THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA LOS ANGELES N. S. E. 312 Confidential! SEARCHLIGHTS AND SIGNAL LIGHTS For the Instruction of Officers and Personnel connected with Searchlights N.WY DEPARTMENT BUREAU OF-^ TE A-M ENGINEERING NOVEMBER, 1918 WASHINGTON GOVERNMENT PRINTING OFFICE 1918 TABLE OF CONTENTS. Chapter 1. Fat*. History of the searchlight ^ Chapteb 2. High-power searchlights 4 Chapteh 3. Beck 36 and 30 inch high-power searchlights 24 Chafter 4. Sperry 36 and 24 inch high-power searchlights 49 Chapter 5. Qeneral Electric Co. 24-inch high-power searchlights 68 Chapter 6. Anna 24-inch high-power searchlight 81 Chapter 7. Sperry high-power searchlights converted from general electric low-power searchlights — 87 Chapter 8. Low-power searchlights 90 Chapter 9. Signaling apparatus 106 Chapter 10. Types of operating gears 116 Chapter 11. Tables of general data on searchlights and blinkers 133 Chapter 12. Carbons for searchlights 139 Chapter 13. Mirrors for searchlights 168 Chapter 14. Care of modern high-power searchlights and control gear 176 Chapter 15. Vicker's ' ' f ollow-the-pointer ' ' system of searchlight control 179 Chapter 16. Current developments 190 m 96706U CHAPTER 1. HISTORY OF THE SEARCHLIGHT. The first use of any light projector which could be called a searchlight in any sense of the word was on board a Union warship blockading a southern port during the Civil War. On a dark night a Confederate ship attempted to run the blockade, think- ing herself secure against detection on account of the blackness of the night. Suspicion, however, was aroused on board the Union ship and the first search- light used at sea was brought into use. From the Union ship there came a feeble, poorly reflected, widely diver- gent beam of light. It swTing around, searching for the enemy, and finally, faintly illuminated, he was discovered. Crude as was this searchlight, it made a place in warfare for the projector which has since been developed to a remarkable degree of efficiency. This first searchlight was merely a "limelight" produced by playing an oxy-hydrogen flame on a candle of calcium oxide, this source of light being backed by a crude, spherical, polished metal mirror which absorbed about 50 per cent of the total light. Shortly after this came the first arc light, which, when used with small, spherical metal mirrors, was useful up to a maximum range of perhaps 300 yards. The next military use of searchlights was at the siege of Paris (1870-71) in which arc lights were used. They bm-ned vertically and the entire arc and flame was used as the source of light, rather than using, as is the present prac- tice, only the very brilliant positive crater. The arc current was about 10 amperes. This light was mounted behind a rather expensive and complicated system of lenses and prisms invented by Fresnel. It had previously found application in lighthouses, and because of the good results obtained by this system in that service, it was tried on searchlights. However, on account of its complication, expense, and low efficiency, it could not stand in the face of later inventions. In 1876, Col. Mangin brought out his silvered glass reflector which gave excellent results and was the forerunner of modern searchlight mirrors. For a long time it had been recognized that a parabolic silvered glass mirror would be the best reflector obtainable, but at that time it was impossible to grind one. Spherical mirrors were useless because of unavoidable distortion of the beam. Mangin's reflector consisted of a mirror ^\^th its front surface and back surface spherical, but with different radii and not concentric. This corrected spherical aberration. So successful was this mirror that it still finds a fairly wide application for small lights. 66438—18 1 1 2 THE SEARCHLIGHT. The limitation of the Mangin mirror was, however, its small effective angle. It could not utilize more than half the available light. Tliis was due to the fact that the mirrors were too thick and too clumsy if they were ground to subtend more than 90° of arc. Moreover, the parallchsm of the reflected light could not be maintained at large angles. Attempts were made to overcome these difficulties by building up the reflector from a large number of separately ground rings, called meniscus rings. Tliese were not successful on account of the trouble of lining up the separate rings accurately and adjusting them to have the same focus. In the year 1886 Schuckert, of Nuremburg, succeeded in producing the first plate glass parabolic mirror. This was the final stop in the development of the optical system of searclilights. The advantages of the parabohc re- flector were immediately recognized and this system has been in almost uni- versal use from 1886 until the present day. The historical outhno above has referred mainly to the development of the optical features. Equally important in connection with the searchlight is the development of the source of light. The history of this phase is very brief. The fii-st useful searchlight in 1870 employed a direct current pure carbon arc, and searchlights are still employing, for the most part, the same pure carbon arc. For over 50 j^ears the carbon arc stood unchallenged as the brightest illurainant known. Tliis period was not, however, without progress. The first crude lights were small vertical arcs of very low amperage. They were necessarily used in a vertical position for increased steadiness of burning. The horizontal arc was almost an impossibility at that time, due to its fhckering and instability. At about the time of the Mangin mirrors a compromise was made between the steadiness of tlie vertical arc and the increased light flux on the mirror of the horizontal arc. Tliis was accomplished by burning the carbons at an angle of 20° to 30°, so that the positive crater (the uppermost carbon being positive) burned off at an angle and presented its face moi-e nearly normal to the reflector. This arrangement was used for over 20 years, and even now these searchlights may occasionally be found on board the older ships. This arc was slowlj' disjJaced by tlie horizontal arrangement of the car- bons. With the improvement in carbon manufacture, the horizontal arc was finally made to burn properly. This horizontal arrangement has since been universally used in searcldiglits employing the pure carbon arc. Until quite recently no notable improvements were made in the source of light. Thick pure carbon electrodes were used and the improvements consisted mostly in arranging the lamp to get the best results and throw the greatest amount of light upon the mirror, and in improving the feeding mechanisms and electrodes. The crater which forms in the positive carbon is the point of maximum intrinsic briffiancj' (greatest light intensity per unit area) and ttiis was faced toward the mirror. The shadow cast by the nega- tive carbon and holder was reduced by reducing the diameter of the negative carbon and plating it heavily \vith copper. This copper plating, however, melted and formed slag, preventing even burning or causing short circuits. Beyond a certain point, an increase in current density produced no increase in intrinsic brilliancy, but merely served to increase the diameter of the crater, THE SEAECHLIGHT. 3 which was of no advantage. The augmentmg power of a searchlight may be roughly expressed mathematically: S quare of diameter of mirror Square of diameter of crater. B\* this it is seen that an increase in the diameter of the crater is undesirable unless the diameter of the mirror be iucreased in the same ratio. The size of the mirror is limited by practical considerations to about 36 inches for use on ships, so it is readily seen that this fixes the size of the positive carbon for most efficient work. That is, the upper limit of efficiency had been reached years ago for this type of low power lamp. The extreme range at which a target could be seen with the aid of binoculars when illuminated with the best Navy searchlight of this type was about 4,000 yards. Good illumination could not be obtained at a greater range than 3,000 yards, nor could range finder readings be taken accurately at much over 2,000 yards. With the increase in effective ranges and accuracy of guns and torpedoes, and the increasing speed of ships, this type of searchhght became rapidy less effective in comparison. It was developed to its highest point and people had to make the best possible use of the limited light available. Very recently, about 1914, there came the modern high-power searchlight. In size and general appearance it is similar to the old low-power light, the difference occurring in the lamp, which employs much smaller carbons of a special kind, having a core of light emitting materials. Greater current densi- ties are also employed. In the new type of searchlight the crater in the positive carbon is much smaller and much deeper than in the old tj-pe, and its intrinsic brilliancy is far greater. Going back to the equation of augmenting power, it is seen that the diameter of the crater "d" has been decreased and with great increase in ivr- trinsic hriUiancy, bringing the efficiency of the searchlight to twice its former value. Kanges may be taken easily at over 4,000 yards with sharper definition of target, objects may be plainly seen at 6,000 yards, and at 8,000 yards the target is plain when binoculars are used. Searchlight power was therefore doubled by one improvement. The color of the beam of the high-power searchlight inclines to blue, making the beam of the old type look yellow b}' comparison. The blue gives sharper definition and better illumination of objects painted war color. There is also less dispersion of the beam, together with greater penetrating power. High- power searchlights are made for the Xavy in 36-, 30-, and 24-inch diameters. CHAPTER 2. HIGH-POWER SEARCHLIGHTS. GENERAL DESCRIPTION. High-powor searchlights differ from the low power in the size and rate of burning of the carbons, the current densitj', the composition of the positive electrode which has a special core, the intrinsic brilliancy of the crater, and the greater arc temperature requiring special provision for cooling. There are other differences which are mostly mechanical and do not differ materially in prmciple from older types. There are four types of high-power searchlights now in use, the Beck alcohol "cooled" light, manufactured by the General Electric Co., the General Electric Co.'s air-cooled light, the Sperry light, manufactured by the Sperry Gyroscope Co., and the Anna light. All have carbons of small diameter and rapid consumption, and deep crater positive carbons. The Beck light has alcohol burners fitted beneath the carbons; the alcohol flame envelopes the exposed part of the carbons and serves to keep the temperature of the carbons down to a safe workmg value. The air-cooled lights employ a sj-stem of forced draft, the air being blown along the carbons througli i)assages in the carbon holders and around drum, or of induced draft, the circulation of air being produced by a fan in the top of the drum. These searchlights work with a steady, quiet arc and require little attention while running. The Sperry and General Electric air-cooled lights are suitable for searching the zenith and may be elevated and used continuously at any angle, while, as stated later, the Beck light is not suitable for high-angle use. The air- cooled lights have further advantages in being less complicated and requiring less time and trouble to start and less attention while running. The illuminating power and target visibility range is about the same for all high-power lights of the same size. Specifications for high-power searchlights are given below. Specifications for 36-inch Hiqh-Power Seabchliohts for Use in the United State Navy. [february 26, 1917.] 1. General specifications for the inspection of material issued by the Navy Department, in effect at date of opening of bid, shall form part of these specifications. 2. The searchlights will be designated by the following types and vdU be designed to be operated on a line voltage of 120 unless otherwise specified. (a) Distant mechanical control, type A, B, C, or D. (6) Distant electrical control. (c) Distant electrical and mechanical control. 4 THE SEABCHLIGHT. 5 (i) Distant electrical control, on truck. (e) Distant electrical control, anti-aircraft, on truck. 3. General for all types. (J) Drum. — The drum tt-ill be made of brass and have openings which permit of easy access to the lamp mechanism and mirror. All openings in the drum will be so covered as to exclude wind and rain and permit the light to be operated without flickering when the wind blows at the rate of 30 statute miles per hour. The covers will be so placed on the drum that when the shutter is closed and the light is burning there will be no light \Tsible at a distance of 10 meters (about 33 feet) in any direction from the searchlight. A calibrated ground glass finder will be fitted in the drum in a convenient position, and will give an upright full-sized image of the arc on the ground glass. It will also show the image of each carbon and be marked to indicate the correct position for same, so that the arc can be kept in correct length and in the focal point of the mirror. Pro\Tsion will be made for varying the intensity of the image on the ground-glasa finder to meet day and night conditions of operation. It will be capable of permitting operator to watch the arc without any light being visible at a distance of 200 meters (about 656 feet) from the searchlight. A metal-hinge cover over ground-glass finder will be provided. Two small arc weld or electric smoked glass obser\'ing openings, ^vith metal covers, will be placed in a convenient section of the drum. They will permit a clear and unblurred view of the arc and make \'isible the electrode holders. A direct current ammeter of approved tj-pe in a weatherproof case with a hinged or sliding door will be provided. It will have an illuminated dial, and the meter scale will go at least 100 per cent higher than the normal current of the arc. It will be so located on the searchlight aa to be accessible to the operator. The drum will be so ventilated that during a continuous run of one set of carbons the tem- perature rise vrill not endanger the mirror or any other parts of the searchlight. The ventilation shall be sufficient to prevent the deposit of enough fumes on the mirror during 10 hours usage to materially impair its reflecting power. It will be of sufficient capacity to carry off heat at such a rate that with the shutter closed for 20 minutes with the arc burning under normal conditions the temperature shall not endanger the mirror. The ventilating system will not cause any flickering of the arc. It will be possible to open the drum doors while the arc is burning. The drum will be so designed that the lamp mechanism can be easily removed. If a cooling gas be used with the carbon flame the tank containing the liquid from which the gas is produced will be placed on the outside of drum and high enough to allow the liquid to flow into the vapor- izing apparatus by the force of gravity. (g) Front door and strips. — The front door shall consist of a light composition ring which will be reaiiily removable from the drum, and be designed to hold the positive carbon holder, front- door strips, iris shutter, and Venetian blind shutter. 