, for which reason it is easy 
 to secure much lower than the maximum strengths 
 by careless methods of brazing, welding, temper- 
 ing, etc. 
 
 CAST IRON 
 
 Cast iron is iron admixed with an excess of 
 carbon over the amount permissible in steels. 
 Aside from the facility of working it by casting in 
 molds, cast iron possesses certain qualities that 
 render it peculiarly suitable for gasoline-engine 
 cylinders. These qualities are its resistance to 
 high temperature, its immunity from corrosion, 
 and its capacity to take and retain a much 
 smoother finish than it is found possible to secure 
 in steel or other metals used for the same purpose. 
 
 ALUMINUM ALLOYS 
 
 Though practically worthless in its pure form 
 for such purposes, some of the alloys of aluminum 
 with other metals stand second only to the best 
 steels among the metals, and are even superior to 
 these in their ease of manufacture without impair- 
 ment of their more valuable characteristics. 
 
 Aluman is an alloy of 88% aluminum with 10% 
 zinc and 2% copper. It is one of the strongest of 
 the aluminum alloys and is readily forged and 
 milled, but its weight is an objection to it. 
 
MATERIALS AND CONSTRUCTION 385 
 
 Argentalium is a recently patented alloy of 
 aluminum and silver, originated in Germany. 
 Little data concerning its qualities are as yet avail- 
 able, though in the preferred proportions its spe- 
 cific gravity is known to be about 2.9. 
 
 Chromaluminum is another German alloy of 
 patented formula, containing aluminum with 
 chromium and other ingredients. It weighs the 
 same as argentalium and is stronger than any 
 other known aluminum alloy, with the pos- 
 sible exception of the very highest qualities of 
 magnalium. 
 
 Magnalium is an alloy of aluminum and mag- 
 nesium, the proportion of the latter varying from 
 2% to 10%. Its weight is less than that of pure 
 aluminum, and in its strongest qualities those 
 containing the most magnesium it has been ex- 
 tensively applied in aeronautical engineering. It 
 resists corrosion about as well as aluminum, and 
 is readily cast, forged, machined, rolled, and 
 drawn, with little difficulty in realizing its excel- 
 lent qualities in the final manufactured shapes. 
 
 Nickel- Aluminum is rather heavier and not as 
 strong as magnalium. 
 
 Partinium, or Victoria- Aluminum, is a more or 
 less secret aluminum alloy much used in Europe 
 for automobile crankcases and gearboxes. It con- 
 tains very small proportions of copper and zinc, 
 casts well, and is very light. 
 
 Wolframinium is an alloy of aluminum with 
 tungsten, with traces of copper and zinc. It is the 
 subject of a German patent and is extensively 
 
386 VEHICLES OF THE AIR 
 
 used in the Zeppelin dirigibles (see Page 87). 
 Wolframinium is readily worked into almost any 
 desired form, and is fully as strong as the more 
 practical qualities of magnalium, but it weighs 
 more than the generality of aluminum alloys. 
 
 BRASSES AND BRONZES 
 
 Copper with zinc, tin, aluminum, phosphorous, 
 etc., constitutes the various qualities of brasses 
 and bronzes, which, while strong and easily 
 worked, tend to be rather too heavy for most 
 aeronautical purposes. 
 
 Aluminum Bronze, of 90% copper with 10% 
 aluminum, is very tough and elastic, almost incor- 
 rodible, and little affected by changes of tempera- 
 ture. It casts and machines well with proper 
 methods, but is very heavy. 
 
 Phosphor Bronze is exceptionally strong in 
 the form of wire and small fit- 
 tings, such as turnbuckles and 
 the like. 
 
 METAL PARTS 
 
 Of the metal parts most used 
 like 'the^pe? in modern aerial vehicles, those 
 
 view, it will either . .. . 
 
 come loose or draw into of greatest importance and in- 
 
 the shape that is shown * 
 
 he e is vi the terest are the various qualities of 
 g? A se st m wire, strut sockets, turnbuckles, 
 
 better method is to use -, , > c* i 
 
 the flattened piece of and wire tighteners. Several ap- 
 
 steel tubing shown at a 
 
 , . . 
 
 P rove <l methods of fastening wire 
 win at hoi 6 d a i? d se?urSy: ch ends are illustrated in Figure 
 
MATERIALS AND CONSTRUCTION 387 
 
 FIGURE 182. Strut Sockets and Turnbuckles. A, B, and C are cast alumi- 
 num sockets for the attachment of struts to the sides of cross members. 
 D is such a socket with the addition of a lug for the attachment of a hinged 
 member. E is for the attachment of a strut to the end of a cross member. 
 F is a strut tip, for hinging to a socket of the type D. G, H, I, L, and M 
 are turnbuckles, with oppositely-threaded ends, for tightening wire stays. 
 These are operated by a pin thrust through the center holes, and are locked 
 by running a wire through this and the wire eyes in the ends. K is a 
 similar turnbuckle, but is kept from loosening by the locknuts at its ends. J 
 is a bolt, eye-ended for the attachment of a wire stay. N is a clip for 
 clamping wooden bars together, and O is a wire tightener, similar to that 
 in Figure 183, the application of which does not involve cutting the wire. 
 
 181, while in Figure 182 are shown groups of 
 strut sockets and turnbuckles, and in Figure 183 a 
 wire tightener that avoids cut- 
 ting the wire. 
 
 CORDAGE AND TEXTILES 
 A 
 
 FIGURE 183. Wire 
 Tightener. 
 
 Cordage is of great utility 
 from many standpoints, and 
 though much weaker than wire for a given size, 
 with some materials it compares most favorably 
 with the metals on the basis of a given weight, 
 
388 VEHICLES OF THE AIR 
 
 while its great flexibility and reliability are posi- 
 tive advantages. It is used for much the same 
 purposes as wire. 
 
 Fabrics for covering wing surfaces probably 
 possess greater all-around advantages than any 
 of the alternative materials that are occasionally 
 proposed or tried, and like the other materials on 
 which the aeronautical constructor must rely are 
 easily worked up and comparatively cheap, in even 
 the best qualities. 
 
 Cotton cord, though very strong, is less used 
 than cotton fabric, which is the commonest mate- 
 rial of aeroplane coverings, of which a variety of 
 typical textures is illustrated in Figure 184. 
 
 Linen fabrics have been discussed on Page 94. 
 
 Silk fabrics also have been considered herein- 
 before (see Page 93). 
 
 PAINTS AND VARNISHES 
 
 Next in importance to the production of a 
 strong and efficient structure are the means of 
 maintaining it so. These particularly involve 
 avoidance of warping, loosening, and rusting, due 
 to the action of moisture, and can be best guarded 
 against by the proper application of suitable 
 finishes. 
 
 Aluminum Paint is used over all wooden sur- 
 faces of the Wright machines for a double pur- 
 pose. One is the protection of the wood and the 
 other is the exposure of the least checking or 
 
MATERIALS AND CONSTRUCTION 389 
 
 cracking, which the inelasticity of this finish makes 
 at once apparent in the form of fine black lines. 
 
 Oils, especially boiled linseed oil, exercise a 
 marked preservative effect upon woods to which 
 they are applied. It is a question though, whether 
 the sometimes recommended soaking of wood in 
 oil does not materially weaken it. 
 
 Shellacs, both yellow and white, because of 
 their quick and smooth-drying qualities, are 
 among the- most convenient as well as one of the 
 best of finishing materials. 
 
 Spar Varnish is particularly to be recom- 
 mended as a covering for glued joints and other 
 elements upon which the action of moisture is to 
 be feared. 
 
 Miscellaneous finishes, other than the fore- 
 going, exist in great variety. Most worthy of 
 present consideration are the various enamels, 
 japans, and lacquers used to protect metal surfaces 
 from rust and corrosion. 
 
 MISCELLANEOUS 
 
 Of other materials interesting to the student 
 of practical aeronautics there is a considerable 
 number. 
 
 Catgut, from the intestines of small animals, 
 resembles rawhide in its quality of stretching 
 when wet and shrinking as it dries, making it 
 excellent for tightly-wrapped bindings of spar 
 ends. It is much used in musical instruments and 
 for stringing snowshoes, tennis racquets, etc. 
 
390 VEHICLES OF THE AIR 
 
 China Grass, used for chair seats, is five-sixths 
 as strong as silk, section for section, and is little 
 if any heavier. 
 
 Hair, especially human hair, is little inferior to 
 silk in strength and lightness. 
 
 Rawhide is much used for covering and bind- 
 ing together the parts of wooden saddle trees, 
 being applied wet and allowed to shrink on. Thus 
 used it would appear to have value in aerial- 
 vehicle elements, as is suggested in Figure 180. 
 
 Silk Cord is, almost without exception even 
 among the metals, one of the strongest structural 
 materials known, as is evident from the tabular 
 comparisons at the end of this chapter. 
 
 Silkworm Gut, the so-called " catgut" of fish- 
 line leaders, is very close to silk in strength. 
 
 ASSEMBLING MATERIALS AND METHODS 
 
 A serious obstacle in the way of making wood 
 or other structures of great strength is that of 
 devising joints of strength equal to that of the 
 unbroken material, the best joints tending to fall 
 much short of the strength that it is easy to secure 
 in unbroken members. 
 
 Nails for fastening together wooden parts are, 
 though a common method, a most inadequate one 
 for anything so delicate and exacting as a flying- 
 machine structure. 
 
 Glues and Cements afford much stronger con- 
 structions, especially when used in combination 
 with wrappings of wire, cord, leather, or rawhide, 
 while reinforcement by metal plates and enlarged 
 
MATERIALS AND CONSTRUCTION 391 
 
 ends to the members is found of great advantage 
 in wood structures. 
 
 Screws, judiciously used to prevent the slip- 
 ping apart of different elements rather than as 
 the sole means of securing them together, are not 
 positively objectionable, though it is desirable to 
 avoid them. 
 
 Bolts, of small diameter and high-quality steel, 
 and with large washers under heads and nuts, are 
 successfully utilized in many modern aeroplanes, 
 through wood and metal members proportioned to 
 receive the bolt holes without weakening. 
 
 Clips, of the type illustrated at N, Figure 182, 
 are excellent for clamping two or more wooden 
 bars together. 
 
 Rivets, while not the best, constitute an easily- 
 applied and fairly effective means of joining light 
 metal parts together. 
 
 Electric Welding is an almost perfect though 
 not always readily applicable method of joining 
 parts of similar or dissimilar metals with mini- 
 mum impairment of strength. 
 
 Autogenous Welding, by the use of the in- 
 tense but readily-localized heat of the oxy-acetyl- 
 ene flame, is an excellent modern method that in 
 expert hands is easily applied to a great variety 
 of assembling operations. 
 
 Brazing, which is practically a means of solder- 
 ing iron and steel with a solder of very soft brass, 
 or " spelter", was first developed into a really reli- 
 able and effective process in the evolution of the 
 bicycle industry. Brazed joints appear well and 
 
392 
 
 VEHICLES OF THE AIR 
 
 hold well, but the prolonged heating they involve 
 weakens all but the softest annealed steels. 
 
 Soldering, properly done, is a dependable 
 means of securing light parts together, or of rein- 
 forcing parts primarily held by other means, as in 
 the case of twisted wire ends (see Figure 181), 
 which may be soldered to afford added security. 
 
 TABULAR COMPARISON OF MATERIALS 
 
 WOODS 
 
 NAME 
 
 Pounds 
 to Cubic 
 Foot 
 
 Tensile 
 Strength 
 (in pounds) 
 
 Length 
 of 
 Material 
 Sus- 
 tained* 
 
 Compressive 
 Strength 
 (in pounds) 
 
 Column 
 of 
 Material 
 Sus- 
 tained* 
 
 Alder 
 
 
 
 
 6 000 7 000 
 
 
 
 
 _ 
 
 
 
 
 Ash . 
 
 43 
 
 11.000 
 
 36800 
 
 4 600 8 000 
 
 26 760 
 
 Bamboo 
 
 20 
 
 
 
 
 
 Beach 
 
 43 
 
 800012,000 
 
 33660 
 
 8 000 9 000 
 
 25 245 
 
 Birch 
 
 35 
 
 7 000 10 000 
 
 41 000 
 
 5 000 10 000 
 
 41 000 
 
 Boxwood 
 
 64 
 
 10 000 15,000 
 
 33750 
 
 8 000 10 000 
 
 22 500 
 
 California Spruce 
 
 
 12 000 14 000 
 
 
 
 
 Cedar 
 
 35 
 
 4,000 9,500 
 
 38950 
 
 4,000 6500 
 
 26 400 
 
 
 
 
 
 5 000 6 500 
 
 
 Chestnut 
 Elm 
 
 *36" 
 
 7,000 12,000 
 8 000 13,000 
 
 '53 bob' 
 
 4,000 4,800 
 8 000 10 000 
 
 40 750* 
 
 Fir (New England Spruce) 
 
 
 5 000 10 000 
 
 
 
 
 Fir (Norway Spruce) 
 
 32 
 
 5,000 12,500 
 
 56250 
 
 
 
 
 Hemlock . . 
 
 23 
 
 
 
 
 
 
 43 
 
 10,000 -14,000 
 
 46880 
 
 8 000 9 800 
 
 32 800 
 
 
 
 10 000 15 000 
 
 
 
 
 
 45 
 
 8,000 15,000 
 
 48,000 
 
 
 
 
 Larch 
 Lignum Vitae . 
 
 
 6,00010,000 
 10 000 12 000 
 
 
 3,000 5.500 
 8 000 9 600 
 
 
 
 Locust 
 
 Mahogany (Honduras) 
 
 35 
 
 10.000 -15,000 
 5 000 8,000 
 
 32 8*00 
 
 7,500 9,500 
 
 
 
 Mahogany (Spanish) 
 Maple 
 
 45 
 40 
 
 8,000 15,000 
 8 000 10.000 
 
 48.000 
 36 000 
 
 7,000 8,000 
 5 000 6 000 
 
 25,600 
 21 600 
 
 Oak(English) 
 
 Oak (Live)... 
 
 *67* 
 
 9.000-12,000 
 10,000 
 
 *21* 500 
 
 6,50010,000 
 8 000 10 000 
 
 21 500 
 
 Oak (White) 
 
 43 
 
 10 000 
 
 33500 
 
 5 500 8 000 
 
 26 800 
 
 Oregon Pine 
 Pear 
 
 
 9,00014,000 
 7 000 10 000 
 
 
 '7*500 
 
 
 Pine (Pitch) 
 Pine (Red) 
 
 .... 
 
 8,000 10,000 
 5 ooo 8,000 
 
 
 
 'g'o'o'o' "7" 566 
 
 
 
 Pine (White) 
 
 29 
 
 3 000 7 500 
 
 37 240 
 
 3 000 6 000 
 
 29 800 
 
 Pine (Yellow) 
 
 34 
 
 5 000 12,000 
 
 50820 
 
 6 500 10 000 
 
 42 350 
 
 Plum 
 Poplar 
 Sprues 
 
 'si' 
 
 7,000-10,000 
 7,000 
 5 000 10 000 
 
 46 450 
 
 '5,000 '8,666 
 
 4 500 6 060 
 
 27 870 
 
 Sycamore 
 
 39 
 
 
 
 
 
 Teak 
 
 
 10 000 15 000 
 
 
 6 00010 000 
 
 
 Walnut (Black) 
 
 Walnut (Hickory) 
 
 42 
 
 8,000 
 
 
 
 5,600- 7,000 
 
 
 
 Walnut (White) 
 
 
 
 
 
 7 500 9 000 
 
 
 Willow.. 
 
 87 
 
 10 000 
 
 28 800 
 
 3 ooo 6 000 
 
 16 280 
 
 Yew 
 
 50 
 
 
 
 
 
 See opposite page. 
 
.- 
 
 
 FIGURE 185. Scale Drawings of Wright Biplane. This biplane particularly differs from al 
 others in its use of a runner alighting gear G G, starting being effected by auxiliary devices, involv 
 ing a small truck on which the machine is mounted, a wooden rail on which this truck runs, and ; 
 derrick and weight arrangement for imparting the initial impulse. The advantages of this systen 
 are several. Other things being equal, the machine is lighter than those in which wheeled starting 
 gears are provided, free flight is attained with a much shorter run, and the runners are decidedl; 
 superior to wheels for alighting on rough ground, over which they slide with a minimum risk o 
 breakage. The main planes C D are double surfaced, with double ribs and enclosed wing bars, am 
 are narrowed at their ends. All of the front rectangles are rigidly trussed by diagonal wires, a 
 also are the center rectangles at the rear, but the four outer rear rectangles are kept in shape onl; 
 by the movable guys F F F F, which pass over the pulleys E E M E. The consequence is that endwis 
 movement of the lower of these wires, effected by the sidewise movement of a lever, oppositel; 
 warps the wing tips in such a manner as to control lateral balance and steering. The double vei 
 tical rudder J, carried on the spars K K, is worked by a forward and backward movement of th 
 same lever that when laterally moved controls the wing warping, so that angular movements of thi 
 lever exert a compound controlling effect. The front elevator H is normally flat in the lates 
 Wright machines but when moved by the operating bar I from the lever N it does not merely pivot- 
 it springs into curved form, with the concavity upwards or downwards, as the case may be, so tha 
 a surface of maximum effectiveness is presented to the air. This construction, which is the subjec 
 of a patent, is shown more in detail in Figure 84. Propulsion is by twin propellers A B, 8$ feet i: 
 diameter, oppositely rotated by the ingenious double-chain driving system originated by the Wrights 
 in which one chain that to the sprocket Q is crossed, while the other to is used in the norms 
 manner. The engine, with shaft at P, is a 25-horsepower, four-cylinder, water-cooled design, weigi 
 ing about 180 pounds. A radiator composed of vertically-placed flat copper tubes extending th 
 whole distance between the main surfaces takes care of the cooling. Two or three passengers can b 
 carried, seated near the center of the lower surface just enough to one side to balance the weigt 
 of the motor with their feet braced against the bar M. For convenience in storing and shippin 
 the outer ends of the main surfaces dismount at E E, while the runners disconnect under the fror 
 edges of the surfaces. The runners in the latest Wright machines are made considerably hight 
 than formerly. The weights of the different Wright machines have ranged from 800 pounds to 125 
 pounds, varying with the design and the weight of fuel and passengers carried. All dimensions ai 
 given in inches, and it is to be noted that the sectional dimensions of the principal wooden membei 
 are included. For further details of the Wright construction, reference should be had to Figures 7- 
 75, 110, 139, 161, 163, 165, 166, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, and 196. 
 
n 
 
 H 
 
 36 M 
 
 k-- 
 
MATERIALS AND CONSTRUCTION 393 
 
 METALS 
 
 NAME. 
 
 Pounds 
 to Cubic 
 Foot 
 
 Tensile 
 Strength 
 (in pounds) 
 
 Length 
 of 
 Material 
 Sus- 
 tained* 
 
 Compressive 
 Strength 
 (in pounds) 
 
 Column 
 of 
 Material 
 Sus- 
 tained* 
 
 
 184 
 
 42 660 
 
 33 380 
 
 
 
 Aluminum 
 
 168 
 
 38 393 
 
 32 910 
 
 
 
 
 Aluminum Bronze 
 
 481 
 
 92 430 
 
 27 460 
 
 
 
 C hronialuminuni 
 
 184 
 
 63990 
 
 50080 
 
 
 
 
 Brass 
 
 526 
 
 85 3^086 742 
 
 23 750 
 
 
 
 
 444 
 
 20 00035 000 
 
 11 350 
 
 75 000 -150 000 
 
 48 640 
 
 Copper 
 
 
 56 88058 302 
 
 
 
 
 Iron (Commercial) 
 
 480 
 
 58 000. 
 
 17 400 
 
 28 000 
 
 8 400 
 
 Iron (Pure Wrought) 
 
 482 
 
 119448 
 
 35650 
 
 
 
 Magnalium 
 
 152 
 
 41 23863 990 
 
 54040 
 
 
 
 
 184 
 
 56 880 
 
 44 560 
 
 
 
 Partinium 
 
 178 
 
 21J330 
 
 16020 
 
 
 
 Steel (Cast) 
 
 485 
 
 
 
 80 000 . 
 
 23 750 
 
 
 483 
 
 
 
 22 000 
 
 6 560 
 
 SteeKcommon pianowire) 
 
 490 
 
 99540-132 246 
 
 40500 
 
 
 
 Steel (tinned piano wire) 
 
 490 
 
 246.006 3R840 
 
 9U40 
 
 
 
 
 MISCELLANEOUS MATERIALS 
 
 Boat Paper j 
 
 
 
 16800... 
 
 
 
 
 
 
 
 39 520... 
 
 
 
 Catgut 
 
 
 
 
 25.000 36,175 
 
 
 
 China Grass. . 
 
 
 22752 
 
 
 
 Glue 
 
 
 500 750 
 6,82517,000 
 9,000 
 
 
 
 
 
 Hemp 
 
 90 
 
 75,000 
 
 
 
 
 
 
 
 
 
 
 50,000 79,000 
 
 
 
 
 
 16000 ... 
 
 
 
 
 
 3,000 5,000 
 
 
 
 
 
 Man'la 
 
 
 
 
 
 
 
 Rawhide 
 Silk 
 
 'ioi 
 
 12,000- 
 35,000 62,028 
 
 15,000 
 88,436 
 
 
 
 
 
 Silkworm Gut 
 
 42,24090,000 
 
 
 
 Whalebone 
 
 
 7,600 
 
 
 
 *This lucid method of making weigh t-for-weight instead of bulk-for-bulk 
 comparisons of strength is borrowed from R. H. Thurston's "Materials of 
 Aeronautic Engineering", a paper that was presented before the International 
 Conference on Aerial Navigation, held at Chicago In 1893, and which contains 
 much information and data hardly excelled in completeness and accuracy In 
 any more up-to-date publication. 
 
 TRANSVERSE STRENGTH OF WOOD BARSf 
 
 MATERIAL 
 
 SIZE 
 
 WEIGHT 
 
 LOAD 
 
 SUSTAINED 
 
 Ei m 
 
 i x I x 12 inches 
 I X 1 x 12 inches 
 1^x1^x12 inches 
 ItV x 1 A x 12 inches 
 1 x 1 x 12 inches 
 1 xl x 12 inches 
 ilxli x 12 inches 
 11 xU x 12 inches 
 J x J x 12 inches 
 |x| x 12 inches 
 i 9 g x ilx 12 inches 
 T"<T x i^x 12 inches 
 
 5 
 
 4 
 3 
 
 ! 
 
 3- 
 3 
 
 2J 
 2 
 2 
 
 ounces 
 ounces 
 ounces 
 ounces 
 ounces 
 ounces 
 t ounces 
 ounces 
 ounces 
 ounces 
 ounces 
 ounces 
 
 900 pounds 
 900 pounds 
 880 pounds 
 760 pounds 
 450 pounds 
 600 pounds 
 390 pounds 
 475 pounds 
 275 pounds 
 280 pounds 
 175 pounds 
 175 pounds 
 
 
 Elm 
 
 Euce 
 
 i . . 
 
 uce 
 
 j Elm .. 
 
 1 Spruce 
 
 Elm 
 
 Spruce 
 
 t Elm . 
 
 J Spruce 
 
 fThese tests were all made with the bars supported at their extreme 
 ends. $ Supported edgewise. 
 
CHAPTER TWELVE 
 
 TYPICAL AEROPLANES 
 
 The information and data contained in this 
 chapter are intended to provide the practical 
 worker with such particulars and details of suc- 
 cessful modern aeroplanes as will enable him 
 readily to reproduce and operate at least the 
 simpler machines, several of which are exceedingly 
 easy and inexpensive to build a fact that is as 
 absolutely true as it is generally unappreciated. 
 
 No attempt has been made, either in the text 
 or in the scale drawings that pertain to this chap- 
 ter, to supply slavishly accurate data concerning 
 every trifling detail of the machines considered. 
 On the contrary, there have been deliberately in- 
 troduced a number of carefully-considered changes 
 in wholly minor details, intended to reduce the 
 labor and cost of construction in directions that 
 otherwise might prove sources of difficulty to the 
 amateur experimenter. 
 
 It seems proper here to emphasize the fact that 
 neither the construction nor operation of the best 
 modern aeroplanes call for the extraordinary 
 knowledge and expertness they are popularly sup- 
 posed to demand. On the contrary, rather than 
 much knowledge the construction of an aeroplane 
 
 394 
 
IS, 
 
 u^ 
 
 
 
 ! *Li 
 
 iff 
 
 
 FIGURE 186. Side View of Wright Machine. 
 
 FIGURE 187. Three-Quarters View of Wright Machine. 
 
TYPICAL AEROPLANES 395 
 
 requires much care the most painstaking atten- 
 tion to the perfection of every last detail. As for 
 the matter of operation, with many of the most 
 successful machines this is absolutely easier than 
 learning to ride a bicycle in so far as mere manual 
 skill is concerned, though the need of a cool head 
 and reasonable daring is not to be escaped. 
 
 By far the most essential points in aeroplane 
 building are provision of the correct wing curva- 
 tures and the proper proportioning, arrangement, 
 and control of the different sustaining, stabilizing, 
 and balancing surfaces with due attention, of 
 course, to structural strength and security. The 
 latter, however, may be quite safely left to any- 
 one possessed of reasonable mechanical ability to 
 carry out largely in accordance with individual 
 ideas and facilities, which with the exercise of rea- 
 sonable judgment are as likely to prove practical 
 and satisfactory in one case as in another. 
 
 The initial practise flights with a new or un- 
 familiar machine should never under any circum- 
 stances be undertaken in the slightest wind, or 
 elsewhere than over an unobstructed and very uni- 
 form surface of great extent, permitting close-to- 
 the-ground flight while avoiding the dangers of 
 running into terrestrial obstacles. 
 
 It should be clearly understood, too, to the ex- 
 tent that the reader may undertake the building 
 and operation of such constructions as may be pro- 
 tected by patents, that the law only permits this 
 when such reproduction is done not merely for 
 exclusively personal use (which many persons 
 
396 VEHICLES OF THE AIR 
 
 imagine is allowed) but solely and only for the 
 purpose of effecting improvement. 
 
 ANTOINETTE MONOPLANES 
 
 These highly successful machines, which in 
 their latest forms have evolved to the construction 
 illustrated in Figure 212, which shows the dimen- 
 sions and outlines of the " Antoinette VII", with 
 which Hubert Latham made his second attempt to 
 cross the English Channel, are much too compli- 
 cated for the amateur to build, as must be very 
 evident from the details of the Antoinette wing 
 structures shown in Figures 71, 72, and 101. 
 
 BLEEIOT MONOPLANES 
 
 These remarkable machines are at present built 
 in three principal models, of which the single pas- 
 senger, the "Bleriot XI", is much the most inter- 
 esting, it being simple and inexpensive to build, 
 light in weight and very portable, and a wonder- 
 fully safe and speedy flier, as is sufficiently attested 
 in the records it holds. In reproducing this 
 machine, it will be sufficient to follow substantially 
 the details given in Figure 197. The exact curva- 
 tures of the wing sections are not to be had in 
 quite exact figures, but the curves shown in this 
 scale drawing are close enough approximations to 
 afford satisfactory operation when enlarged to the 
 actual size. Most of the smaller parts of the mono- 
 plane the clips for assembling the framing, the 
 turnbuckles, the wheels and tires, the motors, and 
 the aluminum-alloy frame braces and strut sockets 
 
-hfr-N 
 
 KM * 
 
398 
 
 VEHICLES OF THE AIR 
 
 are to be purchased at very reasonable prices in 
 Europe. In addition to following Figure 197, for 
 a clear idea of minor parts a study should be made 
 of Figures 1, 73, 112, 118, 157, 164, 171, 199, 200, 
 201, 245, 246, 247, and 249. The weight should be 
 kept down to about 440 pounds for the bare 
 machine, and must not exceed 700 pounds with 
 fuel and passenger. The weight of the 22 horse- 
 power Anzani motor with which one of these ma- 
 chines was flown across the English Channel was 
 144 pounds, that of the wheeled alighting gear was 
 65 pounds, and of the frame, or fuselage, about 60 
 pounds. 
 
 CHANUTE GLIDEES 
 
 These gliders, with which such remarkable 
 work was done at Dune Park, Indiana, in 
 
 Figure 237. Chanute Biplane Glider. 
 
TYPICAL AEROPLANES 399 
 
 1895, were built in a considerable variety of 
 forms, that from which the Wright biplane was 
 developed being illustrated in Figure 237, while 
 the essential details of an improved construction 
 are shown in Figure 261. Though very cheap to 
 build and quite safe and practical for very cau- 
 tious experimenting, these early gliders fail to 
 embody so many superior features used in present 
 machines that it seems hardly advisable for the 
 amateur of today to consider them otherwise than 
 of purely historical interest. 
 
 CODY BIPLANE 
 
 This biplane, which weighs 2,000 pounds and is 
 the largest that has ever flown, is patterned rather 
 closely after the lines of the Wright machines, the 
 chief differences being the greater size and the 
 peculiar system of controlling lateral balance by 
 manipulating the forward elevator elements as 
 ailerons. Interesting and for the most part excel- 
 lent features of design are the arching of both of 
 the main surfaces, the flattening of the main 
 sustaining surfaces towards their ends, and the 
 extensive use of bamboo members, wrapped 
 between joints to prevent splitting. 
 
 Various systems of arranging the main surfaces 
 have been experimented with, by simply changing 
 the lengths of the vertical spars and adjusting the 
 trussing. The latest and most successful is that 
 suggested by the dotted lines in the front view, 
 Figure 202, in which it is seen that the 9-foot sepa- 
 ration of the surfaces at their centers is decreased 
 
400 VEHICLES OF THE AIR 
 
 to 8 feet at their ends, with the lower surface 
 arched about 6 inches and the upper 18 inches. 
 
