JOHN ALEXANDER JAMESON, JR. 1903-1934 NGJNEERING LIBRARY THIS BOOK belonged to John Alexander Jameson, Jr., A.B., Wil- liams, 1925; B.S., Massachusetts Institute of Technology, 1928; M.S., California, 1933. He was a member of Phi Beta Kappa, Tau Beta Pi, the American Society of Civil Engineers, and the Sigma Phi Fraternity. His untimely death cut short a promising career. He was engaged, as Research Assistant in Mechanical Engineering, upon the design and construction of the U. S. Tidal Model Labora- tory of the University of California. His genial nature and unostentatious effectiveness were founded on integrity, loyalty, and devotion. These qualities, recognized by everyone, make his life a continuing beneficence. Memory of him will not fail among those who knew him. vf GILBERT Hydraulic and Pneumatic Engineering BY CARLETON JOHN LYNDE, Ph.D. PROFESSOR OF PHYSICS MACDONALD COLLEGE, QUE., CANADA Under the Direction of ALFRED C. GILBERT Yale University, 1909 Illustrated by The A. C. Gilbert Art Staff Published by THE A. C. GILBERT COMPANY New Haven, Conn., U. S. A. New York Chicago San Francisco London Toronto INTRODUCTION NOWADAYS there are so many very interesting things going on all about us that very often we are likely to overlook things which have an important bearing on our everyday life. Small things which we are so used to having around that we never stop to think what they really mean to us. For instance water. It's nice to drink, and bathe in but very few of us ever stop to consider the innumerable uses water is put to and what a great influence it has on many things we do. Most of us are satisfied to turn on the faucet and get our water in that way. If something is wrong and the water doesn't come from the faucet we call up the plumber, but we do not realize what has gone wrong simply because we do not understand how a house is piped for water nor do we understand why water gets into the pipes, etc. Then air another thing which we couldn't live without and yet few appreciate its value. Air and water give us tremendous results as pneumatic and hydraulic pressure. A knowledge of these great forces which most boys are so familiar with and still do not understand tho- roughly will put you up far ahead of ,yyur, fyby friends. Most boys take things too much for granted; it is th.& -clever boy Who digs into things and find out the reasons/ ' It is the earnest hope of the authors of this book that the boys who read it will have a better understanding of water and air, how they are used, and what they mean to us. Sincerely yours, COPYIUGHTEU, 1920, BY A. C. GlLBERr NEW HAVEN, CONN. ENGINEERING LIBRARY HYDRAULIC AND PNEUMATIC ENGINEERING 3 INDEX TO ILLUSTRATIONS HYDRAULIC APPLIANCES City Water Supply Figs. 1, 2 Pages 5, 6 Private Water Supply Figs. 3, 4 Pages 7, 8 Attic Tank System Figs. 7, 8 Page 10 Water Supply From Spring Figs. 11, 12 Page 12 Pneumatic Tank Figs. 22, 23 Page 16 Siphon Over Hill Figs. 31, 33, 35 Pages 21, 22 Lift Pump Figs. 62, 63 Page 43 Force Pump Fig. 65 Page 45 Hydraulic Press Figs. 68A, 73 Pages 48, 52 Hydraulic Elevator Figs. 68B, 75 Pages 48, 53 Hydraulic Lift Lock Figs. 68C, 79, 81, 82 Pages 48, 55, 58 Depth Bomb Fig. 90 Page 66 Torpedo Figs. 91, 92 Page 67 Submarine Fig. 93 Page 68 Battleship Fig. 98 Page 72 Raising Sunken Ships Figs. 105, 106, 108 Pages 79, 80, 81 Floating Dry Docks Figs. 109, 110 Pages 82, 83 Air Lock in Pipes Figs. 120, 121 Pages 90, 91 PNEUMATIC APPLIANCES Magdeburg Hemispheres Fig. 122 Page 93 Barometer Figs. 129, 130 Page 99 Air Zones Fig. 131 Page 100 Altitude Gauge Fig. 132 Page 101 Air Lift Pump Figs. 139, 140 Pages 105, 106 Balloons Figs. 144, 145 Pages 110, 111 Helium Balloons Fig. 146 Page 112 Air Brakes Figs. 156, 157 Pages 121, 122 Flame Thrower Fig. 158 Page 123 Fire Extinguisher Fig. 160 Page 124 Bicycle Pumps Fig. 165 Page 128 Air Compressor Fig. 167 Page 130 Sand Blast Fig. 168 Page 130 Pneumatic Paint Brush Fig. 170 Page 132 Diving Bell Figs. 172, 173 Pages 133, 134 Pneumatic Caisson Figs. 176, 177 Page 137 Torpedo Discharge Tube Fig. 178 Page 138 Air From Sea Water Fig. 180 Page 140 CHART OF HYDRAULIC AND PNEUMATIC SEPARATE PARTS ft No. NAME DESCRIPTION 3300 TIN TANK 7 7 / 8 " * ? ? f ^ x V^o" i 3301 BOTTLE 7 1/2" High Base, 2 1/2 x 1 3302 GLASS TUBE, Long 5 1/2" x 7/32" diameter 3303 GLASS TUBE, Short 2 3/4" x 7/32 IIS 8tttt ^Il L I L B6w-::::::::::::::::: i ift 3306 GLASS TUBE TEE 3" 7/32^ 3307 GLASS TUBE "U" 3" 7/32* 3308 RUBBER COUPLING 1 1/2" x 1/4" 3309 RUBBER HOSE 16" x 1/4" 3310 RUBBER STOPPER, Laboratory Style No. 2 two hole 3/16" diameter 3311 RUBBER STOPPER, Laboratory Style No. 1 Solid 3312 RUBBER STOPPER, Laboratory Style No. 1 one hole I/JT diameter 3313 RUBBER STOPPER, Laboratory Style No. two hole 1/8 3314 RUBBER STOPPER, Laboratory Style No. one hole 1/8 3315 CLIPS, Metal, with fastener 3316 LARGE GLASS TUBE 1" -80S" diameter 3317 WOOD HANDLES 7" *J* rcd ' 3318 RUBBER VALVES 1 1/2 "x 1/4' 3319 GLASS VALVES NIPPLE 1" x 7/32 3320 BALLOON, Dirigible Type 3321 BALLOON, Observation Type . lnlf 3322 RUBBER COUPLING, Large 2 " x |/ 3323 RUBBER BANDS 3 1/2" x 1/8 3324 RUBBER BANDS 13/4 "x l/}6 3325 SHEET RUBBER PIECE (White) 2" x 11/2 3326 SUBMARINE 1 3/4 < iiam. d am. 1554 GLASS FUNNEL 4 1/2" long, top 2^" bot. V* THE A. C. GILBERT CO., NEW HAVEN, CONN., U.S.A. In Canada: The A. C. Gilbert - Menzks Co., Limited, Toronto, Ontario. Hydraulic and Pneumatic Engineering Hydraulic Engineering is the Engineering which deals with water and other liquids. Pneumatic Engineering is the Engineering which deals with air and! other gases. WATER SUPPLY Boys, have you running water'irl jy'eur homes?. ,,i|' so, do you know how it gets there? You will shpw how with this .Engineering set. If you live in a city, your run^hig w&i3r;is "jEsuplpJi'eji -'iih. one of three ways: first, it is pumped into 'a'stanclpipe or 'reservoir; second, it is brought from a distant lake or stream at a higher level; or third, it is pumped directly into the city mains. The standpipe method is illustrated in Fig. 1. The water is pumped by means of a force pump B from a river or lake A into a standpipe C, from which it runs by gravity through the under-ground pipes or mains to the houses D, fountains E and hydrants F. This system is used in towns and small cities situated in a flat region, because it is the cheap- est means of getting the water above the level of the highest house faucet in the town. If the town is situated near a hill, the usual practice is to build a large cement lined reservoir on the hill and to pump the water into this instead of into a standpipe. In either case the water runs by gravity through the mains and submains to the houses, hydrants, etc. If the city is very large, the usual practice is to bring the water from a lake or stream at a higher level. New York is supplied with water in this way. Fl f- 1. (A) Source of Water Supply (B) Pumping Station (C) Stand Pipe (D) House Supplied with Water (E) Fountain (F) Hydrant for Fire Hose. From the "Ontario High School Physics", By Permission of the Publishers See page 145 for diagram of apparatus needed to perform experi- ments in this book. HYDRAULIC AND PNEUMATIC ENGINEERING If the city is very large and if an elevated lake or stream cannot be found within a reasonable distance, the usual practice is to pump the water directly into the city mains, from the nearest river or lake. In all cases the greatest care is taken to see that the water is pure. The land bordering the elevated lake or stream is kept free from all sources of contamination and in addition the water is filtered. If the water is pumped from a lake, the intake pipe is run out into the lake for a long distance, to get the j>.urest water and in addition the water is filtered. If the watej*.ls pumpe^^;yy^ Fig. 6. Showing that the Water S~','. Pressures are Equal at Faucets on the *&*/ ' vf Same Floor. sv'VC-V Fig. 5. Showing How the Water Flows from an Elevated Tank to the Faucets. 10 HYDRAULIC AND PNEUMATIC ENGINEERING Fig. 7| Water Supplied to an Attic Tank by Means of a Windmill and Pump Courtesy of the Gould Manufacturing Company In Fig. 7 the water is pumped by a wind- mill and force pump into a tank in the attic of the house, and from there it runs by gravity to the various house fixtures as shown in Fig. 8. The force pump is often driven by a gas engine instead of by a windmill. The hand pump (4) Fig. 8 is used only when the gas engine or windmill is out of order. Fig. 8. Showing How Water is Distributed from an Attic Tank. HYDRAULIC AND PNEUMATIC ENGINEERING 11 EXPERIMENT No. 3 To make and operate a private water supply system in which the water is stored in an attic tank. Arrange the appara- tus as in Fig. 9. Hold the nozzles horizontal one above the other and open them to- gether. Is the longer stream from the lower nozzle? That is, is the greater pressure at the lower faucet? Fig. 9. Showing How Water Flows from an Attic Tank to Faucets Arrange the apparatus as in Fig. 10. Hold the nozzles horizontal and open them together. Are the streams of the same length? That is, are the pressures equal? You have shown here again that the greater pressure is at the low- er faucet and that the pressures are equal at faucets on the same level. Fig. 10. Showing Again that the Water Pressures are Equal at Faucets at the Same Level. 12 HYDRAULIC AND PNEUMATIC ENGINEERING In Fig. 11 the water from an ele- vated spring runs by gravity into a storage tank and then through an underground pipe to the house fix- tures. EXPERIMENT No. 4 To show how water is brought from an elevated lake or spring. ' Arrange the apparatus as shown in Fig. 12. Place the tank on a mound of sand or earth and bury the underground pipe to a depth of one or two inches. Allow the water to run. Fig. 11. A Home Supplied with Water from an Elevated Spring and Storage Tank. You have shown here how the water is brought to a city from an elevated lake or stream, or how it is brought to a private house from an eleva- ted spring. Fig. 12. Showing How Water Flows from an Elevated Spring to the Faucets HYDRAULIC AND PNEUMATIC ENGINEERING 13 a A NAVAL BATTLE GAME No. 1 You can invent all sorts of games to be played with this Engineering set. The Naval Battle is one and it is an excellent game for a hot day. Float a number of tin cans, tumblers, or cups on water in a bath tub, or in a wash tub, Fig. 13. Arrange the apparatus as shown. Each player directs his stream against the warships of the other, and the winner is the one who first sinks all the enemy war ships. PNEUMATIC TANK SYSTEM OF WATER SUPPLY The pneumatic tank system of water supply is illustrated in Fig. 14. The water is pumped into the bottom of an air- tight steel tank and compresses the air in the tank to smaller vol- ume at the top. This compressed air then forces the water out Fig. 13. A Naval Battle, through the discharge pipe at the bottom of the tank and lifts it to the faucets in the rooms above. The interior of the tank is repre- sented in Fig. 15. The compressed air at the top of the tank forces water up the discharge pipe when any faucet C is opened. DISCHARGE PIPE COM- PRESSED AIR CHECK VALVE Fig. 14. A House Supplied with Water by Means of a Pneumatic Tank. Courtesy of The Andrews Heating Co, Fig. 15. Showing How the Air is Compressed in a Pneumatic Tank. Courtesy of the MacMillan Co. 14 HYDRAULIC AND PNEUMATIC ENGINEERING EXPERIMENT No. 5 To make and operate a pneumatic tank. Arrange the apparatus as shown in Fig. 16. It is necessary to fasten the stopper in the bottle very securely. Do this as follows : Insert two elbows into the two-hole rubber stopper and twist the stopper firmly into the neck of the bottle. Next loop three strong rubber bands to- gether as shown in Fig. 17, pass a stout cord over the stopper and wind the stretched rubber bands a- round the neck and cord. Now slip the last end of the bands under the last winding to hold it, (1) Fig. 18, then tie the ends of the cord up over the stopper, (2) Fig. 18, and you will find that the stopper is very secure. Fig. 16. Operating a Pneumatic Tank. Fig. 17. The stretched rubber bands make a very secure tie because each Stretched winding grips the cord. You will use this tie often in your experiments. Note You can use the tee and one-hole stopper instead of the elbows and two-hole stopper if you prefer. Fig. 18. Showing How to Make a Stopper Secure by Means of Cord and Looped Rubber Bands. HYDRAULIC AND PNEUMATIC ENGINEERING 15 Now: open the clip on the hose, open the faucet Fig. 16, slightly, run water into the bottle until it is half full, close the faucet, close the clip on the hose, remove stopper from faucet, point the nozzle upward, and open the clip on the nozzle. Does the compressed air force the wa- ter out with surprising force? If you have no water faucet handy, illus- trate the pneumatic tank as shown in Fig. 19. Fill the bottle half full of water, tie the stopper in place, force air in with your mouth or with a bicycle pump, and observe the stream as before. Fig. 19. Operating a Pneu- matic Tank in Another Way. Fig. 20. Fig. 21. Find a larger bottle, which your stoppers will fit, and repeat these experiments. You have shown here how the compressed air in a pneumatic tank forces the water out through the discharge pipe. Repeat and make experiments of your own. Note Do not attempt to fill the bottle more than half full of water because the air pressure increases rapidly as the air is compressed and it blows out the nozzle or separates the rubber tubes from the elbows. 16 HYDRAULIC AND PNEUMATIC ENGINEERING RAPID FIRE WATER GUN GAME No. 2 Arrange the bottle as shown in Fig. 21 and fill it half full of water. Replace the elbow by a nozzle as in Fig. 20 and your rapid fire water gun is complete. Open the clip for an instant only for each shot. Arrange a battle with one or more on a side, each soldier armed with a rapid fire water gun. A man is wounded when hit on the arm or leg and must afterwards fight without the arm or leg; a man is killed when hit on the body or head. The side loses which first has all of its men killed. Use forts, trenches, tanks, etc. EXPERIMENT No. 6 To make and operate a pneumatic tank system of water supply. Arrange the apparatus as in Fig. 22, fill the bottle half full of water as above, open the clip on the discharge tube, and observe the height to which the compressed air lifts the water. Repeat with the apparatus as in Fig. 23. Do you observe that the stream from the lower nozzle is long- er than that from the upper; that is, that in the pneumatic system also the pressure is always greater at the lower fau- cet? Fig. 23. Water Pressure is Greater at the Lower Faucet. Fig. 22. The Compressed Air in a Pneumatic Tank Forces Water Up the Discharge Pipe. A 1 HYDRAULIC AND PNEUMATIC ENGINEERING 17 Repeat with the apparatus as in Fig. 24. Do you observe that the streams are of the same lengths, that is, that the pressures are equal at faucets on the same level? You have shown here how the compressed air in a pneumatic tank forces water up to the faucets above ; also that the greater pressure is at the lower faucet, and that the pressures are equal at faucets on the same level. Fig. 24. The Water Pressures are Equal. A 2 18 HYDRAULIC AND PNEUMATIC ENGINEERING WATER AND AIR EXPERIMENT No. 7 To show that water is incompressible and that air is compressible. Arrange the apparatus as in Fig. 25, fill the tube with water and try to compress it. You cannot do so because water is nearly incom- pressible. Note: Water as slightly compressed by very great pressures; for example, if your tube were 10 in. long and you could apply a pressure of 3000 Ibs. per square inch, the water would be compressed 1/10 inch. Now empty out the water and try to compress the air in the tube as in (2) Fig. 25. You will find that you can do so quite easily because air is quite compressible. You have demonstrated here that water is incompressible (nearly) and that air is compress- ible. You know from this that in the pneumatic tank it is the air which is com- ^\ f pressed and not the water. XJ 1 2 Fig. 25. Showing that water is in- compressible and that air is com- pressible. 1 Fig. 26. Corn- pressure. EXPERIMENT No. 8 To show that compressed air exerts pressure. Use the apparatus shown in Fig. 26. Wet the inside of the tube, wet the plunger and rub it on a cake of soap to make it slippery, shove the plunger into the tube (1) and let it go suddenly. Do you find that the compressed air drives the plunger out violently (2)? Repeat with a little water above the plunger to serve as a lubricant. Note: When you shove the handle into the sto P~ per you expand the stopper slightly. You should expand it until it fits the tube snugly but not too 1 Hold the apparatus as in (3), Fig. 26 and force the handle in until the compressed air drives out the end stopper. You have shown here that compressed air exerts pres- sure and you will understand from this how the com- pressed air drives the water out of a pneumatic tank; HYDRAULIC AND PNEUMATIC ENGINEERING 19 also you will understand why the tank must be made of steel, namely, to stand the pressure of the compressed air. TRENCH GUN GAME No. 3 Fig. 27. Trench Gun. You can imitate the Stokes trench gun as follows. Put two long strips of paper on the ground three feet apart to represent the enemy trench. Now go back 20 or 30 feet or more, point the tube upward and toward the enemy trench, force the plunger in and release it suddenly. The game is to try to drop the bomb, that is, the plunger, into the enemy trench. The winner is the one who does it most often in a given number of trials. Note: Keep the inside of the tube wet, the plunger wet and slippery with soap, and a little water above the plunger. HEIGHT AND DISTANCE CONTEST GAME No. 4 Use the apparatus as above. The game is to see who can shoot the plunger to the greatest height and to the greatest distance. POP GUN GAME NO. 5 Fig. 28. Pop Gun. Use the apparatus as a pop gun, Fig. 28. The games are: first, to try to hit a bull's eye, with the end stopper; second, to see which can shoot it to the greatest distance and the greatest height. 