'U'hen in place it will be so supported by springs and rollers to eliminate breakage due to gun fire. The front door strips will be securely mounted in a composition ring and each strip will be readily removable from the ring. They will be of clear, white, plate glass with surfaces parallel and highly polished. The edges of strips will be at right angles to the surfaces and have a ground glass finish. The outside diameter of strips will be thirty-seven and three-sixteenths inches (37t^ inches) and the thickness of strips one-fourth of an inch (} inch). T\'here parallel strips are furnished they will be 12 in number and reiilforced by metal strengthening strips, to withstand the shock of gunfire. WTiere radial strips are furnished they will be 16 in number and all strips will be identical in shape and reinforced as nece,'pe and must be sufficiently inclosed for pro- tection against injury and at the same time allow effective ventilation. A suitable insulated board containing resistance contacts and rheostat handle will be mounted on the rheostat. The rheostat will consist of two sections, a variable and fixed resistance. The variable resistance will be divided into at least 10 steps, each step giving when hot approximately a drop of 1 volt when a normal current of 150 amperes flows through them. The elements will be thoroughly protected against corrosion in such a manner as not to give off objectionable smoke and securely fastened in the supporting frame at a sufficient number of points to prevent damage from shocks, THE SEARCHLIGHT. 7 and the method of mounting will permit a ready connection of the leads and removal of grids for repairs. A pan will be installed underneath to catch any molten metal or displaced pieces should the elements become melted or broken at any point. The total resistance from cold to hot shall not exceed 12 per cent of cold resistance. Conngctions between rear of panel and resistance unit will be made with commercial fireproof wire. The temperature rise on frame will not exceed 125° C . The rheostat will withstand an overload of 50 per cent in amperes for a period of 10 minutes con- tinuously •without damage. (o) Carbons. — The carbons will be suitable for 150 amperes current and will be hard, fine, and homogeneous in texUire; straight and of accurate circular cross section. They will have no defects such as cracks and blisters, and when burning at 150 amperes current will give a steady light without hissing, spluttering, or flickering, and will not throw off any chips and will give off but a small percentage of ash. The positive and negative carbons will be respectively 16 millimeters (0.62992 inch) and 11 millimeters (0.43307 inch) in diameter with an allowance of plus or minus 1 millimeter (0.03937 inch). They will be straight and not vary more than 1.5 millimeters (0.059 inch) from any point from a straightedge placed in contact with carbon ends. When carbons are burning with a ciuTont of 150 amperes arc voltage 75 and arc length about 2.2 centimeters (0.86614 inch) the maximum light intensity will be at least 100,000 candlepower. The intrinsic brilliancy when the carbons are burning under normal conditions shall be at least 500 candlepower per square millimeter (0.0155 square inch). The carbons shall be of sufficient length to burn two and one-half hours continuously. The carbons to be composed of such material that when burning under normal conditions the searchlight beam shall be of a bluish white color. Bidders shall guarantee satisfactory operation of searchlight ■with carbons of American manu- facture and shall give price at which they will furuish suitable carbons for a period of two years. Acceptance tests of searchlight will be made with carbons of American manufacture. 4, T3rpes of control. (p) Distant mechanical, Type A. — The controller will consist of two separate composition gear boxes in accordance with Bureau of Steam Engineering plan No. 19-S-2832-L. Copies of this plan can be obtained upon application to the Bureau of Steam Engineering, Navy Department, Washington, D. C. (5) Distant mechanical, Type B. — The controller will consist of one composition gear box and handwheels, mounted on composition pedestal and connected by concentric pipe shafts to search- light. The searchlight will be controlled by three handwheels mounted on gear box and con- nected to shafts. Two handwheels on opposite sides of box will control the angle of train and the third handwheel will control the angle of elevation and depression. Illiuminated dials will be installed in gear box to indicate the number of degrees, elevation, or depression, and also the angle of train. Means will be provided for disengaging the mechanical control and operating the search- light by handwheels located thereon. (r) Distant mechanical, Type C. — The controller will consist of gear box, handwheels for con- trol, illuminated dials and means for disengaging from searchlight as specified under (5) but designed to mount in a single searchlight trestle work tower, with handwheels mounted outside of tower sides and connected to gear box by shafting. (s) Distant mechanical, Type D. — The controller will consist of gear box illuminated dials, and means for disengaging from searchlight as specified under {q) but designed to mount in a double searchlight trestlework tower with two handwheels, one for control of elevation and depression, and one for control of angle of train, mounted outside of tower sides and connected to gear box by shafting. (t) Distant electrical. — The distant-electrical controller will consist of two separate composition boxes mounted on composition pedestals, the design of the electric controller will be such as to move the searchlight without jerk. The controller will be capable of training the searchlight at a minimum speed of 3° per minute and a maximum speed of 360° per minute. It will also be capable of elevating or depressing the searchlight at minimum speed of 3° per minute and a maxi- mum speed of 180° per minute. One controller will control elevation and depression and one will control the angle of train. The controller will be as light in weight as possible without sacri- ficing strength and satisfactory operation. Means will be pro\'ided for disengaging the electrical control and operating searchlight by hand. («) Distant electrical and mechanical. — This type of control will consist of controllers of both types described in paragraph 4 (p) and 4 (q). Means will be pro\ided for disengaging either the 8 THE SEAHCHLIGHT, distant electrical control or distant mechanical control or both, and operating searchlights with either type or by hand. (v) Distant electrical, antiaircraft. — This controller will be similar to the one described in paragraph 4 (q) but with one unit designed to tjain the searchlight and the other unit to either elevate the drum or rotate in either direction the ring supporting the mirror suspended in front of searchlight. Means will be provided for disengaging the portable electric control and operating the searchlight and the mirror by hand. 5. Material. — All working parts, Ulterior bolts, nuts, pins, screw^s, springs, brush holders, and studs will be of non-corrodible material thoroughly sheradized, heavily copper plated, or otherwise thoroughl>- coated to prevent corrosion. 6. Insulation. — All insulation shall be of approved insulating material. Hard rubber and porcelain are not approved. 7. Motors and auxiliaries. — .\11 motors and auxiliarici will be in strict accordance ^vith Specifications 17A3, latest issue. K. Wire. — .Ml wire, except fire proof and magncl wire, will bo in strict accordance with Spoci- tications ]')C\, latest issue, and magnet wire will be in strict accordance with Specifications 1.5\V2b unless otherwise specified. !). Finish. — All exterior surfaces of searchlight will be finis'hed in battleship gray. 10. Tool box. — Contractor will furnish a complete list of tools and appliances, as per bureau drawing 9-S-SK-2686-L (or equivalent list) for operation of searchlight and will furnish these tools and accessories in strong hardwood box in accordance with the requirements of Specifications 17A3, late.'^t issue. 11. Spare parts. — Each searchlight will be supplied with a complete set of spare parts for operation of searchlight for a period of three years, as per bureau drawing 9-S-SK-2686-L (or equivalent list). Spare parts will be boxed in accordance with the requirements of Specifications 17A3, lates;' s.'ue. 12. Instructions. — Contractor will furnish with each searchlight a pamphlet containing instructions for operation and care of searchlight. 13. Bids. — Bids will not be considered for searchlights of type which have not been submitted for test at the navy yard, New York, and have operated satisfactorily and been approved as acceptable under these specifications prior to date of opening of bids. 14. Drawings. — Bids will be accompanied by duplicate blue prints showing assembly views giving over-all dimensions and weights of iirincipal jiarts, also additional detailed plans, if neces-sary to give a clear understanding of the apparatus to be furni.shed. After preliminary acceptance of the .searchlights, a complete set of first-class assembly and detail drawings on tracing cloth will be supplied to the Bureau of Steam Engineering, Navy Depart- ment, \Va.shington, D. C. The drawings must be accurate in everj' respect, and must represent all details of the searchlights as they will appear when finally accepted by the Government. If tracings of any of the plans referred to above are on file at the Bureau of Steam Engineer- ing, and are correct in all respects for the material in question, duplication of the same is not required. They shall, however, be referred to in bid by both manufacturer's and bureau's file numbers. All drawings will be made to scale which will be definitely indicated on each plan. (w) All tracings will conform to the following sizes: 27 by 20 inches. 27 by 40 inches. 27 by 60 inches. 27 by 80 inches. 27 by 84 inches. The vertical dimension of tracings in all cases will be 27 inches. Specifications for 24-1 nxh High- Power Searchlights for Use in the United States Navy. (JUNE 5, 1917.] 1. General specifications for the inspection of material issued by the Navy Department in effect at date of opening of bid shall form part of these specifications. 2. The searchlights will be designated by the following types and will be designed to be operated on a line voltage of 120 unless otherwise specified. (a) Hand control; antiaircraft. (6) Distant electrical control; antiaircraft. THE SEAECHLIGHT. 9 (c) DiMant mechanical control; antiaircraft, type A, B, C, or D. 3. General for all types. (/) Drum. — The drum will be made of brass and have openings which permit of easj- access to the lamp mechanism and mirror. All openings in the drum will be so covered as to exclude wind and rain and permit the light to be operated without flickering when the wind blows at the rate of 30 statute miles per hour. The covers will be so placed on the drum that when the shutter is closed and the light is burning there will be no Light visible at a distance of 10 meters (about 33 feet) in any direction from the searchlight. A calibrated ground-glass finder will be fitted in the drum in a convenient position and ivill give an upright full-sized image of the arc on the ground glass. It will also show the image of each carbon and be marked to indicate the correct position for same, so that the arc can be kept in correct length and in the focal point of the mirror. Pro^^sion will be made for vanrTiig the intensity of the image on the ground-glass finder to meet day and night conditions of operation. It will be capable of permitting operator to watch the arc without any light being visible at a distance of 200 meters (about 6.56 feeti from the searchlight. A metal hinge cover over ground-glass finder will be provided. A sighting arrangement, con- sisting of two suitable gun sights mounted on left-hand side of barrel facing mirror, will be pro"vided. Two small arc -weld or electric smoked-glass obser\'ing openings T\-ith metal covers will be placed in a convenient section of the drum. They will permit a clear and unblurred vievr of the arc and make vTsible the electrode holders. The drum will be so ventilated that during a continuous run of one set of carbons the tem- perature rise will not endanger the mirror or any other parts of the searchlight. The ventilation shall be suflBcient to prevent the deposit of enough fumes on the mirror during 10 hours usage to materially impair its reflecting power. It will be of sufficient capacity to carry off heat at such a rate that with the shutter closed for 20 minutes with the arc burning under normal conditions the temperature shall not endanger the mirror. The ventilating sj'stem will not cause any flickering of the arc. It will be possible to open the drum doors while the arc is burning. The drum will be so designed that the lamp mechanism can be easily removed. Handles for control of searchlight will be placed at the back of barrel. (g) Front door and strips. — The front door shall consist of a light composition ring which will be readily removable from the drum, and be designed to hold the positive carbon holder, front-door strips, iris shutter, and venetian-blind shutter. When in place it will be so supported by springs and rollers as to eliminate breakage due to gunfire. The front-door strips will be securely mounted in a composition ring and each strip will be readily removable from the ring. They will be of clear, white, plate