 Further details regarding the structural details 
 of this machine will be found in Figure 202. 
 
 CUETISS BIPLANE 
 
 The main structure of this machine is a central 
 body portion EEK, Figure 228 (also see Figure 
 229), mounted upon three 20x2%-inch pneumatic- 
 tired wheels, and built of bamboo and Oregon 
 spruce. 
 
 The main surfaces are slightly curved, as shown 
 at S, and the chord measurement of the surfaces is 
 41/2 feet, with a span of 29 feet. There are 24 
 light laminated spruce ribs in each main surface, 
 and the fabric, rubber-faced silk, is wrapped 
 around the front crossbars of the wing frames and 
 kept taut at their rear edges by wire edgings 
 drawn tight over each rib end. The silk is applied 
 in laced-on panels a 6-foot center section and four 
 5-foot sections to each surface, with 18-inch 
 extensions at the ends of the wings. 
 
 The horizontal rudder I, with two surfaces, 
 each 2x6 feet and spaced 2 feet apart by five struts 
 along each edge, is placed 10 feet in front of the 
 main surfaces, while a single horizontal surface of 
 the same size is carried 10 feet to the rear to serve 
 as a steadying tail. The vertical rudder is 
 23/2x2M> feet. A fixed triangular steadying sur- 
 face x is placed at the center of this rudder. 
 
 Lateral balance is provided by the two ailerons 
 MM, each 2x6 feet, located half-way between the 
 

 FIGURE 189. Paul Tissandier Seated in Wright Biplane. 
 
 ' 
 
 \ * 
 
 FIGURE 190. Count de Lambert in Wright Biplane. 
 
 FIGURE 191. Wilbur Wright Instructing a Pupil. 
 

 III 
 
402 VEHICLES OF THE AIR 
 
 ends of the main planes and with their centers 
 aligned with the two end pairs of main-surface 
 struts, so that these balancing planes extend far- 
 ther to the sides than any other parts of the 
 machine. 
 
 As the machine stands on the ground the angle 
 of incidence of the chords is about 6. This is said 
 to be reduced when the machine is in flight. 
 
 The main surfaces are separated 4% feet by 
 six spruce struts along each edge, one for every 
 four spaces between ribs except at the center and 
 ends, the latter overhanging the end struts 18 
 inches and the center space having five rib-open- 
 ings between struts. All rectangles thus formed 
 are rigidly braced by stranded diagonal wires. 
 Prom the top and bottom of each of the four struts 
 at the corners of the center section, two similar 
 12-foot bamboo members are carried forward and 
 rearward to junctions with the sides of the front 
 and rear elevators, which are pivoted at these junc- 
 tion points. The ends of the front elevator are of 
 crossed steel tubes, with the pivotal points well 
 forward, under the center of pressure. 
 
 Prom about the centers of the rear pair of extra 
 struts in the middle of the main surfaces, two of 
 the heaviest spruce members (about 1*4x2 inches) 
 used in the machine extend downwardly and for- 
 wardly to a junction with the axle ends of the front 
 wheel of the running gear about 5 feet in front 
 of the front edge of the main surfaces. These 
 members are attached to the front pair of extra 
 struts, immediately in front of which the seat is 
 
FIGURE 192. Details of Wright Biplane Strut Connections. Note the manner in which 
 the struts c are fastened in U-shaped metal sockets at the center of the machine and hooked 
 to the wing bars a in the flexible wing ends. The plate d indicates the point at which the 
 wings unship for convenience in shipping and storing, while 6 & are the double rib members. 
 
 FIGURE 193. The Wright Runner Construction. The solid ribs yz serve to support the 
 motor, operator, etc. The other ribs && are so built up as to enclose the wing bars aa between 
 the double surfacing of fabric. The attachment of the forward curved members of the runners 
 at f is clearly apparent upon close examination. 
 
 FIGURE 194. Side View of Wright Runner Construction, 
 same as in the preceding. 
 
 The reference lettering is the 
 
TYPICAL AEROPLANES 403 
 
 placed for the operator, with a foot rest in front 
 of the seat. 
 
 The front wheel of the running gear is carried 
 in an ordinary bicycle fork, and is additionally 
 braced by a vertical member from this fork to 
 cross members between the four bamboo braces of 
 the front-elevator support. These two cross mem- 
 bers are in turn braced by vertical side bars 
 between their ends, tying together each side pair 
 of bamboo elevator braces. Two struts also run, 
 one from each side of the front wheel, forward to 
 a cross tie about 18 inches from the juncture of 
 each side pair of elevator braces. 
 
 The rear wiieels of the running gear are located 
 under the rear center pair of main frame struts, 
 in bicycle forks, and are stayed laterally and fore- 
 and-aft chiefly by framing of light steel tubes. 
 Prom the center of this steel frame a wooden bar 
 runs forward to the front wheel. Light wooden 
 runners, to protect the lower wing ends in landing, 
 are placed under the end pairs of struts. All parts 
 of the framing are liberally wire-braced. 
 
 Control of height is by a bamboo steering pillar 
 running from the steering wheel to the center front 
 strut of the front elevator, this strut rising above 
 the upper elevator surface to hold the front edge 
 of the triangular steadying surface, previously 
 mentioned. Pushing or pulling on the steering 
 wheel causes the machine to descend or ascend. 
 Turning the steering wheel operates the vertical 
 rear rudder through a wire cable running in a 
 groove in the rim of the wheel. The balancing 
 
404 VEHICLES OF THE AIR 
 
 planes are worked by swinging the body sidewise 
 in a steel crotch, the side of the planes lifted being 
 the side swung away from. 
 
 A spoon brake applied by a bamboo plunger to 
 the tire of the front wheel permits quick stopping 
 after alighting and holds the machine for the start. 
 
 FAEMAN BIPLANE 
 
 This biplane shown in Figures 81, 143, 207, 
 and 208 in a general way copies the earlier Voisin 
 constructions (see Figures 174, 204, and 205), from 
 which it was developed by the addition of the 
 hinged ailerons a a a, Figure 142, the removal of 
 the vertical panel surfaces, and the combination 
 of runners with the wheeled alighting gear. 
 
 LANGLEY MACHINE 
 
 In the opinion of many who should know, the 
 large Langley double monoplane, which plunged 
 in the Potomac because of defects in its starting 
 gear after similar models had proved thoroughly 
 operative, is quite capable of flying in calm 
 weather with probably some doubt as to its 
 ability to land otherwise than on water without a 
 smashup. Its details were simply elaborations of 
 those shown in Figure 70, but its reconstruction 
 in the present era of better proved fliers could 
 possess only technical, rather than practical 
 interest. 
 
 LILIENTHAL'S MACHINES 
 
 These machines, like those of Chanute, Lang- 
 ley, Pilcher, and Maxim, are now properly to be 
 
FIGURE 195. Rudder Frame of Wright Machine. 
 
 FIGURE 196. Elevator Frame of Wright Machine. 
 
TYPICAL AEROPLANES 
 
 405 
 
 FIGURE 230. Early Lilienthal 
 Monoplane Glider. 
 
 regarded as successful only from the standpoint of 
 past rather than of present achievement, so, 
 though they flew, and under certain conditions 
 flew moderately well, 
 they cannot be said to 
 possess any features 
 that would warrant fur- 
 ther experiment with 
 them The earlier Lilienthal gliders were mono- 
 planes, illustrated in Figures 230 and 231, and 
 
 with details given in 
 Figure 263, but the 
 final construction was 
 the biplane sketched in 
 Figure 232. This can- 
 not be said to have 
 proved any great merit 
 up to the time of the accident that resulted from it, 
 though it was the final form to which Lilienthal 
 had evolved his ideas. 
 
 FIGURE 231. Lilienthal Monoplane 
 Glider. 
 
 FIGURE 232. Lillenthal's Biplane. 
 MAXIM MULTIPLANE 
 
 This great machine, the heaviest ever built, 
 proved quite capable of lifting its weight, but there 
 is little reason now to suppose, in the light of more 
 
406 
 
 VEHICLES OF THE AIR 
 
 FIGURE 235. Maxim Multiplane. Weight 8,000 pounds. Propelled by 
 363-horsepower steam engine. Span 126 feet, area 4,000 square feet, cost 
 $200,000. 
 
 recent knowledge, that it could without radical 
 modification have accomplished controlled and 
 continued flight. Its general appearance is very 
 well suggested in Figures 235 and 236. 
 
 FIGURE 236. Maxim Multiplane. When run on rails at Baldwyn's Park, 
 England, July 31, 1894, at 36 miles an hour, this machine lifted so much 
 more than its weight that it broke a set of rails provided to hold it down 
 and thus demolished itself. 
 
 MONTGOMEEY MACHINE 
 
 This glider is of such absolutely proved capa- 
 bilities, and is designed upon such sound prin- 
 
FIGURE 197. Scale Drawings of Bleriot Monoplane Number XI. Besides 
 being one of the most successful of present-clay fliers, this machine is a com- 
 paratively simple and inexpensive one to build. The main element is the fusellage, 
 or frame, A, which is simply built of four main members of of poplar, separated 
 by transverse bars spaced at regular intervals, and the whole rigidly trussed by 
 diagonal wires h crossing all rectangles. This frame is of largest size at the 
 front and in its vertical aspect tapers to a thin edge at the rear, but in its side 
 aspect the taper is not so great. The wings D D are double surfaced, with the 
 wing bars inside the double ribs, and the ends are rounded more from the 
 rear than from the front. They are demountably attached to the sides of the 
 body, which in its forward portion is covered with fabric but at the rear is left 
 open. The front edges of the wings are rigidly stayed by flat steel tapes w w w w 
 and xxx x (not wires) to the overhead framing H and to the chassis. The rear 
 edges can be differentially warped by pulling on the wires 1 1 1 1, which are 
 attached to the pedestal G and operated by the wheel N. The rear rudder F 
 effects horizontal steering, and is controlled by the pedal P. Vertical steering 
 is by the rocking tips K K of the rear surface E. The starting and alighting 
 gear consists primarily of the two fixed wheels B B, which swing on the links a a, 
 against the rods C C. They are strained down by elastic springs, which absorb 
 the shock in landing, but their downward movement is limited by leather straps. 
 It is to be noted, in the construction of the chassis, that the front of the frame A 
 rests upon the two rods N N, which are crossed at top and bottom, respectively, 
 by the bars e m, these bars carrying at their ends the vertical wooden columns on 
 which the sleeves at the tops of fe Z> slide. The single rear caster wheel is mounted 
 to absorb shock by the action of a device closely resembling that employed for 
 the front wheels. Propulsion is by the single wooden tractor screw J, 6J feet in 
 diameter, arid mounted directly on the engine shaft. The engine shown is the 
 three-cylinder, V-shaped, air-cooled Anzani, of 22-25 horsepower, with which the 
 crossing of the English Channel was accomplished, but many other motors have 
 been successfully used on the same machines. The pilot's seat at M is com- 
 fortably located in a small cockpit, as shown. In the side view, the machine is 
 shown in its flying attitude, its ground attitude being indicated by the dotted 
 lines. The machine operates very successfully as a road vehicle with the wings 
 dismounted and tied against the sides of the frame, steering being them effected 
 by the rudder F, the surfaces E K K keeping the rear end off the ground. Dimen- 
 sions are given in feet and fractions of feet. 
 
 "A" 
 
D 
 
 
 ; 
 j^_u. : 
 
 
 ffjfc" 
 
 flr-"^ 
 
 _ J 
 
 C : _ "_:._ - .. 
 
 
 
 l-%;v.'-v .- : . ' 
 i^_ ___' __ 
 
 
 ^ 
 
 
 
 ^* - 
 
 
 r- : .j 
 
 
 ^ 
 
 '.'"'^ 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 7 
 
 
 
 / 
 
 
 X 
 
 
 V 
 
TYPICAL AEROPLANES 407 
 
 ciples, that with substantial construction and 
 proper precautions it is probably one of the safest 
 of all machines with which to practise flying. The 
 drawing and details given in Figure 225 do not 
 conform in certain minor measurements, propor- 
 tions, and details to the machines used in the Cali- 
 fornia flights, but have been compiled from a copy 
 rather hurriedly built by the writer for personal 
 experiment. They are close enough, however, to 
 the description of Montgomery's own machines, 
 as illustrated in Figures 226 and 227 and in the 
 patent drawings in Figure 260, to supply a basis 
 from which the cautious student will be able to 
 secure remarkably successful flights if he will 
 develop the apparatus and his own abilities in a 
 conservative manner, preferably by practise over 
 water. This machine being a patented device, no 
 one can reproduce or use it unless prepared at 
 any time to prove that such reproduction or use is 
 solely for experimental purposes, with a view to 
 improvement. 
 
 PILCHER GLIDEES 
 
 Judged by most of the 
 results obtained, espe- 
 cially When flown Mtewise FIGURE 233. Pilcher Glider. The 
 <J "Hawk." 
 
 by towing through the air 
 
 at the end of a cord, the later Pilcher gliders, 
 sketched in Figures 233 and 234, were very safe in 
 calm weather. Even the tragedy that resulted in 
 the death of their designer was definitely due to 
 a breakage, rather than to any fault fairly ascrib- 
 able to the principle of the machines, though they 
 
408 VEHICLES OF THE AIR 
 
 lacked the stabilizing and balancing elements of 
 current constructions. 
 
 E. E. P. MONOPLANES 
 
 These machines, which have sustained more 
 weight per unit of area than any other built, and 
 on occasion have proved excellent fliers, are still 
 
 the subjects of frequent 
 modification and much ex- 
 perimenting by their de- 
 234. pnchcr Glided The signer, Robert Esnault- 
 Pelterie, besides which 
 
 they are rather difficult to build. For these reasons 
 no drawings are given of their construction, but 
 the views in Figures 119, 222, 223, and 252 have 
 been selected with the special purpose of convey- 
 ing a clear idea of their essential details. 
 
 SANTOS-DUMONT MONOPLANE 
 
 This wonderful little machine, of well-proved 
 flying capabilities, is perhaps more to be com- 
 mended than any other to the attention of those 
 who may wish to reach results at the least possible 
 expense and with a minimum of experimenting. 
 Moreover, Santos-Dumont has unselfishly refused 
 to patent any of the details on which he might have 
 secured protection, frankly desiring that the 
 widest possible use be made of his work. In addi- 
 tion to the working drawing and details in Figure 
 221, Figures 102, 116, 141, 217, 218, 219, 220, and 
 238 should be studied as examples of Santos- 
 Dumont 's experimental and final constructions. 
 
FIGURE 198. Bleriot Monoplane Number XII. 
 
 FIGURE 199. Bleriot Monoplane Number XI. 
 
 FIGURE 200. Front View of Bleriot XI. 
 
 FIGURE 201. Three-Quarters View of Bleriot XI. 
 
TYPICAL AEROPLANES 409 
 
 VOISIN BIPLANE 
 
 The Voisin biplanes are almost as simple and 
 stable as the box kites that they so closely re- 
 semble, besides which it is probably the case that 
 they constitute the least patented and the least 
 patentable of all constructions. For this reason 
 anyone who may choose to work from the draw- 
 ings and details given in Figures 206, and 172, 204, 
 and 205 can do so with the assurance of reaching 
 a successful result with a minimum conflict with 
 patent rights, 
 
 WEIGHT BIPLANE 
 
 This widely known machine is from many 
 standpoints by far the most successful of all power- 
 driven aeroplanes, especially in the hands of a 
 thorough expert in its use, besides which it is 
 quite simple and inexpensive to reproduce. The 
 Wrights, however, very positively assert the 
 broadest possible claims on its construction, and 
 at present evince a disposition to prevent the com- 
 mercial exploitation of all machines not of their 
 design or manufacture. The essential details of 
 the most modern type of Wright biplane are, how- 
 ever, given in Figures 110, 134, 161, 163, 165, and 
 166, and in Figures 185 to 196, inclusive, it being 
 supposed that the reader will use his own judg- 
 ment about avoiding possible infringement. The 
 exact wing curves of the Wright machines have 
 not been published, but it is known that in success- 
 ful models they are parabolic, with the chord very 
 long in proportion to the focal length. 
 
CHAPTER THIRTEEN 
 
 ACCESSORIES 
 
 In considering the development of aeronautical 
 mechanisms, it is evident that besides the flying 
 mechanism proper there is inevitably involved an 
 increasing number of one kind and another of 
 accessory devices, most of which will have to be 
 especially devised or adapted for the new needs. 
 
 Many of these accessories in themselves present 
 problems demanding the best efforts of the ablest 
 investigators. For example, the necessity for the 
 strongest possible lights, to penetrate great dis- 
 tances into foggy atmospheres, the need for de- 
 vices for keeping track of speeds and distances 
 traveled, and particularly to aid in the mainte- 
 nance of straight courses against tendencies to lat- 
 eral drift, are most apparent. In addition to these 
 there is the more perfectly met requirement of 
 means for indicating altitudes, temperatures, etc. 
 
 LIGHTING SYSTEMS 
 
 Naturally, in casting about for means of illumi- 
 nation and light projection suitable for application 
 to aerial vehicles, the most valuable suggestions are 
 in a majority of cases to be derived from the 
 automobile. 
 
 Thus it is found that the various types of acetyl- 
 
 410 
 
FIGURE 238. Santos-Dumont's "Demoiselle" in Flight. 
 
 FIGURE 239. Paulhan's Voisin in the Douai to Arras Flight, 
 of 12% miles, was performed on July 19, 1909, in 23 minutes. 
 
 This flight, over a distance 
 
ACCESSORIES 411 
 
 ene lighting systems oil lamps, electric lamps, 
 etc., found suitable for automobile use can be 
 more or less readily applied to the newer purpose, 
 the chief difficulty in the way of making such appli- 
 cation entirely satisfactory being the necessity for 
 even greater light-giving power with an absolutely- 
 minimized weight. 
 
 ELECTRIC LIGHTING 
 
 Electric lighting so far has not been extensively 
 applied to automobile illumination, though it is 
 rapidly increasing in vogue. 
 
 This appears to be mainly because the storage 
 battery is too decidedly heavy as a source of suf- 
 ficient amounts of current a difficulty that in its 
 present development condemns it utterly for appli- 
 cation to aeronautical vehicles while the difficulty 
 of running a dynamo from a connection with the 
 variable-speed engine that must be used for pro- 
 pelling the car, without at the same time getting 
 into most serious problems in the direction of cur- 
 rent regulation, is the other of the two great diffi- 
 culties that beset the application of electric lighting 
 to automobiles. 
 
 Advantages of Uniform Motor Speed, such as 
 seems invariably to be required in the use of any 
 aeronautical engine, go a long way to relieve the 
 electric dynamo from the shortcomings and dis- 
 abilities that it is found to possess in attempted 
 applications to automobile lighting. 
 
 Arc Lamps constitute the most concentrated 
 and efficient of all devices for utilizing electric cur- 
 
412 VEHICLES OF THE AIR 
 
 rent to produce light, though they hardly can be 
 considered the most convenient, since for their suc- 
 cessful operation the maintenance of the arc in the 
 focus of a paraboloid mirror must be secured either 
 by frequent hand-adjustment or by complicated 
 automatic adjustment. 
 
 Incandescent Lamps are far and away the most 
 convenient, simple, and reliable of all forms of 
 electric illumination, and in the modern metallic- 
 filament lamps the tantalum and particularly the 
 tungsten are remarkably efficient, some modern 
 tungsten lamps consuming little more than one 
 watt of current to the candlepower. By the expe- 
 dient of closely-coiling the filaments, the light 
 source in an incandescent lamp can be very closely 
 located in the focus of the mirror or lens, thus 
 securing a more concentrated and powerful beam 
 with less actual candlepower than is required with 
 most other types of lamps. Another advantage, in 
 providing against burned-out lamps, is that re- 
 placements are very light to carry and are readily 
 placed in the sockets. 
 
 An objection to the tungsten lamp in ordinary 
 uses is the fragility of the filament, especially in 
 lamps of high candlepower worked on high voltages 
 involving very long and fine filaments. Tungsten 
 lamps for automobile service, however, have been 
 made very substantial simply by virtue of the 
 shortness and thickness of the filaments suitable 
 for operating with the low candlepowers and from 
 the low voltages commonly used. With the dynamo 
 as a source of current, as seems the likely develop- 
 
FIGURE 202. Scale Drawings of Cody Biplane. This machine, though an excellent flier, is s 
 and cumbersome that its reproduction is hardly a task for the amateur unless a reduced CH 
 undertaken. In its general details, this biplane is very closely patterned after the Wright maj 
 with numerous differences in minor particulars. The main planes A A are double surface* 
 built-up ribs that enclose the wing bars in such manner as to avoid the possible resistances that 
 set up when these are exposed. In trussing up the wings, the best results are secured withi 
 nounced droop or arching of the surfaces, as is suggested by the dotted lines in the front view^ 
 arching is greater for the upper surface than for the lower. The end ribs are of flatter cu| 
 than those nearer the center, much as in the Montgomery glider, and to this feature doubtless i) 
 attributed the speedy flight of which this biplane is capable, in spite of its combination of gr* 
 with not extraordinarily high power. Lateral ba ance is maintained very peculiarly by dis| 
 manipulation of the rocking elevator surfaces B B, which when worked together serve merely 1| 
 up or down, but which otherwise tilt the machine to right or left. In addition to this means of 
 wing warping has been successfully applied, as also has been the use of ailerons. In fact, af 
 means have been experimented with, both independently and in various combinations. The oper?t 
 B B is by the control rods K K which move in unison with a forward or rearward swinging ; 
 steering pillar and oppositely when the wheel F is rotated. The vertical surface is simply at 
 ing surface, but the single rear rudder J is pedal controlled and serves to counteract the lag; 
 outer side of the machine in turning. Propulsion is by twin propellers E E, oppositely revolv< 
 crossed-chain driving system practically identical with tliat used by the Wrights. The cha> 
 specially built by an English chain manufacturer to provide the lateral flexibility desirable for; 
 ing the best results with crossed drive. The starting and alighting gear consists of a three-- 
 chassis DDE and the springy wooden skid I. Wing wheels C C are used at the ends of th< 
 main surfaces to protect them from damage in case of sidewise tilting in landing. Liberal 
 bamboo is made in the construction of the machine, but all bamboo spars are tightly wrapped wi 
 or wire between joints to prevent splitting. The weight of the finished machine, with fuel an 
 is over a ton. The seat for the pilot is directly behind the control wheel, with that for a pa 
 somewhat higher and further to the rear. While it is not to be recommended that the average 
 menter copy this particular aeroplane, there is no doubt but what its construction embodies ma 
 tures of interest and value that might well be applied in smaller or modified machines. Furth 
 its great size constitutes a striking example of what can be accomplished in this direction, 
 introducing elements of uncertainly or of undue fragility. Dimensions are given in feet and incl 
 
C i 
 
 v 
 
 < e' - 
 
ACCESSORIES 
 
 413 
 
 ment in aeronautics, higher voltage seems certain 
 to be desirable from most standpoints lightness, 
 efficiency, etc. which may direct the use of tung- 
 sten lamps into rather fragile types. Against this, 
 though, is the fact that in any type of flying ma- 
 chine there is no such jolting as exists in the case 
 of the automobile, the machine riding on the air 
 with almost perfect smoothness. 
 
 The Nernst Lamp, the current consumption of 
 which is about 1.5 watts to the candlepower, is 
 a sort of incandescent 
 lamp of very remark- 
 able design, in which 
 the very short and thick 
 filament is composed of 
 oxids of some of the 
 rare metals princi- 
 pally zirconium and 
 yttrium is a good con- 
 d u c t o r of electricity 
 only when heated, and is so refractory that it does 
 not require enclosure in a vacuum to permit its use 
 without burning out. 
 
 ACETYLENE 
 
 Acetylene is one of the heaviest and richest of 
 all the hydrocarbon gases, making it exceptionally 
 well adapted to the production of intensely-lumi- 
 nous flames with only small gas consumption. 
 Acetylene is most conveniently produced by the 
 action of water upon calcium-carbid, the reaction 
 turning the calcium-carbid into quicklime which 
 
 FIGUBE 240. Suggested Nernst 
 Lamp. The glower ft, at the focus 
 of the paraboloid mirror c, receives 
 current from the dynamo g, with the 
 usual balancing coil in the circuit at 
 /. The heating coil e, however, is 
 mounted on the hand-manipulated 
 arm d, so that it is shunted into the 
 circuit by the switch a when it is 
 swung up in proximity to 6. 
 
414 VEHICLES OF THE AIR 
 
 is slacked by the action of the water while the 
 carbon released from the decomposition of the 
 carbid combines with the hydrogen released by 
 the decomposition of the water to produce the 
 acetylene. 
 
 Storage Tanks for transporting acetylene in 
 manufactured form, dissolved under pressure in 
 acetone, are widely used for automobile lighting 
 and are exceptionally safe and convenient. Such 
 tanks containing thirty cubic feet of gas are com- 
 monly made cylindrical, about 6 inches in diameter 
 and 16 inches long, and weigh about 30 pounds. 
 It is somewhat remarkable that such a tank, under 
 the ordinary pressure of something like 225 
 pounds to the square inch, and first filled with 
 asbestos or other absorbent material and enough 
 liquid acetone to fill the tank full, will contain con- 
 siderably more acetylene, dissolved in the acetone 
 (like carbonic-acid gas in the water of soda-foun- 
 tain beverages), than can be placed in the same 
 tank empty. Also, while the gas compressed into 
 the empty tank would be a very dangerous explo- 
 sive, its storage in the acetone seems to make it 
 perfectly safe, it automatically evaporating as 
 required for use only as the pressure is released. 
 
 Acetylene Generators have the advantage over 
 acetylene storage tanks that they are rather lighter 
 for a given gas production than a tank for the 
 storage of an equivalent amount of gas. There are 
 two fundamental systems of acetylene generation 
 one involving the "carbid-feed" generator, and 
 the other the " water-feed." By all means the 
 
I 
 
 FIGURE 203. Latest Model Voisin Biplane With tractor screw and no front elevator. 
 
 FIGURE 204.- Three-Quarters Rear View of Voisin Biplane. 
 
 FIGURE 205. Three-Quarters Front View of Voisin Biplane. 
 
ACCESSORIES 415 
 
 most successful type of automobile generator car- 
 ries the carbid in a wire basket in the upper part 
 of the container, with water above the basket and 
 considerable receiving space below it for the recep- 
 tion of the slacked carbid which is jarred out be- 
 tween the wires. Such generators operate best 
 when subjected to considerable shaking, making 
 them even less available for aeronautical use than 
 for automobile use, and are very prone to heat up, 
 with a consequent production of tarry gas and 
 much obstruction of piping by gummy deposits and 
 condensed moisture. 
 
 Acetylene Burners require provision for admix- 
 ture of the acetylene with a great excess of air, 
 since otherwise a blue-flame or imperfect combus- 
 tion results, but given sufficient air admixture com- 
 bustion is attended with the production of an 
 intensely luminous flame of great brilliancy, and 
 of a quality more nearly approaching sunlight 
 than any other artificial illuminant. The most 
 widely used acetylene burners are of double- jet 
 types, arranged to impinge two round jets upon 
 each other at right angles the two flattening at 
 the point of juncture into a wide, flat flame. 
 
 Within the last year or so a new type of acet- 
 ylene burner has come into use in which only a 
 single flat opening is used, in a general way rather 
 similar to the ordinary straight slit in common 
 illuminating gas-burners but provided with several 
 openings for the inspiration and admixture of the 
 necessary air required, without the complication 
 and objections that apply to the common type. 
 
416 VEHICLES OF THE AIR 
 
 OXYGEN SYSTEMS 
 
 One of the oldest forms of very-concentrated 
 high-power illumination is the calcium light, in 
 which a small button of lime is heated to incan- 
 descence by the exceedingly hot blue flame from 
 an oxy-hydrogen blowpipe. This particular form, 
 which is still much used for stereopticon projec- 
 tion, especially where electricity is not available, 
 requires to be modified to present any possibility of 
 use from aerial-vehicle standpoints. 
 
 With Hydrogen it of course is necessary to 
 carry a tank of hydrogen gas under pressure, as 
 well as the necessary oxygen stored in the same 
 manner. 
 
 With Gasoline, however, used from the regular 
 supply for the engine, only an oxygen tank being 
 carried, there have been developed quite satisfac- 
 tory automobile headlights in which a jet of vapor- 
 ized gasoline is burned in combination with a jet 
 of oxygen, the regulation calcium button being used 
 to produce the white and powerful light by its 
 incandescence. 
 
 With Acetylene and oxygen it is possible to 
 secure a blue flame stated by some authorities to 
 be even hotter than the oxy-hydrogen flame, and 
 therefore capable of producing an even more bril- 
 liant light in combination with the lime. 
 