20 HYDRAULIC AND PNEUMATIC ENGINEERING Fig. 29. A Siphon. Courtesy of The MacMillan Co. THE SIPHON The siphon is used in many wa- ter supply systems to make water flow over the top of a storage tank or over a hill from a spring on one side to a house on the other, and so on. You will first show how the si- phon works, then you will show how it is used in water supply system, and later you will show why it works as it does. EXPERIMENT No. 9 To make and operate a siphon. Arrange the apparatus as in (1), Fig. 30. Place one arm of the siphon in the water and while hold- ing the other arm outside the tank below the water level suck the air out of the siphon until the water runs. Does the water run up hill to the top of the si- phon and then down hill into the tumbler? Siphon water out of a full tumbler into an empty tumbler and while the wa- ter is running stand them side by side on the table, (2), Fig. 30. Does the water stop when the level is the same in both tumblers? (3) (4) Fig. 30. Illustrating the Siphon. HYDRAULIC AND PNEUMATIC ENGINEERING 21 Place one tumbler on a block of wood or a book as in (3), Fig. 30. Does the water flow from the upper tumbler to the lower, and does the flow again stop when the levels are the same? Place the block under the other tumbler. Are the results the same? Repeat the above experiments with the rubber hose, (4), Fig. 30, used as a siphon. You have shown here : that the water runs uphill in one arm of a siphon and downhill in the other; that it always runs from the higher water level to the lower; and that it stops running when the water levels are the same. You will show "why" the water runs, in later experiments. HOW THE SIPHON IS USED IN WATER SUPPLY SYSTEMS EXPERIMENT No. 10 To show how the siphon is used in water supply systems. It is rather difficult to make a water-tight con- nection in the bottom of a water tank and in many cases it is not done, but instead the water is si- phoned out over the top, as shown in Fig. 31. Illustrate this as shown in Fig, 32. Fig. 32. Showing How Water is Siph- oned Out of an Ele- vated Tank. Fig. 31. The Arrangement of Piping Used to Siphon Water Over the Top of a Storage Tank. 22 HYDRAULIC AND PNEUMATIC ENGINEERING In some cases it happens that there is a good spring of water on one side of a hill and the home in which the water is wanted is on the other side. If the highest point Fig. 33. The Arrangement of Piping Used to Siphon Water Over a Hill. of the siphon is not more than about 25 feet (34 feet is the theoretical limit) above the water surface in the spring, and if the house faucets are below the level of the water in the spring, the water can be siphoned over the hill as shown in Fig. 33. Illustrate this as shown in Fig. 34, where the back of the chair represents the hill. Fig. 34. Showing How Water is Siphoned Over a Hill. Fig. 35. The Arrangement of Piping Used to Siphon Water Over a Hill from a Storage Tank. HYDRAULIC AND PNEUMATIC ENGINEERING 23 Water can be siphoned from a storage tank or reservoir over a hill as well as from a spring and the siphon can start at the bottom of the reservoir if this is more convenient, see Fig. 35. Illustrate this as shown in Fig. 36. You have here illustrated three ways in which the siphon is used in water supply systems. You will show later why a siphon cannot lift water over a rise of more than about 25 feet and why the greatest theoretical lift is 34 feet. HOW TO START A LARGE SIPHON EXPERIMENT No. 11 Fig. 36. Siphoning Water Over a Hill from a Tank. To illustrate different ways of siphon. You could not start a large siphon by sucking the air out of it with your mouth. How then are you going to start it? You will illustrate three ways. The object in all cases is to get the air out of the siphon and this is usually done by filling it with water. In the case illustrated in Fig. 37, the faucets are all closed and the air is driven out of the siphon by pumping water into the tank through the siphon. The check valve prevents the water from running back into the pump, and when the faucets are opened the water runs. starting a large V. a '.:-- < f .Sw! R Fig. 37. The Large Siphon is Started by Pumping Water into the Tank through the Siphon. 24 HYDRAULIC AND PNEUMATIC ENGINEERING This experiment is illustrated by means of the apparatus shown in Fig. 38. The faucet here represents the pump. Start with the tube empty except for the air in it, close the clip under the nozzle, open the faucet until the tank is full of water, close the faucet, and open the clip. Does the water run through the siphon to the nozzle? When the water is siphoned over a hill from a spring, the siphon is usually started by connecting it to the suction side of a pump placed on the other side of the hill in or near the house, as shown in Fig. 39. Fig. 38. Illustrating One Method of Starting a Large Siphon. Fig. 39. The Large Siphon is Started by Pumping Water Out of the Spring through the Siphon. To start the siphon, the house fau- cets are closed, the stop cock at the pump is opened and the pump is operated until the water comes freely; then the stop cock is closed and the water runs whenever a faucet in the house is opened. HYDRAULIC AND PNEUMATIC ENGINEERING 25 This is illustrated by arranging the apparatus as shown in Fig. 40; the tee branch represents the pump connection and the end branch represents the house pipe. Close the house pipe, apply your lips to the tee branch (to represent the working of the pump) and suck air out of the siphon until the water flows, then close the tee branch and open the house pipe. Does the water flow? Fig. 40. Starting a Large Siphon. In many cases the water is siphoned over the top of a hillside well to a house at a lower level and the siphon is started by means of a pump near the house as illus- trated in the last experiment. Generally, however, a small storage tank of water at the top of the siphon is used to start it, see Fig. 41. The small storage tank is filled by means of a pump (not shown), or by means of a pail used to dip water from the well. Fig. 41. A Large Siphon is Started by Allowing the Water to Flow Through It from the Small Storage Tank. 26 HYDRAULIC AND PNEUMATIC ENGINEERING Illustrate this method of starting a large siphon with the apparatus shown in Fig. 42. The tee at the top is connected with the metal tank, which here represents the small storage tank, the large pail represents the hillside well, and the long arm of the siphon represents the pipe to the house. Open the house faucet, then open the tee connection to the storage tank. Does the water flow down the long arm of the si- phon? Now close the house faucet and observe that the wfeter runs down the short branch into the pail. Now close the tee connection and open the house faucet. Does the siphon run? Note: The storage tank needs to be filled only when the siphon stops, which may be only once or twice a year. Fig. 42. Showing How a Large Siphon is Started by Means of Water from a Small Storage Tank. OTHER USES OF THE SIPHON EXPERIMENT No. 12 To illustrate other uses of the siphon. You can siphon cider, or other liquids, out of a barrel by means of a rubber tube, (1) Fig. 43. Illustrate this as in (2) Fig 43, where the bottle represents the barrel and the neck of the bottle the bung hole. Fig. 43. Siphoning Cider Out of a Barrel. HYDRAULIC AND PNEUMATIC ENGINEERING 27 --Hi Fig. 44. Siphoning Water Out of a Boat. You can siphon water out of your boat when it is out of the water, (1) Fig. 44, but not when it is afloat. Use a tumbler to represent your boat and show that you can siphon water out of it when it is out of the water, (2) Fig. 44; but that you siphon water into the boat if it is afloat, (3) Fig. 44, because the water outside the boat is higher than that inside. You can siphon sand, gravel, and mud with the water when necessary. Illustrate this by siphoning sand or mud with the water from one tumbler to another, Fig. 45, Fig. 45. Siphoning Sand. 28 HYDRAULIC AND PNEUMATIC ENGINEERING VELOCITY OF FLOW EXPERIMENT No. 13 To show that the velo- city of the water in a si- phon is greater, the great- er the distance, between the water levels about the two arms. Arrange the siphon with a small difference in wa- ter level as shown in (1) Fig. 46 and allow the wa- ter to run for 15 seconds ; then arrange it with a greater difference as in (2) Fig. 46 and again al- low the water to run for 15 seconds. Does more water flow in (2) than in (1), that is, is the velocity greater the greater the difference in a Slphon ' water level? Fig. 46. Velocity of Water in OTHER SIPHONS EXPERIMENT No. 14 To make and operate a double siphon and a three legged siphon. Start a double siphon, (1) Fig. 47. Raise the tumblers one at a time, then two at a time. Does the water always flow from the upper tumbler or tumblers to the lower and does it always stop flowing when the water levels are the same? Start a three legged siphon, (2) Fig. 47 and repeat the above experi- ments. Are the results the same? Fig. 47. Double Siphon and Three legged Siphon. HYDRAULIC AND PNEUMATIC ENGINEERING 29 HOW TO START A SMALL SIPHON EXPERIMENT No. 15 To illustrate two ways of starting a small siphon. Fig. 48. Starting a Small Fountain. You have been starting your small siphon by sucking air out of the long arm. You can also start it as shown in (1) Fig. 48. Fill the siphon with water to force the air out, close the ends with your fingers, in- vert the siphon, and when the upper end is under water in the upper tumbler remove both fingers, (2) Fig. 48. Glass siphons used to siphon acid have a starting tube on the outside arm, (3) Fig. 48. Illustrate the use of this by siphoning water out of a bottle with the siphon shown in (4) Fig. 48. Place the up- per end in the water, close the lower end, suck out a little air, and open the lower end. Practice until you can start the siphon without getting water (representing the acid) on your fingers or lips. TO UPS 30 HYDRAULIC AND PNEUMATIC ENGINEERING AN ENCLOSED FOUNTAIN EXPERIMENT No. 16 To make and operate an enclosed fountain. Arrange the apparatus as shown in (1) Fig. 49; this is really a siphon with a bottle at the top. Start with 2 inches of water in the bottle, insert the stopper with tubes, invert the whole apparatus, Fig. 49. An Enclosed Fountain. and put the short arm in the tank filled with water. Does the water run and is there a fountain in the bottle? Arrange the apparatus as in (2) Fig. 49, lift the tank until there is about 2 inches of water in the bottle, then arrange as shown. Is there a fountain in the bottle? Repeat both of these experiments but use instead of the bottle, a wide glass tube closed at the top with a solid rubber stopper, (1) Fig. 50. Make two fountains as shown in (2) Fig. 50, one enclosed and one in the open. Fig. 50 HYDRAULIC AND PNEUMATIC ENGINEERING 31 ATMOSPHERIC PRESSURE You have made a number of experiments with siphons and you have learned how they act under different circumstances; you will now make some experiments which will help you to understand "why" they act as they do. Water moves through a siphon because it is forced to do so by atmospheric pressure. You will first make a number of experiments to show that the atmosphere exerts pressure and then you will show how and why this atmospheric pressure forces water through a siphon. Fig. 51. Weighing Air. AIR HAS WEIGHT If you were asked the question "How much does air weigh?", you would prob- ably answer off hand, "Air has no weight at all." Air, however, has considerable weight and it would take a very strong man indeed to carry a weight equal to that of the air in a house of medium size. You cannot weigh air with the apparatus you have at hand but this is how it is done. The apparatus used is illustrated in part in Fig. 51. The air is pumped out Courtesy" of the^MacMilianCo. of the flask, by means of an air pump (not shown). The flask is then balanced exactly on the fine scales and air is admitted to the flask again. It is found that the flask weighs more when it is filled with air than when it is empty, and this proves that air has weight. A cubic foot of air, at the surface of the earth and at ordinary temperatures is found in this way to weigh about 1^4 oz. This is not a great weight, but when you come to calculate the weight of air in a house of medium size you find that it amounts to a very great deal, for example, make the following calculation: A house with a flat roof is 40 feet long, by 30 feet wide, by 24 feet high; find the weight of air in it, neglecting the space occupied by partitions, furniture, etc. 32 HYDRAULIC AND PNEUMATIC ENGINEERING The house contains 40 x 30 x 24 28,800 cubic feet of air, and since each cubic foot of air weighs 1J4 ozs. the house contains 28,800 x 1% = 36,000 oz. of air, and since there are 16 ozs. in 1 lb. 36000 the house contains = 2250 Ibs. of air. 16 The house contains 2250 Ibs. of air or over a ton of air (1 ton = 2000tbs). This is a very astonishing fact, especially to those of us who have never thought of air as having any weight at all. AIR EXERTS PRESSURE You have learned from your lessons in Physical Geography at school that we live at the bottom of an ocean of air the atmosphere which is many miles deep; and when you remember that a cubic foot of air weighs 1^4 zs - you are in a position to see that the atmosphere must exert great pressure on everything at the earth's surface. It has been found by repeated experiments that the atmosphere exerts a pressure of 14.7 Ibs. (nearly 15 Ibs.) on each square inch of everything at the earth's surface. This means, for example, that on every square inch of our bodies the atmosphere exerts a pressure of 14.7 Ibs. We might think that this would crush our bodies, until we remember that everything inside our bodies exerts the same pressure outward, our blood, the air in our lungs, etc. A pressure of 14.7 Ibs per square inch is equal to the pressure at a depth of 34 feet under water, that is, if the air could be removed from the earth and be replaced by water, it would require a depth of 34 feet of water all over the earth to produce a pressure equal to that produced by the atmosphere, namely, 14.7 Ibs. per square inch. You will now make experiments to show that the atmosphere exerts pressure EXPERIMENT No. 17 To show that the atmosphere exerts pressure. Make a U tube, Fig. 52, run water through the tube until all the air bubbles are gone, then empty out part of the water until the U HYDRAULIC AND PNEUMATIC ENGINEERING 33 is a little more than half full. The water in the two arms is then at the same level. Now apply your lips to the coupling on one arm, suck out the air, and close the clip. Do you observe that, when you suck out the air, the water in the open arm descends while that in the other arm rises? The explanation is as follows. Everything on the earth is at the bottom of an ocean of air many miles deep, and since this air has weight it exerts pressure on everything on the earth. Now when both arms of the U tube are open, the water level is the same in both and the pressure of the air on the water surface in each is the same, namely, the pressure of the atmosphere. When you remove the air from the closed side, however, you remove the pressure of the atmosphere from this side and the pressure of the atmosphere in the open side forces the water down on the open side and up the closed side. This experiment shows you that the atmos- phere exerts pressure. Repeat and make experiments of your own. t Pressure. EXPERIMENT No. 18 To show that the atmosphere will support a column of water. Arrange the apparatus as in (1) Fig. 53, fill the tube with water, close one end with a clip and hold both ends in the position illustrated. Does the water remain in the tube? It remains because the pressure of the atmosphere downward on the water in the open tube supports the column of water in the long tube. Turn the open end sidewise and then downward. Does the water remain in the tube? It remains because the atmosphere exerts pres- sure sidewise and upward and supports the water. A 3 34 HYDRAULIC AND PNEUMATIC ENGINEERING ATM. ATM t ATM. 1 2 3 Fig. 53. Showing That the Atmosphere Will Support Water. Arrange the apparatus as shown in (2) Fig. 53. Place the lower end of the tube in a tumbler of water, stand on a chair, and suck the air out of the tube, then close the upper end. Does the water remain? It remains because the pressure of the atmosphere downward on the water in the tumbler supports the water in the tube. HYDRAULIC AND PNEUMATIC ENGINEERING 35 Lift the tube out of the tumbler, (3) Fig. 53, and the water will remain in the tube because it is supported by the upward pressure of the atmosphere. This is possible only with very narrow tubes. The tube you have used in these experiments is about 6 feet long and you have shown that the atmosphere will support a column of water 6 feet high. If you had a tube of sufficient length you could show that the atmosphere will support a column of water 34 feet high* but no more. To Air Pump pr Lipa Air To Lipo To Air Pump or *i I 1 3 Fig. 54. Proving That it is the Atmosphere Which Lifts the Water. 