glass with surfaces parallel and highly polished. The edges of strips will be at right angles to the surfaces and have a ground- glass finish. The outside diameter of strips will be 2-5-^ inches and the thickness of strips J^ inch. ^^Tiere parallel strips are furnished they will be 10 in number and reinforced by metal strength- ening strips to withstand the shock of gunfire. Where radial strips are furnished they will be 12 in number, and all strips will be identical in shape and reinforced as necessary to withstand the shock of gunfire. The composition ring holding front-door strips will be securely mounted in the front door and be easily removable. The front door will be fitted for passing through positive carbon. It shall be ea.sily removable. The positive carbon will be incased in a tube which will be insulated on the inside and have weatherproof cap which will be easily removable. (h) Dowe. — The dome shall consist of a composition mirror ring to which are secured a sheet copper mirror covering and two lifting handles. The dome will be fastened by clamps to the dnmi in a manner so as to eliminate breakage due to gunfire. These clamps to be so designed as to enable the operator to readily detach the dome. (i) Trunnion arms. — The trunnion arms will be made of (bronze) pressed or cast steel and will be sufficient height to permit the drum to be elevated at least 100° above or 30° below the hori- zontal train. They will be securely fastened to the rotating section of the base. A suitable scale graduated in degrees will be pro\ided to indicate the amount of elevation of the drum. A small covered light with switch will be placed over the pointer so as to illuminate the pointer and scale immediately under. One trunnion arm will carry a suitable clamp for securing searchlight at any degree of elevation or depression. (j) Base. — The base will consist of two parte. A stationary lower part and a rotating upper part. The base will be hollow, circular in shape and made of iron or composition. A circular 10 THE SEABCH LIGHT. flat graduated (degrees) scale w-ill be securely fastened to the stationary part of the base and an indicator pointer will be placed on the rotating section to indicate the angle of train of the search- light. A email covered light with switch will be placed over the pointer so ae to illuminate the pointer and scale immediately under. The base will contain a clamp arrangement for holding the drum in any fixed angle of train. (t) Mirror and mirror holder. — The mirror will be in strict accordance withSpecification 17-M -3a of February 1, 1917, copies of which can be obtained upon application to the Bureau of Steam Engineering. The mirror will be mounted in the composition mirroring. An asbestos material approximately \ centimeter (0.19G85 inch) thick and 2.5 centimeters (0.98425 inch) wide will be placed between the mirror ring and mirror to assure a snug fit. \ space of J centimeter (0.19685 inch) between the edge of mirror and mirror ring to allow for any expansion of the mirror due to heat will be filled in mth asbestos material. Where mirror is not manufactured by bidder, the bureau will be informed in bid the name of the firm manufacturing same and also supplied with a copy of contract. (/) Lamp mechanism. — The lamp will be constructed so that the operator has easy access to all working parts. The lamp will be designed for both automatic feed (with de\'ice for governing the speed) and hand feed for carbons, and the change in feed will be easily accomplished while lamp is in operation. Pro%-ision will be made for cooling both carbons with air. The automatic feed will be operated by a motor. The lamp will have both hand and electrical devices for rotating the positive carbon. A water-tight switch conveniently located will be provided for momenta- rily stopping the rotation. The feeding arrangement will be so designed as to maintain an arc voltage between values of 55 and 60 volts and to maintain an arc length of about | inch at 75 amperes. The lamp mechanism mil maintain the crater of the positive carbon at the focus of the mirror with a maximum \aiiation of not greater than 1 millimeter (0.04 inch) on each side of the actual focus. The lamp and drum will be so designed that new carbons may be put in and light started up within a period of 8 minutes from the time the light is turned off. The lamp will be designed for 75 an'peres current and the carbon holders shall be so designed that there will not be a wastage of more than 20 per cent. The positive carbon holder va\l be mounted in a hori- zontal position and the negative carbon holder will be placed at such an angle with the horizontal center line of the positive holder as to give the best burning condition of the carbon and maximum intensity of light flux on mirror. A tray sutliciently large to catch all chips from the carbons to prevent them from falling on mirror, but which will not block off more than 15 per cent of the beam, will be furnished. The connections inside the lamp meclianism will be firmly secured in place and the entire lamp mechanism will withstand a dielectric test of 1,500 volts alternating current applied for one minute. (m) Shutters. — All shutters will be made of light noncorrosive material. A suitable hand- wheel for operating the iris shutter through gears will be located on the side of the drum whore it is easily accessible for the operator. The Venetian blind shutter will be operated by a handle located on the side. All searchlights will be supplied with iris shutters and Venetian blind shutters. (n) Rheostats. — The rheostat will be of the unit type and must be sufficiently inclosed for protection against injur}-, and at the same time allow effective ventilation. A suitable insulated board containing resistance contacts and rheostat handle will be mounted on the rheostat. The rheostat will consist of two sections, a variable and fixed resistanre. The varialile resistance will 1)0 divided into at least 10 steps, each step giving when hot approximately a drop of one volt when a normal current of 75 amperes flows through them. The elements will be thoroughly protected against corrosion in such a manner as not to give off objectionable smoke, and securely fastened in the supporting frame at a sufficient number of points to prevent damage from shocks, and the method of mounting will permit a ready connection of the leads and removal of grids for repairs. A pan -will be installed underneath to catch any molten metal or displaced pieces should the elements become melted or broken at any point. The total resistance from cold to hot shall not exceed 12 per cent of cold resistance. Connections I'etween rear of panel and re- sistance unit will be made with commercial fireproof wire. The temperature rise on frame will not exceed 125° C. The rheostat will withstand an overload of 50 per cent in amperes fos a period of 10 minutes continuously without damage. (o) Carbons — The carbons will lie s\iitable for 75 amperes current and will be hard, line, and homogeneous in texture; straight and of accurate circular cross section. They will have no defects THE SEAECHLIGHT. 11 such as cracks and blisters and when burning at 75 amperes current will give a steady light without hissing, sputtering, or flickering and will not throw off any chips and will give off but a small percentage of ash. The positive and negative carbons ^vill be respectively 11 millimeters (0.43307 inch) in diameter with an allowance of plus or minus 1 millimeter (0.03937 inch). They will he straight and not vary more than 1..5 millimeters (0.059 inch) from any point from a straight- edge placed in contact with carbon ends. When carljons are liurning with a current of 75 amperes arc voltage 58 and arc length about ^ inch the minimum useful mean spherical candlepower on mirror 24.000. The intrinsic brilliancy when the carlions are V)urning under normal condi- tions shall lie at least 300 candlepower per square millimeter. The carbons shall be of sufficient length to burn two and one-half hours continuously. The carlions to be composed of such material that when burning under normal conditions the searchlight beam shall be of a bluish white color. Bidders shall guarantee satisfactorj' operation of searchlight with carbons of American manu- facture and shall give price at which they will furnish suitable carbons for a period of two years. Acceptance tests of searchlight will be made with carbons of American manufacture. 4. Types of control. (p) Distant mechanical, type A. — The controller will consist of two separate composition gear boxes in accordance with Bureau of Steam Engineering plan No. 19-S-2832-L. Copies of this plan can be obtained upon application to the Bureau of Steam Engineering, Na^'J' Department, Washington, D. C. (q) Distant mechanical, type B. — The controller will consist of one composition gear box and handwheels, mounted on composition pedestal and connected by concentric pipe shafts to search- light. The searchlight will be controlled by three handwheels mounted on gear box and con- nected to shafts. Two handwheels on opposite sides of box will control the angle of train and the third handwheel will control the angle of elevation and depression. Illuminated dials will be installed in gear Ijox to indicate the numl^er of degrees elevation or depression and also the angle of train. Means will be provided for disengaging the mechanical control and operating the searchlight by handwheels located thereon. (r) Distant meBianical, Type C. — The controller will consist of gear box, handwheels for control, illuminated dials, and means for disengaging from searchlight as specified tinder (g) but designed to moimt in a single searchlight trestle-work tower, with handwheels mounted outside of tower sides and connected to gear box by shafting. (s) Distant mechanical. Type D. — The controller will consist of gear box, ilhuninated dials, and means for disengaging from searchlight as specified under {q) but designed to mount in a double searchlight trestle-work tower, with two handwheels, one for control of elevation and depression, and one for control of angle of train, mounted outside of tower sides and connected to gear box by shafting. {t) Distant electrical. — The distant-electrical controller will consist of two separate composition boxes mounted on composition pedestals; the design of the electric controller will be such as to move the searchlight without jerk. The controller will be capable of training the searchlight at a minimum speed of 3° per minute and a maximum speed of 360° per minute. It viill also be capable of elevating or depressing the searchlight at minimum speed of 3° per minute and a maxi- mum speed of 180° per minute. One controller ^vill control elevation and depression and one will control the angle of train. The controller will be as light in weight as possible without sacrificing strength and satisfactory operation. Means will be provided for disengaging the electrical control and operating searchlight by hand. 5. Material. — All working parts, interior bolts, nuts, pins, screws, springs, brush holders, and studs will be of noncorrodible material thoroughly shearadized, heavily copper plated, or otherwise thoroughly coated to prevent corrosion. 6. Insulation. — All insulation shall be of approved insulating material. Hard rubber and porcelain are not approved. 7. Motors and auxiliaries. — All motors and auxiliaries will be in strict accordance with Specifications 17A3, latest issue. 8. Wire. — All wire except fireproof and magnet wire will be in strict accordance with Speci- fications 15C1, latest issue, and magnet wire will be in strict accordance with Specifications 15W2b unless otherwise specified. 9a. Finish. — All exterior surfaces of searchlights will be finished in battleship gray. 10. Tool Box. — Contractor will furnish a complete list of tools and appliances, as per bureau drawing 9-S-SK-2686-L (or equivalent list), for operation of searchlight and will furnish these 12 THE SEABCHLIGHT. tools and accesaories in strong hardwood box in accordance with the requirementa of Specifications 17A3, latest issue. 11. Spare Farts. — Each searchlight will be supplied with a complete set of spare parts for operation of searchlight for a period of three years, as per bureau drawing 9-S-SK-268&-L (or equivalent list). Spare parts will be boxed in accordance with the requirementa of Specifications 17A3, latest issue. 12. Instructions. — Contractor will furnish with each searchlight a pamphlet containing instructions for operation and care of searchlight. 13. Drawings. — Bids will be accompanied by duplicate blue prints showing assembly views giving over-all dimensions and weii;ht8 of principal parts, also additional detailed plans, if nec- essary to give a clear understanding of the apparatus to be furnished. After preliminary acceptance of the searchlights, a complete set of first-class assembly and detail drawings on tracing cloth will be supplied to the Bureau of Steam Engineering, Navy De- partment, Washington, D. C. The drawings must be accurate in every respect, and must repre- sent all details of the searchlights as they will appear when finally accepted by the Government. If tracings of any of the plans referred to above are on file at the Bureau of Steam Engineering, and are correct in all respects for the material in question, duplication of the same is not required. They shall, however, be referred to in bid by both manufacturer's and bureau's file numbers. ' All drawings will be made to scale, which will be definitely indicated on each plan. (w) All tracings will conform to the following sizes: 27 by 10 inches. 27 by 40 inches. 27 by 60 inches. 27 by 80 inches. 27 by 84 inches. The vertical dimension of tracings in all cases will be 27 inches. Accessories, spare parts, and tools for high power Back 36- and SO-inch starchlighls. (Searchlights: Each to be wired complete sind supplied with fixed and varialjlc rheostat and iris shutter. Orders for material will specify whether mechanical or electrical control, and if required, whether fitted with signaling shutter, antiaircraft features, and whether mounted on truck. Where electrical control is specified, 100 feet of cahlc, couplings, and controller will be furnished with each searchlight.] Spare parts (separately 6oxed). Spare lamp complete (each in box) Set glass front door strips (each set inseparte box) rarbons, positive (10 in each box) Carbons, negative (10 in each box) Spare parti. Box: Containing the following Set, all mica insulation for lamp Relay magnet coll Feeding magnet coil Starting motor shunt field coil Starting motor series field coil Feeding motor field coil Vaporizer heating unit Positive and negative contacts for carbon heads .set. . B urncr for lam p Positive and negative carbon head rollers set.. Rheostat bushings for supporting rods Carbon head noses pairs. . Rheostat grids Lifting bars pairs. . Brush holders and 3 additional springs, each kind and type, for ventilating, lamp starting, and feeding motors Armature for lamp-starting motor Armature for lamp-fooding motor .