 INCANDESCENT MANTLES 
 
 Incandescent mantles kept hot by a blue flame 
 from a more or less modified form of Bunsen 
 burner have within recent years become one of the 
 

 
FIGURE 206. Scale Drawings of Farman 's Voisin. The main planes 
 A A of this machine, which is of the characteristic Voisin construction, are 
 double surfaced, over built-up ribs enclosing the wing bars. Lateral equi- 
 librium is maintained wholly by the automatic action of the vertical panels 
 between the ends of the main surfaces and those of the tail J. Horizontal 
 steering is effected by the vertical rudder K, operated by turning the wheel 
 H, but the machine can turn only in very wide curves. Vertical steering is 
 by the front elevator, the two elements of which, F F, can be rocked only in 
 unison by pushing or pulling on the wheel H, which connects with them 
 through the hinged joint G. M is simply a forwardly extended framework, 
 or prow, to carry F F and brace the alighting gear C C D D. This alighting 
 gear consists of the two wheels C C rigidly mounted in the framework D D, 
 which under shock rises as a unit against the springs E E. Two small caster 
 wheels at N serve to support the tail J, which is merely a stabilizing element. 
 An eight-cylinder, water-cooled, V-shaped Antoinette motor of 50 horsepower 
 furnished the power in the particular machine described, in which the 74- 
 foot single propeller was mounted directly upon the engine crankshaft, but 
 many different engines have been used in different Voisin machines, and 
 in at least one instance flights have been accomplished with a geared-down 
 propeller. The fuel tank is shown at 0, the radiator at P, and the pilot's 
 seat at /. Weights of different elements of a recent Voisin machine are as 
 follows: Main surfaces, 180 pounds; chassis, 250 pounds; tail framing, 40 
 pounds; tail surfaces, 55 pounds; tail wheels, 13 pounds; vertical rudder, 
 10 pounds; elevator, 32 pounds; engine, 320 pounds; radiator and water, 
 80 pounds; pilot, 170 pounds a total of 1,150 pounds. The area of the 
 main surfaces is 445 square feet; of the elevator, 45 square feet; and of 
 the vertical rudder, 164 square feet. All dimensions are given in inches. For 
 further details of the Voisin machines reference should be had to Figure 
 88, showing the frame of the newest biplane of this make, from which the 
 forward elevator is eliminated; Figure 142, showing Farman 's modifica- 
 tion of the Voisin into a triplane; Figure 168, showing a machine of this 
 type rising from the ground; Figure 172, picturing the Voisin alighting 
 gear; Figure 203, showing the most recent model of this machine; and 
 Figures 204 and 205, giving characteristic views of recent Voisins. 
 
|^r 
 
 A 
 
 TV 
 
 _ -go ---> 
 
ACCESSORIES 417 
 
 commonest of all means of illuminating buildings, 
 streets, etc., and are in their best forms very effec- 
 tive, durable, and of sufficiently-concentrated in- 
 tensity to permit of their use with reflectors. 
 
 Latterly the incandescent mantle has been very 
 successfully applied to the illumination of railway 
 cark, in which the jarring unquestionably is much 
 greater than in aerial vehicles. Mantles for this 
 purpose usually are made very small, of the in- 
 verted type, and, if necessary, as hard and almost 
 as strong as porcelain. 
 
 With Gas, ordinary illuminating gas is prefer- 
 able for ordinary use, chiefly because of its cheap- 
 ness, but in railway cars the richer and purer 
 hydrocarbons such as are supplied by the Pintsch 
 system, in which acetylene is used in combination 
 with other gases, are found most satisfactory. 
 
 With Liquid Fuels incandescent mantles can be 
 operated very successfully, the best fuels being 
 gasoline, alcohol, and kerosene, in the order named. 
 
 OIL LAMPS 
 
 That oil lamps are not without points of su- 
 periority over many of the most scientific and 
 highly-developed methods of light production is 
 rather evident from the fact that this in many 
 ways primitive system, for such important services 
 as railway switch lamps, signals, cars, lighthouses, 
 etc., has been found more satisfactory than any- 
 thing more modern. 
 
 Sperm Oil, with or without modifying admix- 
 tures, possesses certain points of superiority over 
 
418 
 
 VEHICLES OF THE AIR 
 
 kerosene and other petroleum oils, for which rea- 
 son it is much used in lighthouses, signal lamps, 
 and for other purposes in which a high degree of 
 reliability and cleanliness is sought. 
 
 Kerosene is superior to most other oils in its 
 calorific value for direct combustion by the use of 
 a wick, besides which it is universally available. 
 
 EEFLECTOES 
 
 Since the light from most ordinary sources of 
 illumination is more or less evenly cast in every 
 
 direction, its projec- 
 tion in a single direc- 
 tion, as is usually re- 
 quired for vehicle use, 
 and as must be espe- 
 cially the case for 
 aerial vehicles, re- 
 quires the use of a re- 
 fracting surface de- 
 ZITZZmrjmi signed to collect and 
 ^GURB 24i. Lens Mirror, show- gather all the radiating 
 
 Ing how the light from the focus is t j. i 
 
 refracted by the glass and reflected raVS aS COmpletelV aS 
 by its mirror backing into a beam of 
 
 parallel rays. possible into a compact 
 
 beam of non-divergent parallel rays. In automo- 
 bile lamps the so-called "lens mirrors" are chiefly 
 used, being composed of glass lenses, parabolically 
 curved in their sections and their rear surfaces 
 silvered with a reflecting coating. Such mirrors 
 naturally possess an immunity from tarnish, par- 
 ticularly with open flames, that is not possessed by 
 metal reflectors. A typical lens mirror is shown in 
 
 
FIGURE 207. Side View of Farman Biplane. This machine, which holds the world's 
 distance and duration records, is particularly interesting because of the use of the wheels g in 
 combination with the runners f in the alighting gear. 
 
 FIGURE 208. Three-Quarters View of Farman Biplane. In both of the above illustrations, 
 
 the fixed wheels g g and the runners f f constitute the main starting and alighting gear, while 
 the small caster wheels u u support the tail. The elevator is at h and the ailerons at a a a a. 
 
ACCESSORIES 
 
 419 
 
 Figure 241. Metallic 
 reflectors, however, in 
 deep paraboloid form, of 
 the locomotive-reflector 
 type, intercept and re- 
 flect in a desired direc- 
 tion a greater quantity 
 of the light than any 
 other type, especially 
 if a plano-convex lens, 
 Figure 242, is placed in 
 front of the flame to 
 gather the cone of rays 
 that would pass out the 
 end of the paraboloid. 
 
 ~ - \"T^^''^ NN \ ^ / 
 
 " ~ X/'/Vl ji . \ \ \ r 
 
 FIGURE 242. Locomotive Head- 
 light. All light rays not intercepted 
 and thrown forward in a parallel 
 beam by the paraboloid metal re- 
 flector are refracted by the plano- 
 convex lens in front of the light 
 source, the portion of the metal re- 
 flector behind this lens being made 
 spherical so as to return the rays it 
 receives back through the focus to 
 the lens. 
 
 ARRANGEMENT OF LIGHTS 
 
 With all land and water vehicles, standard sys- 
 tems of lighting arrangements are established by 
 custom and often by law. For example, all the 
 world over, a modern automobile carries two front 
 headlights (usually acetylene), often in conjunc- 
 tion with two oil or other side lamps showing a 
 beam ahead as well as a less amount of light at the 
 side, and a single red tail lamp. A single, powerful 
 searchlight or projector, mounted high on the cen- 
 ter of the dashboard, is often added for rough 
 cross-country travel. For water craft the most 
 usual requirement is that of a red light showing 
 forward and to the port (left) side with a green 
 light forward and to starboard (right), though 
 various arrangements of masthead lights, stern 
 
420 VEHICLES OF THE AIR 
 
 lights, and not infrequently powerful searchlights 
 shown forward, are in extensive use. 
 
 In case of the really great development and 
 multiplication of aerial traffic which many believe 
 to be impending, there might be a further necessity 
 for distinguishing between the lights of different 
 air craft by characteristic arrangements of lights 
 as is done in the case of ocean liners. 
 
 SPEED AND DISTANCE MEASUREMENTS 
 
 One of the greatest problems in aerial naviga- 
 tion is certain to be the correct or even approxi- 
 mately correct estimation of speed and distance. 
 To begin with there is the sufficient difficulty of 
 constructing any highly-accurate device for ex- 
 actly registering the speed at which the air passes 
 a given point, or, what amounts to the same 
 thing, measuring the progress of any given point 
 through the air. But in addition to this question 
 there is the much greater one of allowing for the 
 drift of the vehicle with the whole body of the 
 atmosphere across the surface below a drift that 
 can add to or subtract from the speed of the ve- 
 hicle over the earth's surface, or that can produce 
 leeway drift far in excess of the most ever encoun- 
 tered in water navigation. 
 
 ANEMOMETERS 
 
 Anemometers, for the estimation of speeds 
 through the air, will doubtless closely resemble the 
 very valuable and satisfactory devices that are 
 widely used by weather-bureau and meteorological 
 
FIGURE 209. Side View of Maurice Farman's Biplane. This machine resembles both the 
 Voisin and the Farman machines the former in its running gear and the latter in the absence 
 of the vertical panels. 
 
 FIGURE 210. Front View of Mauiice Farman's Biplane. 
 
 FIGURE 211. Farman's Modified Voisin. 
 surface, making the machine a triplane. 
 
 Note the ailerons at a a a, and the added upper 
 
ACCESSORIES 
 
 421 
 
 stations for re- 
 cording wind 
 velocities. The 
 commonest form is 
 the four-arm type 
 illustrated in Fig- 
 ure 243, with hemi- 
 spherical cups at 
 the end of each 
 arm, the greater 
 resistance opposed 
 b y the concave 
 sides of these cups 
 over that opposed 
 by the convex 
 
 
 
 P All SI TID 1 
 
 CdUblllg 
 
 i-n -fh 
 in lii 
 
 , , . ,- , 
 
 rotation tnat 
 
 ClOSelV a~D- 
 
 proximates varia- 
 
 tion in the movement of the air or through the 
 air. Another common form of anemometer is that 
 in which a small windmill-like fan is revolved by 
 the passage of the air through its vanes. This 
 type always must be faced to the wind. 
 
 Either of the types of anemometer described 
 can be connected up to ordinary speed-indicating 
 or revolution-counting devices, as pictured in 
 Figure 243. 
 
 MICELLANEOUS 
 
 Another possible method of keeping track of 
 distance traveled through the air is simply by a 
 
 P 
 OI 
 
 FIGURE 243. Anemometer Speed and Dis- 
 tance Recorder. The cups, by the greater re- 
 sistance of their concave over their convex 
 surfaces, cause the vertical shaft to revolve 
 at a rate proportionate to the movement through 
 tha air. The speed and total number of revo- 
 lutions are shown in miles per hour and miles 
 traveled, by the automobile speed indicator 
 an< * tne d meter at the base of the shaft. 
 
422 VEHICLES OF TEE AIR 
 
 revolution counter or a speed indicator, or both, 
 driven from the propeller shaft. An aerial pro- 
 peller of good design gives a very uniform slip 
 from its theoretical rate of pitch progress (see 
 Pages 239 and 244), for which reason each revo- 
 lution of the propeller means a quite definite dis- 
 tance moved through the air. So, with a sufficient 
 amount of preliminary experiment to determine 
 the average amount of such movement with a given 
 number of revolutions, it should be possible to 
 calibrate a speed indicator or revolution counter 
 to register from the propeller turns a closely accu- 
 rate indication of the speed and the amount of 
 travel. Something of this sort is very commonly 
 done in the navigation of steam vessels, the engi- 
 neers of which invariably place greater reliance 
 on the record of propeller revolutions than they 
 do upon any other available means of determining 
 speed or distance. 
 
 COMPASS 
 
 The magnetic compass, the use of which is con- 
 temporaneous with almost the earliest history of 
 navigation, though its really scientific application 
 is more due to the modern mariner, will undoubt- 
 edly serve a purpose in the aerial craft of the 
 future, though in its application to these there are 
 not to be overlooked some most serious difficulties. 
 
 The particular shortcoming of the compass as 
 a useful adjunct to aerial navigation is that 
 while it can be depended upon to show the different 
 directions with absolute or approximate accuracy, 
 it affords little assurance that the vehicle is really 
 
FIGURE 213. Three-Quarters View of Antoinette III. 
 
 FIGURE 214. Rear View of Antoinette V. In this view the ailerons a a and the bal- 
 ancing rollers & 6 are well shown. 
 
 FIGURE 215. Front View of Antoinette VII. 
 
 FIGURE 216. Rear View of Antoinette VII. This is the machine with which Latham 
 flew 20 miles in his second attempt to cross the English Channel. Ailerons are discarded in 
 favor of rocking the whole wing, and the alighting- gear is reduced to tho wheels g g g and u. 
 
ACCESSORIES 423 
 
 progressing in any given direction, even though 
 it be kept headed in this direction and continuously 
 driven at full speed. This is because in addition 
 to the actual movement through the air there also 
 must be considered the movement of the air itself 
 a movement that will be of evident effect if the 
 ground is in sight, but which at night or over water 
 can hardly disclose itself even though it may be 
 causing a lateral or angular drift, or even a direct 
 movement backwards, at greater speed than the 
 air speed of the vehicle. At the time this is writ- 
 ten the most interesting case in which this effect 
 has been observed occurred in Bleriot's flight 
 across the English Channel, in the course of which, 
 during a very few minutes when the land on both 
 sides was out of sight because of fog, several miles 
 leeway were made in spite of a supposed proper 
 direction of the machine, involving subsequent 
 coasting along the English shore to make a landing 
 at the point for which a supposedly straight course 
 had been steered at the outset (see Figure 265). 
 
 FIXED-DIAL COMPASSES 
 
 Compasses in which the dial is fixed, with the 
 needle moving over it, are commonly used for sur- 
 veying because of certain points of convenience 
 that they possess for this purpose. They also are 
 used, though for this purpose they are less suit- 
 able, by explorers and others in going over land. 
 
 FLOATING DIAL COMPASSES 
 
 Compasses in which the dial is fastened to the 
 needle, which is attached with its points in registry 
 
424 VEHICLES OF THE AIR 
 
 with the north and south marks on the dial, and the 
 whole so mounted as to turn very lightly usually 
 by floating in a liquid constitute the common form 
 of mariner's compass. They have the advantage 
 of pointing not only the north and south, but the 
 other cardinal and intermediate directions in such 
 a way that any given direction can be readily seen 
 at a glance, without revolving the case. 
 
 BAROMETERS 
 
 A barometer carried on an aerial vehicle serves 
 two purposes, that of indicating altitude and that 
 of forecasting weather changes. In either case 
 the barometer is simply a pressure gage, indicating 
 the atmospheric pressure at any given time. 
 
 MEECUEIAL BAEOMETEES 
 
 Perhaps the most reliable type of barometer is 
 that in which the air pressure is balanced against 
 that of a column of mercury, the weight of this 
 liquid being so great that a thirty-inch column of 
 it is sufficient to afford a pressure of 14.7 pounds 
 to the square inch balancing the entire pressure 
 of the atmosphere on the given area at sea level. 
 
 ANEEOID BAEOMETEES 
 
 In aneroid barometers the air pressure is indi- 
 cated by the action of the pressure against the thin 
 metal sides of one or more flat vacuum chambers, 
 of thin, elastic, metal disks, between which springs 
 are placed to resist the pressure. A simple multi- 
 plying device converts the very slight movement 
 
FIGURE 217. Side View of Santos-Dumont's Belt-Driven Monoplane. 
 
 FIGURE 218. Front View of Santos-Dumont's Belt-Driven Monoplane. 
 
 FIGURE 219. Side View of Santos-Dumont's "Demoiselle. 
 
 FIGURE 220. Front View of Santos-Dumont's "Demoiselle." This machine, which weighs 
 less and costs less than many motorcycles, is the smallest machine that has successfully flown. 
 
ACCESSORIES 425 
 
 of the vacuum-cell walls into the more ample move- 
 ment of a hand around a circular dial. 
 
 WIND VANES 
 
 The mounting of a small wind vane on an aerial 
 vehicle is useful not in that it can afford any indi- 
 cation of lateral drift of the whole atmosphere, but 
 to the extent that it will show leeway made from 
 a straight course through the effect of unsymmetri- 
 cal forward resistances such as can arise in the 
 manipulation or adjustment of balancing and steer- 
 ing devices. To be of the highest utility such a 
 wind vane should indicate not only lateral but also 
 vertical deviation, for which reason a ball or gimbal 
 mounting would seem to be the proper thing. 
 
 In the Wright brothers' experiments they often 
 use a short strip of tape or cloth, perhaps a half- 
 inch wide and a couple of feet long, tied to some 
 forward part of their biplane so that by the angle 
 of its drifting back towards the operator an indi- 
 cation is had of the performance of the vehicle. 
 
 MISCELLANEOUS INSTRUMENTS 
 
 In addition to the more important instruments 
 already enumerated there are several others that 
 might conceivably prove useful or requisite. 
 
 The use of a level as a sort of grade indicator 
 to show angles of ascent and descent must be of 
 evident utility. Such a level already applied in 
 some aeronautical experiments is that illustrated 
 at Figure 254, in which the body is a light metal 
 cup, covered by a spherically curved glass top and 
 
426 
 
 VEHICLES OF THE AIR 
 
 filled with alcohol except for the small space occu- 
 pied by the bubble at the top. The series of con- 
 centric rings or grooves in the inner side of the 
 glass cover, made visible by filling with black 
 enamel, afford instant indication of longitudinal 
 
 or lateral deviation from a 
 normal level course by forc- 
 ing the bubble away from its 
 normal position at the center 
 of the glass to a position 
 away from this point to a 
 distance corresponding with 
 the change in level and in a 
 direction corresponding with 
 the direction of the change. 
 A quickly manipulable 
 sextant, or some practical or 
 approximate equivalent of this valuable instru- 
 ment of navigation, seems to be the one evi- 
 dent hope aside from methods of dead reckoning 
 for determining and maintaining a course 
 against a lateral drift due to the wind, as sug- 
 gested on Page 423. The difficulties, however, of 
 making reliable observations of sun or stars from 
 aerial vehicles are likely to prove very great. 
 
 The provision of a timepiece of chronometer 
 qualities is an evident necessity if long aerial voy- 
 ages are ever to be undertaken. As is well under- 
 stood by all in the least degree familiar with navi- 
 gation, an accurate chronometer is the modern 
 navigator's chief reliance for determination of his 
 longitude. 
 
 FIGURE 224. Universal 
 Level. This consists of a 
 metal cup with a curved glass 
 top, beneath which a bubble 
 floats in a liquid. The direc- 
 tion of its movement from 
 the center shows the direc- 
 tion of its tilting, while the 
 amount of its movement over 
 the graduated rings on the 
 glass is a measure of th6* ex- 
 tent of the tilting. 
 
FIGURE 245. Side View of Bleriot XI with Wings Tied on Frame. 
 
 FIGURE 246. Front View of Bleriot XI, Showing Demountable Wings. 
 
 ! 
 
 FIGURE 247. Assembling Bleriot XI. 
 
CHAPTER FOURTEEN 
 
 MISCELLANY 
 
 In addition to the more important and more 
 evident considerations that disclose themselves in 
 any survey of the achievements and the prospects 
 of modern aerial navigation, there is discovered a 
 great number of more obscure possibilities possi- 
 bilities at the present time impossible to appraise 
 and even difficult to define, but nevertheless con- 
 stituting proper subjects for some measure of 
 attention. 
 
 In this connection it is perhaps well for the 
 reader to impress upon himself the idea that the 
 aeroplanes of today, despite their decidedly re- 
 markable recent successes, must probably bear to 
 the more nearly perfected mechanism of the flying 
 vehicle of the not distant future some such rela- 
 tion as was sustained by the automobile of ten or 
 fifteen years ago to the wonderful, practical, popu- 
 lar, economical, and in every essential respect suc- 
 cessful vehicles that today throng the streets and 
 roads of all civilization, and around the construc- 
 tion and improvement of which there has devel- 
 oped a science that in itself constitutes a special 
 department of engineering and an industry in 
 which are invested hundreds of millions of dollars. 
 It may seem to the casual reader a venturesome 
 
 427 
 
428 VEHICLES OF THE AIR 
 
 thing to predict any similarly extensive develop- 
 ment of aerial vehicles. Yet it is to be remem- 
 bered that even the most accustomed forms of 
 modern transportation the railway, the steam 
 vessel, the bicycle, the automobile, etc., all had 
 their very inception actually or almost within the 
 lifetimes of people now living, while without ex- 
 ception their development from the experimental 
 stage to the status of unquestioned utility has 
 covered much shorter periods. 
 
 Certainly it cannot be escaped or overlooked 
 that the atmosphere is a medium of travel afford- 
 ing more room with less limitations than apply to 
 any other mode of transportation; that it is the 
 medium used by birds for the transportation of 
 considerable weights at great speeds with absurdly 
 small power; and that, though the bird possesses 
 the almost inimitable coordination of animal 
 mechanism, man has nevertheless proved already 
 capable of imitating this coordination and control 
 not only in a considerable degree, but also with 
 remarkable success and safety the lives so far 
 lost in this growing conquest of the air with 
 heavier-than-air machines being much smaller for 
 given distances traveled than proved the case in 
 the development of apparently much safer means 
 of terrestrial and aquatic travel. 
 
 APPLICATIONS 
 
 Concerning the possible and probable applica- 
 tions of aerial vehicles, it is perhaps easier to argue 
 than it is to convince, but at least it will be admit- 
 
-6- -3* 
 
 FIGURE 221. Scale Drawings of Santos-Dumont Monoplane. This is the lightest, 
 least expensive, and one of the most successful power-driven aeroplanes yet developed. 
 The main frame B consists of three bamboo spars, widely spread in front and brought 
 closely together at the rear. One of these spars is above and the other two below, 
 side by side. All three of these spars are cut at L, so that the machine can be readily 
 taken apart and reassembled by use of the tubular sleeves placed at this point. Closely 
 applied wrappings of wire or cord counteract the tendency of the bamboo to split. 
 The monoplane sustaining wing A is single surfaced, with the wing bars on the rare- 
 faction side of the ribs, and there is no attempt to round the w r ing tips or flatten the 
 curves of the end sections. The lateral balance is maintained by wing warping, by 
 the wires 0, which pass over the small pulleys shown and then connect directly to a 
 laterally-movable vertical lever. This lever is ingeniously operated by a section of 
 tubing sewn into the back of the operator ; s coat and slipped over the lever when he is 
 in the canvas seat E, so that the natural swing of his body maintains the equilibrium. 
 Fore-and-aft balance is secured by movement of the horizontal rudder surface J 
 through the control wires N N and the lever C, the spring Q serving to maintain the 
 wires taut in all positions. Lateral steering is by the vertical rudder 7, operated 
 by the wires M M from the wheel D. Several machines of substantially this same 
 type have been successfully flown with different engines, both air and water cooled, 
 but all of somewhat similar two-cylinder, horizontal-opposed types. The most satisfac- 
 tory results have been secured with the Darracq motor pictured in Figure 116. This 
 engine weighs only 66 pounds, though it develops 35 horsepower, and is water cooled 
 by the radiators K K, which consist simply of a large number of parallel tubes ar- 
 ranged under the wing surfaces. The gasoline tank is at P. The wooden propeller H, 
 6-i feet in diameter, is mounted directly on the engine shaft, a portion of the advanc- 
 ing edge of the sustaining surface A being cut away to accommodate it. The alight- 
 ing gear consists simply of the two bicycle wheels F F, slanted inwards at the top as 
 shown in the front view, and supplemented by the tubular metal skid in front of the 
 rear rudders. The weight of this machine is about 240 pounds. Dimensions are given 
 in feet and inches. For further details of the Santos-Dumont machines, of the par- 
 ticular model above described as well as the various constructions from which it devel- 
 oped, reference should be had to Figures 116, 141, 217, 218, 219, 220, and 238. 
 
 18' 
 
E 
 
 7^ 1 6~ ^K J 6 ;^j 
 
 
 
 3*6" 
 
 20' 
 
 ?' n" 
 06- --3| 
 
 
 , , 
 
 
MISCELLANY 429 
 
 ted that such vehicles must find some fields of use- 
 fulness, whether or not it is to be contended that 
 these fields will prove exceedingly broad or excep- 
 tionally limited. 
 
 WAEFABE 
 
 War being fundamentally an affair of danger 
 and disaster, all possible strictures that can be 
 leveled against the safety of aerial vehicles must 
 lose force when confronted with this application. 
 Much discussion and speculation has been aroused 
 by the contemplation of the possibilities of the fly- 
 ing machine in war even books having been writ- 
 ten in which it has been attempted to portray, 
 often in the most interesting manner, phases of the 
 warfare of the future.* 
 
 The schemes that have been suggested in the 
 way of tactics and methods to be employed in 
 aerial warfare cover the widest possible range, 
 from the ridiculous to the plausible. 
 
 A somewhat discussed aspect of the flying ma- 
 chine 's war possibilities has been that of mounting 
 on dirigibles and other aerial craft firearms of 
 types similar to those of the smaller calibers used 
 in land and naval warfare. Because of the great 
 weight of even the lightest of effective modern 
 weapons, the considerable weights of ammunition 
 required, and the comparatively low accuracy in 
 firing at moving targets from unstable platforms, 
 it is impossible to believe that any real success can 
 attend such plans. Even under the most favorable 
 
 *In this connection, the writer has particularly in mind H. G. Wells' 
 "War in the Air." 
 
430 VEHICLES OF THE AIR 
 
 circumstances, it is one of the well-established sta- 
 tistics of military history that for every man killed 
 as much as or more than his weight in metal must 
 be shot from firearms. It therefore seems scarcely 
 clear how aerial vehicles, necessarily rather lim- 
 ited in their carrying capacities even though 
 great further progress in this regard be made can 
 effect very material damage upon the unconcen- 
 trated troops that commonsense modern tactics 
 have already dictated as a means of minimizing 
 danger from attacks with machine guns and shrap- 
 nel. Elimination of this sort of aerial warfare 
 from consideration leaves the aerial vehicle with 
 only one, but a sufficiently dangerous method of 
 attack by the dropping of high explosives as accu- 
 rately as may prove possible into the weakest and 
 most vulnerable points in the enemy's military and 
 social organization. And this method, as specula- 
 tion upon it is indulged in, becomes sufficiently 
 horrifying to appall the most skeptical tactician or 
 hardened soldier. 
 
 Undoubtedly, the initial points of attack would 
 be on the sea the enormously costly mechanisms 
 the battleships, cruisers, and torpedo-boats of 
 modern navies, which even today seem open to 
 destruction should occasion arise by very ordinary 
 application of the capabilities of such aeroplanes 
 as have been already developed working, it is to 
 be emphasized, not individually but in fleets, with 
 results that seem quite inescapable. On land the 
 points of attack might be the storehouses of mili- 
 tary and food supplies, or even the property in 
 
FIGURE 222. Side View of the R. E. P. Monoplane. 
 
 FIGURE 223. Three-Quarters View of the R. E. P. Monoplane, 
 the twisting rudder h are features of this machine. 
 
 The wing wheels ft 6 and 
 
 FIGURE 224. Captain Ferber's Dihedral Biplane. 
 
MISCELLANY 431 
 
 great cities, which, all action of peace congresses 
 and international tribunals to the contrary, it is 
 very likely that a determined and aggressive foe 
 would ultimately assail after issuing due warnings 
 commanding immediate removal of all non-com- 
 batants, such warnings to be disregarded at the 
 peril of the party attacked. For in the last analy- 
 sis of the bitterness of conflict between militant 
 nations, wars are fought less by rules than to win 
 victories. 
 
 In the face of such tremendous improvement in 
 mechanisms for the destruction of life and prop- 
 erty without which war cannot be successfully 
 waged, the view that warfare can continue indefi- 
 nitely, in a world of civilized and intelligent beings 
 constantly growing more civilized and more intelli- 
 gent, is an incredible one. Altogether more likely 
 than this indefinite continuation of war, or such 
 voluntary disarmament and arbitration as is pro- 
 posed by idealists, seems an unavoidable and en- 
 forced arbitration, imposed upon all by concerted 
 action of the great powers of the world, which 
 instead of maintaining individual armies whose 
 military equipments land, naval, and aerial will 
 be pitted against one another will pool their forces 
 for the maintenance of an international policing 
 force to compel arbitration of international ques- 
 tions, and to punish terribly such benighted nations 
 as may have the hardihood to assert militant 
 dissent from the prescriptions of the intelligent 
 majorities of civilization. 
 
 Almost as significant as its power for de- 
 
432 VEHICLES OF THE AIR 
 
 struction is the invulnerability of the aeroplane. 
 Though without armor or any corresponding pro- 
 tection, yet, operated in fleets, and if necessary 
 under cover of night, no one familiar with modern 
 gunnery or the use of firearms needs to be told 
 how utterly difficult and impracticable will be 
 found all schemes for winging the aerial vehicles. 
 It is difficult enough to hit a fixed target from a 
 substantially-mounted weapon after the range has 
 been accurately found. It is more difficult to strike 
 a moving target on the ground, or afloat on the 
 water, though even in these cases the restriction 
 of the movement to a horizontal plane and the pos- 
 sibility of correcting errors in the determination 
 of the range by noting the splash in the water, or 
 dust thrown up, is a great help. But to strike a 
 vehicle moving through the air, capable of ex- 
 traordinary celerity in maneuvering, capable of 
 three-dimensional travel up and down as well as 
 in all lateral directions and with no means what- 
 ever of finding range, can never happen except by 
 the purest of pure accidents. And when it does 
 happen its effect upon the enemy's strength is so 
 certain to be so utterly trivial involving the de- 
 struction of no more than a few hundred dollars' 
 worth of machinery and the lives of not more than 
 one or two individuals that its futility as a means 
 of winning a victory is almost too evident to 
 
 require discussion. 
 