36 HYDRAULIC AND PNEUMATIC ENGINEERING EXPERIMENT No. 19 To prove that it is the pressure of the atmosphere which lifts the water. Make a U tube (1) Fig. 54, with four tubes on one side and two on the other, fill it half full of water so that the two tubes on the short side are quite full, then close the top of this side with a coupling and clip. Now suck the air out of the long side. Do you observe that the water does not move? It does not move because although you have decreased the air pressure in the long side, the atmosphere cannot get at the water in the short side to force it down. Open the top and repeat the experiment. Does the water move? To show this in another way. Fill a bottle (2) with water, place a glass tube in it and suck the air out of the tube. You observe that when you remove the air pressure from the water in the tube, the atmospheric pressure on the water in the bottle forces the water up into your mouth. Now fill the bottle quite full to exclude the air, and close it with a one hole rubber stopper which has one glass tube stuck in the under side and another in the upper side, (3). Suck the air out of the upper tube. Do you find that the water does not rise? It does not rise because although you have decreased the air pres- sure in the upper tube, the atmosphere cannot get at the water in the bottle to force it into your mouth. You have proved here that it is the pressure of the atmosphere which lifts the water. EXPERIMENT No. 20 To show in other ways that the atmosphere exerts pressure down- ward and upward. Fill the bottle with water, close the top with the hand, invert the bottle in a pail of water, and remove the hand under water, (1) Fig. 55. The downward pressure of the atmosphere on the water surface in the pail supports the water in the bottle. Repeat with the tumbler and tube as shown in (2) and (3). Fill the bottle with water, cover with a piece of paper, hold the paper on with the hand, invert the bottle and remove the hand, (4). The paper is held on by the upward pressure of the atmosphere. Repeat this experiment with a tumbler and tube, (5) and (6). HYDRAULIC AND PNEUMATIC ENGINEERING 37 n ATM. Arr-i. 4 5 Fig. 55. Showing That the Atmosphere Exerts Pressure Downward and Upward. EXPERIMENT No. 21 To illustrate two simple uses of atmospheric pressure. DRINKING SODA WATER When you drink soda water through a straw or glass tube, (1) Fig. 56, you simply produce a vacuum in your mouth and it is the atmosphere which forces the soda water into your mouth. Illustrate this with the apparatus, (2) Fig. 56 in which the bottle repre- sents your mouth. Suck air out of the bottle, close clip 1, and open clip 2. Does the atmosphere force water into the bottle? It forces soda water into your mouth in the same way. 38 HYDRAULIC AND PNEUMATIC ENGINEERING POULTRY DRINKING FOUNTAINS Tb Air ** fcv Fil1 a tumbler witn water, place two Pllttlp Or Lip5 /5& pieces of lead pencil across the top, cover * .a/ with a saucer, and invert tumbler and saucer, (1) Fig. 57. Repeat with the glass bottle, (2). Does the water run out only until the edge of the tumbler or bottle is covered? Atm - ToLii Attn. hiTnT To imitate the poultry drinking the water, suck water out of the saucer by means of a glass tube until the water is below the edge of the tumbler. Does air enter and water run out only until the edge is again covered? The atmosphere supports the water. Note: The atmosphere could support the water in a fountain 34 feet high but no higher. Fig. 56. Drinking Soda Water. HYDRAULIC AND PNEUMATIC ENGINEERING 39 Fig. 57. Poultry Fountain. THE SIPHON (Continued) THE "WHY" OF THE SIPHON The reason "why" water flows through a siphon is as follows : Suppose, for example, you have a siphon, Fig. 58, closed at the top with a clip. The atmospheric pres- sure on the water in the right hand tumbler supports only 1 foot of water, while in the left hand tumbler it supports two feet of water. Now the atmospheric pressure on each is equal to the pressure of a column of water 34 feet high, there- fore at the top of the siphon the pressure : at the right of the clip is 341= 33 feet of water; at the left of the clip is 34 2 = 32 feet of water. The pressure at the right is greater than that at the left and if the clip is opened the water flows from right to left, that is, from the upper tumb- ler to the lower tumbler. This is the "why" of the siphon. Fig. 58. Showing Why the Atmos- phere Drives Water Through a Siphon 40 HYDRAULIC AND PNEUMATIC ENGINEERING PUMPS EXPERIMENT No. 22 To illustrate the action of a syringe. The simplest kind of pump is the syringe, (A) Fig. 59. When you lift the plunger, there is a vacant space or partial vacuum left below the plunger and the atmospheric pressure on the water in the tumbler lifts water into the syringe. Courtesy of The MacMillan Co. Illustrate this by means of the syringe, fB) Fig. 59. Soap the plunger to make it slippery, fill the syr- inge, lift the nozzle end and squirt the water .out, (C) Fig. 59, Fig. 59. The Syringe HYDRAULIC AND PNEUMATIC ENGINEERING 41 WATER GUN SHOOTING GAME No. 6 The syringe makes a fine water gun. Use it as follows : (1) Put up a bent piece of cardboard as a target and try to hit it from various distances, (A) Fig. 60. (2) See who can send the stream to the greatest height. (3) See who can send the stream to the greatest distance. Fig. 60 A. Water Gun Shooting and Big Gun Battle. BIG GUN BATTLE GAME No. 7 Each player here puts up the same number of lead or paper soldiers and at a given signal each starts to knock down the enemy soldiers with his water gun which here represents a large caliber gun firing shells, (B), Fig. 60. The winner is the one who first knocks down all the enemy soldiers. .Fig. 60 B. Water Gun Shooting and Big Gun Battle, 42 HYDRAULIC AND PNEUMATIC ENGINEERING MACHINE GUN BATTLE GAME No. 8 Each player is behind a barricade which represents a trench (A), Fig. 61 and is armed with a syringe which here represents a machine gun. The rules about wounded and killed are the same as in Game No. 2. The winning side is the one which first kills all the enemy. Fig. 61 A. Machine Gun Battle. THE DIABLO WHISTLE GAME No. 9 The apparatus, Fig. 61 B makes a most uncanny whistle when you blow into it as illustrated and move the plunger up and down. The game is : (1) to make the most diabolical sound you can ; (2) to play the eight notes of an octave as well as you can; (3) to play a tune if you can. Fig. 61 B. The Diablo Whistle. HYDRAULIC AND PNEUMATIC ENGINEERING 43 THE LIFT PUMP Common pumps are of two kinds : lift pumps, Figs. 62, 63, which lift water only to the spout; and force pumps, Fig. 65, which force the water to any height above the spout. Both types of pumps have two valves which open upward. The Lift Pump, Fig. 62, has one valve S at the bottom of the barrel C and another V in the plunger P. The atmospheric pressure lifts water from the well into the pump through the suction pipe T. The way the lift pump lifts water is illustrated in drawings 1 to 6, Fig. 63. Fig. 62. A Lift Pump. Courtesy of The MacMillan Co. (3) (4) (5> (6) Fig. 63. Showing How a Pump Raises Water. Courtesy of The MacMillan Co. Before the pump is started the condition is that shown in (1) : both valves are closed and the water level in the suction pipe is the same as that in the well. When the plunger is raised as in (2), the air in the barrel beneath the plunger is given more room, it expands and its pressure on the valve S is decreased; the air in the suction pipe then lifts the valve S and part 44 HYDRAULIC AND PNEUMATIC ENGINEERING of it expands into the barrel; this decreases the air pressure on the water in the suction pipe, and the atmospheric pressure on the water in the well forces some water into the suction pipe. When the plunger is shoved down as in (3), valve S closes and the air in the barrel is forced up through the plunger valve V. When the plunger is raised again as in (4), the operations explained in (2) take place again, and the atmospheric pressure on the water in the well forces more water into the suction pipe and also into the barrel. When the plunger is shoved down again as in (5), valve S closes again and all the air in the barrel, with part of the water, is forced up through the plunger valve V. When the plunger is raised again as in (6), the water above the plunger is lifted to the spout and the atmospheric pressure on the water in the well forces more water into the suction pipe and barrel. After this (5) and (6) are repeated as long as the plunger is operated. EXPERIMENT No. 23 To make and operate a Lift Pump. Arrange the apparatus as shown in (1) Fig. 64. Soap the plunger, place the lower end of the narrow tube in a glass of water, and move the plunger up and down slowly. Do you find that : on the up stroke of the plunger, water moves up through the narrow tube and lower valve into the pump barrel; and on the down stroke, the water remains at the same height because the lower valve closes, but as the plunger moves down, the air and water pass through the plunger valve? Do you no- tice that on the succeeding up strokes, water rises and flows over the top, and on succeeding down strokes it moves through the plunger valve? 1 2 Fig. 64. The Lift Pump. HYDRAULIC AND PNEUMATIC ENGINEERING 45 Attach three or four narrow tubes below the pump barrel to make the suction pipe longer, (2) Fig. 64, and repeat the experiment. Attach all the narrow tubes and the rubber tube to the pump barrel and repeat the experiment. Do you find that the atmospheric pressure on the water in the tumbler lifts the water into the pump barrel when you move the plunger up? The pressure of the atmosphere is equal to the pressure of a column of water 34 feet high and no more, therefore, a pump must be placed at a less height than 34 feet above the water it is pumping and in practice the height is usually 25 feet or less. THE FORCE PUMP The force pump, Fig. 65, has a valve A at the bottom of the barrel, but the plun- ger V is solid, the discharge pipe leaves the barrel below the plunger, and the second valve B is below an air chamber at one side; also the top of the barrel is closed by an inverted U shaped leather ring which surrounds the plunger and prevents the water from escaping. It pumps water in exactly the same way as does the lift pump. The ball valves shown here have the advantage that they wear evenly because they turn continuously. Both lift pumps and force pumps can have either ball valves or common flap valves. The air chamber protects the force pump from excessive strain because the air compresses under excessive pressure; it also tends to keep a steady stream in the discharge pipe because the compres- sed air continues to force the water out of the air chamber while the plunger is making the up stroke. Fig. 65. Force Pump with Solid Plunger and Ball Valves. Courtesy of the MacMillan Co. 46 HYDRAULIC AND PNEUMATIC ENGINEERING Fig. 66. The Force Pump. EXPERIMENT No. 24 To make and operate a Force Pump. Arrange the apparatus as shown in (1), Fig. 66. Soap the plunger, place the suction pipe in a tumbler of water, pour a little water above the plunger to make sure it is air tight; and move the plunger up and down. Do you observe that on the up stroke water enters the barrel through the valve, and that on the down stroke it is forced into the side tube through its valve? If the valves are not quite air tight pour water into both tubes to cover them. Make an air chamber in the side tube by inserting a short narrow glass tube below the upper stopper, (2), Fig. 66. Operate the force pump. Do you observe that the air is slightly compressed in this chamber, on the down stroke of the plunger, and that this compressed air keeps the water flowing for a short time after the stroke is finished. HYDRAULIC AND PNEUMATIC ENGINEERING 47 Repeat the experiment using short quick strokes of the plunger. Do you find that you can keep a fairly steady stream issuing from the nozzle? Water can be forced to any height in the discharge pipe of a force pump but the suction lift should not be more than about 25 feet, that is the pump plunger must be within 25 feet vertically of the water it is pumping. fi EXPERIMENT NO 25 To show how water is pumped into an elevated tank. A lift pump can be used to pump water into an elevated tank only if the top of the tank is not over 25 feet (34 feet theoreti- cally) above the water in the well. If the tank is higher than this, a force pump must be used. Illustrate this use of a force pump by means of the apparatus shown in Fig. 67. Pump water into the tank and then draw off some through the faucet below. This equipment represents a complete water supply system. FORCE PUMP CONTEST GAME No. 10 The game here is to see who can force the water to the greatest height and to the greatest distance. Tie the stoppers in with cord and stretched rubber bands. Use the apparatus shown in (2) Fig. 66. Fig. 67. Pump Water into an Elevated Tank with a Force Pump. 48 HYDRAULIC AND PNEUMATIC ENGINEERING HYDRAULIC APPLIANCES The hydraulic press (A), hydraulic elevator (B). and hydraulic lift lock (C), Fig. 68, are each operated by means of pressure exerted on water, and in order to understand them you will first illustrate Pas- cal's law which tells how pressure is transmitted by water. Fig. 68. Hydraulic Press, Elevator and Lift Lock. A Courtesy Ginn & Co. B Courtesy of The MacMillan Co. CFrom "Ontario High School Physics" by Permission of the Publishers HYDRAULIC AND PNEUMATIC ENGINEERING 49 PASCAL'S LAW Fig. 69. Illustrating Pascal's Law. Pascal's Law is: Pressure exerted on a liquid is transmitted equally and undiminished in all directions. This law is usually illustrated by means of the apparatus shown in (1) Fig. 69. It is a syringe with a glass bulb which has five nozzles of the same size and in the same plane. When the syringe, filled with water, is held with the nozzles horizontal and the plunger is forced in, the streams which issue from the nozzles are of exactly the same length. This shows that pressure exerted on water is transmitted equally in all directions. This is very surprising because since the plunger exerts the pressure in the direction of the front stream we might expect this stream to be the longest: we find, however, that they all have the same length. EXPERIMENT No. 26 To show that pressure on water is transmitted equally in all directions. Use the apparatus (2) Fig. 69. Fill the tube with water, insert fhe plunger, hold the nozzles horizontal, and force the plunger in_steadily, Are the streams of equal length? A 4 50 HYDRAULIC AND PNEUMATIC ENGINEERING 200 100 Ibs uuufimj 71 6. . '^t/t&ff's lq. in. ____--^-__ :3- - __ _= Repeat with the apparatus (3) Fig. 69. With (2) Fig. 69 you show that the pressure is transmitted equally forward and sidewise, and with (3) Fig. 69, that it is transmitted equally in both sidewise directions. This experiment shows that water transmits pressure equally in all directions. The experiments described below show that it transmits it equally and undiminislied in all directions. The two cylinders and connect- ing pipe, Fig. 70, are filled with water and each cylinder is fitted in. with a water tight piston ; the area of cross section of the small piston is 1 sq. in. and of the large piston, 100 sq. in. If now a pressure of 1 Ib is exerted on the small piston,. Fig> 70 _ A Pregaure One Pound it is found that this pressure is on a Small Piston Exerts a Lift of One Hundred Pounds on a Large Piston. Courtesy of The MacMillan Co. transmitted equally and undiminished by the water, and that therefore, the upward pressure on the large piston is 1 ft), on each sq. in. or the total pressure upward is 100 ft>s. That is, 1 Ib. on the small piston supports 100 Ibs. on the large piston. This is very surprising and it looks as if we were getting something for nothing. This is not so, however, because if the small piston is moved down 1 inch, the large piston moves up only 1/100 of an inch. That is, "what is gained in iorce is lost in distance moved." The hydrostatic bellows, Fig. 71, is an appar- atus of this kind and it illustrates Pascal's law beautifully. It consists of two disks of wood connected by a water-proof canvas cylinder to make a collapsible drum. A small pipe passes Fi ge 71. The Hydrostatic tnrou g n the lower disk and opens into the drum. Bellows. The Smalt Amount If now the drum is filled with water and a man of Water, AB, Supports a stands on the upper disk, it is found that a very Man's Weight. sma ll amount of water, AB, in the pipe will sup- his weih t- HYDRAULIC AND PNEUMATIC ENGINEERING 51 This is very striking and it is explained as above. If, for example, the area of the pipe is 1 sq. in. and that of the disk is 500 sq. in. then 1 ft), of water in AB will support a weight of 500 Ibs. on the disk. Similarly y 2 lb. of water in AB will support J^ x 500 = 250 Ibs. on the disk, or J4 Ibs. of water in AB will support % x 500 = 125 Ibs. on the disk, and so on. EXPERIMENT No. 27 To make and operate a hydrostatic bellows. Arrange the apparatus as shown in Fig. 72. Place the book on the empty observation balloon, and fill the balloon with water until it is about half full. Do you observe that a very little water in the tube supports the weight of one end of the book. Place an empty tumbler on the book and fill it with water. Do you find that a small extra amount of water in the tube supports the glass of water? Remove the tumbler and press down on the book with your hand. Do you find that to lift water in the tube you must exert a force much greater than the weight of this water. These experiments are certainly very striking and they illustrate Pascal's law as follows : The weight of the extra water in the tube exerts pressure down- ward on an area equal to that of the inside of the tube; this pressure is trans- mitted equally and undiminished in all directions by the water, and is exerted against each equal area of the inside Fig. 72. Illustrating the Hydro- static Bellows. of the balloon. 