\rmature for lamjvventilating motor Field coil for ventilating motor Alcohol strainers set. . Test rods do Fuses Number installed per vessel. 1 1 150 150 1 2 300 300 1 4 «00 600 6 8 2 2 6 8 900 1,200 900 1 1,200 1 1 (! 8 3 4 3 4 3 4 3 4 3 4 S 10 3 4 i 2- 3 2 3 ■ * 4 2 2 15 20 2 2 I 1 2 2 2 2 2 2 9 2 1 1 12 16 10 2 10 l,.soo 1,500 2 12 1,800 1,800 1 12 « « 6 « 4 4 6 14 6 6 2 .10 3 1 2 2 2 2 4 1 24 THE SEAECHLIGHT. 13 The following will be included in the above-mentioned box when electically controlled Bearchlights arc specified: Number installed Mr veessl. 1 2 4 6 8 10 12 1 2 2 3 3 4 6 contact fingers for controller elevating cylinder sets. . 6 contact Angers for controller training cylinder do 2 3 4 5 6 7 ' 7 arcing contacts or segments for controller elevating cylin- der sets.. 1 1 1 1 2 2 2 2 3 3 2 2 4 4 2 2 5 5 2 2 6 7 arcing contacts or segments for controller training cylinder. 6 23 pieces mica insulation for controller elevating cylinder, 3 23 pieces mica insulation for controller training cylinder, .sets. . 3 3 all springs for controller set . . 1 2 2 2 3 Field coils, each kind and type, for elevating and traming 1 2 2 2 3 Armature, each kind and type, for elevating and training 1 1 2 1 2 1 2 I 3 1 Brush holder and 3 extra springs for training motor 1 1 1 1 I 2 brushes for elevating motors set . . 2 6 8 10 12 2 brushes for traming motors do 2 6 8 10 12 Fuses for control circuit 8 16 24 32 40 48 Starting resistance for elevating motor sets. . 1 2 2 2 3 Starting resistance for training motor do 1 2 3 Tool boxes (furnished as accessories with each searchlight) . . . 2 6 8 10 12 Each contaming the following: I pair blue glass goggles. 1 pair carbon cutters. 2 wrenches for Xo. 8/36 and No. 10/30 nuts. 1 large dust brush. 1 small dust brush. 1 focusing screen. 2 reamers for carbon heads. 1 set (2) ventilating motor brushes. 1 set (17) all springs for lamp. 1 observing screen, made up of 1 red and 1 green col- ored glass mounted in a wooden frame. 1 hand-feed socket wrench. Accessories, spare parts, and tools for high-power 36 and 24 inch air-cooled searchlights Searchlights: Each searchlight wUl be wired complete and supplied with fixed and variable rheostat and iris shutter. Orders for material will specify tvpj of control, whether fitted \vith antiaircraft features and whether mounted on truck. When electrical control is specified, 100 feet of cable, couplings, and controller will be furnished with each searchUght. When mechanical control is specified, the necessary shafts, in length as specified, and controller will be furnished with each searchlight.] Number per vessel. 10 12 Spare parts (each in separate bo.x): Lamp complete Sets glass front-door strips Carbons (positive), 2-5 per bo.x Carbons (negative L 2.5 per box Spare parts (all m one box) All insulation for lamp and drum, including collector rings in base set . . Field coils for feeding motor Field coils for lamp motor Field coils for ventilating motor Coil for magnet Positive and negative contacts for carbon heads set.. Posiliveand negative carbon head rollers do.. Armatiue for lamp motor Armature for ventilating motor Brush holders and 3 additional springs, each kind and type for vent ilating and feeding motors Quartz bushings Thermostat mirror Front cap and stray light shield for positive head Asbestos washers for bushings (large hole) .\sbestos washers for bushings (small hole) Thermostat coil Thermostat condenser Thermostat strips set . . Arc voltage-regulating coil Positive head front casting Negative head casting Insulated coupling for positive and negtivc feed rods Rheostat bushings for supporting rods Rheostat grids (fixed element) Rheostat grids (variable element) Rheostat for negative feed control Pawls for lamp set (3) . . Negative head cups Fuses for azimuth and training scale lamps Insulating compound for screw head (i-pound in can) Lifting bars pairs. . 1 1 150 130 1 1 1 1 1 1 1 1 2 1 2 12 2 6 12 12 1 2 1 1 1 1 1 2 2 2 1 1 2 4 1 1 1 2 300 300 1 2 2 2 2 2 2 2 2 1 4 24 4 12 24 24 1 4 2 1 2 2 1 2 4 4 1 1 4 8 2 1 1 4 600 600 1 4 2 2 2 2 2 2 3 2 4 48 8 24 48 48 1 6 4 1 2 2 2 2 2 6 900 900 1 6 3 3 3 3 3 3 3 2 1,200 1,200 1 2 10 1,500 1,500 1 10 5 5 5 5 5 5 5 3 10 120 20 60 120 120 2 10 10 2 5 5 3 4 20 20 2 5 12 20 5 2 2 12 1,S00 1,800 1 12 6 6 6 6 6 4 12 144 24 72 144 144 2 10 12 2 6 6 4 6 24 24 2 6 12 24 6 3 14 THE SEARCHLIGHT. When electrically controlled eearchlighu are specified, the following additional spare parts will be included in the above "spare-part" box. Number per vessel. 10 12 Spanner wrench for coupling Field colls (each kind and type) (or elevating motor Field coils (each kind and type) for training motor Armature for elevating motor Armature fur training motor Brush holders and set s o( all springs lor elevating motor Brush holders and sets of all springs for training motor Brushes (complete) for eU'viiting motor sets.. Brushes (complete) for training motor do All springs for controller do All contact fingers and contacts for controller do All insulation tor controller parts do Tools (furnished as accessories with each searchlight) ..boxes.. Each containing the following: One pair carbon cutters. Two wrenches for No. 8-36 and No. 10-30 nuts. One chamois skin One large dustbrush. One small dustbrush. One duster in case. One set ventilating motor brushes. Two sets, lamp motor brushes. One focusing screw. One pair carbon tongs. One set, carbon head gauges for aligning heads. Two reamers for carbon heads. One suitable observing screen in frame. One pawl wrench. One ground glass for finder. One hand feed socket wrench. One oil can, J pint. One pair 6-mcri side cutting pliers. One pair 8-inch flat nose pliers. One pair 8- inch combination side cutting gas pliers. One li-inch screw driver. One 4i-inch screw driver. One S-'inch screw driver. One G-inch bicycle wrench. One O-inch monkey wrench. One l-pound can graphite compound. One J-pound ball pecn machinist's hammer. One jVinch diameter pin punch. One 8-inch half round hasp. One grease gun (1 ounce). One sheet 000 crocus paper. 4 4 12 12 12 12 3 7 3 12 Tliere are shown on the following pages curves taken from a test on high and low power searchlight carbons. The tests were made with the aid of a spectrophotometer, an instrument which is a combination of a spectroscope and a photometer. By it, the comparative intensity of light of any wave length may be measured, as the instrument is so constructed that light at any part of the visible spectrum may be compared with the photometer standard. The calibration is in microns, the unit of wave length. (A micron equals 0.001 millimeter.) A comparison of the curves for high-power carbons with those for low- power carbons will show the immense advance made when the modern high- power searchlight was produced (figs. 1 to 9). Not only was the intensity greatly increased, but the spectrophotometer showed the light to be of the most advantageous wave length, i. e., color. THE SEAECHLIGHT. 15 Plate No.l. W.OO 1 A TYPICAL SPECTRUM INTENSITIES \ CARBONS FOR G.E.Co. HIGH POWER ARC FOR NAVALSEARCHLIGHTS \ THESE CURVES AHETHEAVERAGEOf THE RESUaSOBIAWE!) FROMSEVERALREPRESEHTATOE SAMPLES OF CARBOKS SUBMITTEDATVARIOUS TIMES FORTESTS 3S.00 I note: \ CURVEAlSINTENSlTVOFTOTALARC ^ CORVE B IS INTEKSITYOf FLAME0NLY4 CARBOHTIPS / \ 27 SO > ^26.00 ^- z \ \ UJ / \ \ IZSO I0.0O / / ^/ "\ \ \ / / \ \ ,^ / 1 ) y soo !S0 / J \. \ \ A / / \ B A- / X * *o *t * w * oo SI s< 7 X ViouET |P| 'Bi-ue I Wave Lenotm Veluow I Off*wo^ Color Fig. 1. 16 THE SEAEOHUGHT. Plate No.5. 1 SPECTRUM INTENSITY OF HIGH POWER CARBON ARC FOR NAVAL SEARCHLIGHTS MAOt BY 1E SPERRY GV«05C0PE COMPANY, N.YOR CARBONS MADE BY 1E NATIONAL CARBON CO.,CLEVELAND, RC NORnALATlMAHf>7SV0LnAKLENGTH22C^ sdiiigstortotauintensitytakekato'anole • THOSE FOR TlPSifUMEATSO'AHGLE nso ii.00 32.50 30.00 Tt < T r \ RE & / \ f A \ -1 UJ J V \ \ nso / ~j \ \ // \ \ / \ N \ / / ^ \ // V . y / \ \ /' r ^ ^^ V ' Violet |P | Buuc | , Wavelength I Yellow | Orange I Color k'Ui. 2. THE SEARCHLIGHT. 17 Plate No 5* » SPECTRUM INTENSITY OF HIGH POWER CARBON ARC FOR NAVAL SEARCHLIGHTS MADE BY TME SPERRY GYROSCOPE CO.,NEW YORK CARBONS MADE BY THE NATION AU CARBON CO., CLEVEL AN D, 0. ARC NORMAL AT ISO AMP. 75 V01I5 ARC LENGTN2?Mei READINGS FOR TOTALINTENSITYTAKENATO-ANGLES / 37.50 3S00 3o.oa > t ^27.50 Z UJ , 1 HOSE FO RT1P5& FLAME AT 9D°ANGL E / 1 / \ _J liJ a: 22J0 1 \ \ 20.00 \ \ \ \ ^ . j \ \ 1 1 \ 1 / \ \ 7S0 l \1 \ S.OO P / \ \ ^r- jj w 6 * S > s J » J 1 S ! Z 1 S 7 J , , , Wave Length , VioucT |p I Blue \ Gaeew | YELtow | Ouahge [ Red 66438—18- COLOR Fig. 3. 18 THE SEAECHLIGHT. Plate No.tO *2 50 40 CO nso 35.00 TYPICAL SPECTRUM INTENSITV LOW POWER CARBON ARC ">• NAVAL SEARCHLIGHTS SHOWINSTDTALINTENSITYo'ARCCRATEB CARBON TIPS 4 FLAME READINGS TAKEN AT 30 ANGLE ARC NORMAL AT IIOAHP fcOvOLTS.ARC LENGTH US INCHES aRBONS M4DEBY NATIONALCARBON CO CLEVELAND.OMIO AND > 77.50 «) Z ^2SO0 UJ > PURCHASED UNDER SPECIFICATION IK-Sto" 36'SEAR(MLKiHT note: CURVEAlSAHAVTf ST*H0*R0POSrnvtlKITX*Pl,AlNC*ItBOHCGI»t CURVES ISA NAVT STAKMHOPOSIIIVE mrrt riAMt HARD CODE r X -1 UJ / \ I / f --N \ / V \ v \ ^ \ \ J / \ 1 \ / M \ / / V, A ^ / A v_ ;^- ^ 1 6 i 4 4 4 « •- a s s. ? s t s < , . f 8 , S «. ? c- « « » A » 7 Violet |P | Bi-ue , WAVELENGTH 1 Yellow | Opance I Red Color Fig. 4. THE SEAECHUGHT. 19 Plate No.ll SPECTRUM INTENSITY CARBON ARC ro" 36" NAVAL SEARCHLIGHTS MADE BY GFNFR41 Fl FfTRICmMPANY AHO 5UPERCEEDED BYTHE HIGH INTENOTY ARC N ARCNORMALATI10AMPS.60VOnSARCLEKEIHL75l«alES BeADINGSF0RTCnALlNTENSrrVTSKEH«3O*All6LE READmGSF0RFLAMESS'ni>STAK[HAT9O°AH0LE 13.0 \ \ (KITE: CUFNEA ISINTENSITY OF TOTAL ARC CURVEB1S1NTENS1TYOFFLAME0MLY4CARB0HT1PS \ CARBONS MADE fft THE NATIONAL CAR80NC0.,CUEVELAND,0. ANO PURCHASEWnDER SPEC.17-C-Sro«36-SEARCH LIGHTS. II.O J N V SO a.o i \ \ \ 6.0 S.O \ \ ^ *0 V 3.0 1.0 « \ ^ \ A 1.0 f- ^ _ B hf 4 i« 4 la J <0 5 \ 5 < s e s. 5~ 5 - ^ ■ ' '6 * 6 t 6 i 7 Q V 2 WAVeLE:MGTH Violet [P| Blue | Greem [ Yellow | OmNOE | Red Couch Fig. 5. 20 THE SEARCHLIGHT. aAK No. 13. COMPARISON SPECTRUM INTENSITIES ^RC ANO RESULTANT BEAMOF LOW POWER 36 INCH SEARCHLIGHT SHOWING COLOR SELECTION ENERGYEFFICIENCY or ASSR4RAB0LIC MIRROR«FRONTLENS U5IM0 PLAIN CORE POSITIVE MAKE BV 4TI0NAL CARBON C0.,CLEVEUNO,O. PURCHASEDUH0£RSPtC.I7-C-5 / 30.0 GL N CUf rvEBsHC WSSPEC TRUMOf 8EAM > ( \ vt z UJ z 200 UJ «^ uo I2J1 IOC ] \ ^ / \ \, / \ 1 A / A \ // ^^ ^ V / \ \ \ // \ \ \ ,^ / \ B t' / V A ^::::^ r »^« « 6 4 ■d J o E? J ^ J »-■ J « . ^ 6 2 i r* t 6 i I J B WaveLenoth, Violet |P | Bmfc | Gbe£n | Ycluow yomwotl Hep Color Fia. 0. THE SEARCHLIGHT. 21 Plate No.l5. / \ COMPARISON SPECTRUM INTENSITYOFARC ANO RESULTANT BEAM OF / \ 35.0 32.5 \ SPERRYH1GHP0WER36"SEARCHLI6HTARC SHOWING COLOR SELECTION AND ENERGY EFFICIENCY OF GLASS PARABOLIC MIRRORSahdFRONT LENS / \ V . A \ CARBONS MADE BY 27.5 > t g25.0 Ul _z UJ .?•) e \ V \ NOTE : CURVE A SHOWS SPECTRUM iNTENSITYOrARC V CURVE B SHOWS SPECTRUM INTENSITVOFBEAM • 1 / \ V I s \ -I / >--. \\ oc // )\ \ 1 / \ \ i / \ \ P / ^ v^ V / \ \ /^ 1 \ \\' A^ / V^ A 4 k B ^ ^ f p r t — ? »— "6 o 1 2 6 6 B e y J X Violet |P j Blue Gree Wavelength 1 Yellow | Ohanqe j Red Color Fic; 22 THE SEARCHLIGHT. comparison spectrumTntensity BEAMS OF HIGH & LOVI POWER 36 INC H NAVAL SEARCHLIGHTS Curve A- beam ofsperrymigm power spircmlioht CURVE B- BEAM OF NAVY STANDARD LOW POWER SEARCnUGHTUSlNO HARD CORE WrtlTff LAME POSITIVE BURNINOON IIOAMP CURVE C-BEAM Of NAVY STANDARD LOW POWER SEARCHLIGHT USING PUIN POSITIVE C ARBON BURNINOON IIOAMP. CURVE 0-BEAM OF BECK SEARCHLIGHTU&ING CARBONS MADEBYG E.CO Violet jP j Bi-ue | Wavelength YcuLOw [OaAHOE I Color KiG. 8. THE SEAKCHUGHT. 23 ??J0 21.75 2000 /fl.75 Plate No.16* COMPARISON or SPECTRUM INTENSITIES ofARC AND RESULTANT BEAM OF LOW POWER 36" SEARCHLIOHTS SHOWING COLOR SELECTIONS AND ENERGY EFFICIENCY OF GLASS PARABOLICMIRROR&FRONTLEMS USING WHITE FLAME HARDCORE POSITIVE MADE BY THENATIONALCARBONCO..aEVtUlH0.0 / \ / \/ ^^ / v \ 1 ^-\ \ 1- « z 111 /£iC 1- _z y > //« // • \ \ note: CURVE A SKOWSSPECTRUM INTtHSlTYOtARC CURVE B snows SPECTRUM IMTENSITV Of BEAM i / V \ / \ as / \ \ // \ \, i y \^ \ / \ \ S7S I.2S / \ \ r 7 \ ---> A L / ^ /^ / Violet |P I Blue | Wave Length , Yellow | Orange | Color Fig. 9. CHAPTER 3. BECK 36 AND 30 INCH HIGH-POWER SEARCHLIGHTS. Tlie Beck light does not difTer materially in external appearance from the older t3-pe of searchlight, the arrangement of the arc with respect to the mirror being similar to the arrangement in previous lamps. Tlie great differ- ence occurs in the source of light. Smaller carbons and greater current densi- ties are employed than in the low-powered searchlights hitherto in use; more- over, the positive carbon has a core of light-emitting substances, the composition of which is known onl}' to the manufacturers. Another noteworthy feature of the Beck lamp is the method of keeping the carbons cool by surrounding them with an alcohol flame. ITie alcohol flame is a reducing medium and prevents oxidation of carbons back of tips, thereby preventing the heat of this additional burning. Also, the carbons do not ''spindle" and the cross section is constant, therefore no additional heat is developed by PK loss increasing, as it would with constant current and smaller area of conductor. The alcohol feature, however, is objectionable because it prevents the light being used for anti-aircraft purposes to any great extent unless extra mirrors are used in front of searchlight. (These mirrors are inclined 45° to the horizontal and deflect the beam vertically upward.) After the lamp is tilted upward to a certain angle the alcohol ceases to flow, and the carbon "cooling" system is therefore out of service for as long as the light is elevated beyond this angle, absolutely unfitting the lamp for being used to search the zenith or any at very high angles. This searchlight is excellent for use where high-angle searching is not rerjuircd and is far superior to the old type of pure carbon arc searchlight. The following is a reproduction of parts of the instruction book on Beck searchlights furnished by the General Electric Co. From it may be obtained an idea of the operation of the lamp. Further information may be obtained from the report of the test on the sample 44-inch Beck searchlight supplied to the navy yard. New York, for trial. This test report follows extracts from instruction book. Small Carbons. The positive carbon has a special core and develops a deep crater of high intrinsic brilliancy and small diameter, resulting in a beam of high intensity and very small dispersion. The posi- tive carbon is in the axis of the searchlight barrel and the negative carbon is inclined, in the ver- tical plane, to the positive. Rotation. To prevent an uneven burning, due to the rising arc stream, both carbons are rotated by a motor. Alcohol Flame. An alcohol flame envelops both carbons, resulting in the cooling of the electrodes and the removal of combustible gases from the air immediately surrounding the burning carbon tips, thereby reducing the burning rate of the carbons. 