 SPORT 
 
 Under the heading of this much abused term 
 can be perhaps fairly characterized the utilization 
 
FIGURE 225. Scale Drawings of Montgomery Glider. This machine is exceedingly simple, 
 though as in the case of all aeronautical apparatus only the most substantial and well-considered 
 detail construction is to be tolerated if safety is to be assured. The framework consists primarily 
 of the two light upper bars 0, terminating in the spars / /, and of the heavier bottom bar N, 
 connected by the four slanting vertical members H H. Each of the two main wing frames con 
 sists of two wing bars attached on top of 0, and bearing on their under sides 58 equally-spaced 
 curved ribs that pass through pockets sewed into the single surface of light rubberized silk or 
 percale that is considered the preferable material for the wing covering. The front bar of each 
 wing is firmly lashed to 00, rigidly trussed into a pronounced arch by the wires FFF, anc ! 
 braced by the masts G G, but the rear bars are divided at Q Q so that they hinge over ano 
 droop loosely at their ends to a level considerably below that of the front bars. They are, how 
 ever, prevented from lifting above a certain point by the control cords E E, which run over pulleys 
 as shown and are attached to the stirrup bar M, by means of which the operator controls the device 
 with his feet. When in the air the droop or arch of the wings is not as pronounced as shown ic 
 the drawings, which show the machine at rest. The operator sits astride the seat P and steers by 
 pressing on one side or the other of the stirrup bar, the cords from which are so crossed that 
 pressure with the right foot pulls down the rear edges of the left wing ends, and vice versa. This 
 manipulation may be also used as a balancing control, but equilibrium is maintained chiefly by the 
 automatic effect of the very large fin surface C, which though it moves up and down with the 
 rudder D has no lateral movement. In addition to the dissimilar twisting or warping of the wing 
 ends by pressing down on one side or the other of the stirrup bar, by pressing down on both ends 
 simultaneously all the rear wing tip edges are drawn down together a manipulation that sets up 
 a very effective braking action, by which the machine can be brought to land so lightly that the 
 operator is not even jarred. In addition to these control movements there is another, by pulling 
 down the pulleys over which the cords to the wing B are passed, through the action of which the 
 whole angle of the rear wing can be changed in relation to that of the front wing, thus affording 
 control over the longitudinal equilibrium by an elevator-like action of the two wings in relation to 
 each other. The horizontal tail surface D, proximate to the center of the rear edge of B, is 
 controlled by the cords J K, which are attached to the wooden clamp L, automatically locked 
 by the effect of the angular pull upon it in any position at which it may be placed on the sta- 
 tionary wire K, which runs from one of the bars to the bar N. 
 
 The ribs of this machine should be made of clear, well-seasoned spruce, \ inch wide and & inch 
 deep, and each rib must be made of two pieces glued together under pressure in a form, so that 
 they will hold the requisite curve. The wing bars are best made of hickory, about 1J inches by 
 If inches at their centers, and tapered to about half this section at the ends. The frame bars 
 can be of spruce, about 1 inches by 2 inches at their centers and tapered to their ends to a 
 smaller size forward than at the rear. N is likewise about U inches thick, and may be as deep 
 as 3J inches at the center. The tail framing is of light wood edges stayed by wires arranged like 
 the spokes in a bicycle wheel. The machine weighs about 40 pounds. All dimensions are in inches. 
 
or \Lx: jff\ __^>LS s/7 . . \f 
 
 J v Vn\~ f I/ XH^ ^-^ *^ !x^ 
 

MISCELLANY 433 
 
 of aerial vehicles for pleasure travel in one man- 
 ner and another. 
 
 Aeroplane contests already have provided 
 thrills sufficient to satisfy the most blase audiences, 
 and in the near future, when the speeds made seem 
 certain to become vastly higher than any that have 
 been maintained with any other types of vehicles, 
 they will become even more spectacular. More- 
 over the element of safety in such contests is much 
 greater than might be supposed probably much 
 greater than in automobile racing, which has been 
 responsible for a truly appalling list of fatalities. 
 This is because, while land vehicles are built to 
 travel on land, they are built to do so only on espe- 
 cially prepared courses, so when an automobile 
 leaves the road, or a rail vehicle leaves the rails 
 imminent and terrible dangers are introduced, 
 whereas in the case of the vehicle designed to 
 travel in the air even a plunge to the earth in- 
 volves movement through rather than away from 
 its natural route, with corresponding chance if the 
 vehicle be well designed of regaining its normal 
 control and of recovering its equilibrium,, or, at 
 worst, of landing without injury to the occupant. 
 
 MAIL AND EXPRESS 
 
 The first commercial applications of flying ve- 
 hicles must inevitably be to the transport of light 
 commodities, such as it is desirable to convey at 
 great speeds and which can be paid for at high rates 
 per unit of weight. 
 
 The ideal service of this character would be 
 
434 VEHICLES OF THE AIR 
 
 that of a number of vehicles traversing a route of 
 the maximum distance possible to accomplish with- 
 out alighting, dropping mail bags on clear areas 
 where watchers would be waiting to receive them. 
 
 NEWS SERVICE 
 
 Besides for the distribution of mail and ex- 
 press, aerial vehicles may lend themselves to the 
 distribution of newspaper matrices and illustra- 
 tions prepared at central points for quick trans- 
 mission to rural newspaper plants, not provided 
 as at present with expensive editing and composing 
 forces, but chiefly equipped with stereotyping and 
 printing facilities. 
 
 EFFECTS OF LOW COST AND MAINTENANCE 
 
 Most important factors in the further improve- 
 ment and the future applications of aerial vehicles 
 are certain to be the lower first and maintenance 
 costs that are reasonably to be anticipated if what 
 has been already done is any criterion. 
 
 With some of the most efficient modern aero- 
 planes it has been proved possible to transport 
 weights of as great as 1,600 pounds for distances 
 of twelve and fifteen miles on a gallon of gasoline 
 a result that compares most favorably with even 
 the best secured with modern automobiles, espe- 
 cially at anything like similar speeds in the neigh- 
 borhood of 40 or 45 miles an hour. 
 
 An inevitable result of lo^ first and mainte- 
 nance costs must be the extensive acquisition of 
 aerial vehicles by all manner of individuals indi- 
 
Courtesy the Scientific American. 
 
 FIGURE 226. Front View of Montgomery Monoplane Glider, 
 
 FIGURE 227. View from Beneath of Montgomery Double Monoplane Glider. This machine 
 is probably built on more scientific principles than any other so far constructed. On at least 
 three occasions operators have deliberately turned side somersaults with it, besides which many 
 descents have been safely made from heights ranging up to 4,000 feet, at speeds said to have 
 ranged as high as 68 miles an hour. Its equilibrium is so positive that it automatically rights 
 itself when released upside down in the air. 
 
MISCELLANY 435 
 
 viduals of a class today quite unable to afford even 
 the most inexpensive automobiles. More than this, 
 the aerial vehicles not being confined to roads or 
 highways of any kind, there is not the slightest 
 possibility either of monopolies or of limitations in 
 their use other than the direct physical limitations 
 imposed by such mechanical imperfections as, of 
 course, can never be wholly eradicated, however 
 they may be minimized. 
 
 GENERAL EFFECTS 
 
 The wide introduction of aerial vehicles into 
 the hands of the general public, if it ever occurs, 
 and it seems more than likely that it will occur, 
 cannot fail to exert consequent influences of the 
 profoundest importance upon innumerable phases 
 and regulations of the accepted social order. The 
 very independence of movement which only an 
 aerial vehicle can possess will in itself unfailingly 
 modify the whole structure of civilization. 
 
 A most certain result of the new condition in 
 human affairs following upon man's achievement 
 of flight will be the inevitable effect on laws and 
 customs. Assertions to the contrary notwith- 
 standing, it is impossible to see how either exclu- 
 sion laws or customs laws (except perhaps in the 
 case of very heavy commodities) are going to be 
 at all enforceable in the coming era of aerial navi- 
 gation. The boundaries of every nation in the 
 world, except possibly those of the most densely 
 populated, will absolutely cease to exist as barriers 
 that can be policed and safeguarded against pro- 
 
436 VEHICLES OF THE AIR 
 
 gressing humanity's perfectly natural disposi- 
 tion to travel and communicate without let or 
 hindrance. 
 
 A more sinister aspect of this time to come is 
 the tremendous facility with which the aerial 
 vehicle will lend itself to the perpetration of crime 
 with almost perfect assurance for the criminal of 
 escape from punishment and other consequences. 
 Indeed, as a police problem the aeroplane bids fair 
 to become far more serious than the much-appre- 
 hended and now-realized noiseless gun. Neverthe- 
 less, no one with any real optimism can long believe 
 that progress in science and invention can have 
 any permanent injurious or detrimental effect on 
 human affairs. Perhaps the solution will be a 
 greater effort on the part of society as a whole, 
 and especially upon the part of the now more 
 powerful and arrogant elements within it, so to 
 ameliorate and improve the conditions of the 
 " criminal classes", so-called, and more particu- 
 larly of the poverty-stricken classes from which 
 nearly all criminals are recruited by the reactions 
 of oppressive environments so that less crimes 
 will be committed not because of policing and pun- 
 ishment, but because of reduced incentive. 
 
 RADII OF ACTION 
 
 Since almost the only limitation at the present 
 time in the way of indefinitely-continued flight, 
 even with present machines and barring, of 
 course, the matter of more or less violent storms 
 is the difficulty of carrying sufficient supplies of 
 
co cr o 
 
 g-e." 
 
 " o 
 ^ 
 
 " 
 
 
 
 B g e. 
 
 2. S 
 
 s 
 
 
MISCELLANY 437 
 
 fuel, it is clear that as more efficient propellers and 
 engines, or surfaces affording given sustention 
 with smaller head resistances, may be developed, 
 the radii of action is certain to be increased in 
 proportion. 
 
 INFLUENCE OF WIND 
 
 In the case of water travel, excepting in rare 
 instances of river navigation through rapids 
 or of navigation through narrow channels with 
 rapid tidal flows, the currents in navigable waters 
 are not of sufficient speed materially to help or 
 hinder vessels passing through them. With the 
 atmosphere the case is quite the other way. In 
 this lightest of earth's traversable media move- 
 ments of the air in the form of wind, of velocities 
 considerably in excess of the best speeds that have 
 been attained with aeroplanes, are common. In 
 fact, it is a fair assertion that winds of even as 
 high as 100 miles an hour approximately twice 
 as fast as the greatest present aeroplane speeds 
 are occasionally to be reckoned with, even though 
 they will not be commonly encountered and never 
 will be flown in when such flight is avoidable. 
 i 
 
 DEMOUNTABILITY 
 
 Apparently not satisfied with the altogether 
 sufficient difficulties of making flying machines to 
 fly, more than one inventor has in addition at- 
 tempted to construct such vehicles in folding form 
 probably inspired by the beautiful perfection of 
 the bird's wing mechanism with the idea of simi- 
 
438 VEHICLES OF THE AIR 
 
 larly quickly stowing the wings and other parts 
 of the machine in compact and portable shape. 
 
 It being a condition involved in almost any con- 
 ceivable aerial vehicle that considerable dimen- 
 sions must be employed because of the necessity 
 for operating in one way or another upon large 
 areas of air, there is much to be said in favor of 
 any scheme that seems to promise a compacter 
 arrangement of the vehicle elements when the 
 machine is at rest than is required when it is in 
 the air. This is important both for storage and 
 for shipment and, as has been suggested, has its 
 counterpart in all known flying creatures, which 
 without exception fly with surfaces capable of 
 being folded more or less out of the way when 
 not in use. 
 
 But the difficulties in the way of making reliable 
 folding wings are very great so great that in the 
 present state of the art it seems hardly desirable 
 to attempt overcoming them, until after more 
 perfect and dependable results are secured in the 
 more vital functioning of flying mechanisms. 
 
 Demountability, however, is an altogether dif- 
 ferent thing from folding, this term implying only 
 the ready detachability and separation of different 
 parts with corresponding facility in reassembling. 
 Several very successful modern aeroplanes are 
 made demountable in greater or lesser degree. 
 
 A further advantage of demountability is the 
 conversion by its means of the aerial vehicle into 
 a more or less capable road vehicle. Thus the 
 " June Bug" of the Aerial Experiment Association, 
 
MISCELLANY 439 
 
 with its wings off, was still capable of rolling along 
 on its wheeled starting gear. In this condition it 
 proved capable of speeds as high as forty-five miles 
 an hour, simply run on the road under the thrust 
 of its ow r n propeller. 
 
 In the case of the "June Bug", however, the 
 wings when taken off were not carried with the 
 machine, making the scheme employed in the most 
 recent Bleriot monoplanes and illustrated in Fig- 
 ures 245, 246, and 247, altogether superior. As 
 is shown in these illustrations, the two main wings 
 are simply detached from their proper places on 
 the fuselage and tied compactly against the sides, 
 so that the machine, carrying all of its flying ele- 
 ments, makes an excellent vehicle for running on 
 good roads a most desirable feature in case a 
 landing is made on a bad surface and it becomes 
 necessary to prospect about before a suitable place 
 for starting is found. 
 
 Undoubtedly this matter of demountability, 
 especially as machines become more practical and 
 more numerous, is one that will merit further con- 
 sideration by designers, with the result that pres- 
 ent-day shortcomings will decreasingly handicap 
 future progress. 
 
 PASSENGER ACCOMMODATION 
 
 Accommodation for passengers in most of the 
 flying machines so far built has been of a more or 
 less makeshift character, it being appreciated that 
 the most essential thing as yet is to produce ma- 
 chines that will fly, leaving the minor question of 
 
440 VEHICLES OF THE AIR 
 
 comfortable passenger accommodations for subse- 
 quent solution. 
 
 SEATS 
 
 About the least that can be provided in the 
 way of passenger accommodation is some sort of 
 seating arrangement. So far the most of such 
 seats have been of the most elementary construc- 
 tion, as is suggested in the illustrations throughout 
 these pages. Lately, however, some of the more 
 advanced craft are appearing with very comfort- 
 able arrangements for seating the operator, as is 
 particularly evidenced in the boat-like cockpits 
 provided in the Bleriot, Antoinette, and R. E. P. 
 machines, as shown in Figures 249, 250, and 252, 
 respectively. 
 
 HOUSING 
 
 As proved the case in the development of the 
 automobile, it probably will be only a short step 
 from the provision of comfortable seats to the pro- 
 vision of enclosures for these seats, housing the 
 operator and passengers from the weather and 
 from the wind of the movement through the air. 
 
 UPHOLSTERY 
 
 Cushioning of the bottoms and backs of seats 
 is a luxury that has already found application to 
 the aeroplane, though cane and wooden chair seats 
 are found rather lighter. 
 
 Pneumatic Cushions, of covering materials with 
 rubber or other gasproof linings, inflated with air, 
 are much used in boats and yachts and to some 
 extent for the seats of automobiles. Pneumatic 
 
FIGURE 248. Wicker Chair and Foot Control of Ailerons in Sommer's Farman Biplane. 
 
 FIGURE 249. Cockpit of Bleriot Monoplane Number XI. 
 
MISCELLANY 
 
 441 
 
 cushions are exceedingly light, constitute very sat- 
 isfactory life preservers in case of descent into 
 water, and are sufficiently durable to make them 
 thoroughly practical. It therefore seems reason- 
 able to regard them as an ideal type of aerial- 
 vehicle upholstery. 
 
 HEATING 
 
 While it can be considered hardly reasonable, 
 in the present status of aeronautical engineering, to 
 transport special devices for keeping the passen- 
 gers warm as is done in rail and water vehicles 
 and even in auto- 
 mobiles, there is 
 another road to the 
 provision of such 
 comforts without 
 materially adding 
 to the weight or 
 complication. 
 
 BV th6 ExhaUSt 
 
 9 
 
 gases which must be 
 emitted from all internal-combustion engines, 
 which are very hot, and which must be disposed of, 
 it is possible to secure a considerable heating effect 
 in a very simple and practical way. 
 
 A typical exhaust heater such as is to some 
 extent used for automobiles is illustrated in Figure 
 255, in which the principle is simply that of a 
 muffler-like apparatus beneath the passengers' 
 feet, and through which the gases from the engine 
 are caused to follow the intricate course indicated 
 by the arrows and determined by the numerous 
 
 FIGURE 255. Suggested Use of Exhaust 
 ses to Heat Foot Warmer. 
 
 Gases 
 
442 VEHICLES OF THE AIR 
 
 J>affle plates, finally making their exit to the rear. 
 The valve provides means of throwing the heater 
 in and out of action. 
 
 PAKACHUTES 
 
 The use of parachutes antedates the invention 
 of the balloon, it being on record in Loubere's 
 " History of Siam" that 250 years ago an oriental 
 inventor entertained Siamese royalty by leaps 
 from great heights with two parachutes attached 
 to a belt. In 1783 M. le Normand, of Lyons, 
 France, proposed the use of 
 parachutes as fire escapes, and 
 demonstrated their utility by 
 successfully descending with 
 one from the top of a high build- 
 ing in that city. The aeronaut 
 Blanchard was the first to con- 
 ceive of using the parachute in 
 FlGDRB ch 2 u 5 ter Para " ballooning, and in 1783 he tested 
 one by attaching it to a basket 
 in which was placed a dog, whereupon the whole 
 being released at a considerable height settled to 
 the ground in safety. In 1793 he descended him- 
 self from a balloon, but, though the fall was fairly 
 retarded, he nevertheless suffered a broken leg as 
 a result of his daring. On October 22, 1797, the 
 first really successful parachute jump was made 
 by Andre Jaques Garnerin from a balloon a mile 
 and a quarter high over the plain of Monceau, near 
 Paris. 
 
 Modern parachutes, such as that illustrated in 
 
MISCELLANY 443 
 
 Figure 256, are made from twenty to thirty feet 
 in diameter, with a hole at the center to prevent 
 oscillation, and without framing of any kind, the 
 series of cords by which the surface is attached to 
 the weight serving to preserve the umbrella-like 
 form essential to a safe descent, and produced pri- 
 marily by the air pressure. They sustain about 
 half a pound to the square foot. Parachutes 
 capable of safely carrying a man have been made 
 of less than twenty pounds in weight. 
 
 DESIGNING 
 
 In the design of aerial vehicles an exact science 
 is becoming rapidly established, with its recog- 
 nized engineering practises and the possible freak- 
 ish departures therefrom that are found to exist 
 in all departments of technical endeavor. 
 
 For the benefit of the intending designer or 
 experimenter, however, it is possible at the present 
 time only to emphasize the important point that 
 this field of engineering is one in which nothing 
 less than a broad and practical engineering knowl- 
 edge can suffice to produce results. Were suc- 
 cessful aerial vehicles to have been produced by 
 the rule-and-thumb methods that have been more 
 or less advantageously employed in most other 
 fields of mechanical engineering, successful flying 
 or at least gliding machines would have been in- 
 vented two thousand years ago, for failure in the 
 past has been due not to lack of effort or facilities, 
 out to the inadequate technical equipment possessed 
 be experimenters. The conclusion is that the ordi- 
 
444 VEHICLES OF THE AIR 
 
 nary amateur will do best by closely copying 
 proved constructions. 
 
 TESTING AND LEARNING 
 
 In testing new flying machines, and even in 
 learning to operate ones of established qualities, 
 there are a number of things to be considered that 
 are a little different from the conditions surround- 
 ing the tests of other mechanisms and the operation 
 of other vehicles. 
 
 Thus failure of an experiment with a mechan- 
 ism of this type is likely to be not a mere mechani- 
 cal failure, but also may readily result in injury 
 to or the death of its operator unless ingenious 
 and well-considered precautions are taken to 
 assure a maximum prospect of safety. 
 
 Likewise, for a beginner to attempt to drive a 
 machine even of a type known to be well capable 
 of flying, the attempt can easily become most dan- 
 gerous business if gone at in a reckless manner. 
 
 LEAENING FEOM TEACHER 
 
 By all means the best method of learning to 
 operate a flying machine is that possible when the 
 machine can carry two people and the pupil can 
 thus take his first rides with an expert. 
 
 PEACTISE CLOSE TO THE SUEFACE 
 
 When an instructor is not to be had, as in the 
 case of a new machine that no one knows how to 
 fly not even that it will fly or of a machine that 
 will carry only one person, it becomes possible for 
 the operator to acquire the necessary dexterity 
 
MISCELLANY 445 
 
 only by practise. Such practise is most readily 
 and speedily secured by the use of large level areas 
 over which the machine can be run on its wheeled 
 or other running gear, with "low jumps" into the 
 air that extend to greater and greater lengths as 
 the experimenter becomes proficient. 
 
 Practise over Water presents a number of very 
 great advantages over any other sort of practise 
 that can be had, there being in the first place the 
 level and almost ideally smooth surface, in addition 
 to which, if it comes to falling, water is better 
 to fall upon than hard ground. Drowning is suffi- 
 ciently guarded against by the circumstance that 
 almost all modern machines have sufficient wood in 
 their construction to float them, besides which they 
 can be fitted with inflated fabric floats and the 
 operator provided with a life preserver. 
 
 MAINTAINING HEADWAY 
 
 If there is any one point in the operation of 
 most modern aeroplanes that calls for especial 
 emphasis, it is the most imperative necessity for 
 always maintaining headway, since the forward 
 movement through the air is all that sustains the 
 machine in the air. 
 
 LANDING 
 
 Just at the moment of landing, it is possible 
 with most machines to execute an abrupt upward 
 steering movement, with the effect that the wing 
 surfaces strike the air at a very steep angle of inci- 
 dence, causing them to act as a sort of brake. This 
 maneuver will be better appreciated if its relation 
 
446 VEHICLES OF TEE AIR 
 
 is realized to the similar maneuver of birds, which 
 always at the moment of alighting oppose the full 
 areas of their wings to the direction of travel. 
 
 AERIAL NAVIGATION 
 
 Though in its general meaning this is the sub- 
 ject to which the whole of this book relates, in a 
 more specific sense it is to be applied to the details 
 of operating and driving aerial vehicles. 
 
 Considered from this standpoint aerial naviga- 
 tion, like water navigation, presents its special and 
 peculiar problems. 
 
 This being the situation there can as yet be no 
 established science of aerial navigation, but it is 
 nevertheless possible to formulate some of the 
 essential principles of such a science and to per- 
 ceive many of the factors in the problem. 
 
 FLYING HIGH 
 
 Flying very high so far does not seem to have 
 met with the approval of any but the more reckless 
 experimenters, and in no case recorded at this 
 writing has any power-driven aeroplane ascended 
 more than 1,600 feet high, while ascents even to 
 this and to other considerable altitudes have been 
 made not so much from any necessity for flying 
 great heights, as under the more frequent spur of 
 prize competitions. The longest sustained flight 
 made previous to this writing, that of Farman at 
 Eheims, on August 27, 1909, was at a height rarely 
 exceeding ten feet from the ground. 
 
 Steadier Air than is in most cases to be found 
 
MISCELLANY 
 
 447 
 
 nearer the ground is well established to exist at 
 greater heights, particularly over surfaces that are 
 irregular or built-up. 
 
 Choice of Landing, in case of motor breakdown 
 or other reason for descent, is greatly broadened 
 by flight at considerable altitudes. This will be 
 
 FIGURE 257. Effect of Height Upon Choice of Landing. Note that the 
 machine g has a much greater area than the machine h, down to which it 
 can glide in case of motor failure, its angle of descent being indicated by 
 the solid lines c c, those at / f being for the machine h. The dotted lines 
 d d and e e show the distortion from the circle upon which landing is 
 possible, when there is wind blowing in the direction of the arrow. 
 
 more readily understood from reference to A and 
 B, Figure 257, in which the aeroplanes g and h can 
 normally descend in calm air on gliding angles 
 represented by the solid lines c and /, thus afford- 
 ing choice of landing anywhere within a circle of 
 a diameter proportionate to the height of the start 
 and the flatness of the angle of descent. 
 
 FLYING LOW 
 
 Flying low, while introducing safeguards also 
 introduces dangers, especially if attempts be made 
 to fly low over rough country, in which the chance 
 
448 VEHICLES OF THE AIR 
 
 of striking obstacles with the machine flying reli- 
 ably might easily become more serious than the 
 danger of a fall from the remoter possibility of 
 some desperate and unexpected breakdown. 
 
 In all probability the lowest regular flying of 
 the future will be over water areas, where the sur- 
 face is level and uniform and presents no obstacles 
 to throw the atmosphere into irregular motions. 
 
 Falling is one of the possible dangers that can 
 be minimized by low flight, but, as has been already 
 explained, all practical modern aeroplanes being 
 essentially stable as gliders even with their motors 
 inoperative there is apparently very little danger 
 of abrupt falls. 
 
 Striking Obstacles is a much more serious dan- 
 ger, for there is not only the possibility of running 
 into obstacles not seen in time because of the 
 attempt to skim over them too closely; there is also 
 the danger while flying low of being thrust enough 
 out of the intended course by a sudden wind gust 
 to cause such an accident. 
 
 Vortices and Currents in the air are well dem- 
 onstrated to exist in proximity to all terrestrial 
 objects during winds, and are of a violence and 
 complexity of motion varying with the strength of 
 the wind and the character of the obstacles. 
 Travel through such vortices and currents ob- 
 viously is much more dangerous than travel 
 through uniform air, a fact that has already been 
 discovered by some of the pioneers in aerial navi- 
 gation. An interesting example was remarked by 
 Glenn Curtiss at Eheims, in 1909, when over one 
 
FIGURE 250. Seating Arrangement and Control System of Antoinette Monoplane 
 
 FIGURE 251. Sling Seat of Captain Ferber's Biplane. 
 
MISCELLANY 449 
 
 part of the course he found the air to be " literally 
 boiling", as he expressed it. 
 
 TERRESTRIAL ADJUNCTS 
 
 In the impending utilization of the air as a 
 highway for sporting and military operations and 
 probably for the conveyance of mail and express 
 matter, if not absolutely as a medium for all kinds 
 of passenger and commercial traffic, it is inevitable 
 that systems of signalling from the earth's surface 
 to the aerial vehicles must be devised. 
 
 An ideal means would be the use of wireless 
 telegraphy but this in its present development 
 comes nearer to permitting the aerial craft to 
 receive messages than to send them, because of the 
 much greater weights of sending apparatus. 
 
 SIGNALS 
 
 The kinds of information that it is likely to be 
 most essential for the future aerial pilot to have 
 from terrestrial stations will be data in regard to 
 his location, measurements of wind direction and 
 velocity, weather forecasts, etc. To these ends it 
 doubtless will prove feasible to establish lettered 
 or other landmarks easily recognized by day, with 
 systems of lights to serve the same purpose by 
 night. The idea of painting signals, and even the 
 flying machines themselves, with luminous paints 
 capable of emitting a clearly-visible glow in the 
 dark has been suggested, and doubtless could be 
 developed into a considerable safeguard against 
 accident and a means of greatly facilitating navi- 
 
450 
 
 VEHICLES OF THE AIR 
 
 gation. The most recent and interesting work 
 along this line has been done by William J. Ham- 
 mer, of New York, the well known physicist, who 
 is secretary of the Aeronautic Society. 
 
 Fog Horns and Whistles would provide a means 
 of signalling weather and wind conditions, of 
 transmitting orders, etc., at times when view of 
 the earth's surface might be obscured by low-lying 
 fogs or clouds. 
 
 The United States Weather Bureau system of 
 
 0) 
 
 FIGURE 258. United States Weather Signals. A denotes fair weather; 
 B, general rain or snow ; C, local rain or snow ; and D, a rise or fall in 
 temperature, according to whether it is placed above or below the other 
 flag displayed. E indicates approach of a cold wave. 
 
 weather forecasting by means of simple flag com- 
 binations could be readily adapted for display 
 on horizontal surfaces, or even by lights at night. 
 For use in rainy or foggy weather, along sea 
 coasts, etc., the United States Weather Bureau at 
 present announces its forecasts by means of 
 whistle blasts, one long blast repeated at intervals 
 meaning fair weather; two long blasts indicating 
 general rain or snow, three long blasts indicating 
 local rain or snow, one short blast indicating lower 
 temperature, two short blasts indicating higher 
 temperature, and three short blasts indicating a 
 cold wave. The long blasts are of from four to 
 six seconds and the short from one to three. 
 
FIGURE 252. Cockpit and General Details of R. E. P. Monoplane. 
 
 FIGURE 253. Latham's Antoinette Monoplane in the English Channel. Showing that 
 such a machine may be made to constitute an excellent raft. 
 
MISCELLANY 
 
 451 
 
 PATENTS 
 
 The aeronautical patent situation in the United 
 States is a very interesting one so interesting 
 that the full drawings, specifications, and claims 
 of what seem the two most important, No. 821,393, 
 to Orville and Wilbur Wright, and No. 831,173, to 
 John J. Montgomery, are here reproduced in full. 
 
 Other United States patents the claims of 
 which are reprinted herein are numbers 582,718, 
 to Chanute, 582,757, to MouiUard, and 544,816, to 
 Lilienthal. 
 
 Specification and Claims of Wright Patent. 
 
 No. 821,393. 
 
 Filed March 23, 1903. 
 
 To all whom it may concern: 
 
 Be it known that we, Orville Wright 
 and Wilbur Wright, citizens of the United 
 States, residing in the city of Dayton, county 
 of Montgomery, and State of Ohio, have in- 
 vented certain new and useful Improvements 
 in Flying-Machines, of which the following is 
 a specification. 
 
 Our invention relates to that class of fly- 
 ing-machines in which the weight is sustained 
 by the reactions resulting when one or more 
 aeroplanes are moved through the air edge- 
 wise at a small angle of incidence, either by 
 the application of mechanical power or by 
 the utilization of the force of gravity. 
 
 The objects of our Invention are to provide 
 means for maintaining or restoring the equi- 
 librium or lateral balance of the apparatus, 
 to provide means for guiding the machine 
 both vertically and horizontally, and to pro- 
 vide a structure combining lightness, strength, 
 convenience of construction and certain 
 other advantages which will hereinafter ap- 
 pear. 
 