52 HYDRAULIC AND PNEUMATIC ENGINEERING THE HYDRAULIC PRESS The hydraulic press is an application of Pascal's law and of the hydrostatic bellows. It is used where great pressure is required, for example, to compress merchandise, to bend ship plates, to lift great weights, and so on. The press has a force pump with handle P which operates the small pis- ton A in the small cylinder C and pumps water from the reservoir L through the valve d, through the connecting pipe and valve v, and into the large cylinder Fig. 73. The Hydraulic Press. Courtesy of The MacMillan Co. so on. D. The large piston B, or ram as it is called, moves up and down in D. Both A and B have collars which prevent the escape of water. If now the end of ram B has an area 100 times as great as the end of A, then each 1 Ib. exerted on A exerts a lift of 100 Ibs. on B, and EXPERIMENT No. 28 To make and operate a hydraulic press. Arrange the apparatus as shown in Fig. 74, where the tin can in the tank represents the ram and where the balloon represents the collar of the ram. Soap the plunger to make it slippery. Open lower clip, raise the plunger, close lower clip, open side clip and lower the plunger. Repeat until the balloon is partly filled with water. Now fill the tin can with water and repeat the operations above. Do you find that a small force on the plunger will lift the relatively large weight of the tin can full of water? You have shown here that on the hydraulic press a small force moving the small piston a long dis- tance lifts a great weight on the large piston a small distance. Fig. 74. Illustrating the Working of a Hydraulic Press. HYDRAULIC AND PNEUMATIC ENGINEERING 53 THE HYDRAULIC ELEVATOR The simplest form of hydraulic elevator is illustrated in Fig. 75. The passenger cage A is securely fastened to the top of a long ram P which moves up and down 1*1 a deep cylinder C. The elevator is raised by the city water pressure or, if this pressure is not sufficient, by the pres- sure of water pumped into a tank on the roof of the building. The water enters through the pipe m and through the three-way valve if, and it leaves through the three-way valve and the lower pipe. The weight of the cage and ram is partly counter- balanced by the weight shown. When water is admit- ted to the cylinder, it exerts pressure upward on the bottom of the ram and raises the ram and cage; when the discharge pipe of the cylinder is opened, the cage and ram descend by their own weight and drive the water out of the cylinder. The operation of the three-way valve is illustrated in Fig. 76. The lever handle is weighted at the end and is operated by the cord t, t, c, c, which passes through the cage. When the operator pulls the cord up the valve takes the upper posi- tion, water is admitted to the cylinder, and the ram and cage are dra gg g e raised. When the operator pulls the cord down, the valve takes the "Millikan& Gale's Fig. 76. The Three- lower position and connects the First Course way Valve. cylinder with the discharge pipe; From the cage and ram then descend by "Millikan& Gale's their own weight and in doing so First Course , f in Physics." force water from the cylinder to By Permission of th sewer Ginn & Co., Pub. Ine se wer, The Hy- in Physics.' By Permission of Ginn & Co., Pub. 54 HYDRAULIC AND PNEUMATIC ENGINEERING When speed is desired, for example in carrying passengers, the elevator is arranged as shown in Fig. 77. The plunger or ram P moves in a cylin- der C. Both ram and cylinder carry a number of large separate pulleys, side by side, around which a steel cable is passed a number of times and then attached to the counterpoise weight D. If, for example, the steel cable makes 10 loops around the pulleys there are 20 strands between the two sets of pulleys. If then the ram moves 1 foot each strand is lengthened 1 foot and the counter- poise is pulled down 20 feet. Since the cable attached to the passen- ger cage passes around the pulley of the counterpoise as shown, each foot the counterpoise descends raises the cage 2 feet. Thus if the ram moves 1 foot, the counter- poise moves 20 feet and the cage, 40 feet. This gives the passenger cage a speed forty times that of the ram. Fig. 77. A Rapid Hydraulic Elevator for Passengers. From "Millikan & Gale's First Course in Physics." By permission of Ginn 6- Co., Publishers The Tarn is moved by water from the city mains which is controlled by a three-way valve as described above. Fig. 78. Illustrating the Working of a Hy- draulic Elevator. HYDRAULIC AND PNEUMATIC ENGINEERING 55 EXPERIMENT No. 29 To make and operate a hydraulic elevator. Arrange the apparatus as shown in Fig. 78. Soap the plunger well to make it slippery. Open side clip. Is the cage raised? Close side clip. Does it stop? Open lower clip and press down gently on the cage. Does it descend? Close lower clip. Does it stop? Now open and close side clip to raise the cage a short distance at a time. Do you find that you control the elevator perfectly as it rises? Now open and close lower clip while you force the cage down a short distance at a time. Do you find that you can control the elevator perfectly as it descends and that you cannot move it down when the clip is closed? You have shown here how the ram and cage of an elevator are raised by water pressure and how they descend by their own weight. You have shown also that you can stop them anywhere, while rising or descending, by closing the proper valve. HYDRAULIC LIFT LOCKS CANAL LOCKS Fig. 79. A Single Lock. Courtesy of "The Scientific American' 56 HYDRAULIC AND PNEUMATIC ENGINEERING An ordinary canal lock, Fig. 79, is used to raise or lower steamers a few feet to enable them to pass up or down stream, around a rapid, dam or waterfall. It is simply a short canal with a pair of gates at each end. If the steamer is going up stream, it sails through the lower gates of the lock; the lower gates are closed behind it; water is admitted to the lock until its level is equal to that of the water above the lock; the upper gates are then opened, and the steamer sails out of the lock at the upper level. If the steamer is going down stream the reverse operation takes place. If the difference in level is considerable but over some distance, a number of these locks are used, for example, if the difference in level were 80 feet in a distance of two miles, there might be, in the two miles, 4 locks with a difference of level of 20 feet each or 8 locks with a differ- ence of 10 feet each, and so on. When the difference in level is great in a short distance, however, a lift lock must be used. LIFT LOCKS Lift locks are so called because the whole lock, with the water in it and the ship, is lifted vertically from the low level to the high, or is lowered vertically from the high level to the low. They are always in pairs and the weight of one balances the weight of the other. The lift lock shown in Fig. 80, is one that it is proposed to build on a canal between Lake Erie and Lake Ontario. It will take ships 650 feet long and of 30 foot draft, and will lift or lower them through a vertical height of 208 feet. The inner side of one will be connected with the inner side of the other by 56 steel cables which pass over 56 sheaves of 20 foot diameter. The outer side of each will be connected with large concrete counterweights by means of steel cables passing over 56 sheaves on each side. The locks will be raised and lowered by means of electrical power applied to the rims of each sheave. The gates at the ends of each lock and at the ends of the upper and lower canal will be opened and closed by being moved down and up vertically. The diagram shows how the locks will look when one ship is being raised and another lowered. The building at the right is a plant in which electrical power will be developed from the excess water from the upper canal. A small part only of this power will be used to operate the locks. HYDRAULIC AND PNEUMATIC ENGINEERING 57 Fie. 80. A Proposed Lift- Lock. Courtesy of "The Scientific American' 58 HYDRAULIC AND PNEUMATIC ENGINEERING HYDRAULIC LIFT LOCKS Hydraulic lift locks are so called because they are operated by means of water. Each lock is a large steel tank securely attached to the top of a very large ram which moves up and down in a deep cylinder. The two cylin- ders are connected by a pipe through which the water flows from one to the other, the flow being controlled, or stopped entirely, by means of a valve. Fig. 81. The Hydraulic Lift-Lock. ig. 81. The Hydraulic Lift-Lock From the "Ontario High School Physics." By permission of the Pubishers. The operation of the locks will be un- derstood from Fig. 82. If the steamer is going up stream : it sails into the lock B which is down and the lock gate is closed; a little water is admitted to the lock A which is up, to make it weigh more than the lower lock B and the steamer; the valve R is opened; the upper lock descends and its ram Pi forces water from its cylinder into that of the lower lock; the pressure of this water raises the ram P 2 , the lower lock Fte. 82. Showing How Lift-Locks Operate. and the steamer, to the upper level; the From the "Ontario High School Physics." ea tes are opened; and the steamer sails By Permission of the Publishers out at the upper level. HYDRAULIC AND PNEUMATIC ENGINEERING 59 If the steamer is going down stream; it sails into the upper lock and the gates are closed; water is admitted to the upper lock to make it weigh more than the lower lock; the valve R is opened; water is forced from the cylinder of the upper lock to that of the lower as the upper lock descends and the lower lock rises; the gates are opened; and the steamer sails out at the lower level. Note. You might think that the presence of the steamer in one lock would make it weigh more than the other lock, but you will learn in Experiment 36 that a ship displaces its own weight of water and that therefore the one lock, plus water, plus steamer, weighs the same as the other lock plus water. EXPERIMENT No. 30 To make and operate a hydraulic lift lock. Use the apparatus shown in Fig. 83. The wide tubes and plungers represent the cylinders and rams of a real lift lock, and the clip repre- sents the control valve. The inverted tumblers represent the locks, they should of course be right side up but you have no way of fastening them. Place a button or pebble on the lower lock to represent a ship, open the clip and press down on the upper lock. Is the ship raised? Lower a steamer in the same way. Now place a steamer in the lower lock and press down on the upper lock while you open and close the clip from time to time. Do you find that the plungers stop as soon as you close the clip? This shows how the rams of a real lift lock can be stopped anywhere by closing the valve R, Fig. 82. Water is incompressible, as you know from Exper- iment, No. 7, and when valve R is closed the rams cannot move because the water in the cylinders cannot be compressed and cannot move. Repeat this but close the clip only partly. Do you find that the plungers can move slowly Fig. 83. Hlustrat- and that you can regulate the speed by opening gf the clip more or less? Lock. 60 HYDRAULIC AND PNEUMATIC ENGINEERING This shows how the rams in a real lift lock can be allowed to move rapidly or slowly by opening the valve R more or less In this experiment you have illustrated the working of a hydraulic lift lock: you have shown that the downward movement of one ram drives water into the second cylinder and that the pressure of this water raises the ram in the second cylinder; you have shown also that the rams can be stopped anywhere by closing the valve R or that they can be made to move very slowly by closing the valve partly. THE PRESSURE EXERTED BY WATER Fig. 84. The Height of the Stream is Independent of the Size or Shape of the Tank and Pipe. HYDRAULIC AND PNEUMATIC ENGINEERING 61 A very astonishing fact is illustrated in Fig. 84, namely that the pressure at the nozzles is the same no matter what size and shape the tank may be and no matter what size and shape the pipe may be, provided the water level in the tank is at the same distance above the nozzle in all cases. You will now prove this. EXPERIMENT No. 31 To show that the pressure at a nozzle is independent of the size and shape of the tank and pipe. Fig. 85. Showing That the Pressure at a Nozzle is Independent of the Size or Shape of the Tank or Pipe. Make the experiments illustrated in Fig. 85 one after the other using the same nozzle in all. Are the streams of the same height in all cases if the water level in the tank is at the same distance above the nozzle? 62 HYDRAULIC AND PNEUMATIC ENGINEERING You have shown here that the pressure exerted by water is inde- pendent of the volume of the water but that it depends upon the height of the water above the nozzle. This is known as the Hydrostatic Paradox which you will now illustrate. THE HYDROSTATIC PARADOX The Hydrostatic Paradox is stated as follows : The pressure exerted by a liquid on any base is independent of the volume of the liquid, but depends only on the area of the base, the depth of the liquid, and the density of the liquid. Note. The density of a liquid is its weight per cubic foot, or per cubic inch, or per cubic centimeter. The hydrostatic paradox is illustra- ted by means of the apparatus shown in Fig. 86. The three tops are of diff- erent sizes and shapes, but they fit a common base. The bottom of this base is covered by a sheet of rubber or by a sheet of corrugated metal. The base sinks as the pressure in- creases and moves the pointer, which indicates the pressure. If the tops are screwed to the base, one after the other, and then filled with water to the same height, the Fig. 86. Illustrating the Hydrostatic pointer indicates the same pressure in Paradox. _ii ,.--- Courtesy of The MacMillan Co. a11 cases - The volume of water in the tops is different in each case, but the pressure is the same in all. This shows that the pressure exerted by a liquid is independent of the volume of the liquid, provided the area of the base, the depth and the density of the liquid are the same in all cases. Another form of this apparatus is shown in Fig. 87; the three tops fit the same base, but the bottom is a brass plate AB which is held on by a cord attached to one arm of a balance (not shown). The plate AB falls in each case when the water reaches the same height. The hydrostatic paradox is also illustrated in 4; the three tubes are of very different volumes but the water stands at the same height in all. HYDRAULIC AND PNEUMATIC ENGINEERING 63 Fig. 87. A Second Method of Illustrating the Hydrostatic Paradox Courtesy of The MacMillan Co. These experiments show that the pressure a liquid exerts on a given base is independent of the volume of the liquid, provided the area of the base, depth of the liquid, and density of the liquid are constant. EXPERIMENT No. 32 To illustrate the hydrostatic paradox. B C Fig. 82, Illustrating the Hydrostatic Paradox. 