24 36 inch High Powered Mechanical Control Searchlight FIG. to— BECK HIGH POWER SEARCHLIGHT. RIGHT SIDE. THE SEAECHLIGHT. Arc rating and carbon dimensions. 25 Size of lamp, inches. Amperes. Arc volts. Positive. Negative. Diameter. Length. Diameter. Length. 36 30 150 120 75 72 mm. 16 13 mm. 1,100 1,000 mm. 11 11 mm. 340 270 Descrxption. lulion. — This Mixture is Poisonous and the Warning "Wood Alcohol Poison" is JILLED on the Side of the Alcohol Tank, Part 1, Figure 11. Table of specific gravity . For the best results, a mixture of methyl (graiu) and ethyl (wood) alcohol should be used. Low grades of alcohol /■ contain an excess of water and the mixture should be of the specific gravity shown in the table.] Grade. Per cent. Specific gravity at fi0° F. (15° C). 50 .50 100 0.815 .811 .813 Wood .. Tank. — The alcohol should be strained through a chamois skin and kept in clean receptacles. In fUUng the tank, remove the cap, part 2, figure 10, and pour the alcohol slowly into the opening. In entering the tank the alcohol passes through a 200-mesh wire screen. Indicator. — In one end of the tank there is an indicator, part 3, figure 12, with a scale marked in pints. This indicator is of the magnetic t>T)e there being a permanent magnet inside the tank attached to a float. The movement of the magnet, caused by changes in the level of the alcohol, causing a corresponding movement of the pointer on the outside of the tank. Valves, pipes, filter, and vaporizer. — Directly below the tank is the shut off valve, part 4, figure 11. The tank is connected by a pipe, part 9, figure 11, to the filter, part 5, figure 11, in which the alcohol passes through one 200-mesh and one 65-mesh wire screen. From the filter the alcohol passes through an opening 0.012 inch diameter, a valve and a coil pipe to the vaporizer part 10, figures 13 and 16, where it passes through four thicknesses of 32-mesh wire screen to the inner wall of the vaporizer. A heating unit, part 11, figures 13 and 16 vaporizes the alcohol. At the aide of the filter is a push rod, part 7, figure 11, carrying a fine wire which when the rod part 7 is pushed in enters the small filter outlet hole and clears it of any obstruction. Burners and Jlame. — The vapor passes up the pipe, part 12, figures 13 and 16, to the burners, parts 13 (positive) and 14 (negative), figures 13 and 16. The positive burner has two narrow, tapered openings which divide the positive flame, causing one jet to pass on one side and the other on the opposite side of the carbon. The negative burner has one narrow opening. It is important that these openings be kept free from dirt. Vent screw. — Part 6, figure 11, is a vent screw which should be opened to allow trapped air in the pipe, part 9, to escape. This should })e left open until the alcohol flows through the vent. It should be unnecessary to open this vent except in case of leakage in the pipe, part 9, or the supply of alcohol has become exhausted. THE THERMOST.^T AND ABC IMAfiE SYSTE.M. The image of the crater of the positive carbon is focused on the strips of the thermostat, part 32, figures 18 and 20, Ijy means of the lens, part 36. and the muror. part 37. figure 21. This thermo- stat controls a feeding magnet, part 41, figures 16 and 17, which in tui-n controls the positive feed rod, part 42, figures 13 and 16. 26 THE SEAKCHUGHT. By means of a lens mounted in a tube in the searchlight barrel and projecting into the thermo- stat box, part 43, figure 10, the image of the arc is projected on a mirror, part 34, figure 18, and reflected to mirror, part 33, figure 18, then reflected to the ground glass, part 35, figure 18. The image of the arc is inverted on the ground glass. Two vertical linee on the ground glass mark the correct position for the tips of the carbons. ROTATION OF CAHBONS. Motor, shafts, gears, and rollers. — The feeding and rotating motor, part 15, figures 16 and 17, is connected by gearing to the positive rotation rod, part 16, figures 13 and 16, and the negative rotation rod, part 17, figures 13 and 16. These rods have at their upper ends bevel gears, parts 18 and 19, meshing with gears, parts 20 and 21, figure 10, by means of which the movable portion of the carbon head is rotated. This rotary movement is transmitted to the carbons by means of the spring- pressed knife-edged rollers, parts 26 and 28, figure 16. Contacts. — Supported on the stationary part of the carlion heads are contact arms, parts 46 and 47, figure 16, fitted with flexible silver connection strips, parts 48 and 49, and silver contact blocks, parts 50 and 51, having concave contact surfaces pressed against the carbons by the weight arms, parts 22 and 23, figure 16. Guiding of carbons. — The carbons are guided by the bore in the carbon head nosee, parts 24 arid 25, figure 16, and by the rollers, parts 26, 27, 28, 29, figure 16. FEEDING OF CARBONS. Gearing and ratchets. — In the revolving mechanism of each carbon head is a star wheel con- nected by a worm and a worm wheel to the shaft carrying the knurled faced feeding rollers, parts 27 and 29, figure 16. The negative feed. — The negative feed is set by hand by means of the lever, part 30, figures 15 and 16, moving over a notched and graduated dial, part 52, and connected to the cam, part 52, figure 16. which raises or lowers the feed rod, part 32, figures 13 and 16. The upper end of this rod engages the star wheel at the lower point of the path of its rotation around the axis of the carbon, rotating the star wheel through a few degrees or several degrees depending on the setting of the arm, part 30, thus increasing or diminishing the rate of feed of the carbon. The positive feed — Thermostatic regulation. — When the positive carljon tip is on its line on the screen, part 35, figure 18, the crater image is on the edge of the first thermostat strip, part 32, figures 18 and 20. As the carbon bums away, the crater image is reflected further onto the first thermostat strip deflecting it and closing the contacts, parts 53 and 54, figures 17 and 20, com- pleting the circuit to the feeding magnet, part 41, figures 16 and 17. The feeding magnet armature in closing raises the positive feed rod, part 42. figure 13 and 16. bringing it into the path of the rotating ratchet connected to the feeding rollers and feeding the carbon ahead. This advance of the carbon occurs during each revolution of the carbon head until the positive carbon tip is again in the exact focus of the mirror and the crater image has moved to the edge of the thermostat strip opening the circuit to the feeding magnet which, in turn, lowers the feeding rod and stops the feeding. Hand regulation. — If the thermostatic regulation becomes inoperative, it is cut out of the circuit by opening the switch, part 55, figures 10 and 18. The hand feed is then operated in the same manner as the negative feed. Emergency quick feed. — For the purpose of moving the carbon rapidly forward the positive feed lover, part 41, figures 14 and Ifi, may be moved to the extreme left-hand end of the dial, part 45, figure 14, against a stop. This lowers the quick feed rod, part 43, figures 13 and 16, and raises the latch, part 56, figures 13 and 16, locldng the internal gear, part 57, figure 16, which, through a pinion rapidly revolves the worm shaft geared to the feed rollers, and the carbon is fed ahead at a rapid rate. THE STARTING MOTOR. A starting motor, part 58, figure 16, is connected by gears, sprockets, and chain with the nut, part 69, figure 16, engaging with the screw, part 60. The rotation of this nut causes the screw to move forward or back. The screw is attached to the negative carbon carriage. HAND START. The lamp may be started by hand, using the handwheel, part 61, figures 15 and 16. FIG. 11. BECK HIGH POWER SEARCHLIGHT. LEFT SIDE. FIG. 12.— BECK HIGH POWER SEARCHLIGHT, BACK VIEW. THE SEABCHUGHT. 27 VENTILATION. A fan, direct connected to a motor, is mounted in the top of the barrel and exhausts through the opening, part 69, figure 12. This fan removes the gases from the arc and cools the mirror. LIMrr SWITCH. The lim it switch, part 62, figures 16 and 19, consists of a base sliding on guide rods and held in position by a spring. It carries insulated contacts and contact arms and is operated by an insulated stud on the negative carbon carriage. The functions of this switch are as follows: First. In connection with the reversing relay, to connect the starting motor as a series motor in advancing the negative carbon carriage. Second. To limit the forward motion of the negative carbon carriage in case the carbons fail to meet due to the carbons being improperly adjusted or breakage of either carbon. Third. In connection with the reversing relay, to reverse the starting motor in striking the arc. Fourth. To open circuit and apply a dynamic brake to the armature of the starting motor when the arc has been established. The limit switch may be moved along the guide rods by the push rod, part 63, figures 15 and 19, to produce an arc shorter than normal. CONNECTIONS OF LAMP. Refer to figure 17. The rheostat is in series with the lamp and is connected in the negative side of the circuit. The negative potential wire A, the main negative lead B, and the main positive lead C are brought to the lamp through contact rings and plungers in the base and on the turntable of the projector. The main leads B and C are connected to the insulated carbon sup- ports through flexible connection strips. The series wound ventilating motor part 64 and the heating unit, part 11, of the vaporizer are connected directly across the positive lead C and the negative potential wire A so that they receive the full Une voltage. The feeding and rotating motor, part 15, has its field connected between the main negative lead B and the negative potential lead A, and its armature connected through the switch, part 66, figure 18, to the same source. This connection is essentially across the rheostat and the motor operates only when the lamp is burning and current is passing through the rheostat. The relay, part 67, figure 16, is also connected between the main negative lead B and the negative potential lead A, or across the rheostat, and closes when current passes through the rheostat. The feeding magnet, part 41, is connected on one side to the negative potential lead A and on the other side, through the contacts of the thermostat, and the thermostat switch, part 55, to the main positive lead C. Part 68 is a discharge resistance for the feeding magnet. The starting motor, part 58, has a series and a shunt field with a switch, part 70, in the armatiu'e circuit. With the limit switch, part 62, and the relay, part 67, in the starting positions, the starting motor is connected as a series motor across the line or between the main positive lead C and the negative potential lead ,\ and advances the negative carbon carriage until the carbons touch. With the limit switch part 62 and the relay part 67, in the running position, the motor is reversed and operates as a shunt motor separating the carbons until the arc has been drawn out to the proper length, when the motor is stopped by the limit switch part 62 opening the circuit. Operation. inserting carbons. If partially burned carbons are to be used, see that the end of the positive carbon is cut off squarely, using the carbon cutters furnished in the tool box. Rotate the negative carriage by means of the handle part 65, figures 13 and 16, until the carriage strikes a stop. Separate the carbon head rollers by rotating the negative releasing handle part 71, figures 15 and 16, and the positive handle part 72, figures 13 and 16, counterclockwise facing the ends of the lamp. This separates the feeding and rotation rollers. On account of the ratchet in the hand rotation mechanism, it is necessary to grasp both the positive and the negative releasing handles at the same time, as rotation of either positive or nega- 28 THE SEARCHLIGHT. tive releasing handle without locking the other drives back through the gearing and rotates the other carbon head. Raise the contact arm weights parts 22 and 23, figures 13 and IG, and insert the negative carbon from the front of the negative head. Insert the positive carbon through the carbon tube part "3, figures 10 and 11. Rotate the negative carriage back to its running position and adjust the carbons so that the negative projects 1% inches and the positive projects l^ inches from the ends of the noses, as shown in figure 16. Lower the contact arm weights and rotate the releasing handles clockwise back to their former positions. This causes the rotating and feeding rollers to grip the carbons. Contumption of alcohol. — Note the position of the alcohol indicator and make sure there is a supply of alcohol sufficient for the run. The conauraption of alcohol is 1.5 pints per hour. Setting negative support. — Pull the hand starting hand wheel part 61, figure 15, outward and rotate in a clockwise direction, facing the handwheel until the negative carriage strikes a stop; then rotate counterclockwise 2^ turns. Push the handwheel in throwing it out of engagement with the starting gearing. The carbons should now be J inch apart. Vaporization. — Open the main alcohol valve part 4, figure 11. Close the main switch in the projector base. This will .start the ventilating motor and complete the circuit through the vaporizer heating unit. Allow from one and one-half to two minutes for the vaporizer to become hot, then open the alcohol valve in the base of the lamp by turning the knob part 7-1, figures 12, 15, and 16. Apply a match to the burners and observe the height of the alcohol flames. Height of flame. — The positive should be 12 inches and the negative 10 inches high. The vapor will ignite from the arc, but it is better to light the flame before starting, so that the height of the flames may be noted. If the flames are not the proper height, push in the rod part 7, figure 11, once or twice. See that the thermostat switch part 55, figure 10, is closed. Starting stifitch. — Close the starting switch part 70, figures 15 and 16. This will start the lamp. If the arc drops repeatedly owing to the absence of a crater in a new positive carbon, push in the rod part 63, figures 15 and 19 and hold until a crater is formed. RUNNING. Adjustment of feed. — Observe the image of the burning carbons on the screen part 35, figure 18. The tips should touch the vertical lines on the screen. Adjust the lever part 30, figures 15 and Ifi, until the rate of feed is such that the negative carbon tip holds to its line on the screen. If the negative carbon tip is to the right of this line the arc is too long and the lever should be moved a small amount to the right. This increase.