 To these ends our invention consists In cer- 
 tain novel features, which we will now pro- 
 ceed to describe and will then particularly 
 point out in the claims. 
 
 In the accompanying drawings, Figure 1 Is 
 a perspective view of an apparatus embody- 
 ing our invention In one form. Fig. 2 is a 
 plan view of the same, partly in horizontal 
 section and partly broken away. Fig. 3 is a 
 side elevation, and Figs. 4 and 5 are detail 
 views, of one form of flexible joint for connect- 
 ing the upright standards with the aeroplanes. 
 
 In flying-machines of the character to 
 which this invention relates the apparatus is 
 supported in the air by reason of the contact 
 between the air and the under surface of one 
 or more aeroplanes, the contact-surface be- 
 ing presented at a small angle of incidence to 
 the air. The relative movements of the air 
 and aeroplane may be derived from the mo- 
 tion of the air in the form of wind blowing in 
 the direction opposite to that in which the 
 apparatus Is traveling or by a combined 
 downward and forward movement of the ma- 
 chine, as in starting from an elevated posi- 
 tion or by combination of these two things, 
 and in either case the operation is that of a 
 soaring-machine, while power applied to the 
 machine to propel it positively forward will 
 cause the air to support the machine in a siml- 
 
 Issued May 22, 1906. 
 
 Expires May 22, 1923. 
 
 lar manner. In either case owing to the va- 
 rying conditions to be met there are numer- 
 ous disturbing forces which tend to shift 
 the machine from the position which it should 
 occupy to obtain the desired results. It is 
 the chief object of our invention to provide 
 means for remedying this difficulty, and we 
 will now proceed to describe the construction 
 by means of which these results are accom- 
 plished. 
 
 In the accompanying drawings we have 
 shown an apparatus embodying our invention 
 in one form. In this illustrative embodi- 
 ment the machine is shown as comprising 
 two parallel superposed aeroplanes 1 and 2, 
 and this construction we prefer, although our 
 Invention may be embodied In a structure 
 having a single aeroplane. Each aeroplane 
 Is of considerably greater width from side to 
 side than from front to rear. The four cor- 
 ners of the upper aeroplane are indicated by 
 the reference-letters a, b, c, and d, while the 
 corresponding corners of the lower aeroplane 
 2 are indicated by the reference-letters e, f, 
 g, and h. The marginal lines a b and e f Indi- 
 cate the front edges of the aeroplanes, the 
 ateral margins of the upper aeroplane are in- 
 dicated, respectively, by the lines a d and b 
 c, the lateral margins of the lower aeroplane 
 are indicated, respectively, by the lines e h 
 and f g, while the rear margins of the upper 
 and lower aeroplanes are indicated, respec- 
 tively, by the lines o d and g h. 
 
 Before proceeding to a description of the 
 fundamental theory of operation of the struc- 
 ture we will first describe the preferred mode 
 of constructing the aeroplanes and those por- 
 tions of the structure which serve to connect 
 the two aeroplanes. 
 
 Each aeroplane is formed by stretching 
 cloth or other suitable fabric over a frame 
 composed of two parallel transverse spars 3, 
 extending from side to side of the machine, 
 their ends being connected by bows 4, ex- 
 tending from front to rear of the machine. 
 The front and rear spars 3 of each aeroplane 
 are connected by a series of parallel ribs 5, 
 which preferably extend somewhat beyond 
 the rear spar, as shown. These spars, bows, 
 and ribs are preferably constructed of wood 
 having the necessary strength, combined 
 with lightness and flexibility. Upon this 
 framework the cloth which forms the sup- 
 porting-surface of the aeroplane is secured, 
 
452 
 
 VEHICLES OF TEE AIR 
 
 the frame being inclosed in the cloth. The 
 cloth for each aeroplane previously to its at- 
 tachment to its frame is cut on the bias and 
 made up into a single piece approximately 
 the size and shape of the aeroplane, having 
 the threads of the fabric arranged diagonally 
 to the transverse spars and longitudinal ribs, 
 as Indicated at 6 in Fig. 2. Thus the diag- 
 onal threads of the cloth form truss systems 
 with the spars and ribs, the threads consti- 
 tuting the diagonal members. A hem is 
 formed at the rear edge of the cloth to receive 
 a wire 7, which is connected to the ends of 
 the rear spar and supported by the rear- 
 wardly-extending ends of the longitudinal 
 ribs 5, thus forming a rearwardly-extending 
 flap or portion of the aeroplane. This con- 
 struction of the aeroplanes gives a surface 
 which has very great strength to withstand 
 lateral and longitudinal strains, at the same 
 time being capable of being bent or twisted 
 in the manner hereinafter described. 
 
 When two aeroplanes are employed, as in 
 the construction illustrated, they are con- 
 nected together by upright standards 8. 
 These standards are substantially rigid, be- 
 ing preferably constructed of wood and of 
 equal length, equally spaced along the front 
 and rear edges of the aeroplane, to which 
 they are connected at their top and bottom 
 ends by hinged joints or universal joints of 
 any suitable description. We have shown 
 one form of connection which may be used 
 for this purpose in Figs. 4 and 5 of the draw- 
 ings. In this construction each end of the 
 standard 8 has secured to it an eye 9, which 
 engages with a hook 10, secured to a bracket- 
 plate 11, which latter plate is in turn fas- 
 tened to the spar 3. Diagonal braces or stay 
 wires 12 extend from each end of each stand- 
 ard to the opposite ends of the adjacent 
 standards, and as a convenient mode of at- 
 taching these parts I have shown a hook 13 
 made integral with the hook 10 to receive 
 the end of one of the stay-wires, the other 
 stay-wire being mounted on the hook 10. 
 The hook 13 is shown as bent down to retain 
 the stay-wire in connection to it, while the 
 hook 10 is shown as provided with a pin 14 
 to hold the stay-wire 12 and eye 9 in position 
 thereon. It will be seen that this construc- 
 tion forms a truss system which gives the 
 whole machine great transverse rigidity and 
 strength, while at the same time the jointed 
 connections of the parts permit the aero- 
 planes to be bent or twisted in the manner 
 which we will now proceed to describe. 
 
 15 indicates a rope or other flexible con- 
 nection extending lengthwise of the front of 
 the machine above the lower aeroplane, pass- 
 ing under pulleys or other suitable guides 16 
 at the front corners and f of the lower aero- 
 plane, and extending thence upward and 
 rearward to the upper rear corners o and d 
 of the upper aeroplane, where they are at- 
 tached, as indicated at 17. To the central 
 portion of this rope there is connected a lat- 
 erally-movable cradle 18, which forms a 
 means for moving the rope lengthwise in one 
 direction or the other, the cradle being mov- 
 able toward either side of the machine. We 
 have devised this cradle as a convenient 
 means for operating the rope 15, and the 
 machine is intended to be generally used with 
 the operator lying face downward on the 
 lower aeroplane, with his head to the front, 
 so that the operator's body rests on the cra- 
 dle, and the cradle can be moved laterally by 
 the movements of the operator's body. It 
 will be understood, however, that the rope 15 
 may be manipulated in any suitable manner. 
 
 19 indicates a second rope extending trans- 
 versely of the machine along the rear edge of 
 the body portion of the lower aeroplane, pass- 
 ing under suitable pulleys or guides 20 at the 
 rear corners g and h of the lower aeroplane 
 and extending thence diagonally upward to 
 
 the front corners a and b of the upper aero- 
 plane, where its ends are secured in any suit- 
 able manner, as indicated at 21. 
 
 Considering the structure so far as we have 
 now described it and assuming that tLe 
 cradle 18 be moved to the right in Figs. 1 and 
 2, as indicated by the arrows applied to tho 
 cradle in Fig. 1 and by the dotted lines in 
 Fig. 2, it will be seen that that portion of the 
 rope 15 passing under the guide-pulley at the 
 corner e and secured to the corner d will be 
 under tension, while slack is paid out 
 throughout the other side or half of the rope 
 15. The part of the rope 15 under tension 
 exercises a downward pull upon the rear up- 
 per corner d of the structure and an upward 
 pull upon the front lower corner e, as indi- 
 cated by the arrows. This causes the corner 
 d to move downward and the corner e to move 
 upward. As the corner e moves upward it 
 carries the corner a upward with it, since the 
 intermediate standard 8 is substantially rigid 
 and maintains an equal distance between the 
 corners a and e at all times. Similarly, the 
 standard 8, connecting the corners d and h, 
 causes the corner h to move downward in uni- 
 son with the corner d. Since the corner a 
 thus moves upward and the corner h moves 
 downward, that portion of the rope 19 con- 
 nected to the corner a will be pulled upward 
 through the pulley 20 at the corner h, and the 
 pull thus exerted on the rope 19 will pull the 
 corner b on the other side of the machine 
 downward and at the same time pull the cor- 
 ner g at said other side of the machine up- 
 ward. This results in a downward movement 
 of the corner b and an upward movement of 
 the corner c. Thus it results from a lateral 
 movement of the cradle 18 to the right in 
 Fig. 1 that the lateral margins a d and e h at 
 one side of the machine are moved from their 
 normal positions, in which they lie in the nor- 
 mal planes of their respective aeroplanes, into 
 angular relations with said normal planes, 
 each lateral margin on this side of the ma- 
 chine being raised above said normal plane at 
 its forward end and depressed below said nor- 
 mal plane at its rear end, said lateral margins 
 being thus inclined upward and forward. At 
 the same time a reverse inclination is impart- 
 ed to the lateral margins b c and f g at the 
 other side of the machine, their inclination 
 being downward and forward. These posi- 
 tions are indicated in dotted lines in Fig. 1 of 
 the drawings. A movement of the cradle 18 
 in the opposite direction from its normal po- 
 sition will reverse the angular inclination of 
 the lateral margins of the aeroplanes in an 
 obvious manner. By reason of this con- 
 struction it will be seen that with the particu- 
 lar mode of construction now under consider- 
 ation it Is possible to move the forward corner 
 of the lateral edges of the aeroplane on one 
 side of the machine either above or below the 
 normal planes of the aeroplanes, a reverse 
 movement of the forward corners of the lat- 
 eral margins on the other side of the machine 
 occurring simultaneously. During this op- 
 eration each aeroplane is twisted or distorted 
 around a line extending centrally across the 
 same from the middle or one lateral margin to 
 the middle of the other lateral margin, the 
 twist due to the moving of the lateral mar- 
 gins to different angles extending across each 
 aeroplane from side to side, so that each aero- 
 plane-surface is given a helicoidal warp or 
 twist. We prefer this construction and 
 mode of operation for the reason that it gives 
 a gradually-increasing angle to the body of 
 each aeroplane from, the central longitudinal 
 line thereof outward to the margin, thus giv- 
 ing a continuous surface on each side of the 
 machine, which has a gradually Increasing or 
 decreasing angle of incidence from the center 
 of the machine to either side. We wish it to 
 be understood, however, that our invention is 
 not limited to this particular construction, 
 
FIGURE 259. Wright Patent Drawings. 
 
454 
 
 VEHICLES OF THE AIR 
 
 since any construction whereby the angular 
 relations of the lateral margins of the aero- 
 planes may be varied in opposite directions 
 with respect to the normal planes of said 
 aeroplanes comes within the scope of our in- 
 vention. Furthermore, it should be under- 
 stood that while the lateral margins of the 
 aeroplanes move to different angular posi- 
 tions with respect to or above and below the 
 normal planes of said aeroplanes it does not 
 necessarily follow that these movements 
 bring the opposite lateral edges to different 
 angles respectively above and below a hori- 
 zontal plane, since the normal planes of the 
 bodies of the aeroplanes are inclined to the 
 horizontal when the machine is in flight, said 
 inclination being downward from front to rear, 
 and while the forward corners on one side of 
 the machine may be depressed below the nor- 
 mal planes of the bodies of the aeroplanes 
 said depression is not necessarily sufficient to 
 carry them below the horizontal planes pass- 
 ing through the rear corners on that side. 
 Moreover, although we prefer to so construct 
 the apparatus that the movements of the lat- 
 eral margins on the opposite sides of the ma- 
 chine are equal in extent and opposite in di- 
 rection, yet our invention is not limited to a 
 construction producing this result, since it 
 may be desirable under certain circumstances 
 to move the lateral margins on one side of the 
 machine in the manner just described with- 
 out moving the lateral margins on the other 
 side of the machine to an equal extent in the 
 opposite direction. Turning now to the pur- 
 pose of this provision for moving the lateral 
 margins of the aeroplanes in the manner de- 
 scribed, it should be premised that owing to 
 various conditions of wind-pressure and other 
 causes the body of the machine is apt to be- 
 come unbalanced laterally, one side tending 
 to sink and the other side tending to rise, the 
 machine turning around its central longitu- 
 dinal axis. The provision which we have 
 just described enables the operator to meet 
 this difficulty and preserve the lateral bal- 
 ance of the machine. Assuming that for 
 some cause that side of the machine which 
 lies to the left of the observer in Figs. 1 and 2 
 has shown a tendency to drop downward, a 
 movement of the cradle 18 to the right of said 
 figures, as hereinbefore assumed, will move 
 the lateral margins of the aeroplanes in the 
 manner already described, so that the mar- 
 gins a d and e h will be inclined downward 
 and rearward and the lateral margins b c and 
 f g will be inclined upward and rearward with 
 respect to the normal planes of the bodies of the 
 aeroplanes. With the parts of the machine 
 in this position it will be seen that the lateral 
 margins a d and e h present a larger angle of 
 Incidence to the resisting air, while the lat- 
 eral margins on the other side of the machine 
 present a smaller angle of incidence. Owing 
 to this fact, the side of the machine present- 
 ing the larger angle of incidence will tend to 
 lift or move upward, and this upward move- 
 ment will restore the lateral balance of the 
 machine. When the other side of the ma- 
 chine tends to drop, a movement of the cradle 
 18 in the reverse direction will restore the 
 machine to its normal lateral equilibrium. 
 Of course the same effect will be produced in 
 the same way in the case of a machine employ- 
 ing only a single aeroplane. 
 
 In connection with the body of the ma- 
 chine as thus operated we employ a vertical 
 rudder or tail 22, so supported as to turn 
 around a vertical axis. This rudder is sup- 
 ported at the rear ends of supports or arms 
 23, pivoted at their forward ends to the rear 
 margins of the upper and lower aeroplanes, 
 respectively. These supports are preferably 
 V-shaped, as shown, so that their forward 
 ends are comparatively widely separated, 
 their pivots being indicated at 24. Said sup- 
 ports are free to swing upward at their free 
 
 rear ends, as indicated in dotted lines in Fig. 
 3, their downward movement being limited 
 in any suitable manner. The vertical pivots 
 of the rudder 22 are indicated at 25, and one 
 of these pivots has mounted thereon a sheave 
 or pulley 26, around which passes a tiller- 
 rope 27, the ends of which are extended out 
 laterally and secured to the rope 19 on oppo- 
 site sides of the central point of said rope. 
 By reason of this construction the lateral 
 shifting of the cradle 18 serves to turn the 
 rudder to one side or the other of the line of 
 flight. It will be observed in this connection 
 that the construction is such that the rudder 
 will always be so turned as to present its re- 
 sisting-surface on that side of the machine on 
 which the lateral margins of the aeroplanes 
 present the least angle of resistance. The 
 reason of this construction is that when the 
 lateral margins of the aeroplanes are so turned 
 in the manner hereinbefore described as to 
 present different angles of incidence to the 
 atmosphere that side presenting the largest 
 angle of incidence, although being lifted or 
 moved upward in the manner already de- 
 scribed, at the same time meets with an in- 
 creased resistance to its forward motion, and 
 is therefore retarded in its forward motion, 
 while at the same time the other side of the 
 machine, presenting a smaller angle of inci- 
 dence, meets with less resistance to its for- 
 ward motion and tends to move forward more 
 rapidly than the retarded side. This gives 
 the machine a tendency to turn around its 
 vertical axis, and this tendency if not prop- 
 erly met will not only change the direction of 
 the front of the machine, but will ultimately 
 permit one side thereof to drop into a posi- 
 tion vertically below the other side with the 
 aeroplanes in vertical position, thus causing 
 the machine to fall. The movement of the 
 rudder hereinbefore described prevents this 
 action, since it exerts a retarding influence on 
 that side of the machine which tends to move 
 forward too rapidly and keeps the machine 
 with its front properly presented to the direc- 
 tion of flight and with its body properly bal- 
 anced around its central longitudinal axis. 
 The pivoting of the supports 23 so as to per- 
 mit them to swing upward prevents injury to 
 the rudder and its supports in case the ma- 
 chine alights at such an angle as to cause the 
 rudder to strike the ground first, the parts 
 yielding upward, as indicated in dotted lines 
 in Fig. 3, and thus preventing injury or 
 breakage. We wish It to be understood, 
 however, that we do not limit ourselves to 
 the particular description of rudder set forth, 
 the essential being that the rudder shall be 
 vertical and shall be so moved as to pre- 
 sent its resisting-surface on that side of the 
 machine which offers the least resistance to 
 the atmosphere, so as to counteract the tend- 
 ency of the machine to turn around a vertical 
 axis when the two sides thereof offer different 
 resistances to the air. 
 
 From the central portion of the front of the 
 machine struts 28 extend horiontally for- 
 ward from the lower aeroplane, and struts 29 
 extend downward and 'forward from the cen- 
 tral portion of the upper aeroplane, their 
 front ends being united to the struts 28, the 
 forward extremities of which are turned up, 
 as indicated at 30. These struts 28 and 29 
 form truss-skids projecting in front of the 
 whole frame of the machine and serving to 
 prevent the machine from rolling over for- 
 ward when it alights. The struts 29 serve to 
 brace the upper portion of the main frame 
 and resist its tendency to move forward 
 after the lower aeroplane has been stopped 
 by its contact with the earth, thereby reliev- 
 ing the rope 19 from undue strain, for it will be 
 understood that when the machine conies 
 into contact with the earth further forward 
 movement of the lower portion thereof being 
 suddenly arrested the inertia of the upper 
 
MISCELLANY 
 
 455 
 
 portion would tend to cause It to continue to 
 move forward If not prevented by the struts 
 29. and this forward movement of tue upper 
 portion would bring a very violent strain 
 upon the rope 19, since it is fastened to the 
 upper portion at both of its ends, while Its 
 lower portion is connected by the guides 20 
 to the lower portion. The struts 28 and 29 
 also serve to support the front or horizontal 
 rudder, the construction of which we will 
 now proceed to describe. 
 
 The front rudder 31 is a horizontal rudder 
 having a flexible body, the same consisting of 
 three stiff cross-pieces or sticks 32, 33, and 34, 
 and the flexible ribs 35, connecting said cross- 
 pieces and extending from front to rear. The 
 frame thus provided is covered by a suitable 
 fabric stretched over the same to form the 
 body of the rudder. The rudder is supported 
 from the struts 29 by means of the interme- 
 diate cross-piece 32, which is located near the 
 center of pressure slightly in front of a line 
 equidistant between the front and rear edges 
 of the rudder, tbe cross-piece 32 forming the 
 pivotal axis of the rudder, so as to constitute 
 a balanced rudder. To the front edge of the 
 rudder there are connected springs 36, which 
 springs are connected to the upturned ends 
 30 of the struts 28, the construction being 
 such that said springs tend to resist any 
 movement either upward or downward of the 
 front edge of the horizontal rudder. The 
 rear edge of the rudder lies immediately in 
 front of the operator and may be operated by 
 him in any suitable manner. We have 
 shown a mechanism for this purpose com- 
 prising a roller or shaft 37, which may be 
 grasped by the operator so as to turn the 
 same in either direction. Bands 38 extend 
 from the roller 37 forward to and around a 
 similar roller or shaft 39, both rollers or shafts 
 being supported in suitable bearings on the 
 struts 28. The forward roller or shaft has 
 rearwardly-extending arms 40, which are 
 connected by links 41 with the rear edge of 
 the rudder 31. The normal position of the 
 rudder 31 is neutral or substantially parallel 
 with the aeroplanes 1 and 2; but its rear 
 edge may be moved upward or downward, so 
 as to be above or below the normal plane of 
 said rudder through the mechanism provided 
 for that purpose. It will be seen that the 
 springs 36 will resist any tendency of the for- 
 ward edge of the rudder to move in either di- 
 rection, so that when force is applied to the 
 rear edge of said rudder the longitudinal ribs 
 35 bend, and the rudder thus presents a con- 
 cave surface to the action of the wind either 
 above or below its normal plane, said surface 
 presenting a small angle of incidence at its 
 forward portion and said angle of incidence 
 rapidly increasing toward the rear. This 
 greatly increases the efficiency of the rudder 
 as compared with a plane surface of equal 
 area. By regulating the pressure on the up- 
 per and lower sides of the rudder through 
 changes of angle and curvature in the man- 
 ner described a turning movement of the 
 main structure around its transverse axis 
 may be effected, and the course of the machine 
 may thus be directed upward or downward 
 at the will of the operator and the longitudi- 
 nal balance thereof maintained. 
 
 Contrary to the usual custom, we place the 
 horizontal rudder in front of the aeroplanes 
 at a negative angle and employ no horizontal 
 tail at all. By this arrangement we obtain a 
 forward surface which is almost entirely free 
 from pressure under ordinary conditions of 
 flight, but which even if not moved at all 
 from its original position becomes an effi- 
 cient lifting-surface whenever the speed of 
 the machine is accidentally reduced very 
 much below the normal, and thus largely 
 counteracts that backward travel of the cen- 
 ter of pressure on the aeroplanes which has 
 frequently been productive of serious injuries 
 
 by causing the machine to turn downward 
 and forward and strike the ground head-on. 
 We are aware that a forward horizontal rud- 
 der of different construction has been used in 
 combination with a supporting-surface and a 
 rear horizontal rudder; but this combination 
 was not intended to effect and does not effect 
 the object which we obtain by the arrange- 
 ment hereinbefore described. 
 
 We have used the term "aeroplane" in this 
 specification and the appended claims to in 
 dicate the supporting-surface or supporting- 
 surfaces by means of which the machine is 
 sustained in the air, and by this term we wish 
 to be understood as including any suitable 
 supporting-surface which normally is sub- 
 stantially flat, although of course when con- 
 structed of cloth or other flexible fabric, as 
 we prefer to construct them, these surfaces 
 may receive more or less curvature from, the 
 resistance of the air, as indicated in Fig. 3. 
 
 We do not wish to be understood as limit- 
 ing ourselves strictly to the precise details of 
 construction hereinbefore described and 
 shown in the accompanying drawings, as it 
 is obvious that these details may be modified 
 without departing from the principles of our 
 Invention. For instance, while we prefer the 
 construction illustrated in which each aero- 
 
 Rlaue is given a twist along its entire length 
 i order to set its opposite lateral margins at 
 different angles we have already pointed out 
 that our invention is not limited to this form 
 of construction, since it is only necessary to 
 move the lateral marginal portions, and where 
 these portions alone are moved only those 
 upright standards which support the mov- 
 able portion require flexible connections at 
 their ends. 
 
 Having thus fully described our invention, 
 what we claim as new, and desire to secure 
 by Letters Patent, is 
 
 1. In a flying-machine, a normally flat 
 aeroplane having lateral marginal portions 
 capable of movement to different positions 
 above or blow the normal plane of the body 
 of the aeroplane, such movement being about 
 an axis transverse to the line of flight, where- 
 by said lateral marginal portions may be 
 moved to different angles relatively to the 
 normal plane of the body of the aeroplane, so 
 as to present to the atmosphere different 
 angles of incidence, and means for so mov- 
 ing said lateral marginal portions, substan- 
 tially as described. 
 
 2. In a flying-machine, the combination, 
 with two normally parallel aeroplanes, su- 
 perposed the one above the other, of upright 
 standards connecting said planes at their 
 margins, the connections between the stand- 
 ards and aeroplanes at the lateral portions of 
 the aeroplanes being by means of flexible 
 joints, each of said aeroplanes having lateral 
 marginal portions capable of movement to 
 different positions above or below the normal 
 plane of the body of the aeroplane, such move- 
 ment being about an axis transverse to the 
 line of flight, whereby said lateral marginal 
 portions may be moved to different angles 
 relatively to the normal plane of the body of 
 the aeroplane, so as to present to the atmos- 
 phere different angles of incidence, the stand- 
 ards maintaining a fixed distance between 
 the portions of the aeroplanes which they con- 
 nect, and means for imparting such move- 
 ment to the lateral marginal portions of the 
 aeroplanes, substantially as described. 
 
 3. In a flying-machine, a normally flat 
 aeroplane having lateral marginal portions 
 capable of movement to different positions 
 above or below the normal plane of the body 
 of the aeroplane, such movement being about 
 an axis transverse to the line of flight, where- 
 by said lateral marginal portions may be 
 moved to different angles relatively to the 
 normal plane of the body of the aeroplane, 
 and also to different angles relatively to each 
 
456 
 
 VEHICLES OF THE AIR 
 
 other, so as to present to the atmosphere dtf 
 ferent angles of incidence, and means for si- 
 multaneously imparting such movement to 
 said lateral marginal portions, substantially 
 as described. 
 
 4. In a flying-machine, the combination, 
 with parallel superposed aeroplanes, each 
 baring lateral marginal portions capable of 
 movement to different positions above or be- 
 low the normal plane of the body of the aero- 
 plane, such movement being about an axis 
 transverse to the line of flight, whereby said 
 lateral marginal portions may be moved to 
 different angles relatively to the normal plane 
 of the body of the aeroplane, and to different 
 angles relatively to each other, so as to pre- 
 sent to the atmosphere different angles of in- 
 cidence, of uprights connecting said aero- 
 planes at their edges, the uprights connecting 
 the lateral portions of the aeroplanes being 
 connected with said aeroplanes by flexible 
 joints, and means for simultaneously impart- 
 ing such movement to said lateral marginal 
 portions, the standards maintaining a fixed 
 distance between the parts which they con- 
 nect, whereby the lateral portions on the 
 Bume side of the machine are moved to the 
 same angle, substantially as described. 
 
 6. In a flying-machine, an aeroplane hav- 
 ing substantially the form of a normally flat 
 rectangle elongated transversely to the line 
 of flight, In combination with means for Im- 
 parting to the lateral margins of said aero- 
 plane a movement about an axis lying in the 
 body of the aeroplane perpendicular to said 
 lateral margins, and thereby moving said lat- 
 eral margins into different angular relations 
 to the normal plane of the body of the aero- 
 plane, substantially as described. 
 
 6. In a flying-machine, the combination, 
 with two superposed and normally parallel 
 aeroplanes, each having substantially the 
 form of a normally flat rectangle elongated 
 transversely to the line of flight, of upright 
 standards connecting the edges of said aero- 
 planes to maintain their equidistance, those 
 standards at the lateral portions of said aero- 
 planes being connected therewith by flexible 
 joints, and means for simultaneously impart- 
 ing to both lateral margins or both aeroplanes 
 a movement about axes which are perpendic- 
 ular to said margins and in the planes of the 
 bodies of the respective aeroplanes, and 
 thereby moving the lateral margins on the 
 opposite sides of the machine into different 
 angular relations to the normal planes of the 
 respective aeroplanes, the margins on the 
 same side of the machine moving to the same 
 angle, and the margins on one side of the ma- 
 chine moving to an angle different from the 
 angle to which the margins on the other side 
 of the machine move, substantially as de- 
 scribed. 
 
 7. In a flying-machine, the combination, 
 with an aeroplane, and means for simultane- 
 ously moving the lateral portions thereof into 
 different angular relations to the normal 
 plane of the body of the aeroplane and to 
 each other, so as to present to the atmosphere 
 different angles of incidence, of a vertical 
 rudder, and means whereby said rudder is 
 caused to present to the wind that side there- 
 of nearest the side of the aeroplane having 
 the smaller angle of incidence and offering the 
 least resistance to the atmosphere, substan- 
 tially as described. 
 
 8. In a flying-machine, the combination, 
 with two superposed and normally parallel 
 aeroplanes, upright standards connecting the 
 edges of said aeroplanes to maintain their 
 equidistance, those standards at the lateral 
 portions of said aeroplanes being connected 
 therewith by flexible Joints, and means for si- 
 multaneously moving both lateral portions 
 of both aeroplanes into different angular re- 
 lations to the normal planes of the bodies of 
 the respective aeroplanes, the lateral por- 
 
 tions on one side of the machine being moved 
 to an angle different from that to which the 
 lateral portions on the other side of the ma 
 chine are moved, so as to present different 
 angles of Incidence at the two sides of the ma 
 chine, of a vertical rudder, and means where- 
 by said rudder is caused to present to the 
 wind that side thereof nearest the side of the 
 aeroplanes having the smaller angle of inci- 
 dence and offering the least resistance to the 
 atmosphere, substantially as described. 
 
 9. In a flying-machine, an aeroplane nor- 
 mally flat and elongated transversely to the 
 line of flight, in combination with means for 
 imparting to said aeroplane a helicoidal warp 
 around an axis transverse to the line of flight 
 and extending centrally along the body of the 
 aeroplane in the direction of the elongation 
 of the aeroplane, substantially as described. 
 
 10. In a flying-machine, two aeroplanes, 
 each normally flat and elongated trans- 
 versely to the line of flight, and upright 
 standards connecting the edges of said aero- 
 planes to maintain their equidistance, the 
 connections between said standards and aero- 
 planes being by means of flexible joints, in 
 combination with means for simultaneously 
 imparting to each of said aeroplanes a heli- 
 coidal warp around an axis transverse to the 
 line of flight and extending centrally along 
 the body of the aeroplane in the direction of 
 the elongation of the aeroplane, substantially 
 as described. 
 