64 HYDRAULIC AND PNEUMATIC ENGINEERING Make the experiments A, B and C, Fig. 88, one after the other. Is the water in the small tube always at the same height as that in the funnel or large tube? Arrange the apparatus as in D, Fig. 88. Is the water at the same level in all cases? The funnel and wide tube, each contain more water than the small tube; nevertheless, the downward pressure of the water in each is bal- anced by the downward pressure of the water in the small tube. You have shown here that the pressure exerted by a liquid is inde- pendent of the volume of the liquid, that is, you have illustrated the hydrostatic paradox. EXPLANATION OF THE HYDROSTATIC PARADOX The hydrostatic paradox seems impossible, and that is why it is called a paradox. It would seem to be self evident that the greater the volume of water above a base, the greater would be the pressure; ijB Fig. 89. Explanation of the Hydrostatic Paradox. HYDRAULIC AND PNEUMATIC ENGINEERING 65 and the less the volume, the less the pressure. You have shown above, however, that the pressure on a given base is independent of the volume of water and that it depends only on the depth. The paradox is explained as follows : In 1, Fig. 89, the base AB is subject to the pressure of the water in the cylinder above it, and in this case, the pressure is equal to the weight of the water. In 2, Fig. 89, the same base AB has a much larger volume of water above it but the pressure is the same as in 1. You will understand why, if you consider the water outside the dotted lines. This water exerts a force perpendicular to the sides of the cone, and another force horizontally against the water between the dotted lines, see the arrows. Neither of these forces has any effect downward on the base and there- fore the base is subject only to the weight of the water between the dotted lines. This weight is the same as in 1 and therefore the pressure on AB is the same as in 1. In 3, Fig. 89, the base AB has a much smaller volume above it than in either 1 or 2, but still the pressure is the same as in 1 and 2. You will understand why from your knowledge of Pascal's law. The water above AB is exerting pressure downward, and according to Pascal's law this pressure is transmitted equally and undiminished in all di- rections. The pressure per square inch downward on the whole of AB, therefore, is equal to what it would be if the whole space between the outer dotted lines were filled with water. This pressure is equal to that in (1) and this is why the pressure in (3) is equal to that in (1). HOW TO CALCULATE THE PRESSURE EXERTED BY WATER The density (weight) of fresh water is 62 l / 2 Ibs. per cubic foot and if in (1) Fig. 89, the base AB is 1 square foot and the height of the water is 10 feet, there are 10 cubic feet of water in the tank and the total pressure on the bottom is 10 x 62.5 = 625 Ibs. Since the pressure exerted by water is independent of the volume of the water and depends only on the area of the base, the height, and the density of the water, the pressure on AB in (2) and (3) is 625 Ibs., the same as in (1). The rule for calculating the pressure in any case is : Pressure on any base = area of base in square feet x height of water in feet x density of water (weight of 1 cubic foot) or, Pressure = area x height x density. A 5 66 HYDRAULIC AND PNEUMATIC ENGINEERING In the example given : Pressure = 1 x 10 x 62.5 = 625 Ibs. per square foot. To find the pressure per square inch, first find the pressure per square foot and then divide the result by 144, the number of square inches in 1 square foot. For example, the pressure on 1 square inch of AB in any of the tanks illustrated is 625 -r- 144 = 4.34 Ibs. PRESSURE UNDER WATER THE DEPTH BOMB TORPEDO SUBMARINE THE DEPTH BOMB 90. The Depth Bomb. Courtesy of "The Scientific American" HYDRAULIC AND PNEUMATIC ENGINEERING 67 The depth bomb is used by submarine chasers to destroy submarines. It is a steel cylinder filled with high explosives and equipped with a trigger which sets off the explosive at any desired depth under water. The trigger is released by means of a small plunger which is exposed to the pressure of the sea water on the outside and is supported by a spring on the inside. The pressure of the water increases as the bomb sinks and forces the plunger in farther against the spring, but the spring can be so adjusted that at any desired depth the plunger releases the trigger and the bomb explodes. When the chaser sights a submarine it steams for it and if it is still above water, attacks it with guns; but if it has submerged, the chaser steams in circles around the spot where it disappeared and drops or fires bombs adjusted to explode at different depths. THE TORPEDO WADHCAD U001A CQ*T*Ql* Fig. 91. The Principle Parts of the Torpedo. Reproduced by Permission from the "Boy's Book of Submarines" by Frederick Collins. Copyright by Frederick A. Stokes Co. The torpedo is a cigar shaped tube loaded in the head with high explo- sives which are set off by a contact pin. It is driven by means of a com- pressed air motor and is steered by horizontal and vertical rudders. We are interested in the horizontal rudder particularly at this point. It steers the torpedo to a depth of 20 feet under water and keeps it at this depth. It does this by means of the pressure of the sea water. The horizontal rudder is controlled by a piston, Fig. 92, which is exposed to the pressure of the sea water on the Mt/Z* *>tSt.) and 30 cubic inches of mercury weigh .49 x 30 = 14.7 ft>s. The pressure of the atmosphere is therefore 14.7 Ibs. per square inch, (nearly IS tbs. per square inch). It is a very astonishing fact that the atmosphere exerts 14.7 Ibs. pressure on each square inch of every thing at the surface of the earth. It is at first almost unbelieveable, but you have already made exper- iments which illustrate this pressure and you will make others as you proceed. EXPERIMENT No. 47 To measure the pressure of the atmosphere. If you have a spring balance you can measure the pressure of the atmosphere directly with the apparatus, Fig. 128, as follows. The diameter of the plunger is a little over ^ inches and therefore its area is 3/10 square inch. If then the pressure of the atmosphere is 15 Ibs. on 1 square inch it is IS x 3/10 = 4^ Ibs. on 3/10 square inch. Soap the plunger well to make it slippery, shove it about ^ way into the tube, fill the remaining % of the tube with water, and insert a solid rubber stopper in this end, (1). Now turn the tube so that the plunger handle points vertically upward, and pour a little water in above the plunger to make it air-tight, (2). A I 98 HYDRAULIC AND PNEUMATIC ENGINEERING Fig. 128. The Atmosphere Exerts the Pressure of 15 Ibs. per square inch, But No More Now to measure the pressure of the atmosphere, attach the plunger handle to a spring balance, hold the tube firmly against the table, and ask your partner to pull upward on the spring balance while you observe the pull recorded on the balance, (3). Ask him to lift the balance slowly until the plunger is about two inches above the water, then ask him to allow the balance to go back slowly until the plunger is only about 1 inch above the water. While he is doing this you must read the average pull on the balance. Do you find this average pull to be 72 ozs. or 4^ Ibs? Note: While your partner is raising the plunger, the friction of the plunger against the sides of the tube is work- ing against the balance and the pull will be over A l / 2 Ibs; but while he is lowering the plunger, the friction will be working with the balance and the pull will be less than 4^ Ibs. The average will be about 4> Ibs. You have shown here that the pres- sure of the atmosphere is 4Vj Ibs. on 3/10 sq. in. or 4^ x 10/3 = 15 Ibs. on 1 square inch. THE BAROMETER The barometer, Fig. 129, is the chief instrument used by the Weather Bu- reau in forecasting the weather. It Is an apparatus similar to that used by Torricelli in his experiment. The pressure of the atmosphere on the mercury in the open tube or cup sup- ports a column of mercury about HYDRAULIC AND PNEUMATIC ENGINEERING 99 1 2 Fig. 129. Barometers l-Courtesv of the MacMillan Co. 2-From the "Ontario High School Physics' ' . By Perm ission of the Publishers tight metal box from which the air is ex- exhausted. The atmos- pheric pressure would force together the top and bottom of this box if they were not kept apart by the strong spring shown 30 in. high in the long closed tube. The pressure of the atmosphere varies from hour to hour and the height of the mercury column varies with it. Weather forecasts are based on this variation. It has been found that when the mercury falls much below 30 in., be- cause the atmospheric pressure is low, bad weather may be expected; and when the mercury rises much above 30 inches, because the atmospheric pressure is high, good weather may be expected. The extreme variations are from about 29 in. to 31 in. The barometer (2) is the type used on ships, and when a sailor says "the glass is falling" he means that the mercury in the glass tube is sinking below 30 in. and that bad weather is to be expected; when he says "the glass is rising," he means that the mercury is rising above 30 in. and that fine weather is to be expected. Another type of barometer is shown in Fig. 130. It is called an aneroid barometer because it contains no liquid. It has a flat, round, air- Fig. 130 Fig. 130. Aneroid Barometer Courtesy vf The liltclltilan Co. 100 HYDRAULIC AND PNEUMATIC ENGINEERING above the box. If the atmospheric pressure increases, the spring is forced down; if the pressure decreases, the spring rises. The move- ments are very small, but they are magnified by levers and are com- municated to the pointer by means of a rack and pinion. HOW AIRMEN KNOW THEIR ALTITUDE THE ALTITUDE GAUGE sum e*rru tuna Air Zones of Modern Battle (1918) The air zones of a modern battle are illus- trated in Fig. 131 and the altitude guage by means of which the air- men know their height is shown in Fig. 132. This altitude gauge is a recording aneroid barometer called a bar- ograph. It records the height of the airplane in feet and is suspend- ed free of the airplane by four elastic straps which protect it, to some extent, from the vibration of the ma- chine. The construction of the barograph is as fol- lows. It has five or six flat metal boxes, ex- hausted of air, similar to the box in the or- dinary aneroid. These boxes are expanded by a strong spring, as the height increases, and this movement is com- municated to the long Fig. 131. Air Zones Courtesy of "The World's Work", Garden City, N. Y. pointer. On the end of the pointer there is a pen, with a supply of ink, which bears against a sheet of paper on a drum revolved by clockwork. The pen makes a continuous record on the paper of the height in feet. HYDRAULIC AND PNEUMATIC ENGINEERING 101 I Mercury Barometer " : tfig! ij2.*-The' 'Altitude Gauge or Fig. 133. Water Barometer THE WATER BAROMETER Any liquid can be used in a bar- ometer but liquids lighter than mer- cury require longer tubes. This is true of the water barometer. Mer- cury is 13.6 times as heavy as water and since the atmosphere supports a column of mercury 30 in. high it will support a column of water 13.6 x 30 = 408 in. high, that is, a column 408/12 = 34 feet high. Otto von Guericke, the inventor of the Magdeburg hemispheres, made a water barometer in 1650, and had it so arranged that the top of the tube stuck up through the roof of his house. He had a small wooden figure floating on the water in the tube and in fine weather, when the water column rose, the figure rose above the roof, but in bad weather the figure retired from sight. This frightened and mysti- fied his neighbors very much and they accused him of being in league with the evil one. 102 HYDRAULIC AND PNEUMATIC ENGINEERING EXPERIMENT No. 48 To show that the vertical height to which the atmosphere will lift water in a tube is independent of the length or slant of the tube. Make the experiments (1), (2) and (3), Fig. 134. Suck air out through the upper coupling on the tee and close the clip. Is the vertical height of the water in one tube above the water in the tum- bler always the same as that in the other? Make experiments of ypur own. Fig. 134. The Height is independent of the Length and Slant of the Tube EXPERIMENT No. 49 To show that the height to which the atmosphere will lift water in a tube is inde- pendent of the size or shape of the tube and of the water sur- face outside the tube. Make the experiments (1), (2), (3) and (4) Fig. 135. Is the height of the water always the same in the two tubes? Make experiments of your own. Fig. 135 HYDRAULIC AND PNEUMATIC ENGINEERING 103 EXPERIMENT No. 50 Fig. 135. The Height is independent of the size or shape of the Tube and of the Water To show that the atmosphere Surface outside the Tube lifts heavy salt water to a less height, and light gasoline to a greater height, than it lifts fresh water. Make the experiments illus- trated in Fig. 136. EXPERIMENT No. 51 To show that the atmosphere will lift weights. Make the experiments illus- trated in Fig. 137. Fig. 136. Salt Water is raised to a less' height than Fresh Water, and Gasoline to a greater height. Fig. 137. ^howing that the At- mosphere will lift weight. 104 HYDRAULIC AND PNEUMATIC ENGINEERING ini Fig. 138. Showing that the Atmosphere will lift 15 tt>s. per sq. in. but no more. EXPERIMENT No. 52 To show that the atmosphere will lift 15 Ibs. per sq. in. but no more. The plungers have an area of 3/10 sq. in. If then, the atmosphere will lift 15 Ibs. on 1 sq. in., it will lift 3/10 x 15 = V/ 2 Ibs. on 3/10 sq. in. Soap the plungers, have water be- tween them but no air, pour an inch of water above the upper plunger to make it air-tight, attach a pail weigh- ing less than 4^2 Ibs. to the lower plunger, Fig. 138 and raise the upper plunger. Does the atmosphere lift the lower plunger and weight? Add water to the pail until the to- tal weight is tyz Ibs. and raise the upper plunger. Do you find that the atmosphere does not lift the lower plunger? It does not do so because the atmospheric pressure on 3/10 sq. in. cannot lift 4^ Ibs. and also OTCF- come the friction. Hold the upper plunger and lift the tube. Does the atmosphere now lift 4^ Ibs. weight? It does so because the friction helps it in this case. HYDRAULIC AND PNEUMATIC ENGINEERING 105 Repeat with the water and pail weighing 6 Ibs. Do you find that the atmospheric pressure on 3/10 sq. in. will not lift 6 Ibs. even with the help of the friction. You have shown here roughly that the atmospheric pressure on 3/10 sq. in. will lift 4^ Ibs. but no more. This shows that the atmospheric pressure on 1 sq. in. will lift 4.5 x 10/3 = 15 Ibs. but no more. Make your own experiments. AIR-LIFT PUMPS The air-lift pump, Fig. 139, is operated by compressed air. It consists of two pipes one inside the other, both open at the bottom and without val- Fig. 139.-An Air-Lift Pump ves - Th P" m P w at least half-submerged, that is, the bottom is at least as far below the surface of the water in the well as the top is above it. The air which is compressed in the storage tank passes into the outer pipe of the pump, forces the water down to the bottom of the inner pipe, and forces the water in the inner pipe up into the tank. After the first lot of water has been forced out of the inner pipe the pump settles down to its regular operation which is as follows. Compressed air from the outer pipe enters the inner pipe, the pressure in the outer pipe is thereby lowered and the water rises in the outer pipe above the bottom of the inner pipe, more compressed air comes from the tank and forces the water down in the outer pipe but up in the inner pipe. This operation takes place over and over again rapidly, and alternate layers of air and water are forced up the inner pipe as shown in Fig. 139. The water thus flows from the inner pipe into the tank in spurts as you will show in your next experiment. Another form of air-lift pump is illustrated in Fig. 140. Here the air enters through the inner pipe and the mixture of water and air is 106 HYDRAULIC AND PNEUMATIC ENGINEERING forced out through the outer pipe. The water comes out as a continuous heavy spray because the air is mixed with the water in bubbles rather than in layers. These are called air-lift pumps but the water is not raised by the air pressure. It is raised by the weight of the water in the well out- side the pump, because the water rising in the pump is really a mixture of air and water and is lighter than a water column of the same height. You can illustrate this by means of ex- periments shown in Fig. 141. In (1) both sides of the U tube are filled with water and you know from your experi- ments that the water will be at the same level in both sides. In (II) one side is filled with kerosene oil which is only 8/10 as heavy as water, and you know that a column of water 8 in. high will support a column of oil 10 in high. Similarly in (III) a depth of water of 8 inches will support a column of oil 10 inches high. If now the oil in (III) were replaced by a mixture of air ond water which was only 1/2 as heavy as water, you can see that the 8 inch depth of water would support a column of the mixture 16 inches high, and so on. The bottom of the air-lift pump is al- ways placed at least as far below the sur- compressed air s Fig. 141. A Column of Water sup- ports a longer column of a Light Oil. Courtesy of the MacMillan Co. Fig. 140. Another type of Air-Lift Pump HYDRAULIC AND PNEUMATIC ENGINEERING 107 face of the water as the top is above, and the water outside the pump lifts the lighter mixture of air and water to the top. You will illustrate this in the next experiment. EXPERIMENT No. 53 To make and operate two air-lift pumps. Make an air-lift pump. (1) Fig. 142. Use a quart sealer to represent the well, fill it to the top with water, and insert the air-lift pump until it is half submerged, that is, until the water in the sealer is at a point half way between the bottom of the wide tube and the top of the elbow of the discharge pipe. Force air in through the hose and observe what takes place near the bottom of the pump. Do you observe that the water level in the pump moves alternately down below the end of the dis- charge pipe and then up above it, and that altern- ately water and air are forced up the discharge pipe? Do you observe further that when you force air in at just the right rate the pump works steadily and the water 1 2 comes up the dis- Fig. 142. Illustrating the working of ... two different Air-Lift Pumps. charge pipe in 108 HYDRAULIC AND PNEUMATIC ENGINEERING spurts at regular intervals. In the other type of air-lift pump the compressed air passes down the inside pipe and the mixed air and water move up the other pipe. Make a pump of this kind, (2) Fig. 142 and blow air in through the inside pipe. Do you find that air and water are forced up over the top of the outside pipe? Repeat the experiment with the pump deeper in the water. Do you find that it works better the deeper it is in the water? LAWS WHICH APPLY TO GASES PASCAL'S LAW In the remaining pages of this book you will study three laws which apply to gases and you will illustrate many practical applications of these laws. They are Pascal's law, Archimedes' law, and Boyle's law. You will begin with Pascal's law. You learned on pages 49, 50 and 51, Pascal's law which states one pro- perty of liquids; namely, pressure exerted on a liquid is transmitted by the liquid equally and undiminished in all directions. This law also states a property of gases as follows : pressure applied to a gas is trans- mitted by the gas equally and undiminished in all directions. You are very familiar with one application of this law, namely in the pneumatic tire. The air in a bicycle or automobile tire exerts pressure outward equally at every part of the tire. EXPERIMENT No. 54 To illustrate Pascal's law as it applies to gases. Shove the plunger in (1) Fig. 143, down, and feel the air at the nozzles. Are the pressures equal? Blow a soap bubble (2). Is it a perfect sphere? This shows that the air exerts pressure equally in all directions against the inside of the bubble. Make a three legged siphon filled with air (3), place two legs in tumblers of water, place the third leg in the wide tube partly filled with water, and raise and lower the wide tube. HYDRAULIC AND PNEUMATIC ENGINEERING 109 Fig. 143. Showing that Air transmits Pressure Equally and Undimin- ished in all directions. The water in the wide tube exerts pressure on the air in the third leg. Is this pressure exerted equally and undiminUhed by the air, that is, is the water level in the three legs always at the same distance below the water outside? Repeat this with the apparatus (4). Is the result the same? You have here proved Pascal's law, namely that a gas transmits pressure equally and undiminished in all directions. 