^ the rate of feed. If the negative carbon tip is to the left of this line (between the negative and positive lines), the arc is too short and the feed too rapid. Move the lever to the left a small amount. Repeat tliis operation until the rate of feed is equal to the carbon consumption and the negative carbon tip holds to its line. This adjustment will need very little change during a run. Variation in the burning rate of different carbons will make a slight change in adjustment necessary from time to time. The lever part 44, figures 14 and 16, should be sot at zero. If the image of the positive ciubon is to the left of its line, the arc is beyond the focus of the mirror. Turn the adjusting knob part 75, figures 10 and 20, a slight amount in the direction marked ''Back." If the image ia to the right of the line (between the lines), turn the knob slightly in the other direction. This adjustment must be made whenever a change in the temperature of the air in the thermostat box affects the curvature of the thermostat strips, part 32. In case the thermostatic regulation is inoperative, place the switch part 55 in the off position. The lever part 44 must then be adjusted to hold the positive carbon on its line, as described above for the negative carbon. Stopping carbon rotation.— li the positive carbon starts to burn irregularly, stop the rotation of the carbons by opening the switch patt 66, figure 18, when the projection is uppermost (at the lowest point on the screen part 35), allowing the rising flame to burn it off. Then close the switch, allowing the carbons to resume rotation. Quirk feed.— In case the positive carbon should be burning some distance back of its line or if it becomes broken, move the lever part 44 to the left against the stop and hold until the carbon is fed up to its line. 36 inch High Powered 5edrch//ght Lamp FIG. 13.— BECK HIGH POWER SEARCHLIGHT LAMP. RIGHT SIDE. FIG. U.-BECK HIGH POWER SEARCHLIGHT LAMP. THREE-QUARTER FRONT VIEW. THE SEARCHLIGHT. 29 In case enough of the carbon is broken off to cause the arc to drop, the rotation motor will stop. Open the starting switch part 70, figure 15, return the negative carriage to the starting position by means of the hand starting handwheel, part 61, figure 15. Hold the positive feed lever part 44, figure 14, to the extreme left of the dial, insert the hand rotation wrench in the opening in the side of the lamp, rotating the wrench counterlockwise until the positive carbon tip is again on its line. This can be seen by aid of the alcohol flame. Release the positive feed lever and close the starting switch. ShoTl-arc pxtsh rod. — If the arc drops, due to air blast from gun fire, push in the rod, part 63, figure 15, and at the same time rotate the hand start wheel, part 61, figure 15, counterclock^vise to shorten the arc. The rod part 63, figure 15, should be held in as long as the short-arc condi- tion is required. Hand feed and rotation of carbons. — If the feeding and rotating motor fails to operate insert the hand feed wrench through the opening in the side of the lamp and rotate counterclockwise about 50 revolutions per minute. Hand rotation should start as soon as the arc strikes and must be continuous. If the positive carbon burns irregularly the hand rotation must be stopped when the projecting lip of the carbon is uppermost until the lip is burned off. STOPPING. Open the main switch in the searchlight. Open the starting switch, part 70, figure 15. Close the valves, parts 4 and 74, figure 12. Observe alcohol supply for the next run. Remove the dust from the mirror and front door strips. A duster is furnished in the tool box for this purpose. CAHE OP L.VMP. Keep the lamp clean, remo^-ing all carbon du.st after each run. Note paiis marked oil and grease, on figure 16, and keep oil and grease cups full. Use a good grade of light machine oil and a light grease or mixture of grease and graphite for the grease cups. Apply only a small amount of oil through the oil hole each time, wiping away any excess. The switch, relay, thermostat, limit switch, and other connections should be kept clean. Use fine sandpaper in cleaning contacts, do not use emery cloth or paper. The carbon contacts, parts 50 and 51, figure 16, should be inspected frequently and kept clean. The curvatures of the contact surfaces must be kept in their original forms to correspond with the curvature of the carbons. The brushes of the rotating, starting, and ventilating motors should be kept clean by occa- sionally sandpapering. Lenses and mirrors in the thermostat box should be kept clean and free from dust. In clean- ing care should be taken not to disturb the adjustment of the mirrors. Carbon heads should be reamed out occasionally, with reamers furnished in the tool box, to remove accumulations of carbon dust or scale. ADJUSTMENTS. Focusing. — In previous searchlights not using the high powered lamp, focusing was accom- plished by moving the entire lamp toward or from the mirror. In the high-powered searchlights the lamp is fixed in the drum, with respect to the parabolic mirror and the essential condition which must be maintained is the projection of the positive carbon 1-^ inches from the end of the carbon head. A positive carbon carriage adjusting screw, part 77, figure 16, and a nut, part 78, figure 14 and 16, provide means of moving the carriage toward or from the mirror, with the lamp in its fixed position, but should only be used when adjusting the lamp to a new parabolic mirror having a different focal length than the mirror with which the lamp was adjusted, or in replacing the lamp with a spare lamp. Replacing mirror. — Proceed as follows: First. Open the thermostat switch, part 55, figure 10, and set carbons as shown in figure 16. Second. Start the lamp, observe the beam and if the rays cross (hourglass in shape) move the nut, part 78, figure 14, counterclockwise. If the beam spreads move the nut, part 78, clockwise until the beam, when thrown on a distant object, is as small in diameter as it is possible to obtain. 30 THE SEARCHLIGHT. \Vhenever the positive carbon carriage is moved by the nut, part 78. figure 14, it is necessary to adjust the push rod, part 63, figure 15, by removing the lamp side cover and loosening the set screw at point marked 86, figure 19, and turning the rod, part 63, until it can be pushed in -ff inch. Third. Stop the lamp, readjust the carbons and repeat adjustment No. 2, until the proper beam is obtained with the positive carbon projecting IfJ inches. Fourth. Adjust the thermostat mirror, part 37, figure 18, until the image of the crater is ^ inch on the first thermostat strip, part 79, figure 20. The arc image should be in the center of the thermostat strip, vertically. This mirror is adjustable in two planes by means of the screws, parts 80 and 81, figure 18. Fifth. Close thermostat switch. Fia. 16. — Beck high-power searchlight lamp. Sectional assembly. Sixth. Adjust the arc-image mirror, part 34, figure 18, until the image of the positive carbon tip is on its line on the screen, part 35. Installing spare lamp. — The thermostat and arc-image mirrors having been properly set for the mirror which is in the projector require no adjustment. First. Set the carbons as shown in figure 16 and start the lamp. Second. Rotate the nut, part 78, figure 14, until the tip of the positive carbon is on its line on the screen, part 35. •Third. Check the length of the positive carbon beyond the carbon head. This should be l-fi inches. If not correct reset and repeat adjustment No. 2. Arc-image and thermostat mirrors. If the adjustment of the arc-image or thermostat mirrors has become accidentally changed, adjust the arc image mirror by use of the adjusting screws until the im^e of the positive carbon tip is on its line on the screen, part 35, noting carefully that the TSB SEAKCHLIGHT. 31 positive carbon is in focus and projects lyj inches from the head. Adjust the thermostat mirror aa described in the fourth adjustment under replacing mirror. Thermostat co/'i(ac(5. ^Referring to figure 20, the pivot point, part 82 should be so set that there is 0.001 inch between the point and the thermostat strip. (WWW- 64 o 63 o S^.- Fig. 17.— Beck high-power searchlight. Wiring diagram. ' "The screws, part 53, figure 20, should be adjusted so that they are the same distance from the contacts, part 54. "f IFeed rods. — When the levers, parts 30 and 44, are set at zero there should be ^ inch between the upper ends of the feed rods, parts 32 and 52, figure 13, and the points of the star-wheel teeth when the star wheel passes the feed rod. Burners. — If burners are replaced they should be adjusted exactly as shown in figure 16. 32 THE SEABCHLIGHT. Carbon head springs. — If the tension springs on the feed rollers are replaced the new springs should be adjusted so that the rotation and feed rollers mark faint lines of the carbons. A splinter- ing of the carbons indicates that the springs are too tight. Carbon support guide. — If it becomes necessary to move the carbon supports to bring the carbons into the vertical plane of the axis of the mirror, adjust the guide, part 87, figure 19, by Fio. 18.— Beck Wgh-powcr searchlight l&mp. Thermostat and arc Image system. the screws, part 12, being careful to put no strain on the guide by unequal movements of the adjusting screws. Limit switch. — In case it is necessary to replace limit switch contacts or the contact springs have become distorted, set the carbons as in figure 16 and back off the small set screw at 88, figure 19. FIG. 15— BECK HIGH POWER SEARCHLIGHT LAMP, SHOWING CARRYING BARS IN PLACE. THREE- QUARTER BACK VIEW. THE SEAECHUGHT. 33 Then push ia the rod. jiart i;:i, and rotate the rod opposite the push rod until contact 84 just touches contact 83. All of the above adjustments are carefully made at the factory and should not be changed unless uecesaar>'. 66- 1 ri'i 1 1 iilu\ft» I'.k'.'.^'.'.'.V'A'.'.'.l.^'. v.. kk'. '.'.'.'. kV U^■vv.■.^^v^^kk^^kl.^..k^^^■^^^^^^'.^^^M"^^u^^^n .^'.'.W',^^■.^^^^-.k^'.^'.>.^k■.^^^^'.UA^^A.A.A^^..^^^^J'l Fig. 19. — Beck high-power searchlight lamp. Sectional views. 66438—18 3 34 THE SEARCHLIGHT. Fio. ao.— Beok high-power searchlight lamp. Arc length regulator and thermostat. THE SEAECHUGHT. 35 Fio. 21 .—Beck high-power searchlight lamp. Relay and starting switch. Report ok Tests on Beck Searchliobt. [August, 1914.] 1. Tests have been conducted on the searchlight submitted by Mr. H. Beck, of Meiningen, Germany, through his representative, Mr. Auerbacher, of New York City, to determine tlic s\:it- ability for use on shipboard as compared with the apparatus now in use. Tlie searchlight appara- tus consists of the searchlight and rheostat. 2. Tlie mechanical construction of the searchlight is as follow: The metal searchlight drum is suspended in two bearing.-!, the pede.stals of which are fa^teued by bolts to the top of a hea\ y ca^t-iron ciniilar base. Tliis base (its over an iron housing used as the base of the searchlight. In the drum of the searchlight Ls placed the light projector. In the back of the drum is fastened by meaiw of clutches the searchlight dome and the parabolic glass mirror. On the front of the drum is placed the front-door strips. These strips are placed in an iron flat ring and this ring is suspended on two sets of iron grooved rollers placed 180° apart which re.st on two tracks lastened to the drum. On either side of this iron ring are placed springs, the function of which is to act as a cu-hion. This arrangement is used to minimize the shock of the front-door strips (hie to gun fire and prevent breakage. .\n iris shutter arrangement is placed in front of thc^e gla.ss strips and the opening and clo.