 11. In a flying-machine, two aeroplanes, 
 each normally flat and elongated trans- 
 versely to the line of flight, and upright 
 standards connecting the edges of said aero- 
 planes to maintain their equidistance, the 
 connections between such standards and 
 aeroplanes being by means of flexible joints, 
 in combination with means for simultane- 
 ously imparting to each of said aeroplanes a 
 helicoidal warp around an axis transverse to 
 the line of flight and extending centrally 
 along the body of the aeroplane in the direc- 
 tion of the elongation of the aeroplane, a ver- 
 tical rudder, and means whereby said rudder 
 is caused to present to the wind that side 
 thereof nearest the side of the aeroplanes 
 having the smaller angle of Incidence and of- 
 fering the least resistance to the atmosphere, 
 substantially as described. 
 
 12. In a flying-machine, the combination, 
 with an aeroplane, of a normally flat and sub- 
 stantially horizontal flexible rudder, and 
 means for curving said rudder rearwardly 
 and upwardly or rearwardly and down- 
 wardly with respect to its normal plane, sub- 
 stantially as described. 
 
 13. In a flying- machine, the combination, 
 with an aeroplane, of a normally flat and sub- 
 stantially horizontal flexible rudder pivotally 
 mounted on an axis transverse to the line of 
 flight near its center, springs resisting verti- 
 cal movement of the front edge of said rudder, 
 and means for moving the rear edge of said 
 rudder above or below the normal plane 
 thereof, substantially as described. 
 
 14. A flying-machine comprising super- 
 posed connected' aeroplanes, means for mov- 
 ing the opposite lateral portions of said aero- 
 planes to different angles to the normal 
 planes thereof, a vertical rudder, means for 
 moving said vertical rudder toward that side 
 of the machine presenting the smaller angle 
 of incidence add the least resistance to the 
 atmosphere, and a horizontal rudder pro- 
 vided with means for presenting its upper or 
 under surface to the resistance of the atmos- 
 phere, substantially as described. 
 
 15. A flying-machine comprising super- 
 posed connected aeroplanes, means for mov- 
 ing the opposite lateral portions of said aero- 
 planes to different angles to the normal 
 planes thereof, a vertical rudder, means for 
 moving said vertical rudder toward that side 
 of the machine presenting the smaller angle 
 
MISCELLANY 
 
 457 
 
 of Incidence and the least resistance to the at- 
 mosphere, and a horizontal rudder provided 
 with means for presenting its upper or under 
 surface to the resistance of the atmosphere, 
 said vertical rudder being located at the rear 
 of the machine and said horizontal rudder at 
 the front of the machine, substantially as de- 
 scribed. 
 
 16. In a flying-machine, the combination, 
 with two superposed and connected aero- 
 planes, of an arm extending rearward from 
 each aeroplane, said arms being parallel and 
 free to swing upward at their rear ends, and a 
 vertical rudder pivotally mounted in the rear 
 ends of said arms, substantially as described. 
 
 17. A flying-machine comprising two su- 
 perposed aeroplanes, normally flat but flexi- 
 ble, upright standards connecting the mar- 
 gins of said aeroplanes, said standards being 
 connected to said aeroplanes by universal 
 joints, diagonal stay-wires connecting the 
 opposite ends of the adjacent standards, a 
 rope extending along the front edge of the 
 lower aeroplane, passing through guides at 
 the front corners thereof, and having its ends 
 secured to the rear corners of the upper aero 
 plane, and a rope extending along the rear 
 edge of the lower aeroplane, passing through 
 
 guides at the rr corner* thereof, and baring 
 its ends secured to the front corners of the 
 upper aeroplane, substantially aa described. 
 
 18. A flying-machine comprising two su- 
 perposed aeroplanes, normally flat but flexi- 
 ble, upright standards connecting the mar- 
 gins of said aeroplanes, said standards being 
 connected to said aeroplanes by universal 
 Joints, diagonal stay-wires connecting the 
 opposite ends of the adjacent standards, a 
 rope extending along the front edge of the 
 lower aeroplane, passing through guides at 
 the front corners thereof, and having its ends 
 secured to the rear corners of the upper aero- 
 plane, and a rope extending along the rear 
 edge of the lower aeroplane, passing through 
 guides at the rear corners thereof, and having 
 its ends secured to the front corners of the 
 upper aeroplane, in combination with a verti- 
 cal rudder, and a tiller-rope connecting said 
 rudder with the rope extending along the 
 rear edge of the lower aeroplane, substan- 
 tially as described. 
 
 ORVILLB WRIGHT 
 WILBUR WRIGHT. 
 Witnesses: 
 
 Chas. E. Taylor, 
 
 E. Earle Forrer 
 
 No. 831,173. 
 
 Specification and Claims of Montgomery Patent. 
 
 Filed April 26, 1905. Issued September 18, 1906. 
 
 Expires September 18, 1923. 
 
 To all whom it may concern: 
 
 Be it known that I, John J. Montgomery, 
 a citizen of the United States, residing at 
 Santa Clara, county of Santa Clara, State of 
 California, have invented certain new and 
 useful Improvements in Aeroplanes; and I do 
 hereby declare the following to be a full, 
 clear, and exact description of the same. 
 
 My invention relates to the class of aero- 
 planes; and it consists in certain surfaces 
 with means for adjusting them, as I shall 
 hereinafter fully describe. 
 
 The object of my invention Is to proTide a 
 controllable aeroplane device. 
 
 Referring to the accompanying drawings, 
 Figure 1 is a side elevation of my aeroplane 
 device. Fig. 2 is a top plan of the same. 
 Fig. 3 is a front view of the same. Fig. 4 is a 
 plan, enlarged, of one side of one wing-sur- 
 face. Fig. 5 is a cross-section on the line x x 
 of Fig. 4. Fig. 6 is a detail view of the con- 
 trolling wires and cords which change the 
 surface of the aeroplane. Fig. 7 is a detail 
 view of the same adapted for the rear wing- 
 surface of the aeroplane. Fig. 7 is a detail 
 view of the same adapted for the rear wing- 
 surface in order to vary its inclination to the 
 front wing-surface. 
 
 In the form of the device here Illustrated, 
 there is a front wing-surface A, a rear wing- 
 Burface B, and a horizontal tail-surface C. 
 The wing-surfaces A and B in fore-and-aft or 
 transverse section are curved, the most per- 
 fect form of the curve being that of a parab- 
 ola, whereby the curve in front Is sharp and 
 that in the back Is relatively more gradual, 
 as seen in Fig. 5. These two surfaces A and 
 B are connected by the bars D of a frame. 
 
 The front portions a and b, respectively, of 
 the wing-surfaces are best curved down from 
 center to ends, as seen in Fig. 3, and are 
 firmly attached to the fore-and-aft bars D at 
 the points d. They are also strongly braced 
 in all directions by wires d', running to ver- 
 tical frame-posts d 2 and to the frame-bars D. 
 The rear portions a' and b', respectively, of 
 the wing-surfaces are hinged midway of 
 their length, where their stiffener-bars are 
 severed and hinged together at a 2 and b 2 , so 
 that said rear portions are free to droop, but 
 are restrained from upward movement by a 
 series of wires E, attached to the lower beam 
 F of the frame in a manner which I shall 
 
 presently describe. These rear portions a' 
 and b' simply rest on the frame-bars D, and 
 thereby having their freedom of movement 
 can assume various positions, like the arms of 
 a balance, thus causing a change in the form 
 of the wing-surfaces on the two sides. This 
 change of surface is for the purpose of guid- 
 ance and partly for equilibrium and is pro- 
 duced by the following means. The wires 
 E, which are attached above to the rear por- 
 tion a' of the front wing-surface A, pass 
 downwardly from each side of said portion, 
 the group of wires from each side being 
 united below, as shown in Fig. 6, to opposite 
 ends of an equalizing-cable e through the in- 
 tervention of a ring. The equalizing -cable e 
 illey e', secured on 
 of the frame of the 
 
 plays freely through a 
 top of the lower beam 
 
 machine. Secured to the wing terminals of 
 the equalizer-cable e are cords e 2 , which pass 
 therefrom to the beam and cross each other 
 through a guide e 4 on said beam, and thence 
 said cords pass downwardly and backwardly, 
 as seen in Fig. 1, and are attached to the ends 
 of a cross-foot or stirrup-bar G, aa seen in 
 Figs. 2 and 3. The wires E, which are at- 
 tached above to the rear portion b' of the 
 rear wing-surface B, pass downwardly from 
 each side of said portion, the groups of wires 
 from each side being united below, as shown 
 in Fig. 7, to opposite ends of an equaliiing- 
 cable similar to the cable e in front and simi- 
 larly lettered through the intervention of a 
 ring. This rear equalizing-cable instead of 
 being guided by a pulley firmly attached to 
 the beam F is guided and plays freely 
 through the upper pulley of a triple sheave, 
 (lettered e 3 ), which sheave is connected with 
 and held by a cord J, attached to it. This 
 cord J passes freely through a hole in beam F, 
 as seen in Fig. 7, and is thence guided by a 
 pulley j under the beam to a point forward, 
 as shown in Fig. 1, to within reach of the 
 operator. Cords e 2 are secured to the ter- 
 minal rings of the rear equalizer-cable, e, as 
 shown in Fig. 7, and thence are guided by the 
 lateral pulleys of the triple sheave e* down- 
 wardly and backwardly to the foot or stirrup 
 bar G', as seen in Figs. 2 and 1. By pressing 
 down on the stirrup-bar on one side the rear 
 portions of the wing-surfaces on one side are 
 drawn down, while those on the opposite side 
 are allowed to yield to the air-pressure be- 
 
458 
 
 VEHICLES OF THE AIR 
 
 neath. By these means the wing-surfaces 
 change their form. The pressures on the 
 two sides of the device are varied, and the 
 device may keep its course when meeting a 
 gust, which would tend to tilt it and turn it 
 aside, or it may be made to change its course. 
 A feature of the arrangement of the cords e 2 
 (indicated in Fig. 6) is that the one attached 
 to the left arms passes through the guide E* 
 to the right end of the stirrup-bar, and vice 
 versa. Thus a pressure with the right foot 
 will force down the left rear surfaces, making 
 this the stronger side of the device, while the 
 right rear surfaces yielding become the 
 weaker. These changes cause the device to 
 swing to the right. 
 
 By simultaneously pressing on both ends 
 of the stirrup-bar all the rear portions of both 
 wing-surfaces are depressed for the purpose 
 of partly meeting the requirements of the 
 fore and aft equilibrium; but this is mainly 
 done by varying the relative inclination of 
 one of the wing-surfaces to that of the other. 
 This last-named variation involves both fore 
 and aft equilibrium and continuance of flight, 
 as I shall presently explain. This adjust- 
 ment of inclination is accomplished by al- 
 lowing the free rear portion of the rear wing- 
 surface B to rise under the pressure of the 
 air and by pulling it down again as required 
 by means of its wires E and cords e 2 , hereto- 
 fore described, which, as shown in Fig. 7, are 
 adapted for this independent use as the 
 pulleys e 8 of the rear control are not secured 
 to the beam F, but are held by a separate 
 cord J, which passes within reach of the op- 
 erator, being guided by a pulley j. 
 
 In the rear of the device in connection with 
 the tail-surface C there is a large surface H 
 perpendicular to the tail-surface, attached to 
 It and extending both above and below it. 
 The tail-surface is adapted to swing vertically 
 by being hinged at c to the rear of the wing- 
 surface B and its movement is effected by 
 means of a cord L, secured to it on each side, 
 Fig. 1, said cord being suitably guided and at- 
 tached to a sliding handhold 1 within reach 
 of the operator. 
 
 The surface H moves vertically with, the 
 tail-surface; but it has no side movement, be- 
 cause its function is that of a keel or fin and 
 not that of a rudder. It serves to maintain 
 the side equilibrium, which it does by per- 
 forming an operation different from that of a 
 rudder. The essentials of this fin-like sur- 
 face H are, first, that it shall be relatively 
 large; second, that it shall be proximately to 
 the rear surface, and, third, that it shall ex- 
 tend above and below the tail-surface C. 
 
 Concerning the fore and aft alined wing- 
 surfaces A and B there are two essential ad- 
 justments, first, that of the rear portions of 
 each relatively to the front portions and, sec- 
 ond, that of the inclination of one surface 
 relatively to the other. By the first adjust- 
 ment the surfaces undergo changes of form 
 and the effect is to vary the air-pressures on 
 the two sides of the machine, whereby the 
 device may keep its course, being prevented 
 from tilting or turning aside and may change 
 its course. These results are based upon the 
 essential character of a wing-surface. In- 
 vestigation has shown me that a wing is a 
 specially-formed surface placed in such a po- 
 sition as to develop a rotary movement in 
 the surrounding air. This position is deter- 
 mined by mathematical considerations. The 
 various requirements of gliding are met by 
 changes in various parts of the wing. The 
 movements in the air are of such a nature as 
 to make it possible to separate the wing-sur- 
 face, as I have done in my device, into front 
 and rear sections and maintain the special 
 rotary movement of the air which lies at the 
 basis of this phenomenon. The sections 
 though separated have a form and adjust- 
 ment suitable to themselves, based upon the 
 fundamental formula of formation and ad- 
 
 justment, but these must be coordinate to 
 the idea of one larger wing of which they are 
 supposed to be parts. By the second ad- 
 justment namely, that of the inclination of 
 one wing-surface relatively to the other the 
 machine maintains equilibrium and flight. 
 If a surface moves at a slight angle through 
 the air, the center of pressure is near the 
 front edge, and the weight carried must be 
 below this point. To meet the requirements 
 of varying speeds of motion, it is necessary to 
 either change the position of the weight or 
 the angle of the surface. This in my device is 
 done by changing the angle between the 
 front and rear wing surfaces A and B. In 
 the process of gliding there must be a con- 
 tinual change in the angle of these surfaces 
 to maintain the proper speed and equilibrium. 
 
 Concerning the tail-surface C there must 
 be an up-and-down or vertical adjustment. 
 The tail-surface is in reality but an extension 
 of the rear wing-surface B. By the varia- 
 tion of its angle the pressures in the rear are 
 varied. The same variations are, indeed, pro- 
 duced if the tail be dispensed with and the 
 rear wing-surface is changed in its angle. In 
 other words, whether the tail be a separate 
 surface or only an extension of the rear wing- 
 surface it is enough to say that the rear sur- 
 face must be adapted to change its angle in 
 part or whole. 
 
 The effect of the fin-like surface H is this: 
 If from any cause the machine is tilted to one 
 side and it commences to glide sidewise, 
 though the front parts have an unimpeded 
 side movement, the rear part having the large 
 fin H meets resistance and as a consequence 
 the machine is swung around and continues 
 to travel in the direction it started to fall. 
 This of course takes the machine out of its 
 course. To bring it back again, the wings 
 must be operated as before described. Thus 
 it will be seen this vertical fin-like surface 
 has a distinctive character, due to its size 
 and position, and, though apparently a rud- 
 der, is the reverse and not designed to perform 
 the office of a rudder. 
 
 Heretofore I have described the wing-sur- 
 faces as being curved in cross-section, the 
 best form being parabolic. It must now be 
 noted that for the best results the form of 
 each side of each wing-surface is specialized, 
 as follows: All the fore-and-aft or cross sec- 
 tions are parabolic curves; but those curves 
 nearer the center are most inclined to the 
 path of movement and thence toward the 
 ends their inclination is gradually decreased, 
 thereby producing a sinuousity of the wing, 
 as shown in Figs. 3 and 5, which is the nor- 
 mal surface from which the various changes 
 are made. In addition to this adjustment 
 or arrangement the curved cross-sections, 
 beginning about two-thirds from the center, 
 are less sharply curved in front, and so con- 
 tinue decreasing in sharp curvature to the 
 ends. This is shown in Figs. 4 and 5, where- 
 in the successive sections 1, 2, 3, and 4 show 
 the gradual cutting off at the front of the 
 Bharp beginning of the several parabolic 
 curves. The first of these arrangements 
 namely, the gradual change in inclination of 
 the cross-curves to the path of movement 
 is for the purpose of properly meeting and 
 cutting the rising current of air immediately 
 in front of the wing-surface, analysis and 
 experiments having shown that the action of 
 the under surface of a wing is to cause an as 
 cending current of air immediately in front of 
 the wing-surface, this ascending tendency 
 being greatest at the center and gradually 
 diminishing toward the tips. The second ar- 
 rangement namely, the diminishing curva- 
 ture near the ends of the wing of the for- 
 ward end of the curves is for the same pur- 
 pose, but is rendered necessary by the fact 
 that if the foregoing adjustment of the sur- 
 faces were continued to the end the sharp 
 curvature of the front edge would force the 
 
FIOUEE 260. Montgomery Patent Drawings. 
 
460 
 
 VEHICLES OF THE AIR 
 
 rear portions of the surface Into a too abrupt 
 position relative to its path, thus building up 
 a large unnecessary resistance to the forward 
 movement. 
 
 In using the aeroplane the operator sits 
 astride the beam F, with his feet on the stir : 
 rup-bar G. With one hand he holds onto the 
 frame and with the other he holds and oper- 
 ates the cord L for adusting the taiL The 
 machine, with the operator in place, is car- 
 ried to a height by means of a balloon and is 
 launched from any desired elevation by trip- 
 ping its connections with the balloon. 
 
 Having thus described the invention, what 
 I claim as new, and desire to protect by Let- 
 ters Patent, is 
 
 1. In an aeroplane device, a curved wing, 
 with means for changing its curvature. 
 
 2. In an aeroplane device, a curved wing, 
 with means for adjusting its rear portion rela- 
 tively to its front portion, to change its cur- 
 vature. 
 
 3. In an aeroplane device, a curved wing, 
 with means for adjusting either side of its 
 rear portion either similarly to or diversely 
 from the other, relatively to the front por- 
 tion, to change its curvature. 
 
 4. In an aeroplane device, a curved wing, 
 having a rigid front portion and an adjust- 
 able rear portion with means for adjusting 
 gaid rear portion relatively to the front por- 
 tion to change the curvature of said wing. 
 
 5. In an aeroplane device, a curved wing 
 having a rigid front portion, and an adustable 
 rear portion, with means for adjusting either 
 side of its rear portion eithed similarly to or 
 diversely from the other, relatively to the 
 front portion, to change its curvature. 
 
 6. An aeroplane curved parabolically from 
 front to rear, with means for changing its 
 surface. 
 
 7. An aeroplane curved parabolically from 
 front to rear with means for adjusting its 
 rear portion relatively to its front portion, to 
 change its surface. 
 
 8. An aeroplane curved parabolically from 
 front to rear with means for adjusting either 
 side of its rear portion either similarly to or 
 diversely from the other, relatively to the 
 front portion, to change its curvature. 
 
 9. An aeroplane curved parabolically from 
 front to rear, its front portion being rieid, and 
 its rear portion adjustable, with means for 
 adjusting said rear portion relatively to the 
 front portion, to change the surface of the 
 aeroplane. 
 
 10. An aeroplane curved parabolically 
 from front to rear, its front portion being 
 rigid, and Its rear portion adustable, with 
 means for adjusting either side of its rear por- 
 tion either similarly to or diversely from the 
 other, relatively to the front portion, to 
 change its curvature. 
 
 11. In an aeroplane device, plural curved 
 wings, one in advance of another, with means 
 for varying the angle of one relatively to an- 
 other and changing the curvature of each. 
 
 12. In an aeroplace device, plural aero- 
 planes curved parabolically from front to 
 rear, one in advance of another, with means 
 for varying the angle of one relatively to an- 
 other. 
 
 13. In an aeroplane device plural aero- 
 planes curved parabolically from front to 
 rear, one in advance of another, with means 
 for varying the angle of one relatively to an- 
 other, and changing the curvature of each. 
 
 14. In an aeroplane device, plural aero- 
 planes, one in advance of another, with means 
 for varying the angle of one relatively to an- 
 other, and means for adjusting either side of 
 the rear portion of each aeroplane either simi- 
 larly to or diversely from the other side, rela- 
 tively to the front portion, to change the sur- 
 face of each aeroplane. 
 
 15. In an aeroplane device, plural aero- 
 planes, curved parabolically from front to 
 rear, one in advance of another, with means 
 
 for varying the angle of one relatively to an- 
 other, and adjusting the rear portion of each 
 aeroplane relatively to its front portion to 
 change the surface of each. 
 
 16. A curved aeroplane with means for 
 changing its curvature, and a horizontal tail 
 behind, with means for swinging it vertically. 
 
 17. In an aeroplane device, plural curved 
 aeroplanes one in advance of another, and a 
 horizontal tail-surface behind the last aero- 
 plane with means for swinging said tail-sur- 
 face vertically. 
 
 18. In an aeroplane device, plural curved 
 aeroplanes, one in advance of another, with 
 means for varying the angle of one relatively 
 to another and a horizontal tail-surface be- 
 hind the last aeroplane with means for swing- 
 ing said tail-surface vertically. 
 
 19. In an aeroplane device, plural aero- 
 planes, one in advance of another, with means 
 for varying the angle of one relatively to an- 
 other and changing the surface of each, and a 
 horizontal tail-surface behind the last aero- 
 plane with means for swinging said tail-sur- 
 face vertically. 
 
 20. In an aeroplane device, plural aero- 
 planes, one in advance of another, with means 
 for varying the angle of one relatively to an- 
 other, means for adjusting either side of the 
 rear portion of each aeroplane either simi- 
 larly to or diversely from the other side, rela- 
 tively to the front portion, to change the sur- 
 face of each aeroplane, and a horizontal tail- 
 surface behind the last aeroplane with means 
 for swinging said tail-surface vertically. 
 
 21. In an aeroplane device, plural aero- 
 planes, curved parabolically from front to 
 rear, one in advance of another, with means 
 for varying the angle of one relatively to an- 
 other, and adjusting the rear portions of each 
 aeroplane relatively to its front portions to 
 change the surface of each, and a horizontal 
 tail-surface behind the last aeroplane with 
 means for swinging said tail-surface verti- 
 cally. 
 
 22. An aeroplane having at its rear a hori- 
 zontal tail-surface with means for swinging it 
 vertically, and a relatively large fin-surface 
 fixed to the tail-surface perpendicularly. 
 
 23. A curved aeroplane with means for 
 changing its curvature said aeroplane having 
 at its rear a horizontal tail-surface, with 
 means for swinging it vertically, and a rela- 
 tively large fin-surface fixed to the tail-sur- 
 face perpendicularly. 
 
 24. An aeroplane device comprising plural 
 aeroplanes one in advance of another, a hori- 
 zontal tail-surface at the rear of the last aero- 
 plane with means for swinging it vertically, 
 and a relatively large fin-surface fixed to the 
 tail-surface perpendicularly. 
 
 25. In an aeroplane device, plural aero- 
 planes one in .advance of another, with means 
 for varying the angle of one relatively to an- 
 other and changing the surface of each, and a 
 horizontal tail-surface behind the last aero- 
 plane, with means for swinging said tail-sur- 
 face vertically, and a fin-surface fixed to the 
 tail-surface perpendicularly. 
 
 26. In an aeroplane device, plural aero- 
 
 E lanes, one in advance of another, with means 
 OT varying the angle of one relatively to an- 
 other, means for adjusting either side of the 
 rear portion of each aeroplane either simi- 
 larly to or diversely from the other side, rela- 
 tively to the front portion, to change the sur- 
 face of each aeroplane, and a horizontal tail- 
 surface behind the last aeroplane with means 
 for swinging said tail-surface vertically, and a 
 fin-surface fixed to the tail-surface perpen- 
 dicularly. 
 
 27. In an aeroplane device, plural aero- 
 planes, curved parabolically from front to 
 rear, one in advance of another, with means 
 for varying the angle of one relatively to an- 
 other, and adjusting the rear portion of each 
 aeroplane relatively to its front portion to 
 change the surface of each and a horizontal 
 
MISCELLANY 
 
 461 
 
 tail-surface behind the last aeroplane, with 
 means for swinging said tail-surface vertically, 
 and a fin-surface fixed to the tail-surface per- 
 pendicularly. 
 
 28. A curved aeroplane with means for 
 changing its curvature and provided with a 
 fin-surface perpendicular thereto. 
 
 29. A curved aeroplane with means for 
 changing its curvature and provided with a 
 fin- surf ace perpendicular thereto and extend- 
 ing both above and below said aeroplane. 
 
 30. An aeroplane curved parabolically 
 from front to rear. 
 
 31. An aeroplane curved parabolically 
 from front to rear, its curves, in successive 
 eections from center to ends, decreasing in in- 
 clination to the path of travel. 
 
 32. An aeroplane curved parabolically 
 from front to rear, its sections near the ends 
 being less sharply curved at their front ends 
 than the forward ends of sections nearer the 
 center. 
 
 33. An aeroplane curved parabolically 
 from front to rear, its curves in successive 
 sections from center to ends decreasing in in- 
 clination to the path of travel, and its sec- 
 tions near the ends being less sharply curved 
 at their forward ends than the forward ends 
 of sections nearer the center. 
 
 34. An aeroplane curved parabolically 
 from front to rear, its curves in successive 
 sections from center to ends decreasing in in- 
 clination to the path of travel, its sections 
 near the ends being less sharply curved at 
 their forward ends than the forward ends of 
 sections near the center, and means for 
 changing the surface of said aeroplane. 
 
 35. An aeroplane curved parabolically 
 from front to rear, its curves in successive 
 sections from center to ends decreasing in in- 
 clination to the path of travel, and its sec- 
 tions near the ends being less sharply curved 
 at their forward ends than the forward ends 
 of sections nearer the center, and means for 
 adjusting the rear portion of said aeroplane 
 relatively to its front portion. 
 
 36. An aeroplane curved parabolically 
 from front to rear, its curves in successive 
 sections from center to ends decreasing in in- 
 clination to the path of travel, and its sec- 
 tions near the ends being less sharply curved 
 at their forward ends than the forward ends 
 of sections nearer the center, the front por- 
 tions of said aeroplane being rigid, and means 
 for adjusting its rear portion relatively to its 
 front portion, to change its surface. 
 
 37. In an aeroplane device, an aeroplane 
 curved parabolically from front to rear, its 
 curves, in successive sections from center to 
 ends, decreasing in inclination to the path of 
 travel, and a horizontal tail-surface approxi- 
 mate to the rear of said aeroplane, with 
 means for vertically swinging said tail-sur- 
 face. 
 
 38. In an aeroplane device, an aeroplane 
 curved parabolically from front to rear, its 
 curves, in successive sections from center to 
 ends, decreasing in inclination to the path of 
 travel, a horizontal tail-surface approximate 
 to the rear of said aeroplane, with means for 
 vertically swinging said tail-surface, and a 
 fin-surface secured perpendicularly to the 
 tail-surface. 
 
 39. In an aeroplane device, an aeroplane 
 curved parabolically from front to rear, its 
 curves, in successive sections from center to 
 ends, decreasing in inclination to the path of 
 travel, a horizontal tail-surface approximate 
 to the rear of said aeroplane, with means for 
 vertically swinging said tail-surface, and a 
 fin-surface secured perpendicularly to the 
 tail-surface and extending both above and 
 below said surface. 
 
 40. In an aeroplane device, an aeroplane 
 curved parabolically from front to rear, its 
 curves in successive sections from center to 
 ends decreasing in inclination to the path of 
 travel, and its sections near the ends being 
 
 less sharply curved at their forward ends 
 than the forward ends of sections nearer the 
 center, and a horizontal tail-surface approxi- 
 mate to the rear of said aeroplane, with 
 means for vertically swinging Miid tail-sur- 
 face. 
 
 41. In an aeroplane device, an aeroplane 
 curved parabolically from front to rear, its 
 curves in successive sections from center to 
 ends decreasing in inclination to the path of 
 travel, and its sections near the ends being 
 less sharply curved at their forward ends 
 than the forward ends of sections nearer the 
 center, a horizontal tail-surface approximate 
 to the rear of said aeroplane, with means for 
 vertically swinging said tail-surface, and a 
 fin-surface secured perpendicularly to said 
 tail-surface. 
 
 42. In an aeroplane device, an aeroplane 
 curved parabolically from front to rear, its 
 curves, in successive sections, from center to 
 ends, decreasing in inclination to the path of 
 travel, with means for changing the surface 
 of said aeroplane, and a tail-surface approxi- 
 mate to the rear of said aeroplane, with 
 means for vertically swinging said tail-sur- 
 face. 
 
 43. In an aeroplane device, an aeroplane 
 curved parabolically from front to rear, its 
 curves in successive sections from center to 
 ends decreasing in inclination to the path of 
 travel and its sections near the ends being 
 less sharply curved at their forward ends 
 than the forward ends of sections nearer the 
 center, with means for changing the surface 
 of said aeroplane, and a tail-surface approxi- 
 mate to the rear end of said aeroplane, with 
 means for vertically swinging said tail-sur- 
 face. 
 
 44. In an aeroplane device, an aeroplane 
 curved parabolically from front to rear, its 
 curves in successive sections from center to 
 ends decreasing in inclination to the path of 
 travel, and its sections near the ends being 
 less sharply curved at their forward ends 
 than the forward ends of sections nearer the 
 center, with means for changing the surface 
 of said aeroplane, a tail-surface approximate 
 to the rear end of said aeroplane, with means 
 for vertically swinging said tail-surface, and 
 a fin-surface secured perpendicularly to the 
 tail-surface. 
 
 45. An aeroplane device, comprising plu- 
 ral aeroplanes, one in advance of another, 
 with means for changing the surface of each, 
 and means for varying the angle of one rela- 
 tively to another, each of said aeroplanes 
 being curved parabolically from front to rear, 
 its curves in successive sections from center 
 to ends decreasing in inclination to the path 
 of travel, and its sections near the ends being 
 less sharply curved at their forward ends 
 than the forward ends of sections nearer the 
 center, a horizontal tail-surface approximate 
 to the rear portion of the last aeroplane, and 
 means for vertically swinging said tail-surface. 
 