110 HYDRAULIC AND PNEUMATIC ENGINEERING BALLOONS AND THE BUOYANT FORCE OF AIR The Law of Archimedes applied to Gases Balloons float in air and this fact is due to a property of air which is expressed by the law of Archimedes. You have already made experiments on this law with liquids and you have shown that the buoyant force of a liquid on a body is equal to the weight of the liquid displaced by the body. This is the law of Archi- medes as it applies to liquids. The law of Archimedes in regard to gases is : the buoyant force of a gas on a body is equal to the weight of the gas displaced by the body. Fig. 144. The Buoyant Force on the Balloon is Equal to the Weight of Air displaced by the Balloon Courtesy of "The Scientific American" How the Total Lift of a Balloon is Calculated The weight of air is about \Y$ ounces per cubic foot at ordinary tem- peratures and at the surface of the earth. If then a balloon displaces 1,000,000 cubic feet of air, its total lift or buoyancy is 5/4 x 1,000,000 = 1,250,000 ounces = 1,250,000/16 Ibs. = 78,125 ibs. and so on. The useful load a balloon can lift is its total lift minus the weight of the envelope, of the gas in the envelope, of the cars, of the engines, and of the fuel. In Fig. 145 we show the relative strengths in dirigible balloons of Germany, France and Great Britain at the beginning of the war. Britain HYDRAULIC AND PNEUMATIC ENGINEERING 111 and France built many dirigibles during the war and one of the latest built by Britain displaces 1,600,000 cubic feet of air. Its total lift there- fore is 1,600,000/16 x 5/4 = 125,000 Ibs. The balloon is filled with hydrogen which weighs about 1/14 as much as air, and therefore 1/14 of the total lift is used up in lifting the hydrogen gas. The weight of the hydrogen is 125,000/14 = 8928 Ibs. Fig. 145. Comparative Zeppelin Strength of Germany, France Great Britain at the Outbreak of the Great World War. On the left, thirteen German ships in commission and four (in white) building. On the right, above, one French ship built and two building. On the right, below, two British ships building. Courtesy of The Scientific American Hydrogen gas has been used in balloons because it is the lightest gas known. It has one great drawback, however, in that it burns very readily. There is another gas called helium which is twice as heavy as hydrogen but which has the great advantage that it does not burn. Before the war helium was very expensive but during the war it was found that the helium which occurs in some of the natural gases of the United States could be separated at a reasonable cost. It is expected that the dirigibles of the future will be filled with helium, and since it does not burn, it will be possible to put the engines in a room inside the balloon as shown in Fig. 146. 112 HYDRAULIC AND PNEUMATIC ENGINEERING Fig. 146. Conception of the Passenger-Carrying Dirigible of the Near Future making use of Helium Gas Courtesy of the Scientific A merican Although helium is twice as heavy as hydrogen its lifting power is only 1/13 less because the lift of a balloon depends primarily on the weight of air displaced. You can show this as follows : If a balloon displaces 140,000 Ibs. of air and it is filled with hydrogen, it holds 140,000/14 = 10,000 Ibs. of hydrogen, since hydrogen weighs 1/14 as much as air. If the balloon is filled with helium it holds 140,000/7 = 20,000 Ibs. of helium, since helium weighs 1/7 as much as air. The lift minus the weight of hydrogen = 140,000 10,000 = 130,000 Ibs. The lift minus the weight of helium = 140,000 20,000 = 120,000 Ibs. That is, the lift with helium is only 1/13 less. EXPERIMENT No. 55 To illustrate the buoyant force of air. Blow a soap bubble with illuminating gas (1) Fig. 147. Does the bubble rise? HYDRAULIC AND PNEUMATIC ENGINEERING 113 HYE Fig. 147. Filling a Bubble and a Balloon with Illuminating Gas Blow up a balloon with illuminating gas by means of the force pump (2) Fig. 147. Does the balloon rise? The bubble and balloon rise because they displace a greater weight of air than their own weight plus the weight of the gas in them. EXPERIMENT No. 56 To illustrate the buoyant force of air by means of a balloon filled with hydrogen. A 8 114 HYDRAULIC AND PNEUMATIC ENGINEERING If the metal zinc is placed in an acid, the metal is dissolved by the acid and hydrogen gas is produced. You can make hydrogen gas and fill the large balloon with it as follows. Purchase at a drug store 2 ounces of strong hydrochloric acid (also called muriatic acid) which should cost about 5 or 10 cents ; also pur- chase at an electrical shop a zinc rod for a Leclanche battery, which will also cost about 5 or 10 cents, or purchase two zinc strips. Pour the acid into the bottle and add an equal volume of water. This dilutes the acid and slows up the production of the hydrogen. If the hydrogen is produced too fast it will bubble acid up into the balloon. Now to make hydrogen and to fill the balloon, proceed as follows : Arrange the bottle as shown in Fig. 148 and attach the large bal- loon to the elbow by means of a short piece (about \Y 2 in.) of a stretched rubber band. When you have done this place the zinc rod or zinc strips gently in the bottle, insert the stopper at once, and al- low the hydrogen to fill the balloon. It will take about 5 minutes to fill the large balloon completely. When the balloon floats well in the air, slip it off the elbow with its stretched rubber band. The band will contract and close the balloon. Now release the balloon. Do you find that it floats up to the ceiling? Precautions. Be very careful not to get any of the acid on your hands or clothes. It will burn very bad holes if it does. When you are through empty out the liquid left in the bottle, as it is of no further use, and rinse the bottle and rod very thoroughly with water. You must not use the zinc in small pieces because it produces the hydrogen too fast and makes the acid bubble up into the balloon. Use the zinc in the shape of a rod or strips. Fig. 148. Filling a Balloon with Hydrogen HYDRAULIC AND PNEUMATIC ENGINEERING 115 EXPERIMENT No. 57 To shoot down a balloon. We show in Fig. 149 three views of a balloon shot down by means of incendiary bullets. These bullets set the hydrogen on fire, the en- velope burns, and the car and machinery fall to the ground. r * Fig. 149. Three Phases of a Successful Attack on an Obseravtion Balloon 1 Immediately after the "hit" has been scored. Note the aeroplane and balloon. 2 Balloon enveloped in flames is fast reduced to a shapeless mass. 3 Wreckage of the observation balloon falling to earth, with a smoke trail in its wake. Courtesy of the Scientific American A toy balloon filled with hydrogen as in the last experiment floats up to the ceiling. It will come down by itself in a few hours because the hydrogen gradually passes out through the rubber. If you are in a hurry to get the balloon down, and if you have an air riflle, you can shoot a hole through the balloon : the hydrogen will then escape and the balloon will fall at once. This method, however, spoils the balloon. 116 HYDRAULIC AND PNEUMATIC ENGINEERING You can shoot the balloon down with a syringe without destroying it as shown in Fig. 150. The water on the balloon will make its weight greater than the buoyancy of the air displaced by the bal- loon and this will bring it down. If you let the water evaporate, the balloon will rise again because it again becomes lighter than the air it displaces. You can then shoot it down again with water. EXPERIMENT No. 58 To illustrate the buoyant force of a gas heavier than air by means of a soap bubble filled with air. Purchase at a drug store one ounce of ether and pour it into an empty 12 qt. pail, cover the pail with a newspaper and allow it to stand for about 10 minutes. The ether will evaporate and produce ether gas. This being heavier than air will remain in the bot- Fig 150 Shooting tom of the pail an< * * orce the lighter air out at the Down a Small Balloontop. Now dip the end of the wide tube in the soap suds and shake off the excess soapy water. Blow a large bubble and detach it about 6 in. above the bottom of the pail. Do you find that the soap bubble filled with air floats on the heavy ether gas? The buoyant force of the ether gas is the weight of this gas displaced by the bubble. This buoyant force is sufficient to support the soap bubble film and the air inside of it. Fig. 151. Illustrating the Buoyant Effect of a Heavy Gas. 1 Fig. HYDRAULIC AND PNEUMATIC ENGINEERING 117 COMPRESSED AND EXPANDED GASES BOYLE'S LAW You will now illustrate Boyle's law and then make a number of appliances which make use of this law, namely, the air brake, flame thrower, fire extin- guisher, air pump, bicycle pump, sand blast, pneu- matic paint brush, diving bell, pneumatic caisson, and submarine air supply. Boyle's law is : The vol- ume of a. gas varies inver- sely as the pressure on it. This is illustrated in Fig. 152. In (1) the tube is full of air and the pressure on the air is one atmos- phere because the tube is open to the atmosphere. In (2) the pressure on the air is 2 atmospheres and the volume of the air is 1/2 what it was in (1). In (3) the pressure on the air is 3 atmospheres and 1/3 what is was in (1) and so on. 152.- 3456 -The Volume of a Gas Varies Inversely as a Presure on it the volume of the air IS In (4) the air in the tube below the plunger is under 1 atmosphere pressure because the tube is open to the atmosphere. In (5) the tube is closed, the plunger is raised until the pressure on the air is 1/2 at- mosphere and its volume is two times what it was in (4). In (6) the plunger is raised until the pressure on the air . in only 1/3 and its volume is three times what it was in (4). These illustrate Boyle's law. 118 HYDRAULIC AND PNEUMATIC ENGINEERING Boyle's law is usually illustrated by means of the apparatus shown in Fig. 153. The glass tube A is closed at the top and is partly filled with air, the second glass tube B is open at the top, and the two tubes are con- nected by a rubber tube filled with mercury. The mercury surfaces at the beginning are at the same level, (1) Fig. 154, and since the pressure on the mercury surface in B is 1 atmosphere, the pressure on the air in A is also 1 atmosphere. If now B is raised until its mercury surface is 30 in. above that in A, the air in A is under 2 atmospheres pres- sure and it is compressed to 1/2 its first volume, (2). If B is raised until its mercury surface is 60 in. above that in A, Fig. 153. Apparatus used to Illustrate Boyle's Law Courtesy of The MacMMan C*. the air in A is under 3 atmospheres pressure and it is compressed to 1/3 its first volume (3), and so on. If on the other hand, B is lowered, (5), until its mercury surface is 15 in. 2 3 Fig. 154. Illustrating Boyle's Law HYDRAULIC AND PNEUMATIC ENGINEERING 119 Vol. 2 15' Vol. 3 Illustrating Boyle's Law below that in A, the air in A is under a pressure of only 1/2 atmosphere and it expands until its volume is 2 times its vol- ume in (4). If B is lowered (6) until its mercury surface is 20 in. below that in A, the air in A is under a pressure of only 1/3 atmosphere and it expands until its volume is 3 times its vol- ume in (4), and so on. Note: A column of mer- cury 30 inches high exerts a pressure equal to that of one atmosphere. Sim- ilarly 15 in. = 1/2 atmos- phere and 10 in. = 1/3 atmosphere. EXPERIMENT No. 59 To illustrate Boyle's law. If you have a spring balance you can prove Boyle's law as follows : Use the apparatus (1) Fig. 155 and compress the air to one half its volume as in (2). Is the average pull on the balance 4^ Ibs.? Note: Friction opposes the plunger when it is moving in, but it helps the plunger to remain in. You will find that it takes more than 4*/ 2 Ibs. to compress the gas, but less than 4^ Ibs. to hold it after it is compressed, the average is 4 l / 2 Ibs. 120 HYDRAULIC AND PNEUMATIC ENGINEERING The area of the plunger is 3/10 sq. in., therefore the pressure per square inch is 4.5 x 10/3 = 15 Ibs. or 1 at- mosphere, but the air on the outside exerts a pressure of 1 atmosphere on the plunger, therefore the total pressure the plunger exerts on the air in the tube is 1 + 1 = 2 at- mospheres. You have shown here that when you double the pressure on a gas you compress the gas to one half its first vol- ume. To show that when you halve the pressure on a gas its volume doubles, use the apparatus (3) Fig. 155. Start with a distance of 2 inches between the plungers, (3) then pull up the spring balance until the distance is 4 inches, (4). Is the average pull on the balance 2% Ibs.? A pull of 2% Ibs. on 3/10 sq. in. is 2.25 x 10/3 = 7.5 Ibs. per sq. in. or y 2 atmosphere. Since the pull of the balance is only */ 2 atmosphere, the air in the tube must be exerting the other */ 2 atmosphere. Fig. 155. Double the Pressure on Air and you You have shown here that Half the Volume. Half the Pressure and you when the pressure on air is Double the Volume. halyed { ^ yolume increases to double what it was at first. HYDRAULIC AND PNEUMATIC ENGINEERING 121 THE AIR BRAKE Fig. 156. Air Brakes for Trains From the "Ontario High School Physics", By Permission of the Publishers One of the commonest applications of compressed air is in the air brakes on trains. The air compressor A, on the side of the engine boiler, is operated by steam from the boiler. It compresses air in the large tank B, on the locomotive, and this compressed air is carried through the train pipe under the cars to the air brake under each car. The air brake on each car consists of a triple valve F, an air tank E and a cylinder C containing a piston P. The brake beam is attached to D. The operation of the air brakes is as follows : Air is pumped into the locomotive tank B until its pressure is about 75 tbs. per sq. in. This compressed air moves through the train pipe, through the triple valve F, and into the car tanks E. When the train is running, the pressure in each car tank E is equal to that in the locomotive tank B ; but there is no air in the cylinder C and the brakes are "off", because the spring holds the piston P in the position shown. When the engineer puts "on" the brakes, he turns a lever which closes the valve between B and the train pipe, and which at the same time, lets the air out of the train pipe. When the air pressure in the train pipe 122 HYDRAULIC AND PNEUMATIC ENGINEERING decreases, the triple valve shifts in such a way that compressed air passes from the tank E into the cylinder C; this compressed air drives the piston out with a pressure of 75 Ibs. per sq. in. and puts the brakes "on." When the engineer wishes to take the brakes "off" again, he turns the lever back. This closes the train pipe and at the same time allows air to flow from tank B through the train pipe to the triple valve F. When the pressure in the trian pipe increases, the triple valve shifts back in such a way that it lets air pass from B into E, also it closes the passage from E to C, and lets the air out of C. The spring then forces the plunger in and takes the brakes "off". It will be noticed that if the train should break in two by the breaking of a coupling, the rubber air hose connection on the train pipe is broken and the air is let out of the train pipe. This automatically sets the brakes on each car and both parts of the train are brought to a standstill. You will now make and operate an air brake and illustrate the working of the cylinder, triple valve, and air tank. EXPERIMENT No. 60 To make and operate an air brake and to illustrate the working of the triple valve, cylinder, air tank, and train pipe. Use the apparatus as shown in Fig. 157, open clip 1, and blow air into the rubber tube. Your mouth here repre- sents the compressor and air tank on the locomo- tive, and while you are blowing air into the tank E you are representing Fig. 157. Illustrating the Working of the Air Brake the conditions when the train is running and the brakes are "off". You will notice here that when clip 1 is open and 2 is closed the triple valve is admitting air to the tank E, the cylinder C is open, and the brakes are "off". Clips 1 and 2 represent the triple valve. Now close clip 1 and open clip 2. Do you observe that the compressed air in E forces the piston out? This is exactly what happens when the HYDRAULIC AND PNEUMATIC ENGINEERING 123 engineer puts the brakes "on". You will notice here that when clip 1 is closed and 2 is opened, the triple valve has closed the passage between the cylinder and train pipe, and has opened the pipe between E and the cylinder. This is the condition when the brakes are "on". If you have a bicycle pump, use it instead of your mouth and pump more air into the tank E. You will then find that the piston is driven out with greater force. At the next