^ing of the .shutter is manipulated by means of the turning of a haiidwheel placed on the side of the searchlight drum. .V small iron tube used to protect the positive carbon projects from the front side of the searchlight. On top of the drum is a protected opening which permits the proper dissipation of heat radiated from the arc. There is also placed on top of the drum a ventilating fan which exhausts all the gases and smoke given off from the arc and the burning alcohol gas. On one side of the drum is a square opening having an iron hinge cover. This opening permits an easy access to any part on the inside of the housing, mirror, or lamp. On this side also is fastened a small 5 liter capacity tank used for storage of alcohol used in con- nection with the burning of the lamp. .Vttached to this tank is a flexible brass protected rubber tube which conveys the alcohol to the lower side of the searchlight projector. On the bottom of the drum is fastened a ratchet device operated by a handwheel for elevating the drum. On the other side of the drum is a square ground glass used for the indication of the position of the arc with respect to the focal center of the mirror and also to observe the jirojjer burning of the arc. On the same side is also fastened a long metal box containing the electrical mechanism by means of which the positive carbon is kept in a constant position. On the same side is also placed a small ratched arrangement operated by means of a small handwheel, by means of which the searchlight lamp can be moved backward and forward in the drum. The drum with the pedestal can be trained in azimuth in either direction and the amount of turning is indicated by a scale fastened on the base. The mechanical construction of the lamp is as follows: The lamp consists of a rectangular housing in which is placed the motor with mechanical arrangements for feeding the carbons together and apart on initial striking of the arc. Another motor with mechanical arrangements is placed in this housing for the purpose of rotating the car- bons. The housing also contains a vaporizer, superheater, and feed regulator for the alcohol. The mj^net controlling the operation of the position of the positive controlling rod is also located in this housing. On top of the lamp housing are placed the carbon holder pedestals. The positive carbon holder pedestal is securely fastened to the lamp housing and remains in a fixed position. The negative carbon holder pedestal is clamped by moans of screws to the lamp housing. By loosen- ing the screws the negative carbon holder pedestal can be given a small turn and the negative carbon can he easily replaced by a new one. On top of each pedestal is placed the carbon holder. The positive carljon holder is in a horizontal position and the negative holder is placed at an angle of 14° with the horizontal plane. Each carbon holder consists of two parts, the stationarj' |)art used as a guide for the rotating carbons. This section also contains the current contact round shoes which are made of silver. The other part of the carbon holder is a rotating clamp arrangement for clamp- ing and rotating the carbons. This arrangement rotates constantly and causes the carbons to 36 38 THE SEARCHLIGHT. rotate with it. The rotation is accomplished by means of a mechanical arrangement connected with the motor used for that purpose in the lamp housing. The clam])ing arrang(>ment is com- posed of two rollers so adapted as to effect a simultaneous advance of the carl)ons while rotating. The speed of feeding of the carbons is controlled by means of control rods located alongside of the carbon holder pedestals. \Mien these control rods are raised they come in contact with a little 10-tooth star wheel which in turn is connected mechanically with the clamp. As the teeth of the star wheel come in contact with the control rod the carbon is advanced. The speed of advancing depends entirely upon the position of the control rod with respect to the teeth of the star wheel — as, for example, the shorter the distance between the upper edge of the control rod and the center of the star wheel the greater the speed of feeding of the carbons. In the case of the negative carbon the position of the control rod is regulated mechanically by a switch placed on the outside of the lamp housing. This control rod remains in this fixed position until it is changed mechanically by the switch gi\ ing a constant feed of the negative carl)on depending upon the siieed of rotation of the negative carlion and the position of the rod. If the adjustment of the negative feed is incor- rect, giving too fast a feed, the point of the carbon projects beyond the flame, causing a rapid com- bustion of the negative carbon, so that the distance between the carbons (the arc length) remains practically the same. Inversely, if the feed is too slow the rate of combustion slackens and tends to keep the arc length constant. It is only necessary to watch the position of the negative carbon on the ground-glass finder and make adjustment of feed about ever)- 10 minutes. The feed of the positive carbon, however, has an additional electrical arrangement governing the position of the control rod. On the side of the searchlight drum is a rectangular box. This box is so placed so that when the ray of light from the arc is reflected by means of mirroi-s placed conveniently inside of the drum, upon the first contact in the bottom of the box the metal contact becomes heated and expands, thereby closing an electric circuit which operates a magnet, which in turn operates mechan- ically the poedtion of the positive control rod. If the positive carbon is in the exact focal center of the mirror, the ray of Light will not fall on this metal contact and the electric circuit will be open, the positive controlling rod will be down, and the positive carbon will not be advancing, liut only rotating. There is also a small mechanical device for adjusting the amount of raising of the posi- tive controlling rod when the electric circuit is closed. The speed of feed in this case again depends upon the speed of the rotating of the positive carbon and the position of the control rod. Directly underneath the positive and negative section of the carbons composing the arc there are placed two nozzles, the larger nozzle directlj' under the positive carbon and the smaller under the negative. The purpose of these nozzles is to give a spray of vaporized alcohol to the positive aud negative carbons, thereby preventing rapid combustion of the carlions. The feeding of this vaporized alcohol is accomplished by having a tube connected from the two nozzles to the super- heater in the lamp housing, which in turn is connected to the vaporizer, which is connected to an electrical regulating device which regulates the supply of alcohol received from the alcohol tank. The supply of alcohol is forced down to the regulator by means of gravity pressure. The rheostat consists of a number of resistances connected in a multiple arrangement, part of these sets being connected across snap switches, thus enabling certain sections to be conveTiiently cut out. There are also located in this rheostat two coil resistances which are connected according to the Wheatstoue Bridge principle with the arc and another constant resistance in the rheostat. Those resistances are used to operate the motor feeding the carbons together and apart on the initial lighting of the searchlight. On the outer side of the rheostat are also placed terminals for the ammeter and voltmeter measuring, respectively, the current consumption of the searchlight and the line voltage. 3. The electrical construction of the searchlight mechanism is as follows: The essential electrical features are shown in the diagram. The search-light carbons are connected through a knife switch in series with a resistance (D) across a constant direct supply of 120 ^•olts. The negative side of switch (A) also is connected to the negative carbon brush of the striking motor used to move the negative searchlight carbon forward and backward on the ignition of the lamp. The positive side of this motor is connected to the positive terminal of the switch (B) and through this switch to mid-point of a resistance (E), the one terminal of whicli is connected to the negative side and the other to the positive side of the main supply. The field of the striking motor is connected directly to the main voltage supply. The electrical arrange- ment makes a wheatsone arrangement in which the arc and resistance D and E (a and 6) are the arms of the bridge and the striking motor takes the place of the galvanometer. The annexed THE SEABCHLIGHT. 89 diagram shows this arrangement diagrammatically. If the carbons are apart the current in the motor armature flows in one direction due to the state of potential between the points (X and Y) and this direction of the motor armature tends to luring the carbons mechanically together. As soon as the carbons are together, the direction of the current flowing through a wc -M VA w ^'^ A1 f£/ r \Aj HP Ti S7 1 '/^ /Vf, r ''\ vy 37. Wl !4^ fl 'S' ^•f WC\ W. C/* /-/ llfi to. P /fiS w, r. ),« w w n n AA ai. ky IT 2L Oi r 7 so if w CO VC /v lA Mi /I/, 'I, HM = ( ■se s^ irf T o^ Tf %. f* 4 !^ L£l r / !£lf f/? 'EC 9C " , $ ^ ~ S^ Mr R£ ■£fL S£l Si • '^ S ^ f. ^ ^ N Y> \ \\ 3 rif ^ \V 2 >i i: 1 S 0/i TA VC. ^ /, // vo tfi V, » ._ _ Fig. 24. the motor will be reversed to the state of potential of points (X and Y). This reversed direction of the current tends to rotate the motor armature in the opposite direction, and therefore the carbons are separated until the potential difference between points (X and Y) is zero; theu the motors will be at rest. The field excitation of this motor remains always in one direction. There is also connected across switch (A) another circuit. This circuit consists of a switch (F) and a series-connected starting motor. Tliis motor is used for constant rotation of the carbons. Across the positive terminal of switch (F) and the nega- tive terminal of switch (B) is connect- ed a circuit that contains the solenoid which operates the positive controll- ing rod, and in series with this is con- nected the contact switch (G), which automatically opens and closes this circuit as the reflected ray of light from the arc strikes the metal con- tact of the switch. Also in multiple with this circuit are two multiple circuits, one containing a resistance used in a small tube to vaporize the alcohol. In the circuit is also connected in series (not shown in the diagram) another resist- ance which is used to superheat the alcohol vapor. The other circuit contains a magnetic solenoid which regulates the supply of alcohol flowing through the vaporizer. From the diagram it can be seen that the circuits containing the arc and the one containing the motor 120 v: suppiy E=<5r-i-b 40 THE SEARCHLIGHT. vised to rotate the carbons are operated from tlie same switch (A), and the rcHl of tlic rircuits can oidy lie operated when both switches (A and H) are closed. Switch ((!") opens and closes the circuit which contains a shunt motor used for ventilating fan (used to take fumes and Riisos from searchlight drum). A more detailed description can be obtained from the blue print under in- dosure (B). 4. The following tests were coudiicteil: (A) Sun spot test on mirror. (B) Screen tests on mirror. (C) Concentrated filament lamp test on mirror. (D) Heat run test on searchlight. (E) Voltage regulation test on projector. (F) Carbon testa. (G^ Night illumination tests. (H) Candlepower measurement of s<':ircldia:lit projeffor. ~" ~ - " ■■^ ~ f I ■y ^ ,^ i ^ ^a V. ■»/ 'M ep ?/>. "/? oA rA vc. " c (//? If. r ^ (. f , ME ^ I •£A Sf/i U ai cr, ?/c eo 'Si w CH yo V? ^ i>r A ii on TA. m a ^ ^ as 0/ r \A. fp BO m wt : !^ Wi £A /^ 7/f/ Ml a Wi. f/-/ '/K r //o ''* 1 § g ^ 6 f^ 5 'i S s X y ^ ^ z -V ^ y " ■~1 ■^ =»■ Al ■a f v/- endpnt THE SEABOHLIQHT. 41 upon the voltage and thus a fluctuation of voltage does not change the position of the carbons. Cur-\-es plotted from the results obtained can be found under inclosure (E). Tests made on the carbons showed the following results: The dimensions of the positive carbon are | inch diameter by 43 inches length, as against 1 [ inches diameter by 12 inches in length, the dimensions of the Navy standard carbons now in use, and l-^ inches diameter by lOf inches length of the Harle 44-inch searchlight. The dimen- sions of the German negative carbon are -^ inch diameter by 10.7 inches length, as against 1 inch diameter by 7 inches length, those of the Navy standard 36-inch negative carbons now in use, and i inch diameter by 10} inches length for the Harle negative. Both the positive and negative carbons of both types are cored. The core in the German positive carbon is made of a composition vastly different from those now used and when the German carbons burn in the Beck lamp there is no jumping, flaming, and hissing of the carbon while burning. The German carbons burn very evenly and the length of burning of the carbons is two and three-fourths hours. With me- chanical changes in the position of the carbon holders the carbons can be burned for approximately a period of four hours. Comparative night-illumination tests were conducted between the General Electric Co.'s Sfi-inch and CO-inch searchlights and the 44-inch Beck searchlight. The German searchlight -1 ^~ ^ -.01 CE VTf •Al A7 •/? oo ^7 H on \-6 'C Vt M \la yt£A 'T •A/

ri ^ - fes ■», 5a =^ ^ ^ ^ _ O/J TA, ya //\ //, Vff. 'S 4 a /!< / s t z 4 a ? J 2 3. S Fig. 26. beam was a more concentrated beam tlian that obtained from either the 30 or 00 inch beam of the General Electric Co.'s lamp and the color of the Beck beam was a whiter one than that obtained from the Navy standard 36 and 60 inch searchlights. With the carbons burning in a normal con- dition and placed in the proper focal centers of their respective mirrors, foot-randlepower reading at intervals of 24 feet were taken across the beam at a distance of 2.850 feet from the searchlight.'^. Under inclosure (F) there will be found four cross-section sheets containing curves plotted from the results obtained from these night-illumination tests. Two cross-section sheets each contain- ing one curve showing the illumination across the beam of the Beck searchlight compared with the 60-inch General Electric searchlight. These results were obtained on August 10, 1914. From these two curves it can be seen that the illumination obtained from the Beck Light is two and one-half times as great as that obtained from the General Electric Co.'s 60-inch light, antl these curves also show that the illumination in the General Electric Co.'s light is more uniformly dis- tributed acros.s the beam than that obtained in the Heck-light beam. In the Beck searchlight the beam shows a ver\' lurge iHumination at the center and falls off very rapidly at the edge of the beam. The other two cross-section sheets under inclosure (F) contain the plotted result? 4fi THE SEARCHLIGHT. obtained in comparing the Navy xtandard 36-inch pearchlight with the Beck light. The curve sheet containing the re.sults of the 36-inch General Electric searchlight consists of five curves. The curves indicated by 1, '1, and 3 are plotted from actual results obtained. Curve 4 Ls a result- ant curve of curves 1, 2, and 3 and curve No. 5 is curve plotted from the theoretical results that would have been obtained if a 41-inch Navy standard searchlight had been used in place of a 30-inch light. The other curve sheet, with the results obtained from the Heck light, contains four curve.s; three plotted from the actual result.s obtained, and curve No. 4 is the resultant curve of these three. From the comparative data obtained it can be seen that the illumination obtained with the Beck searchlight Ls about five times as great as that obtained from the General Electrii' light. The spherical candlepower of the Beck arc was measured and the results can be found Fio. 27. plotted under inclosure (G). The ma.ximum candlepower obtained with the use of our present Navy standard carbons is 4,500 candlepower, as against 84,000 candlepower obtained from the Beck lamp. This result obtained from the Beck lamp is a trifle low in comparison with previous results obtained abroad, but this is due to atmospheric conditions. 