 46. An areoplane device, comprising plu- 
 ral aeroplanes, one in advance of another, 
 with means for chaging the surface of each, 
 and means for varying the angle of one rela- 
 tively to another, each of said aeroplanes 
 being curved parabolically from front to rear, 
 its curves in successive sections from center 
 to ends decreasing in inclination to the path 
 of travel, and its sections near the ends being 
 less sharply curved at their forward nds 
 than the forward ends of sections nearer the 
 center, a horizontal tail-surface approximate 
 to the rear portion of the last aeroplane, 
 means for vertically swinging said tail-sur- 
 face, and a fin-surface secured perpendicu- 
 larly to the tail-surface. 
 
 In witness whereof I have hereunto set my 
 hand. 
 
 JOHN J. MONTGOMERY. 
 In presence of 
 J. Compton, 
 D. B. Richards. 
 
462 
 
 VEHICLES OF THE AIR 
 
 Claims of Chanute Patent. 
 
 No. 582,718. Filed December 7, 1895. Issued May 18, 1897. 
 
 Expires May 18, 1914. 
 
 1. A soaring-machine having a rigid frame 
 comprising a hoop A, plates K pivoted to said 
 hoop, on upright pintles, wings L attached to 
 said plates, and contractile members N lying 
 
 I, the wings L having ribs 1 hinged in said 
 plates, and the elastic cords N connecting the 
 front ribs with the hoop A, substantially as 
 described. 
 
 FIGURE 261. Chanute Patent Drawing. 
 
 in the plane of the wings and attached at one 
 end to the hoop and at the other end to the 
 fronts of the wings, substantially as described. 
 2. In a soaring-machine, the combination 
 with the framework comprising the hoop A, 
 of the plates K pivoted thereto on the pintles 
 
 In testimony whereof I affix my signature 
 in presence of two witnesses. 
 
 OCTAVE CHANUTE. 
 Witnesses: 
 
 Charles J. Roney, 
 Edw. Barrington. 
 
 No. 582,757. 
 
 Claims of Mouillard Patent. 
 
 Filed September 24, 1892. Issued May 18, 1897. Expires May 18, 1914. 
 
 1. A soaring-machine consisting of an aero- 
 plane composed of two wings, each hinged 
 upon a vertical axis and capable of forward 
 and backward movement only, substantially 
 as described. 
 
 2. A soaring-machine consisting of two 
 wings, each hinged upon a vertical axis, 
 an automatic regulating device controlling 
 the angular position of the wings with the 
 variation in speed, substantially as described. 
 
 3. A soaring-machine consisting of two 
 wings, each hinged upon a vertical axis, and 
 a mechanical device attached to said wings 
 for throwing forward the tips of the wings, 
 substantially as described. 
 
 4. A soaring-machine consisting of two 
 wings, each hinged upon a vertical axis, and 
 a spring attached to said wings, substantially 
 as described. 
 
 5. A soaring-machine consisting of two 
 wings, each hinged upon a vertical axis, and 
 a spring normally holding the tips of the 
 wings in advance of said axis, substantially 
 as described. 
 
 6. A soaring-machine consisting of two 
 wings, each hinged upon a vertical axis but 
 In different approximately parallel planes, so 
 that one can close partly over the other, sub- 
 stantially as described. 
 
 7. A soaring-machine consisting of two 
 wings, each hinged upon a vertical axis, and 
 each having a tail portion adapted to close 
 one over the other, substantially as described. 
 
 8. A soaring-machine consisting of two 
 wings, each hinged upon a vertical axis, and 
 adapted to close one over the other, and a 
 mechanical device attached to said wings for 
 positively closing them at will, substantially 
 as described. 
 
 9. A soaring-machine consisting of two 
 wings, each hinged upon a vertical axis, and 
 a cord attached to each wing and running 
 through an eye in the other wing, for clos- 
 ing said wings together substantially as de- 
 scribed. 
 
 10. A soaring-machine consisting of two 
 wings, each hinged upon a vertical axis, and 
 provided with stop-cords to limit their angu- 
 lar movement, substantially as described. 
 
 11. A soaring-machine consisting of two 
 wings, each hinged upon a vertical axis, and 
 having a portion movable out of the plane of 
 the wing, substantially as described. 
 
 12. A soaring-machine having wings adapt- 
 ed to move in horizontal planes, a portion of 
 the fabric covering each wing being stiffened 
 by flexible slats and having its rear edge free 
 from the frame of the wing, and cords at- 
 tached to said rear edge for pulling it down- 
 ward, substantially as described. 
 
 13. A soaring-machine consisting of two 
 wings, each composed of a framework, a net 
 spread under the framework, and a covering 
 of fabric fastened below the net, substan- 
 tially as described. 
 
 14. A soaring-machine consisting of an ar 
 
MISCELLANY 
 
 463 
 
 taiflcial sternum adapted to be fastened to the 
 body of the aviator and two wings, hinged to 
 said sternum on an upright axis, substantially 
 as described. 
 
 15. A cuirass or sorset for an aviator con- 
 sisiting of a rigid breastplate provided with 
 means for firmly attaching it to the body, and 
 having attachments for receiving and sup- 
 
 ed to hold a spring, as G, substantially as de- 
 scribed. 
 
 18. The combination with the rigid breast- 
 plate A carrying the hooks C, D of the wing, 
 each having arms F provided with eyes f f' 
 to fit on the hooks, substantially as described. 
 
 19. The combination with the rigid breast- 
 plate A having the hooks C, D and the clamp 
 
 FIGURE 262. Mouillard Patent Drawing. 
 
 porting an aeroplane, substantially as de- 
 scribed. 
 
 16. A cuirass or corset for an aviator, con- 
 sisting of a rigid breastplate provided with 
 means for firmly attaching it to the body, and 
 having hooks upon which a pair of wings may 
 be hinged on a vertical axis, substantially as 
 described. 
 
 17. The combination with the cuirass hav- 
 ing a rigid breastplate A, of the hooks C, D, 
 one above the other, and a clamp, as H, adapt- 
 
 H, of the wings each having arms F hinged 
 upon the hooks, and the flat steel spring G 
 held at its middle by the clamp, and having 
 its ends attached to the wings, substantially 
 as described. 
 
 In testimony whereof I affix my signature 
 In presence of two witnesses. 
 
 LOUIS PIERRE MOUILLAED. 
 Witnesses: 
 
 S. Nuripoy, 
 C. P. Lugold. 
 
 Claims of Lilienthal Patent. 
 
 No. 544,816. Filed February 28, 1894. Issued August 20, 1895. Expires August 20, 1912. 
 
 1. In a flying machine, the combination of 
 two crossed carrying rods a, two wings vaulted 
 upward, and strings or wires i extending from 
 the ends of the carrying rods toward the pe- 
 ripheries of the wings, substantially as set 
 forth. 
 
 2. In a flying machine, the combination of 
 two crossed carrying rods a, two wings vaulted 
 upward, strings or wires i connecting the two 
 carrying rods with the wings, and a vertical 
 fixed rudder substantially as set forth. 
 
 3. In a flying machine, the combination of 
 a crossed frame, two wings connected there- 
 with, strings or wires i, a vertical fixed rudder 
 r and a horizontal tail q, adapted to turn up- 
 ward automatically, substantially as set forth. 
 
 4. In a flying machine, the combination 
 with a supporting frame, of a wing adapted to 
 be folded together and having its ribs diverg- 
 ing from a common support, and suitably 
 hinged thereto a string connecting the outer 
 points of the ribs, and continuous fabric at- 
 tached to a series of ribs, substantially as set 
 forth. 
 
 5. In a flying machine, the combination 
 with a supporting frame comprising a hoop, 
 of a wing having its ribs diverging from a 
 common support, a string connecting the outer 
 
 points of the ribs, a wire, as g, fastened to the 
 first rib of the wing and attached to the hoop 
 and fabric stretched over the ribs and such 
 wire, substantially as set forth. 
 
 6. In a flying machine, the combination 
 with a supporting frame, of a wing having its 
 ribs diverging from a common support, fabric 
 stretched over the ribs and wires, as i, ex- 
 tending from the ribs downward to the sup- 
 porting frame for the purpose of adjusting 
 thereby the tension of the ribs, substantially 
 as set forth. 
 
 7. In a flying machine, the combination 
 with a frame comprising a hoop and crossed 
 bars connected therewith, of wings supported 
 by said frame, substantially as set forth. 
 
 8. In a flying machine, a supporting frame 
 for the wings comprising a hoop h, rods ex- 
 tending from it for supporting the operator 
 and a tail and a rudder, and pockets as d for 
 receiving the ends of the ribs of the wings, 
 substantially as set forth. 
 
 9. In a flying machine the combination 
 with a supporting frame, of wings with suit- 
 able ribs connected therewith, front tension 
 wires g, and pockets d for receiving the Inner 
 ends of the ribs, the ribs being made capable 
 of turning around their centers in such pock- 
 
464 
 
 VEHICLES OF THE AIR 
 
 ets for the purpose of folding up such wings, 
 substantially as set forth. 
 
 10. In a flying machine, the combination 
 with a supporting frame, of wings, a fixed 
 rudder and a pivoted tail adjusted to come to 
 rest upon the rudder when swinging down- 
 ward, substantially as set forth. 
 
 Signed at Berlin this 1st day of February, 
 1894. 
 
 OTTO LILIBNTHAL. 
 Witnesses: 
 
 Herman Muller, 
 Eeinhold Weidner. 
 
 FIGURE 263. Lilienthal Patent Drawing. 
 
 GLOSSARY OF AERONAUTICAL TERMS 
 
 The rapid and extensive recent development 
 in aeronautics has given rise to a pressing need 
 for proper technical terms wherewith to charac- 
 terize the different elements of the new mechan- 
 isms without ambiguity or awkward circumlo- 
 cution. In the English language this need has 
 been met largely by borrowings from the French, 
 supplemented by a number of new significances 
 given to common woods. Undoubtedly it is the 
 superior richness of the French language in its 
 technical nomenclatures, coupled with a quite char- 
 acteristic fertility in the invention of timely words 
 and phrases, that has enabled France thus to fasten 
 so much of its aeronautical terminology upon us. 
 
 That there is anything objectionable in this 
 situation, or in the often railed-at warping of 
 modern meanings away from archaic significances, 
 
MISCELLANY 465 
 
 is likely to be maintained only by extreme patriots 
 or purists. The generality of readers and writers, 
 knowing that the language of progressing mankind 
 must itself progress, and recognizing that usage 
 is here the court of last resort, will welcome the 
 needed additions to the dictionary with as little 
 ado as may be, preferring to seek definition rather 
 than to giv^e ear to denunciation. 
 
 In the following list are given the terms from 
 the vocabulary of aeronautics most in use and most 
 in need of definition. No pretension to complete- 
 ness, finality, or authority is made for the selection, 
 which is offered with full appreciation that it will 
 meet both criticism and amplification. The words 
 here given are from a variety of sources. Some, 
 as has been suggested, are common words that new 
 needs have invested with new meanings. Others 
 are foreign or coined. A few have been frankly 
 originated by the writer in the hope that they may 
 meet needs not otherwise met. And many, of 
 differing forms, are of synonymous meanings 
 included with the idea that only time can decide 
 between them. 
 
 adjusting- plane, same as ADJUSTING SURFACE. 
 
 adjusting 1 surface. Commonly, a comparatively small surface, usually at 
 the end of a wing tip, used to adjust lateral balance ; preferably restricted 
 to surfaces capable of variable adjustment but not of movement by con- 
 trolling devices. See STABILIZER and WING TIP, and compare AILERON 
 
 and BALANCING SURFACE. 
 
 advancing* edge. The front edge of a sustaining or other surface. See 
 
 FOLLOWING EDGE. 
 
 advancing* surface. A surface that precedes another through the air, as 
 in a double monoplane. See DOUBLE MONOPLANE and FOLLOWING SURFACE. 
 
 aerocurve, n. A proposed substitute for AEROPLANE, which see. 
 
 aerodrome, n. A substitute proposed by Langley for AEROPLANE, which see. 
 Strictly applicable to a course rather than to a vehicle. 
 
 aerofoil, n. Another proposed substitute for AEROPLANE, which see. 
 
 aeroplane, n. A generic term applied in common use in all classes of 
 sustaining surfaces ; a misnomer to the extent that it is strictly applicable 
 only to flat surfaces. 
 
 aileron, a'ler-on, n. A small hinged or separated wing tip or surface, 
 capable of independent manipulation for the purpose of maintaining 
 lateral balance. See BALANCING PLANE and BALANCING SURFACE, and 
 compare ADJUSTING SURFACE, STABILIZER, and WING TIP. 
 
466 VEHICLES OF THE AIR 
 
 air speed, n. The speed of an aerial vehicle through the air, as dis- 
 tinguished from its LAND SPEED, which see. 
 
 alighting gear. The under mechanism of an aeroplane, used to cushion its 
 descent and to bring it to a stop as it reaches the ground. See RUNNER 
 
 and STARTING DEVICE. 
 
 angle of entry. In a curved aeroplane surface, the angle made by a tangent 
 to the advancing edge with the line of motion. See ANGLE OP INCIDENCE 
 
 and ANGLE OF TRAIL. 
 
 angle of incidence. In a curved or a flat aeroplane surface, the angle made 
 by the chord or by the surface with its line of travel. See ANGLE OP 
 
 ENTRY and ANGLE OF TRAIL. 
 
 angle of trail. In a curved aeroplane surface, the angle of a tangent to 
 the rear edge with the line of travel. See ANGLE OP ENTRY and ANGLE 
 OP INCIDENCE. 
 
 apteroid, ap'ter-oid, a. A term coined by Lanchester to designate that type 
 of wing which is short and broad, as opposed to PTEKYGOID, which see. 
 
 arc. Any portion of a circle or other curve. See CHORD. 
 
 arch. A down curve given to the ends of a wing surface. Compare DIHEDKAL. 
 
 aspect. The top or plan view of an aeroplane surface. See ASPECT RATIO. 
 
 aspect ratio. The proportion of the length to the width of a wing or 
 aeroplane surface. See ASPECT. 
 
 aspiration, n. The little-understood phenomena by which under certain 
 circumstances an air current flowing against the edge of a properly 
 curved wing or aeroplane surface, is said to draw such surface towards 
 the current. See TANGENTAL. 
 
 attitude. Same as ANGLE OF INCIDENCE, which see; also see FLYING ATTITUDE 
 and GROUND ATTITUDE. 
 
 automatic stability. Applied to lateral or longitudinal stability maintained 
 by the action of suitable elements on mechanisms independent of any 
 control exercised by the operator ; there is a tendency to restrict the 
 term to such stability secured by automatic manipulation of controlling 
 devices, rather than to systems in which balance is maintained by the 
 use of fins or dihedral arrangements. See BALANCING SURFACE and 
 
 STABILIZER. 
 
 aviation, a-vi-a'shun. Dynamic flight by means of HEAVIER-THAN-AIB mechan- 
 
 aviator, a'vl-a-ter. The operator or pilot of a heavier-than-air flying machine. 
 
 B 
 
 balance, v. To maintain equilibrium by hand or automatic movement of 
 balancing surfaces, as opposed to equilibrium maintained by stabilizing. 
 See BALANCING SURFACE, and compare STABILIZE. 
 
 balancing plane. Same as BALANCING SURFACE. 
 
 balancing surface. Any surface capable of automatic or other manipula- 
 tion tor the purpose of steering, or of maintaining lateral or longitudinal 
 balance. See ADJUSTING SURFACE, AILERON, ELEVATOR, and WING WARPING, 
 and compare STABILIZING SURFACE and SUSTAINING SURFACE. 
 
 beat. Occasionally used to refer to the periodicity of revolving-blade or 
 flapping-wing movements. 
 
 biplane, U'plan, n. an aeroplane with two superposed main surfaces. See 
 
 DOUBLE MONOPLANE, MONOPLANE, TRIPLANE, and MULTIPLANE. 
 
 body. The center portion of an aeroplane or other aerial vehicle, in which 
 the motor, fuel tanks, passenger accommodation, etc., are placed. See 
 
 FUSELAGE and NACELLE. 
 
 brace, n. In the structure of an aerial vehicle, a frame member in com- 
 pression ; preferably restricted to diagonal compression members, in 
 contradistinction to STAY, which see, and therefore not the same thing 
 as a STRUT, which see. 
 
 C 
 
 camber, n. The maximum depth of curvature given to a surface as measured 
 at right angles from the chord to the highest point of the surface. 
 
 caster wheel. In an alighting gear, a wheel mounted on a vertical pivot 
 forward of its center of rotation, so that it automatically turns with 
 changes in the course of the vehicle. Compare FIXED WHEEL. 
 
 cell. A boxlike unit, consisting of upper, lower, and side surfaces, as in a 
 box kite ; used to afford lateral stability by the action of its vertical 
 surfaces and longitudinal stability by its horizontal surfaces. 
 
MISCELLANY 467 
 
 center of effort. The point or axis along which the propulsive effort or 
 
 thrust of one or more propellers is balanced, 
 center of gravity. The center of weight, about which the vehicle balances 
 
 in all directions. 
 center of lift. The center or mean of one or more centers of pressure. See 
 
 CENTER OF PRESSURE. 
 
 center of pressure. Really a line of pressure, along the under side of a 
 wing or aeroplane surface, on either side of which the pressures are equal. 
 
 center of resistance. The point or axis against which the various forward 
 pressures balance. 
 
 center of thrust. Same as CENTER OF EFFORT. 
 
 chassis, sha-se', n. The under structure or running gear of a vehicle. 
 
 chord. A straight line drawn between the ends of the arc of a circle or 
 other curve. See ARC. 
 
 compound control. A system of control in which two separate manipula- 
 tions, as of a vertical or horizontal rudder, are effected by compound or 
 two-directional movement of a single lever or steering wheel. 
 
 compression side. That side of a surface or propeller blade which acts 
 against the air ; usually the lower surface in the case of wings and aero- 
 planes. Compare RAREFACTION SURFACE. 
 
 curtain, n. Same as PANEL. 
 
 deck, n. A main aeroplane surface, used particularly with reference to BI- 
 PLANES and MULTIPLANES, which see. 
 
 demountable, di '-mount' 'able, a. Said of a mechanism designed with special 
 provision for ready taking apart and reassembling. 
 
 derrick, n. A tower in which a falling weight is dropped to start an aero- 
 plane. 
 
 diagonal. A diagonal brace or stay in a frame-work. 
 
 dihedral, dl-he'dral, a. Said of wing pairs inclined at an upward angle to 
 each other. Compare ARCH. 
 
 dirigible, dlr-ig'iUe, a. Steerable or navigable ; applied to balloons. 
 
 double monoplane, n. A monoplane with two supporting surfaces, one in 
 advance of the other. See ADVANCING SURFACE, FOLLOWING SURFACE, 
 
 MONOPLANE, and- MULTIPLANE. 
 
 double rudder, n. Any rudder in which there are two surfaces, usually simi- 
 lar in size and outline. 
 
 double-surfaced, a. Said of wings or aeroplanes with upper and lower sur- 
 faces, between which the ribs, wing bars, etc., are concealed. Compare 
 
 SINGLE-SURFACED. 
 
 down-wind, adv. Movement in the direction of or with the wind. Compare 
 UP-WIND. 
 
 drift, n. The aerodynamic resistance of a wing or aeroplane surface to for- 
 ward movement, as distinguished from HEAD RESISTANCE and SKIN FRIC- 
 TION, which see. Compare LIFT. 
 
 droop, n. Same as ARCH. 
 
 elevator, n. A term that has come into general use to describe horizontally 
 
 placed rudders for steering in the vertical direction, 
 ellipse. One of the conic sections, certain portions of which are closely 
 
 related to formation and development of correct wing sections. See 
 
 PARABOLA and HYPERBOLA. 
 
 entry, n. A term that refers generally to the whole form, angle of entry, 
 angle of incidence, etc., of an aeroplane or wing surface moving through, 
 the air. See ANGLE OF ENTRY, ANGLE OF INCIDENCE, WING SECTION. 
 
 equivalent head area. For purposes of calculation, an area of unbroken flat 
 surface having a head resistance equivalent to the total of that of the 
 various struts, bars, braces, stays, etc., of an aerial vehicle. See PRO- 
 JECTED AREA. 
 
 feathering, a. Said of surfaces moved in such manner that in one direction 
 they pass edgewise and in the other flatwise through the air. 
 
 fin, n. A single fixed vertical surface, not capable of movement out cf its 
 normal plane. See STABILIZING SURFACE. 
 
468 VEHICLES OF THE AIR 
 
 fish section, n. A term applied to cross sections roughly resembling the 
 body of a fish, blunt in front and more finely tapered towards the rear ; 
 a form that opposes a minimum resistance to mevoment through the air. 
 
 fixed wheel. In an alighting gear, a wheel not capable of being turned out 
 of its normal plane of rotation. See CASTER WHEEL. 
 
 flapping flight, n. Flight by means of more or less rapidly reciprocating sur- 
 face. iSee HELICOPTER ORNITHOPTER, and SOARING FLIGHT. 
 
 flexible propeller, n. A propeller consisting of fabric more or less loosely 
 mounted on a framework, so that it can adapt its iorm to the air pressures. 
 
 flying* attitude, n. The angle of incidence of a wing or aeroplane surface in 
 flight, as opposed to its angle when the machine is resting on a hori- 
 zontal surface. Compare GROUND ATTITUDE. 
 
 flying angle. Same as FLYING ATTITUDE. 
 
 following edge. The rear edge of a wing or aeroplane surface. Compare 
 
 ADVANCING EDGE. 
 
 following surface. A sustaining surface that is preceded by another, usu- 
 ally similar. Compare ADVANCING SURFACE. 
 
 footpound, n. The amount of energy required to raise one pound one foot ; 
 not involving the element of time. See HOKSEPOWEE. 
 
 forced pressure. An increase in the pressure of air adjacent to a surface 
 that acts upon it. Compare FORCED VACUUM. 
 
 forced vacuum. A lowering in the pressure of air adjacent to the surface 
 that acts upon it. Compare FORCED PRESSURE. 
 
 fore-and-aft stability. Same as LONGITUDINAL STABILITY. 
 
 fuselage, fu'sel-aj, n. The framework of an aerial vehicle ; preferably re- 
 stricted to aeroplane frameworks. 
 
 gap, n. The distance between two adjacent surfaces in a biplane or multi- 
 plane. 
 
 gliding, n. Flying down a slant of air without power. 
 
 gliding angle, n. The angle at which gliding descent is made ; usually the 
 flattest angle at which a machine is capable of descending. Compare 
 
 RISING ANGLE. 
 
 gliding speed, n. The speed at which an aerial vehicle glides at its flattest 
 angle of descent. See GLIDING ANGLE. 
 
 ground attitude. The angle of incidence of an aeroplane surface with the 
 machine standing on the ground, as opposed to its angle when the ma- 
 chine is in flight. Compare FLYING ATTITUDE. 
 
 guy, n. A wire or cord connecting with a more or less remote element of the 
 mechanisms of a flying vehicle ; preferably restricted to such wires and 
 cords as constitute parts of the controlling system. 
 
 gyroscope, ji'ro-skop, n. See GYROSCOPIC EFFECT. 
 
 gyroscopic effect. The property of any rotating mass whereby it tends to 
 maintain its plane of rotation against disturbing forces. 
 
 hangar, Mng'dr, n. A shed for housing balloons or aeroplanes, generally the 
 
 latter. 
 head resistance. The resistance of a surface to movement through the 
 
 air ; closely proportionate to its projected area. See DRIFT and PROJECTED 
 
 AREA, and compare SKIN FRICTION. 
 heavier-than-air, a. Applied to dynamic flying machines weighing more 
 
 than the air they displace. Compare LIGHTER-THAN-AIR. 
 
 height, n. Specifically, the maximum vertical dimension of an aerial vehicle. 
 helicopter, n. A dynamic flying machine, of the heavier-than-air type, in 
 
 which sustension is provided by the effect of screws or propellers rotating 
 
 on vertical axes. 
 horizontal, n. A term suggested for a level plane through a flying machine 
 
 when it is in flight, as opposed to a similar level taken when the machine 
 
 is standing on a horizontal surface. 
 horizontal rudder, n. A horizontally placed rudder for steering in vertical 
 
 directions. Compare VERTICAL RUDDER. 
 horsepower, n. A rate of work equivalent to the lifting of 33,000 footpounds 
 
 a iuinute. See FOOTPOUND. 
 
MISCELLANY 469 
 
 hoveling 1 , a. Said of flying in which practically a fixed position in the air 
 is maintained. 
 
 hyperbola. One of the conic sections, believed by Lilienthal to be the cor- 
 rect form for a wing section. See ELLIPSE and PARABOLA. 
 
 keel. A longitudinally placed under-framing for stiffening the structure of a 
 flying machine ; chiefly employed in the design of elongated dirigible 
 balloons. 
 
 lattice girder, n. A stiff and light structural element so named because of 
 the resemblance of its cris-crossed members to lattice work. 
 
 lateral stability, n. Stability in the lateral or side-to-side direction. Com- 
 pare LONGITUDINAL STABILITY. 
 
 land speed. The speed of an aerial vehicle over the land as distinguished 
 
 from its AIR SPEED, which see. 
 landing area. A special surface upon which flying machines can alight with 
 
 minimum risk of injury from obstructions. See STARTING AREA. 
 landing* skate. Same as RUNNER. 
 leading- edge. Same as ADVANCING EDGE. 
 leeway, n. Movement at right angles to a correct or desired course caused 
 
 not by errors in steering, but by lateral drift of the whole body of the 
 
 atmosphere. 
 lift, n. The sustaining effect, expressed in units of weight, of an aeroplane 
 
 or wing surface ; usually compared with DRIFT, which see. 
 lighter-than-air, a. Applied to an airship weighing less than the air it dis- 
 places. Compare HEAVIER-THAN-AIR. 
 longitudinal stability. Stability in the longitudinal or fore-and-aft direction. 
 
 Compare LATERAL STABILITY. 
 
 M 
 
 main deck. Same as MAIN PLANE, which see. 
 
 main plane. Usually the largest or lowest supporting surface of a multi- 
 surfaced aeroplane. 
 
 main landing* wheels. In an alighting gear, the wheels that take the chief 
 shock in landing. 
 
 mast, n. A spar or strut used for the attachment of wire or other stays to 
 stiffen wings or other parts of a structure. 
 
 monoplane, n. An aeroplane with one or more main surfaces in the same 
 horizontal plane. See DOUBLE MONOPLANE, and compare BIPLANE, MULTI- 
 PLANE, and TRIPLANE. 
 
 multiplane, n. An aeroplane with two or more superposed or otherwise 
 arranged main surfaces ; often, and perhaps preferably, applied to aero- 
 planes having three or more main surfaces. See BIPLANE, DOUBLE MONO- 
 PLANE, MONOPLANE, and TRIPLANE. 
 
 nacelle, na-seT, n. The framework or body of an aerial vehicle, preferably 
 restricted to dirigible balloons. See FUSELAGE. 
 
 negative angle of incidence, n. An angle of incidence below the line of 
 travel ; capable, despite a common impression to the contrary, of affording 
 considerable sustension with correctly curved wing surfaces. 
 
 ornithopter, n. A dynamic flying machine, of the heavier-than-air type, in 
 which sustension is provided by the effect of reciprocating wing surfaces. 
 
 See FLAPPING FLIGHT, ORTHOGONAL FLIGHT, and AEROPLANE. 
 
 orthogonal, or-tJiog'd-nal, a. Flapping flight in which sustension is pro- 
 duced by direct reaction of the air in a certical direction, as opposed 
 to sustension secured by a feathering movement of the wings. See FLAP- 
 PING FLIGHT. 
 
470 VEHICLES OF THE AIR 
 
 panel, n. A vertical surface in a box-kite-like structure. 
 
 parabola, n. One of the conic sections, which is, with certain proper modifi- 
 cations, the correct curve for the section of a wing surface ; a parabola 
 is practically an ellipse with its other focus at infinity. See ELLIPSE and 
 
 HYPERBOLA. 
 
 partition, n. Same as PANEL. 
 
 phugoid theory, fu'goid, n. A theory advanced by Lanchester to the effect 
 that all types of aeroplanes naturally fly in undulating paths with the 
 undulations of an amplitude and a period determined by the form and 
 size of the structure. 
 
 pilot, n. A widely preferred term for the operator of an aerial vehicle. 
 
 pitch, n. The amount of forward movement that would be made by a pro- 
 peller in the course of one rotation were it to progress through a solid 
 nut. See PROPELLER, STRAIGHT PITCH, and UNIFORM PITCH. 
 
 plane, n. Practically a flat surface, though "aeroplane" has come to mean 
 curved surfaces as well. See AEROPLANE. 
 
 polyplane, n. Same as MULTIPLANE. 
 
 port, n. The left side of a vehicle. Compare STARBOARD. 
 
 projected area, n. The equivalent flat area of an irregular structure ; the 
 same as the area of the shadow of such a structure cast by parallel rays 
 on a plain surface. See EQUIVALENT HEAD AREA. 
 
 propeller reaction. The tendency of a single or unneutralized propeller re- 
 volving in one direction to revolve the vehicle to which it is attached 
 in the other direction. 
 
 pterygoid, a. A term coined by Lanchester to designate that type of wing 
 which is long and narrow, as opposed to APTEROID., which see. 
 
 pylon, n. Same as DERRICK. 
 
 radial spoke, n. In a wire vehicle wheel, a spoke extending radially from 
 the hub to the rim. Compare TANGENT SPOKE. 
 
 rarefaction Bide, n. That side of a surface or propeller blade, opposite that 
 which acts against the air ; usually the upper surface in the case of 
 wings and aeroplanes. See COMPRESSION SIDE. 
 
 reactive stratum, n. The compressed stratum of air flowing beneath an 
 aeroplane surface or behind a propeller blade. 
 
 rib, n. An aeroplane member parallel to and used to maintain the correct 
 form of the wing sections. Compare STIFFENER and WING BAR. 
 
 rising* angle, n. The angle at which an aeroplane ascends in the air ; usu- 
 ally the steepest angle at which it is capable of ascending. Compare 
 
 GLIDING ANGLE. 
 
 rudder, n. A vertical or horizontal surface for steering in a horizontal or 
 vertical direction. See HORIZONTAL RUDDER and VERTICAL RUDDER. 
 
 runner, n. Used in some alighting gears in preference to wheels because of 
 the better action upon contact with the ground. 
 