opportunity examine the air brakes under a box car or flat car on a railway siding. Identify the air tank, cylinder, piston rod end, the triple valve, and the train pipe. Notice that the outward move- ment of the piston rod, moves a lever, and that this lever in turn sets the brakes. THE FLAME THROWER You have read of the flame throw- ers, which were used during the war. You will illustrate their action in the next experiment. A flame thrower is a strong metal tank with a pipe and nozzle leading from the bottom. It contains a mix- ture of inflamable oils in the lower Fig. 158. A Flame-Thrower in Action part and above this, hydrogen gas under great pressure. The tank is carried on the back of the soldier, as shown in Fig. 158, and when the nozzle is opened the com- pressed hydrogen drives the oil out with great force. The oil is set on fire by a pilot light just beneath the nozzle and the moving stream be- comes a stream of flame or liquid fire. Fig. 159. Showing how the Compressed Hydrogen drives the Oil out of a Flame Thrower 124 HYDRAULIC AND PNEUMATIC ENGINEERING EXPERIMENT No. 61 To illustrate the action of the flame thrower. It is dangerous to illustrate the action of a flame thrower with oil and you will use water instead. Arrange the apparatus as shown in Fig. 159. To load the flame thrower, place a clip on the rubber tube, put a stopper and elbow on the end, insert the stopper into a water faucet, open the faucet gently, open the clip, and allow water to enter the bottle until it is one half full, then close the clip. The flame thrower is now loaded; the water represents the oil and the compressed air represents the compressed hydrogen. Now to use the flame thrower; replace the elbow and stopper at the end of the rubber tube by a nozzle, turn the bottle upside down, point the nozzle at the thing you wish to hit, and open the clip. THE FIRE EXTINGUISHER The common household fire ex- tinguisher, Fig. 160, is a strong brass cylinder with a short piece of hose attached at the top; this hose and its nozzle are open at all times. The extinguisher is charged as follows : In the bottom there is a solution of \y 2 Ibs. of sodium carbonate (Na 2 CO 3 ) and 2 l / 2 gal. of water, and above this there is an 8 oz. bottle containing 4 ozs. of strong sulphuric acid (H 2 SOO. This bottle is fitted with a loose lead stopper which falls out when the extinguisher is turned upside down. To use the extinguisher, you carry it right side up to the fire, then turn it upside down and di- Fig. 160. Showing the Outside and rect the stream of water and gas Inside of a Fire Extinguisher upon the fire by means of the Courtesy of the MacMillan Co. ghort hose Use all of the waterj because once you have turned the extinguisher upside down, the liquids are mixed, and the extinguisher is of no further use until you have re- B*ca> soumoi HYDRAULIC AND PNEUMATIC ENGINEERING 125 U" charged it. You should do this at once in order to be prepared again for a fire. In recharging you should follow the directions printed on the case. The action which takes place in the extinguisher is as follows : when you turn it upside down, the sulphuric acid and sodium carbonate react chemically and produce a large quantity of carbon dioxide gas. The volume of carbon dioxide gas produced is much greater than the volume of the cylinder and therefore the gas exerts pressure on the water and drives it out with great force. The fire is extinguished, partly by the water, and partly by the gas. It seems strange to speak of putting out a fire by means of gas, but carbon dioxide gas has three properties which make it very valuable for this purpose: first, it does not burn; second, it does not support combustion, that is, it does not help other things to burn; third, it is heavier than air. The carbon dioxide gas surrounds /^x-57--^^ the fire and smothers it, because it does not support fffft' combustion and it takes the place of the air which I'M v,\ does support combustion. EXPERIMENT No. 62 To make and operate a fire extinguisher. You will not use strong sulphuric acid because it burns practically everything it touches, but instead you will use a dilute acid, vinegar; also you will use baking soda which is sodium carbonate. Arrange the apparatus as shown in Fig. 161. Pour six tablespoonsful of vinegar into the bottle, fill the bottle four fifths full of water and shake, measure out one level tablespoonful of bak- ing soda and place it on a piece of paper ready for use. Now to use the fire extinguisher, go outside and let one experi- menter hold the bottle and stopper while the other holds the baking soda and the nozzle. Dump the soda into the bottle, put in the stopper quickly and hold it very Fig. 161. A Home-Made Fire-Ex tinguisher in Action 126 HYDRAULIC AND PNEUMATIC ENGINEERING firmly, turn the bottle upside down and shake. Does the gas drive the water out with considerable force? Repeat the experiment but this time make a cigarette shaped tissue paper package of the baking soda and attach the open end to the under- side of the stopper by means of a pin. The extinguisher then will work when you turn it upside down. Repeat but use the white and blue packages of a Seidlitz powder instead of the vinegar and soda. Dissolve the contents of the blue package in the water and dump in the contents of the white. They pro- duce carbon dioxide gas. EXPERIMENT No. 63 To show how carbon dioxide gas puts out a fire. Fig. 162. Putting Out a Match and a Candle by means of Heavy Carbon Dioxide Gas POURING CARBON DIOXIDE OAJ. You can show that the carbon dioxide gas (CO) is heavy and that it will put out a fire as follows : Pour six tablespoonsful of vinegar into an empty ten-quart pail, Fig. 162, and add one level tablespoonful of baking soda. Stir with a spoon until the fizzing stops. You now have the bottom of the pail full of carbon dioxide gas. You cannot see it but it is there. Now light a match and lower it slowly into the pail. Does it go out when it gets a certain distance into the pail? It goes out because it is surrounded by carbon dioxide gas which does not support combustion. HYDRAULIC AND PNEUMATIC ENGINEERING 127 Light a candle and lower it into the pail in the same way. Does it go out? It goes out for the reason stated above. You know that (CO 2 ) gas is heavier than air because it remains in the bottom of the pail. If it were lighter, the air would sink to the bottom of the pail and lift it out. You can show that the (CO 2 ) gas is heavy and that it will pour just like water, as follows : Put a lighted match or a very short lighted candle at the bottom of an empty pail, then lift the pail containing the CO 2 gas and pour it into the empty pail just as you would pour water. Does the gas put out the match or candle? This shows that the gas pours and therefore that it is heavier than air. It also shows again that the CO 2 gas puts out a fire. THE AIR PUMP Fig. 163. An Air Pump Courtesy of the MacMillan Co. The air pump shown here has a solid plunger and two valves A and B ; valve A opens inward and valve B outward. The vessel R, out of which the air is being pumped, has an open bottom with a ground edge which fits air-tight on the smooth greased sur- face of the stand. The air is pumped out through a hole in the center of the stand and through the pipe F. When the plunger is pulled up, valve B closes and part of the air expands from the vessel R through A into the pump cylinder C. When the plunger is forced down, valve A closes and the air in C is forced out through the valve B. When the plunger is again raised part of the air remaining in R expands into C and when the plunger is forced down this air is forced out through B, and so on. If you wish to pump air into R you attach it to B instead of to A and operate the plunger. Each stroke of the plunger fills the cylinder C with air and each down stroke forces this air into R. 128 HYDRAULIC AND PNEUMATIC ENGINEERING EXPERIMENT No. 64 To make and operate an air pump. Fig. 164. Illustrating the Working of an Air Pump Arrange the apparatus as in (1) Fig. 164 and operate the plunger. Do you pump air out of the bottle? Arrange the apparatus as in (2) Fig. 164 and operate the plunger. Do you pump air into the bottle? THE BICYCLE PUMP AND TIRE Fig. 165. The Bicycle Pump Courtesy of the MacMillan Co. The bicycle pump is a very simple air pump. It consists of a cylinder C and a plunger P; one valve is the cup shaped piece of leather on the bottom of the plunger, and the other is the valve S which remains on the bicycle tire, T, HYDRAULIC AND PNEUMATIC ENGINEERING 129 When the plunger is moved up there is a vacuum left in the space C beneath, and the pressure of the atmosphere forces air into this space around the sides of the cup valve which bends in. When the plunger is forced down, the air in C is forced into the tire through the valve S, because the cup leather is forced outward by the air pressure and be- comes air-tight. This is repeated at each stroke. The hand pump, at the right has a hollow plunger stem through which the air passes to the tire. A cup leather on the plunger is one valve and the valve on the tire, the other. 2 3 Fig. 166. The Bicycle Pump in Action EXPERIMENT No. 65 To make and operate two bicycle pumps. Arrange the apparatus as in (1) and operate the plunger. The bottle with its valve represents the bicycle tire with its valve. Do you pump air into the tire? Arrange the bottle as in (2) and pump air into it. Does the com- pressed air force the water out? The above represents the action of a large bicycle pump. Make the experiments (3) and (4). The pump here represents a hand bicycle pump. A 9 130 HYDRAULIC AND PNEUMATIC ENGINEERING THE AIR COMPRESSOR The commercial air compres- sor is simply a large air pump as shown in Fig. 167. It has a solid plunger P and two valves. When the plunger is raised, the pressure of the atmosphere lifts valve Vi and forces air into the pump barrel; when the plunger is driven down, valve Vi closes but valve V 2 opens and the air is forced into the storage tank R. This operation is repeated at each stroke. The pump is driven by a steam engine, gasoline engine, electric motor, or water wheel. Fig. 167. Air Compressor Pump and Storage Tank From the "Ontario High School Physics" By Permission of the Publishers THE SAND BLAST The sand blast, one form of which is illustrated in (1) Fig. 168, is used to clean metal castings, etch glass, cut the letters in marble, clean the walls of buildings, and so on. The sand is driven by compressed air with great force against the object to be cleaned. Each particle of sand pulverizes the material which it strikes and since millions of grains strike the material each minute, the surface is worn away very rapidly. Fig. 168. Interior of a Sand Blast. From "Hitchcock's Compressed A ir and Its Apohcations 1 ' Courtesy of the Norman W. Henley Publishing Co. Fig. 168. A Sand Blast HYDRAULIC AND PNEUMATIC ENGINEERING 131 The inside of the machine is represented in (2) Fig. 168. The sand is dumped into the V shaped top and is admitted to the chamber CC below through the valve A. The compressed air enters at B and passes out to the hose and nozzle through the tube D. The sand is dropped into the moving air through the valve F and is carried through the hose and nozzle to the object. EXPERIMENT No. 66 To make and operate a sand blast. Arrange the apparatus as shown in Fig. 169. The sand is held in the funnel and drops down into the moving air when the clip is opened. Fill the funnel with dry, coarse sand and ask your partner to hold his hand over the funnel and open the clip, while you blow air into the hose and hold your hand Fig. 169. Illustrating the Working of * a Sand Blast opposite the tee opening to feel the effect. Your partner's hand must be held over the funnel, otherwise part of the air will blow up through the sand. Repeat this with the bottle used as a compressed air tank. Pump air into the tank by means of a bicycle pump, and close the hose with a clip. Connect the hose with the tee, ask your partner to hold his hand over the funnel and open the funnel clip, then hold your hand in front of the tee opening, and open the clip on the hose. Do you find that the sand strikes your hand with considerable force? PNEUMATIC PAINT BRUSH The working of the pneumatic paint brush is as follows : The com- pressed air enters through the hose and handle and issues from a small nozzle. The current of air thus produced carries out with it the air around the nozzle and creates a partial vacuum. The atmospheric pres- sure on the paint in the tank then forces paint into the vacuum around the nozzle, and this paint is carried out through the large nozzle by the air current. The air pressure is from 50 to 80 tbs. per sq. in. and the stream of paint can be regulated from a fine mist to a solid stream. 132 HYDRAULIC AND PNEUMATIC ENGINEERING Fig. 170. A Pneumatic Paint Brush Paint Nozzle From "Hitchcock's Compressed Air and Its Applications" Courtesy of the Norman W. Henley Publishing Co. This form of paint brush is used in all kinds of painting and per-- mits very rapid work. It is used in painting buildings, bridges, machin- ery, railway cars, furniture and even pictures, also in calsomining and white-washing walls, houses and fences, and in spraying disinfectants in hospitals, camps, trenches, hen houses, etc. The common atomizer is made on the same principle. EXPERIMENT No. 67 To make and operate a pneumatic paint brush. Arrange the apparatus as in Fig. 171 and blow hard into the rubber tube. Do you observe that water rises from the tumbler into the wide tube, and issues from the narrow tube in the form of a light spray? HYDRAULIC AND PNEUMATIC ENGINEERING 133 Fig. 171. Showing how the Pneumatic Paint Brush works This is very interesting, because it shows that al- though you blow air into the wide tube you create a partial vacuum in the tube. The reason for this is as follows : The com- pressed air from the noz- zle enters the narrow tube with great velocity and in doing so carries air from the wide tube along with it. This creates a partial vacuum in the wide tube and the pressure of the atmosphere lifts water from the tumbler into the wide tube. The water is then carried into the narrow tube by the stream of compressed air and issues from the end. THE DIVING BELL The diving bell, Fig. 172, is simply a large iron bell open at the bottom. It is used to enable men to work on the bottom of a river, lake, or ocean, for example, to lay the foundations of bridges, wharves, light- houses, etc. The bell is made large enough to hold a , AIR PUMPS number of men, heavy enough to sink read- ily in the water, and strong enough to stand the great pressure of the water on the out- side. It is usually carried in a ship in a AIR BUBBLE special compartment called a well : this is simply a hole in the bottom of the ship, lined up on all sides to prevent water from entering the ship. The bell is raised and lowered by means of a winch and pulleys, and is supplied with compressed air through a strong rubber tube attached to an air pump on the ship. Fig. 172. A Diving Bell used to Work under Water Courtesy of the MacMillan Co. When it is desired to use the diving bell, the sailors first anchor the ship fore and aft over the spot where the work is to be done, then the workmen get into the bell through the bottom, the air pump is started, and the bell is lowered by means of the winch and pulleys. 134 HYDRAULIC AND PNEUMATIC ENGINEERING Fig. 173. A Large Diving Bell used as an Undersea Storehouse by Divers Courtesy of the Scientific A merican The compressed air which is forced into the bell supplies the men with fresh air and also prevents the water from entering the bottom of the bell; the excess air escapes in bubbles under the edge of the bell. A form of diving bell used by divers is illustrated in Fig. 173. It is lowered by a heavy cable from a ship at the surface, from which it is supplied with compressed air, electricity, and telephone connec- tion. The diver carries his air in a tank on his back and is there- fore not encumbered by a heavy air hose; the light cable which he drags is his telephone connection. The bell serves as a store house for tools and as a place to which the diver can retreat to repair his suit if necessary. He enters and leaves the bell through an opening near the bottom as shown. EXPERIMENT No. 68 To make and operate a diving bell. Place a piece of a match stick on the surface of the water in a wash bowl. Invert an empty tumbler over the match and force the tumbler to the bottom of the bowl without letting air escape. Do you notice that the water enters the tumbler only to a very sligh extent and that you can make the match rest on the bottom of the bowl. The tumbler represents the diving bell and the match stick represents the man, who could now go to work on the bottom of the river or lake. Of course, the man in a regular diving bell would not get into the water first but would stand or sit on a shelf inside the bell. Raise the tumbler gradually and notice that the water lifts the match up again. In this experiment the lower edge of the diving bell, the tumbler, is only six or eight inches under the surface of the water, therefore the HYDRAULIC AND PNEUMATIC ENGINEERING 135 Fig. 174. Illustrating the Working of the Diving Bell pressure of the water upward on the air in the bell is small, and the air is only slightly compressed. When the regular diving bell is sunk in water, however, the pres- sure of the water upward on the air in the bell increases as the bell 5 sinks deeper and deeper and the water would rise in the bell, were it not that the compressed air is pumped in at sufficient pressure to overcome this water pressure and to keep the water out. Repeat the experiment with the hose as in (2). Open the hose. Is the air forced out? Blow air into the hose. Is the water forced out? Lift a boat above the water level as in (3), (4) and (5). Make the experiment with the metal tank used as the diving bell (6). EXPERIMENT No. 69 To make a home-made diving bell. You can have fun in your swimming pool by using either a 12 qt. pail, a wash boiler, or a wash tub, as a diving bell. Do this as follows : Place the inverted pail over your head and let yourself sink. You will find that you can breath under the pail for a short time but that the 136 HYDRAULIC AND PNEUMATIC ENGINEERING air soon needs renewing. You will find also that you cannot sink very far, because the buoyancy of the inverted pail is greater than the weight of your body in water. Repeat the experiment with a wash boiler or wash tub. You will find again that you can breath under the boiler or tub. You will find also that you cannot sink the boiler or tub because their buoyancy, when inver- ted and filled with air, is much greater than the weight of your body in water. Make this experiment. Go to a part of the swimming pool where you can sit on the bottom with your head above water. then let tw * VOur friends P lace the tub upside down and full of air, over your head and force it down gently until the bottom of the tub is slightly under the surface. Your head is now below the level of the water outside, but you will find that you have plenty of air in the tub because the water level in the tub is only slightly above the level of the edge of the tub. Make experiments of your own. PNEUMATIC CAISSONS A caisson similar to that shown here is used to remove the earth down to the rock for the foundations of bridge piers. It is filled with compressed air which drives the water out at the bottom and leaves the earth dry for the workmen. The caisson is closed in on all sides to keep out the water. It is open at the bottom but is closed above by well braced timbers weighted down by concrete C.D. The bottom is let down into the mud, the com- pressed air is turned on to force the water out of the working chamber, and the workmen then enter the working chamber to excavate the mud. The weight of the concrete CD. gradually sinks the caisson, as the mud is excavated, until the solid rock is reached. The men enter the caisson through the air lock L, as follows : The lower door B is closed, compressed air is let out of L, the door A is HYDRAULIC AND PNEUMATIC ENGINEERING 137 opened, the workmen enter, the door A is closed and compressed air is admitted slow- ly to L until its pressure is equal to that below; the door B is then opened and the men climb down a ladder into the caisson. The men leave, and ttiud is lifted out through the air-lock by the reverse pro- ceedure. When the caisson is down to the rock, the working chamber and the space above are filled with concrete to serve as the foun- dation of the bridge. Sometimes the outer casing of the caisson is removed, but more often it is left where it is. EXPERIMENT No. 70 To make and operate a pneumatic caisson -Section of a Pneumatic Caisson. The sides of tho caisson are extended upward and are strongly braced to keep back the water Masonry or concrete, C. D, placed on top el the caisson, press it down upon the bottom, while compressed air. forced through a pipe />, drives the water out of tho working chamber. To leave the caisson the workman climb* up and pauses through the open door B Into the air-lock L. The door B is tben closed and the air u allowed to escape- from L until it is at atmospheric- pressure. Then door A to opened. In order to enter, this process it reversed. Material i hoisted out in the same way or ii sucked out Fig. 176 From the "Ontario High and to show how a man enters it through School Physics", By Permission the air-lock. of the Publishers Arrange the apparatus as shown in Fig. 177. The wide tube represents the caisson and the narrow tube at the top, the air-lock; the clips represent the upper and lower doors of the air-lock. Put the caisson, with both clips open, in the sealer full of water. Do you find that the water level inside the caisson is the same as that outside? Now blow air in through the air lock and close one or both clips. Do you find that the water level inside the caisson is now at the bottom? This illustrates the manner in which compressed air forces the water out at the bottom of a real caisson. Now to show how a man enters the caisson without Fig. 177. Illus- letting out the compressed air, proceed as follows : trating the Working __ . , A , , , ,. of a Pneumatic ^se a pm to represent the man, be sure that both Caisson doors are closed, then open the upper door and drop the pin into the air-lock head downwards, not that the 138 HYDRAULIC AND PNEUMATIC ENGINEERING man enters head downwards, but the head of the pin will not stick into the rubber as the point might. Now open the lower door. Does the pin drop to the bottom and has the whole operation been completed without letting air out of the caisson or water into it. This represents the way a man would enter the caisson. It is called "locking in". The man of course would not drop from the air lock to the bottom of the caisson; he would climb down a ladder. Tools and materials are admitted to the caisson in the same way, and removed by reverse operation. EXPERIMENT No. 71 To show how a torpedo is shot out of a submarine or battle ship. Fig. 178. The Revolver Torpedo Tube in Submarines By carrying the torpedoes in a revolving cradle back of the torpedo tube, it is possible to fire several torpedoes in rapid succession while the submarine is bearing on the enemy A torpedo is fired out of a submarine or battle ship by means of compressed air and is kept in motion after it is fired by means of a compressed air motor. Show how the torpedo is fired, by means of the apparatus Fig. 179. The bottle here represents the compressed air tanks on the battleship, the wide tube represents the torpedo tube and the plunger, the torpedo. HYDRAULIC AND PNEUMATIC ENGINEERING 139 1 2 Fig. 179. Showing How a Ship is Torpedoed Close the bottle by means of cord and rubber bands and compress air in it by means of a bicycle pump (1) if you have one ; if not, attach the rubber tube to a water faucet by means of an elbow and stopper (2) and fill the bottle half full of water in order to compress the air to half its first volume and thereby give it a pressure of 15 ft>s. per sq. in. Connect the bottle with the torpedo tube, point the tube at the ship (3) and open the clip. Do you torpedo the ship in a very realistic manner EXPERIMENT No. 72 To show how the men in a submarine could be supplied with air taken from sea water. Arrange the apparatus as in (1) Fig. 180. The space between the stoppers is completely filled with water and is free from air; the plunger is covered with water to make it air-tight. 140 HYDRAULIC AND PNEUMATIC ENGINEERING Fig. 180. Showing How a Submerged Submarine could take Air from Sea Water Now lift the plunger as in (2). Do you observe that air bubbles come out of the water? Let the plunger go back (3). Do you observe that there is a small bubble of air between the rubber stoppers? This is extremely interesting and is explained as follows : All water on the earth which is exposed to the air has air dissolved in it, (the fish in water live on this air). When you lift the plunger you produce a vacuum above the water and thereby reduce the pressure on the water to zero. The air in the water then expands into bubbles and escapes from the water. Submarines could be supplied with pure air when under water as follows : They would need a pump similar to your apparatus above but arranged as follows : During the upstroke of the plunger the inlet valve would open for say only 54 of the stroke and then close for the re- maining 24 f tne stroke. The plunger would thus draw in water during ]/4 stroke, and would produce a vacuum above the water for the remain- ing $4 stroke, the air in the water would then expand and escape from the water. On the down stroke of the plunger the air and water would be forced out of the pump but on their way out of the submarine they would pass through a tank, the air would escape into the tank but the water would pass on out. The air accumulated in the tank could then be used in the submarine. FINIS HYDRAULIC AND PNEUMATIC ENGINEERING 141 TABLE OF CONTENTS HYDRAULIC ENGINEERING WATER SUPPLY. Experiment 1. To make and operate a city water supply system in which the water comes from a standpipe, reservoir, or lake. 2. To make and operate a private water supply system in which the water is stored in a tank on a tower. 3. To make and operate a private water supply system in which the water is stored in an attic tank. 4. To show how water is brought from an elevated well or spring. Game 1. A Naval Battle. PNEUMATIC TANK SYSTEM OF WATER SUPPLY. Experiment 5. To make and operate a pneumatic tank. Game 2. Rapid Fire Water Gun. Experiment 6. To make and operate a pneumatic tank system of water supply. WATER AND AIR. 7. To show that water is incompressible and that air is compressible. 8. To show that compressed air exerts pressure. Game 3. Trench Gun. 4. Height and Distance Contest 5. Pop Gun. THE SIPHON. Experiment 9. To make and operate a siphon. HOW THE SIPHON IS USED IN WATER SUPPLY SYSTEMS. 10. To show how the siphon is used in water supply systems. HOW TO START A LARGE SIPHON. 11. To illustrate different methods of starting a large siphon. OTHER USES OP THE SIPHON. 12. To illustrate other uses of the siphon. VELOCITY OF FLOW. 13. To show that the velocity of the water in a siphon is greater the greater the vertical distance between the water levels about the two arms. OTHER SIPHONS. 14. To make and operate a double siphon and a three-legged siphon. HOW TO START A SMALL SIPHON. 15. To illustrate two ways of starting a small siphon. AN INCLOSED FOUNTAIN. 16. To make and operate an inclosed fountain. 142 HYDRAULIC AND PNEUMATIC ENGINEERING ATMOSPHERIC PRESSURE. AIR HAS WEIGHT. AIR EXERTS PRESSURE. Experiment 17. To show that the atmosphere exerts pressure. 18. To show that the atmosphere will support a column of water. 19. To prove that it is the pressure of the atmosphere which lifts the water. 20. To show in other ways that the atmosphere exerts pressure downward and upward. 21. To illustrate two simple uses of atmospheric pressure THE "WHY" OF THE SIPHON, PUMPS. 22. To illustrate the action of a syringe. Game 6. Water Gun Shooting. 7. Big Gun Battle. 8. Machine Gun Battle. 9. The Diablo Whistle. Experiment THE LIFT PUMP. 23. To make and operate a lift pump. THE FORCE PUMP. 24. To make and operate a force pump. 25. To show how water is pumped into an elevated tank. Game 10. Force Pump Contest. HYDRAULIC APPLIANCES. PASCAL'S LAW. Experiment * 26. To show that pressure exerted on water is transmitted equally in all directions. 27. To make and operate a hydrostatic bellows. THE HYDRAULIC PRESS. 28. To make and operate a hydraulic press. THE HYDRAULIC ELEVATOR. 29. To make and operate a hydraulic elevator. HYDRAULIC LIFT LOCKS. CANAL LOCKS. LIFT LOCKS. 30. To make and operate a hydraulic lift-lock. THE PRESSURE EXERTED BY WATER. 31. To show that the pressure at a nozzle is independent of the size and shape of the tank and pipe. THE HYDROSTATIC PARADOX. 32. To illustrate the hydrostatic paradox. EXPLANATION OF HYDROSTATIC PARADOX. HOW TO CALCULATE THE PRESSURE EXERTED BY WATER. HYDRAULIC AND PNEUMATIC ENGINEERING 143 PRESSURE UNDER WATER. THE DEPTH BOMB, TORPEDO AND SUBMARINE. Experiment 33. To show that the pressure under water increases with the depth and that it is equal in all directions at any depth. 34. To show that water exerts pressure upward on anything under its surface and that this upward pressure is equal to the downward pressure at any depth. HOW TO CALCULATE THE PRESSURE ON DEPTH BOMB, TORPEDO, AND SUBMARINE. BUOYANCY WHY DOES A STEEL SHIP FLOAT? Experiment 35. To illustrate the buoyant effect ot water. THE LAW OF ARCHIMEDES. 36. To illustrate the law of Archimedes. 37. To illustrate the law of Archimedes for bodies which sink in -water. RAISING SUNKEN SHIPS. 38. To show how sunken ships are raised by means of air. FLOATING DRY DOCK. 39. To make and operate a floating dry-dock. THE SMALL SUBMARINE. 40. To make the small submarine submerge and rise in water. RUNNING WATER. FRICTION. 41. To illustrate the effect of friction on running water. NOZZLES. 42. To show why the stream is longer with a nozzle than without. Experiment 43. To show that you put less water on a road in a given time with a nozzle than without. VELOCITY OF FLOW. 44. To show that the velocity of water is doubled when the head is made four times as great. AIR LOCK. 45. To illustrate an air lock. PNEUMATIC ENGINEERING ATMOSPHERIC PRESSURE. Experiment 46. To show that the atmosphere exerts pressure. HOW ATMOSPHERIC PRESSURE WAS FIRST MEASURED. 47. To measure the pressure of the atmosphere. THE BAROMETER. HOW AIRMEN KNOW THEIR ALTITUDE. THE ALTITUDE GAUGE. 144 HYDRAULIC AND PNEUMATIC ENGINEERING THE WATER BAROMETER. 48. To show that the vertical height to which the atmosphere will lift water is independent of the length and slant of the tube. 49. To show that the height to which the atmosphere will lift water is inde- pendent of the size and shape of the tube and of the water surface outside the tube. 50. To show that the atmosphere lifts heavy salt water to a less height, and light gasoline to a greater height, than it lifts fresh water. 51. To show that the atmosphere will lift weights. 52. To show that the atmosphere will lift 15 Ibs. per square inch but no more. AIR-LIFT PUMPS. 53. To make and operate two air-lift pumps. LAWS WHICH APPLY TO GASES. PASCAL'S LAW. 54. To illustrate Pascal's law as it applies to gases. BALLOONS AND THE BUOYANT FORCE OF AIR. THE LAW OF ARCHIMEDES APPLIED TO AIR. HOW THE TOTAL LIFT OF A BALLOON IS CALCULATED. Experiment 55. To illustrate the buoyant force of air. 56. To illustrate the buoyant force of air by means of a balloon filled with hydrogen. 57. To shoot down a balloon. 58. To illustrate the buoyant force of a gas heavier ,than air by means of a soap bubble filled with air. COMPRESSED AND EXPANDED GASES. BOYLE'S LAW. 59. To illustrate Boyle's law. THE AIR BRAKE. 60. To make and operate an air brake and to illustrate the working of the triple valve, cylinder, air tank, and train pipe. THE FLAME THROWER. 61. To illustrate the action of the flame thrower. THE FIRE EXTINGUISHER. 62. To make and operate a fire extinguisher. 63. To show how carbon dioxide gas puts out a fire. THE AIR PUMP. 64. To make and operate an air pump. THE BICYCLE PUMP AND TIRE. 65. To make and operate a bicycle pump. THE AIR COMPRESSOR. THE SAND BLAST. 66. To make and operate a sand blast. PNEUMATIC PAINT BRUSH. 67. To make and operate a pneumatic paint brush. THE DIVING BELL. Experiment 68. To make and operate a diving bell. 69. To make a home-made diving bell. PNEUMATIC CAISSONS. 70. To make and operate a pneumatic caisson and to show how men enter it through the air-lock. 71. To show how a torpedo is shot out of a submarine or battle ship. 72. To show how the men in a submarine could be supplied with air taken from sea water, MEMORANDUM MEMORANDUM MEMORANDUM MEMORANDUM MEMORANDUM MEMORANDUM MEMORANDUM MEMORANDUM MEMORANDUM MEMORANDUM MEMORANDUM WATER AND AIR Two very common yet important substances and very powerful too when you learn how to use them. Do you know why water comes out of a faucet when you turn it on? Why air compresses ? You will become familiar with a great many facts that at one time were difficult problems in engineering, if you have a GILBERT Hydraulic and Pneumatic Engineering An outfit which shows you how your house is piped for water, why it is water comes out of a faucet up stairs just as easily as it does on the ground floor. It also shows you how a hydraulic elevator operates, how to make a rapid fire water gun, how to make a trench gun, how a siphon operates, the effect air pressure has on water and any number of intensely interesting things that I bet you never thought of. The outfit contains all of the apparatus complete together with a book on Hydraulic and Pneumatic Engineering that is very easy to understand and illustrates many interesting experiments you can perform. Your dealer should have this outfit If not write us. THE A. C. GILBERT COMPANY 505 BLATCHLEY AVENUE NEW HAVEN, CONN. In Canada : The A. C. 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GILBERT CIVIL ENGINEERING (SURVEYING) Not only can you lay out your own tennis court with a Gilbert Surveying Outfit, but you can also survey your own yard or farm, find the height of a building, or find the distance to a building if you know its height, find the distance across a river, and any number of other intensely interesting experiments. They are all things that will come in handy to you in many ways. Each outfit contains a regular surveyor's transit. It comes knocked down with full instructions for assembling and using. There is also included a well-illus- trated book telling you many things about surveying that will be very useful to you at home or whenever you go camping, or on a hike. It is packed in a hardwood cabinet, size 20 x 12 x 3^ inches. You will like this outfit mighty well. It is on sale at all good toy dealers'. If you are unable to get it, write us and we'll tell you where you can. THE A. C. GILBERT COMPANY 505 Blatchley Ave., New Haven, Conn. In Canada The A. 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