 S 
 
 screw, n. Same as PROPELLER. 
 
 semichord, n. The part of a chord on either side of the highest point of the 
 curve ; not necessarily an exact half of the chord. See CHORD. 
 
 single-surfaced, a. Said of wings or aeroplanes with single surfaces, above 
 or below which the ribs and wing bars are placed. Compare DOUBLE- 
 SURFACED. 
 
 ekid, n. Same as RUNNER. 
 
 skin friction, n. The friction of the air against the surfaces of an aerial 
 vehicle. 
 
 slip, n. The amount of distance lost in the travel of a propeller, estimated 
 by comparison of the distance actually travelled in a given number of 
 turns with the distance that theoretically should be travelled as figured 
 from the PITCH. See PITCH. 
 
 soaring 1 flight, n. The flight of certain large birds without wing flapping, 
 differing from gliding in that it commonly involves upward movement 
 apparently in defiance of the laws of force and motion, though some, 
 without well-established reason, suppose it to be accomplished by taking 
 
MISCELLANY 471 
 
 advantage of rising air currents, internal air movements, etc. Its solu- 
 tion and imitation constitute one of the problems of aerial navigation. 
 
 spar, n. A term in more or less common use to describe struts, masts, 
 braces, etc. 
 
 stabilize, v. To maintain equilibrium by the action of surfaces rather than 
 by the manipulation of devices. 
 
 stabilizer, n. An anglicised form of the French "stabllisator." Any surface 
 for automatically maintaining lateral or longitudinal balance. See 
 
 AUTOMATIC STABILITY, FIN, LATERAL BALANCE, and LONGITUDINAL BAL- 
 ANCE. 
 
 stabilizing 1 surface, n. Any surface placed in a vertical or other position, 
 primarily for the purpose of maintaining equilibrium. See CELL, DIHE- 
 DRAL, FIN, LATERAL STABILITY, and PANEL, and Compare BALANCING SUR- 
 FACE and SUSTAINING SURFACE. 
 
 stable equilibrium, n. said of machines In which any tendency to tip over 
 automatically corrects itself without the use of automatic balancing 
 devices. See FIN. 
 
 starboard, n. The right side of a vehicle. Compare PORT. 
 
 starting* area. A special surface from which flying machines can be 
 launched either with or without starting devices. See LANDING AREA and 
 
 STARTING DEVICE. 
 
 starting 1 device. Any device for launching aerial vehicles. See DERRICK, 
 
 STARTING IMPULSE, STARTING HAIL, and STARTING TRUCK. 
 
 starting* impulse. The initial thrust required for starting aeroplanes ; se- 
 cured either by the propeller thrust or other means within the vehicle 
 itself, or by special extraneous appliances. See DERRICK, STARTING DE- 
 VICE, STARTING RAIL. 
 
 starting* rail, n. A rail on which an aeroplane is run in starting. See 
 
 STARTING DEVICE, STARTING IMPULSE, and STARTING TRUCK. 
 
 starting* truck, n. A small truck upon which an aeroplane Is mounted 
 while there is imparted to it the initial impulse. See STARTING DEVICE, 
 
 STARTING IMPULSE, and STARTING RAIL. 
 
 stay, n. In the structure of an aerial vehicle, a frame member of wire or 
 other material. See BRACE. 
 
 stiff ener, n. A straight bar used to stiffen a flat surface, in contradistinc- 
 tion to a rib, which maintains the curvature of a curved surface. Com- 
 pare RIB. 
 
 straight pitch, n. In an aerial propeller, a uniform angle of blade surface 
 from hub to tip, so that the different portions of the blade do not ad- 
 vance through the air at the same speeds. Compare UNIFORM PITCH. 
 
 strainer, n. Same as TURNBUCKLE. 
 
 strut, n. A compression member in a structure ; particularly applied to 
 vertical members separating the sustaining surface of biplanes and multi- 
 planes. See BRACE and SPAR. 
 
 strut socket. A metal or other socket or corner piece for joining struts and 
 other frame members. 
 
 supplementary surface, n. A comparatively small surface used in conjunc- 
 tion with larger surfaces for some special purpose, as the maintenance 
 of equilibrium, for steering, etc. See AILERON, FIN, and RUDDER. 
 
 sustaining* surface, n. Any surface placed in a horizontal, or approximately 
 horizontal position, primarily for the purpose of affording sustension. 
 See AEROPLANE and compare BALANCING SURFACE and STABILIZING SUB- 
 FACE. 
 
 tail, n. A rear element of an aeroplane adapted to improve its stability and 
 often affording a place for the attachment of vertical and horizontal 
 rudders, stabilizing devices, etc. See CELL, ELEVATOR, and RUDDER. 
 
 tail wheel, n. A wheel mounted under the tail of an aeroplane to support 
 it on the ground. See CASTER WHEEL and RUNNING GEAR. 
 
 tang-ental, a. Applied to the forward inclination of the sustaining force 
 with certain surfaces at certain angles, so that the surface tends to 
 move into the wind. See ASPIRATION and DRIFT, and compare LIFT. 
 
 tangent spoke. In a wire vehicle wheel, a spoke extending on a tangent 
 from the hub circle to the rim, this construction affording a wheel 
 adapted to transmission of power. Compare RADIAL SPOKE. 
 
 tie, n. A wire or other tension member connecting two points in a struc- 
 ture. See STAY. 
 
472 VEHICLES OF THE AIR 
 
 tightener. Any device for tightening a stay wire, but preferably restricted 
 to tighteners of types that do not involve cutting the wire. Compare 
 
 TUBNBDCKLE. 
 
 tractor screw. A propeller placed in front of a vehicle, so that it pulls in- 
 stead of pushes it through the air. 
 
 traveling 1 speed, n. Same as GLIDING SPEED, which see; also used to refer 
 to the maximum speed of an aeroplane. 
 
 triplane, n. An aeroplane with three main surfaces. Compare BIPLANE, 
 
 DOUBLE MONOPLANE*, and MONOPLANE. 
 
 trochoidal, trd'koyd-til, a. A term coined by Hargrave, a trochoidal plane 
 being defined by him as "a flat surface, the center of which moves at a 
 uniform speed in a circle, the plane being kept normal to the surface 
 of a trochoidal wave, having a period equal to the time occupied by the 
 center of the plane in completing one revolution." 
 
 turnfcuckle. A device with a right and left-hand screw for tightening wire 
 ties and stays. Compare TIGHTENER. 
 
 uniform pitch. In an aerial propeller a varying angle of blade surface from 
 hub to tip, so that all portions of the blade tend to advance through 
 the air at the same rate of speed. See PITCH and STRAIGHT PITCH. 
 
 np-wind, adv. Movement in a direction directly against the wind. Compare 
 DOWN-WIND. 
 
 vertical rudder. A vertically-placed rudder for steering in horizontal direc- 
 tions. Compare HORIZONTAL RUDDEB. 
 
 W 
 
 wake, n. The trail of disturbed air left by a moving aerial vehicle, invis- 
 ible, but in a way resembling the wake of a ship in its effect upon other 
 vehicles that pass into it. See WASH. 
 
 wash, n. Lateral oscillations of air sent out from the sides of an aerial 
 vehicle; invisible as in the case of the foregoing except by their effect 
 upon adjacent vehicles. See WAKE. 
 
 wing- arc, n. The arc of movement of a flapping wing. See FLAPPING 
 
 FLIGHT and ORNITHOPTER. 
 
 wing 1 bar. A longitudinal strengthening member in a wing or aeroplane, 
 
 running from tip to tip and crossed at right angles by the ribs. See 
 
 BIBS. 
 wing 1 girder, n. Same as wing bar, excepting that it usually implies a 
 
 more elaborately built-up construction. 
 wing 1 plan, n. The outline of a wing or aeroplane surface viewed from 
 
 directly above or below. 
 wing- section. The fore-and-aft curvature, to the path of movement, in the 
 
 sections of a wing or aeroplane. See AEROPLANE, ELLIPSE, HYPERBOLA, 
 
 and PARABOLA. 
 wing 1 skid. A small runner under the tip of a wing to protect it from 
 
 damage by coming in contact with the ground. Compare WING WHEEL. 
 wing* tip. The extreme outer end of a wing, often made movable or capable 
 
 of warping, to control lateral balance. See AILERON and WING WARPING. 
 wing* warping*. A system of maintaining lateral balance by differential 
 
 twisting of wing tips, in such manner as to increase the sustension on 
 
 one side and decrease it on the other. 
 wing 1 wheel. A small wheel under the tip of a wing to protect it from 
 
 damage by coming in contact with the ground. 
 
CHAPTER FIFTEEN 
 
 FLIGHT EECORDS 
 
 Much interest naturally attaches to the various 
 records that have been made with flying machines, 
 for which reason there is herein presented in tabu- 
 
 FIGURE 264. Diagrammatic Comparisons of Modern Aeroplanes. A, Santos- 
 Dumont Monoplane; B, Bleriot Monoplane; G, Curtiss Biplane; D, Volsin, 
 Biplane ; E, R. E. P. Monoplane ; F, Antoinette Monoplane ; &, Wright Biplane ; 
 H, Cody Biplane. 
 
 473 
 
474 
 
 VEHICLES OF THE AIR 
 
 lar form the most complete record yet published 
 of such flights, together with maps of the more im- 
 
 FIGURE 265. Flights over English 
 Channel. The Boulogne - Folkstone 
 flight has not been accomplished, but 
 a prize is offered for it. 
 
 portant cross-country trips. 
 Of the latter, the greatest 
 interest perhaps attaches Fiightsf^haloSslo Yt 
 
 j -ri j_i 2.1 and Chalons to Suippes. 
 
 to Bleriot s crossing 01 the 
 
 English Channel with his re- 
 markable little monoplane (see 
 Figure 265), Henry Farman's 
 first trip from Chalons to Rheims 
 and then, at a later date, from 
 Chalons to Suippes (see Figure 
 266); Louis Bleriot 's flight from 
 Toury to Artenay, France, and 
 back, and then from Etampes to 
 Orleans (see Figure 267) ; F. W. 
 Cody's 40-mile flight over Alder- 
 shot and Farnboro, England (see 
 Figure 268) ; and Count de Lam- 
 FIGURE 267. Bie- bert 's flight with a Wright bi- 
 
 riot Flights, Toury . 
 
 Etam^s^o^Orle^. P laB6 fl * Om J^VlSy to PariS (see 
 
FLIGHT RECORDS 
 
 475 
 
 Figure 269). 
 
 In the tabu- 
 
 1 a r history 
 
 that follows 
 
 are given the 
 
 full particu- 
 lars of every 
 
 flight of special importance or int- 
 erest from the earliest times to the 
 present. These flights aggregate a 
 distance of over 20,000 miles, occu- 
 pying a total time of over 700 hours with over 150 
 
 FIGURE 268. Cody's 40-Mile 
 Cross-Country Flight in Eng- 
 land. 
 
 FIGURE 269. 
 
 APRIL i. -. - ----- 
 
 JULY Z . 
 cfifLY 31 . 
 A.UG- 4 . 
 
 FIGURE 270. Map Showing Principal Zeppelin Flights. 
 
476 
 
 VEHICLES OF THE AIR 
 
 different persons carried. It is to be noted that in 
 all this experimenting there have been only three 
 individuals killed a showing that compares well 
 with the earlier, and even later, periods of much 
 longer established developments in transportation. 
 
 TABULAR HISTORY OF FLIGHTS 
 
 PL4CS. 
 
 MACHIMB. 
 
 3ae. MIN. SBC. RKHAEKS. 
 
 From tower ; tell and broke [eg. 
 
 ;;;;;; *im whig warping. Started u kite, 
 et 6:66':ii Monoplane model. 
 
 , 
 
 sfeittB. 
 
 S^ 3 ?: Hi 
 
 SS:^.?ggg:: 
 JSSSii^:: 
 
 July 18, 190(,. . 
 
 "'f: 
 
 I: iSSS:: 
 
 ia, woe.. 
 
 BK: 
 
 r:::^::::::::S^^;;;;;^^-:::::::: 
 : : : : fiSTK* iiiuii : : : SISS :: : : : : : : : : : : 8^v L P ; Sa a L; 'i : ^i 
 
 600 tcet 
 
 iftSI 
 
 J&1& 
 
 1,000 ft 
 
 3> r e *t 
 
 COO to* 
 
 6-6a'9 
 
 :: gW3#* 
 
 :: feft 1 ^*'** 1 "**" 
 
 Went in water. 
 
 Frccj balloon. 600 feet biith 
 
 From balloon 2,500 leet ll^h. 
 
 S iiiiii HJBF"* 
 
 Without re radder. 
 
 
 :^: ;: ^::::::::::^:::::::;:;;:^1?!^;::T -- : 
 
 :'l^wSfe\ : S!!S:*fi: : i: : gi^^E: 
 
 Hoverin^rwI^M^Ster 
 ^fKffl** 
 
 "JJj^g*"* glMe8 o:> > lrt y <us 
 
 
 ahdral kite ; towed. 
 
 = ,S : ;SlS~Sfi : ::::::. : iJ&fiSm- 
 
 
 ssS 
 
 SS ;=;! 
 
 ill 
 
 & iS ! 
 
 SKJihos- 
 
 P. 12, iocs:: 
 
 ^ i* 2 ; 112!:: 
 SK i5 i 1 ^ 8 -- 
 
 opt. IT; leog 
 
 't'ljt. 21, 10OS 
 Seyt. 22, 180S 
 Rept. 24, 1608 
 
 Seltrldge killed. 
 
 ijiljfg* Ar "^ ?5 feet hi, 
 0:04 :3S Elghteea LJlij w!n4 . 
 
FLIGHT RECORDS 
 
 477 
 
 ill: 
 
 .82 IBS:: 
 
 Oet D, 1908.. 
 
 Oct 0, 1908.. 
 
 Oct. T, 1908.. 
 
 Oct. 10, 1908. . 
 
 Wilbur W 
 
 France. , Biplane 
 
 .CUalons, France Biplane 
 
 . Chalons, France. Biplane 
 
 . Chalons, France. Biplane 
 
 _ 25474 miles 
 
 Farmani '. 24.854 miles 
 
 . . Wili.iir Wright and Fran* 
 
 . . Wilbur ' WrieSt" "and "bran 
 
 . . W *bur**Wriebt'tnd' Arnold 
 
 Fordyce 40 mile* 
 
 ..Wilbur Wright aad Mrs. 
 
 Hart Cv Berg 
 
 sii* 
 HI 
 
 0:56:3?% 
 
 :04 :00 Bollee'. 
 
 1. -04:26% 
 
 0:02:03 
 
 rfftjHIw'^nlie* n Hour. -lth tad 
 .. Eisuty-two r* high 
 
 6":26':66 Partly crow-country. 
 
 .-05 .00 Ninety fwt M*h. 
 - Twelve-mile wind. 
 
 c 
 
 .J. A. I>. M^uidy ; 
 
 . J A. D. McCirdy 
 
 . \.-Mvir and Katberlue 
 
 .). A^ D. McCardyl ! '.'.'. '. '. '. 
 
 T*o circle*. This fllgM oakcc tota 
 
 1.000 aillne over 100 trips OTt. 
 
 :::::fi[KSi 
 
 June" 6, 19U9. 
 June 6, l0i). 
 
 June T, 1809. 
 
 ..Antoinette 
 
 ..Golden flyer". 
 . . Antoinette 
 
 . Juvlay, France 
 
 , Huborf Tatl 
 
 "rasiL . 
 
 - ' a ^,nTe l r. ndi ff.." nd .. M ; 
 . Paul Tlisandior and M. Le- 
 
 :SS^'i:::':H:: I&S 
 
 :*'igS. ::::::::: s .i SIS 
 
 '. Hubert Latham 3 ": : : : '. :.'. : : 10 8 miles 
 
 . Louis Blerlot and Andre 
 
 Fouraler ,. 1.0T8 feet 
 
 .Leon Delajfrange l-.^i L-illf* 
 
 . Hubert Latiiau a mllet 
 
 i -n elides. 
 
 . .-,-.; flight*. 
 uiJiuK ram. 
 
 i':07':3Y I" *'!>! eud '/Bin. 
 . FUvrv-eiKbt curves. 
 Cro-cocntrj. At 56 mlV j. - ur 
 
 SiWit? * Dd 81 " lie * - CCUf 
 '.:::::'. intwoaieht>. 
 
 ..;.... Five parsciigers, one after snother. 
 
478 
 
 VEHICLES OF THE AIR 
 
 June 8, 1909 Antoinette Hubert Latham 
 
 ijp 
 
 ]K 11: ji 
 
 . Morris Park, N. T. . 
 "rJ-SiS"-*" 
 
 . . Glenn H. Curtiss 
 
 . . Glenn H. Curtlss 
 
 . . Louis Blerlot 
 
 ..Louis Blerlot 
 
 ..Louis Blcnot and M.Guyot. 
 
 . . Leon Delagrauge 
 
 ..Louis Blerlot, Alberto San- 
 Dumont and Adre 
 
 2,040* 
 
 1,640 fi 
 1.24 mil 
 4,920 f( 
 3.7 ml! 
 
 Cut^oS power at JO feet^hlgh^atart 
 gilded again * to" ground OJ 'in 1 
 
 Went over 500 feet high. 
 Machine wrecked. 
 
FLIGHT RECORDS 
 
 479 
 
 lu : | 38S: 
 iSiUSS: 
 
 Ai. 26, 1909. 
 
 iS II: 1SS8: 
 IS i?:.iSS8:- 
 
 iS I?' iSS: 
 iS. S: iS8S: 
 IS I 8 7 : a 9 : 
 
 illl 
 fills;:;; 
 SI H;;;; 
 
 ::::::: ^Sit sir-. Y.-.Y: 
 
 ! ithelirV, France! ...!. .Biplane 
 
 .Riielras, France "Blsriot XI".... 
 
 . Rheimj, France .'. .Antoinette ..,. .. 
 
 .BkelOM, France Wrvht 
 
 . fchciina,, France Biplane ...;... 
 
 Louis- Blerlot ............ 
 
 Hubert Latham ........... 
 
 Hubert Latham...;.' ..... 
 
 Bferlot m and M.'Ee'tn'. 
 H. Curtlss. ........ 
 
 Hlerlot ............ 
 
 ubert Latham ..... '..... 
 
 19'mnes 
 
 24.85 miles 
 
 ' 
 
 0:28:59% 
 l':38:05Vi 
 3:04:50% 
 
 .Rhelms, Frtmce Farmau 
 
 nu'i' Farman 
 
 1 - oat bi-.ux 
 
 . ithfl.i.H, |.'.i3u- Antoinette 
 
 . Dunkerqnft. -France. . . .'Wright 
 
 , Rheims, F.-an :t- Wrl^at 
 
 :S^^S:::::::^ E r?o e txi"Y.Y. 
 
 . Rbiinis. France Blpune 
 
 .rn iau, i';.iu^- '!;:<! i.,t XI". . . . 
 
 . i;i, .;:..'.-. i-nu.-e "illi-rM XI".... 
 
 .Bheiou, Vr?->x- Antoinette 
 
 .Rhelms, France Biplane 
 
 . HerliM, CTHiC-ay Blplapa 
 
 . Uaeiu'-a, France Bipiaiie ,,' 
 
 .Bbelm*, France ItipldM 
 
 .Rhelms, France Blplniie 
 
 .K>>;-t!.,, France Aijujl-ieite 
 
 .Bheima, tr^-.nv r.l:,'^aa 
 
 .Rheims, Fi-i.n^e ivlr.ne ....... 
 
 .,::, ^ Franot Biplane 
 
 .KhelTis, France Wright 
 
 .I'.hei-aa, France Biplane 
 
 !Rnln3 France Antoinette 
 
 . Aldershot England Biplane ....... 
 
 .htershot, England Biplane 
 
 At 42 miles per hour. 
 Smashed wlafr 
 
 No distance Allowed for curvet. Time 
 taken at 111.78 mile*. Barely 
 10 feti high. 
 
 At 47.65 miles an hour. 
 
 Sept. 4, 1909. 
 
 Sept 5. 1009. 
 
 Sept 6, 1909. 
 
 fe'pt 7 6 : iSS?: 
 
 Sept. 7, 1909. 
 
 7.;V.;.KoechlUi 
 
 uvlay', Franc-- Voigln 
 
 orouto, Canada "Golaea Flyer" . 
 
 .'. Biplane ., 
 
 . rnal, France., Voisin ... 
 
 . Nancy, France Farman . 
 
 .'juTlsy! France.'.'.'.'.'.'.'.' Wright ..", 
 
 . St. Cyr, France Monoplane 
 
 . Berlin, Germany Biplane . 
 
 . Boulogne to Wlmereux, 
 
 France. Volsln ... 
 
 Bept 8, 1909 Berlin, Germany Biplane . 
 
 Sept 8, 1909 Berlin, Germany Biplane . 
 
 Bept 8, 1909 Alderahot, England Biplane . 
 
 Sept, 9, IftOH Berlin, Germany Biplane . 
 
 Bept 9. 1909 Berlin, Germany... Biplane . 
 
 .Voisin ... 
 
 Glenn II. Curtlss ......... 
 
 l-nn il. CnrtlEs ...... . . 
 
 Hubert Latliam .......... 
 
 Glenn H. Curtiaa ........ . 
 
 . Glean H. Curtisa .... 
 
 Glenn H. Curtiss ........ 
 
 Count d? Lambert ........ 
 
 Henry Farman.... 
 
 Hubert Latham ...... '.... 
 
 S. F. Cody ........ ____ 
 
 S. F. Co<1y and mechanic. . 
 Orville Wright ......... 
 
 M. fie Nabas ........... .. 
 
 ( f pt rerher ............ 
 
 Charles Foster WUlard.... 
 
 Orville Wright ..... 
 
 iii Ills 
 
 Eugene Lefebvre 
 
 Alberto Santos-Duxiont. . . 
 
 Orville Wright : 
 
 . Capt. Ferber . 
 
 " ville Wrisbt 
 
 and Capt 
 
 1,800 feet 
 10 miles 
 40 miles 
 
 1.86' mile. 
 
 .Biplane . 
 
 r. .Biplane 
 
 . Nancy, France.". .-. Fr.imim 
 
 . Nancy, Fiance Farnum, 
 
 11,1909 Nancy to Lenoncourt, 
 
 and Leon Cody 
 
 10.0 miles 
 
 . Roger Somm 
 .M. Pnulhan 
 ,M. Paulhan 
 
 . Boier Sommer, Mdlle. Som- 
 mcr, and Mdlle. Mar- 
 vlngt .-... 
 
 Jfas 
 
 Brescia, Ita 
 Bivscta, I ta 
 
 Brescia, 
 
 SSb ii' i 
 
 |!]fe 
 
 aly Volsln .. 
 
 i:' .;].. id.... Biplane . 
 
 Bept 12, 1909.. 
 Sept. 12, 1009.. 
 Sept. 12, 1909. 
 
 . Brescia, Italy Wright . 
 
 . Brescia, Italy Biplane . 
 
 . Nancy, France. , Farnma 
 
 . Nancy, France Farnnm 
 
 . M T Rou ler" 
 
 '. '. Lieut. Calder'aVa and' Leut 
 
 Savola ............... 
 
 Lieut. Calderara and Ga- 
 
 brlele d'Annunzlo ....... 
 
 ..Glenn H. Curtlss and Ga- 
 
 brlele d'Annunzio ....... 
 
 ..Roger Sommer. Mdlle. Lar- 
 
 6.3 miles 
 1 mile 
 
 int, M. Munler, . 
 Thlry, Mme. Thlry, Mme. 
 Larmoyer, Mme. Som- 
 
 Bept 13, 1909.. 
 Bept 13, 1909.. 
 Bept. 13, 1909.... 
 
 Sept, 13, 1909 
 
 Sept) 15, 1909.... 
 
 Bept 17, 1909..., 
 
 Ill IE;;;: 
 
 Bept. 18, 1909.... 
 
 Sept. 22. 1909.... 
 
 Sept. 23. 1909.... 
 
 Sept. 24, 1909.... 
 
 Sept 2.7! 1909.... 
 
 Bept. 28, 1909.... 
 Sept. 28, 1909. . . . 
 Sept 29, 1909.... 
 
 . Tournal to Talntegnles, 
 
 France. Volsln 
 
 . Berlin, Germany Biplane 
 
 . St Cyr to Buc, France. Monoplane . 
 
 . Chs'ons, France Volsln 
 
 . Brescia, Italy Wright 
 
 .St. Cyr to Wlderllle, 
 
 France. Monoplane 
 
 .Berlin, Germany Biplane .. 
 
 .O*ten4. Belgium Volsln 
 
 .St. Cyr, France Monoplane 
 
 mer, and Sommer, Jr. . f 
 
 lo'rvl^lrVht'and'Pro'f: 
 . A.lbert g o e8 |antos'-i>umont.'.'.' 
 
 .Berlin, Germany. 
 
 .'M. Sanehez-Besa 
 
 ilclerara and Lieut 
 Savola 
 
 . . Alberto Santos-Dumont . . . 
 
 .Orville Wright 
 
 ..'Louis Paulhan 
 
 . Alberto Santos-Dumont. . . 
 
 .Orville Wright and Capt 
 Eiiglehart't 
 
 '.Fung Joe" Guey. . " .'*.' '.'.'.'. 
 .Adolph Herff ...- 
 
 X>ct 
 Oct 
 
 2, 1909.. 
 
 2, 1909.. 
 4, 1909.. 
 Oct. 6. 1909.. 
 
 8ft "Ulo!:: 
 82: 8-.J885:: 
 
 Oct. 11, 1909.. 
 
 oTt 11: iSS:: 
 
 Oct. 19, 1909., 
 Oct 21, 1909.. 
 
 I; US: 
 11 
 
 Nov. 1, 1 
 Nov. 8, 1 
 
 mles 
 
 6.2 miles 
 
 6.6 miles 
 
 10:56 miles 
 
 1.24 'miles 
 
 2,640 'feet 
 
 4.5 nillea 
 21 'miles 
 
 :::: 
 
 Glenn 1 H. Curtlss. ...- 
 
 Const de Lambert 
 
 Wilbur Wright and Lieut 
 
 Henry Farman 
 
 Count de Lambert :.. 
 
 Latham . 
 
 Humphreys and 
 
 Huber 
 Lleuts. 
 
 1.55 ' 
 
 :19 :00 
 6:35:66 
 
 In three flights. 
 
 s 
 
 with passenger, 
 e. Spire as passen 
 
 Bound trip cross-country, with landing. 
 
 Cross country. 
 
 Beached holeht of 328 feet. * 
 
 Five 2-mlle trips, each with fllffcrect 
 
 passengers. 
 In three flight* 
 
 croae-co 
 Stopped engine 
 
 -Two flights ; one passenger In each. 
 
 H. Curtlss. 31.06 miles :49 :24 
 
 . oVviiie wHgn '. '. '. '. '.'. !:!. 
 
 Orville Wright and Capt 
 "'"" ""'""' 
 
 JSS 
 
 :00 :00 Six flights, four with passengers. 
 
 Eight flights, seven with passenger* 
 
 1 :35 :00 Cross-country, with one landing. 
 
 One flight alone ; both In h!jrh wind. 
 Off ground with 130-foot run; round 
 
 Cross-country. 
 
 Reached height of 765 feet 
 
 Circled over . sea. 
 
 Flew with hands off, waving handker- 
 
 1 :35 :00 
 6'J7':66 
 
 :54 :00 
 :24 :23 
 
 :06 :30 
 
 Ferber killed. 
 Details not confirmed. 
 Details not confirmed. 
 
 With wind. Said to hare reached speed 
 of 74 H miles an hour. 
 
 Circled Statue of Liberty. Made one 
 
 other flight 
 
 Circled Governor's Island. 
 Reached height of 902 feet 
 In three flights. 
 
 Reached height of 1,637 feet. 
 Over Hudson River. 
 Reached holebt of 900 feet 
 
 Plunge h d 7 t O fl ile 1 t "to ground without In- 
 
 oo 
 
 0:4:00 
 :19 :00 
 
 1:32:18 % 
 0:12:09% 
 
 Made complete circle In this time. 
 Cross-country ; circled Eiffel Tower. 
 
 Said to have made 80 and 100 mllei 
 
 an hour at times with wind. 
 Engine stopped. Glided safely to ground. 
 
 Beached height of 720 feet 
 41 miles In 1 :00:14%. 
 
 1 :01 :15 
 4 :08 :26 
 
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 AUG 27 1953 
 
 TD MAR 4 19B2 
 
 
 
 
 
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 UNIVERSITY OF CAUFORNIA LIBRARY