6. In considering the question of searchlights and their relative efliciencies it becomes natural to consider them as made up of the following separate parts: (1) Searchlight drum, pedestal, system of control in azimuth and in elevation, shutters. • and other purely mechanical details. (2) Rheostats. (3) Searchlight mirror. (4) Lamp mechanism. (5) Searchlight arc. THE SEAECHLIGHT. 43 One type of searchlight may show increased efficiency over another because some of these parts have been worked out to give the very best results, but a searchlight to give the very best results must have all these details wor];ed out separately and then joined together in the proper relation to give the maximum efficiencies. 7. Searchlight drum and other mechanical details are questions of design which effect the efficiency of the light very little. They should be worked out carefully, however, so that the searchlight is properly lialanced. may be easily trained in azimuth and elevation from a distant control station or at the light itself. The drum should be so made that air currents can not be set up inside, thereby causing fliclcerLag of the arc. ventilation should be sufficient so that light may be kept on at full intensity with shutter closed or other means adopted for keeping the light burning at lower intensities with shutter closed and bringing it to full intensity instantly upon opening of shutter. It Is also considered advantageous to have permanent ammeter and volt meter mounted on the seirchlight drum or conne'tioa on it so that portable instruments can be connected. A ground glass finder which shows the position of the arc, tlie arc length, and the variations of the positive crater from the focus of the rau-ror is considered an essential in a properly designed search- va iT, Ci ■-/; £6 UL \Ti OH CL '/?! 'Ei. 0/ - 7 Ma B. SC Y. m !/?( 7/y iG HI L \m P '/■ -/ 4 L ^M f ' fill m \o NC KM UL /oo ■ 7/< ?-?/ -N vn vs !9 ISO 1 \ / \, 1 ^ / \ / ■N. =^ \ f^ \ t^o \ / \ r \ 1 > / *■ \ / \ / s / \ \ y g vo tA G£ a //n ■e V Si / ■> ■s J, >, s S f. ^ s. / ■>> ^ S ^ \ / s ^ / s _, '■s r V, — ' r' Til 1£ IN M NU T£ ) Q A 4 c - 6 1 Q 1 I 1 ■J / 6 / 3 i 2. 2 2 4 Z •6 2 a 3 i 2 J 1 J e j 8 < 4 2 4 4 4 i" S i i 2 i •4 i 6 i 9 i Fia. 28. ight. The mirror should be so secured that it may be readily removed and the miiTor and front door strips should be mounted in such a manner as to eliminate shock and breakage. 8. The searchlight as submitted by Mr. Beck was not designed for shiplioard use but only for laboratory' experimental purposes and can not justly l)e compared in regard to the external mechani- cal construction with the Navy standard type now in use. It has however many mechanical featm-es which are considered advantageous for a searchlight. Thus the method of mounting the mirror and front-door strips are considered liefter than those obtained in the past, the ground-glass finder of the Beck light is of great advantage. 9. The rheostat used in connection ^rith searchlight consists of two parts, a fixed and variaVde resistance. A certain amount of fixed resistance is necessary' to overcome the natural unstalpiUty of a carbon arc and its value must be, at least, sufficient to give a voltage drop in the resistance equal to one half the arc stream voltage. This has lieen explained in more detail in pre^■ious report on searchlight carl;on3. The variable resistance is neressar.' in order to obtain the pi'oper arc voltage for various carbons and various lengths of line. The resistance elements must be of sufficient area to carr\' the maximum currents used without undue heating of any parts and of such material that the resistance does not change excessively with temperature changes. The steps should l)e of not greater than one volt each. 44 THE SEARCHLIGHT. The rheoetat supplied with the Beck searchlight meets in general the above requirements. It was not constructed for shiphoard use and would refjuire some mechanical changes. 10. The eflSciency of searchlight mirrors depends upon its truenesa to parabolic form, its trueness of svu-face grinding, the color and structure of the glass, and the thickness of the glass, the losses in searchlight mirrors being due to stray rays outside of the conical beam and to absorption in the mirror. The methods employed in the test of mirrors have been described in detail in past reports by this division. The intensity of illumination on a distant ob- ject, provided equal amounts of light to fall on the mirror, is de- pendent on the efficiency of the mirror and the angle of dispersion SB shown (that is, at a distance the area of illuminated plane). It will be noted that the results on the Beck mirror test show up poorer than the Schuckert or Bausch & Lomb mirrors of 36-inch size. Tlie source of illumination being the same and the diameter of the Beck mirror being greater and with a smaller angle of dispersion we should expect a greater foot candlepower illumination with this mirror. The results obtained show this mirror to be less effi- cient than the present ones in use and with a more efficient mirror still better results would have been obtained with the Beck light. The relation between the local lengtli and diameter of tlie mirror should be such that the angle (which is one-half the total zone of light falling on the mirror) should be such that 2 in- cludes the majority of light given off by the arc. By increasing the focal length the diameter of mirror remaining constant the ratio of the light falling on the mirror to the total given out b>- the arc is decreased, but also the angle of dispersion is decreased and therefore the correct focal length is that which changed in either direction decreases the foot candle illumination of a distant object. If we increase the diameter of the mirror at the same time as the focal length is increased the angle <* can be maintained constant and at tl)e same time the dispersion decreased, thus giving greater /fOCVS r ^~ r r r^ & ^ s li '^ ?5 K, "0 IT- :ai wi ff \>M. */<■ 0/. TA (VC c Vf> £ !2 Of Tn 'fA eci fr ^ -/ •>£. \/f(. HI C/i r "l TA ■£/ Ai fa ss TH 'i fA ■n , \T ? / y^ OL TA ViTj ^'\ c a? 'iO r7 I. sA W< HL OH T w> 'M vo »\ «» ■AL f/ y- V /■f y \ /. f" A f y \ 1 (/ 8 V \ y 7, 'J \ 1 \ V" y y .? 1 £ \i \ ^ / ^ •O '\ ' in \, ^ ^ ^f a ■/fi £i ^ K£ V . f'. V/6 vr 4 Psi \ N^ f 3 Ct/ 9\/. ■s W/ ■£/ •2 IVO V/C V7 %' \ f 4 A\/ f/a \C. "C '/A l/i. s Z 3 ' 'v _^ fiO' IO 20' o' eo' ■fO' 60 ANCi^e w MiNures turneo 7Z' ■»e ^■» 0' io ■*e' 7£' DISrAMCe in fCET 1 Fio. 29. intensity of illumination on a distant object. On board ship, however, the size of the searchlight and thus the diameter of the mirror is limited and service tests on 60-inch searchlights showed them to be unsuited. However, it is believed that the 44-inch searchlight (110 centimeters) is a size which can be readily handled and that the use of such a size is desirable to obtain a greater focal length is also of advantage in that it takes the arc farther from the mirror and thus decreases the chances of breakage of the mirror due to the heat of the arc. THE SEABCHUGHT. 45 11. The lamp mechanism of a searchlight should be such as to keep the crater of the positive carbon at the focus of the mirror, should keep the arc length that which is desired, should carry the current of the carbons, should contain mechanism for rotating at least the positive carbons, should be sufficiently rigid to keep the carbons in proper alignment, and should require little care and adjustment. 12. The lamp mechanism of the Beck lamp apparently meets all of the above requirements; the care required and its ability to stay in adjustment will be better determined by the tests now being carried out on the Texas. During the tests conducted at this yard the lamp mechanism functioned very satisfactorily, variation of the crater of the positive carbon from the focus was about 1 millimeter (hardly noticeable), and the arc length was kept practically constant. .\"o trouble in maintaining the arc was experienced while rotating both carbons, the crater of the positive carbon remained even and there was no noticeable hissing and jumping of the arc. On the other hand while the General Electric motor controlled lamp mechanism functioned success- fully maintaining practically a constant voltage, the arc length did not remain constant and the positive crater did not remain at the focus, due to the impracticability of constructing positive and negative carbons which will be consumed at a certain ratio. Also the positive crater tended to — [ — 1 — — — — — — "" *~ "^ ■^ """ "~ — — ~ "~ >: n 07 o 4 CB °a V£ >?- 0/t TA IVC. T (. Ut 'Vi. - — i Of m ^1 !6' CI V6 VA. ~^ 11 /^ ',a Hi AA ta m ^ — — — i TAt -£A t^At W ■S5 m Jf . m 9M A /"A 3 5// M 1-t — % ?f z\ 15C ■/ r — — — \ 5£ Rt W 'Oi fr Si '/?/ l/A o M '/?A lAi e 'J. ±L ^ — — ~ M — "^ ~ lj 1 I _ _ ' i "~ ^ 1 _J e _ — ~ j 7 z f/ 1— ." < / •? ta // Nl >A r ~ ^ s = ■=^ ^ ^ ~ ^ ^ s_ '3 z ATO m 7/1 r — — — — — ^ ^ ■< — T ¥ i — f ^0 TA/ SO ICA 'ffT % "X /£ 'a' o s 9 O' 6 6 7 O' 2' 4 O' g '0 4' L 'IG r a 0. o' a' o are the thermostat, the gi-ound-glass finder, the arc length regulator, and a peep- sight. The box is accessible to the operator in all positions of the searchlight from horizontal to vertical. 'llie ground-glass fintler is a simple and compact lens system which gives a full-size image of the arc, right side up, on a small square of ground glass. The proper positions of the two electrodes are marked on the ground glass, so that the operator can at all times determine whether tlio crater is in focus without watching the beam itself. lie may, fuithermore, watch the behavior of the arc image from which he can legulate negative and positive feetl and amperage. The negative regulator, or arc length regulator, is placed just below the finder. It consists of a small adjustable resistance connected in series with the solenoid of the voltage-control mechanism. Increasing the resistance with the series rheostat weakens the solenoid jjull and thus causes the arc length to increase until the arc voltage increases sufTiciently to re-establish the equi- librium of the pawl system. Decreasing the resistance causes a similar reduc- tion in arc voltage, and, consequently, in arc length. The positive feed is controlled by means of a theiinostat which is located in the instrument box. The operator, however, does not have to relj* on the automatic thermostat control, and in emergencies may use a push button which is mounted on the thermostat case, thus feeding the positive by hand. THERMOSTAT COXTROl. OF POSITIVE ELECTRODE. The function of the thermostat is to maintain the positive crater of the arc at the focus of the parabolic muror. While the arc is burning, the positive carbon is being rapidly consumed. This must be compensated for by feeding the carbon forward sufficiently to hold the crater in a fixed position. The thermostat accomplishes this by closing an electrical circuit when the crater has burned back out of focus. This ch-cuit energizes the thermostat magnets located in the control box of the searchlight lamp, which then causes the i)osi- tive electrode to feed forward as described under the positive feeding mechanism. The positive crater of the arc is in the center Ime of the drum. On the side of the drum opposite the mstrument box is a small concave miiTor of such a focal length as to concentrate the rays from the arc into a sharp nanow beam on the instrument side of the drum. Exactly opposite to this mirror is a narrow slit m the drum, behind which is located the sensitive clement of the theraiostat. The line joining the center of the mirror and the thermostat element is slighth* in front of the crater so that direct light from tlic crater will not fall on the thermostat strip. The function of the mirror is to focus the hght from the positive crater in a narrow strip. The radius of curvature of the niiiTor is such that the focus will be at the same distance from the minor as the thermostat element is. The operation is as follows: Wlien the positive crater is at the focus of the parabolic mirror, the position of the thermostat mirror is adjusted so that the strip of light falls on the theiTiio- stat element. As the crater burns back, the stri|) of reflected light naturally moves. As the thermostat is more than twice as far from the mirror as the positive crater, the strip of light moves more than twice as fast as the posi- THE SEARCHLIGHT. 55 tive burns away. This adds materially to the sensitiveness of the arrangement. As soon as the strip of light has moved off the sensitive element, the thermostat closes the controlling circuit which feeds the positive up until the light strip is agaia on the element. Then the circuit is reopened until the crater has again burned back. The coastruction of the thermostat is extremely simple. It consists essen- tially of two zinc strips as sensitive elements. One strip is -exposed so that it will be struck by the beam of light, while the other is protected from it. These strips are fixed at one end. The other end of each strip is attached to the short arm of a lever. At the extremity of the long lever arms are fixed platinum contacts. The zinc strips are held in tension by means of springs. Now when the light beam falls on the exposed zinc, the zinc is heated. It expands and the contactor arm is pulled back by the spring. The contacts are then separated. As the spot of light moves off the zinc, the zinc cools, contracts, and pulls the contactor arm over until the contacts meet and the circuit is closed. The motion of the zinc strip is considerably amplified by the l6ver an-angement, so that the thermostat is not only very sensitive, but the circuit is made and broken with comparative rapidity — a point to be desired. The object of the second zinc strip is to compensate for all temperature changes in the instrument box itself. If the temperature in the instrument box changes, both strips expand or contract equally, so that the action of the thermostat is not affected. The multiplying arms of the thermostat are counterbalanced by small adjustable weights at the top so that the instrument is not subject to vibration or jars. The tension in the exposed zinc strip is adjustable to the desired sensitiveness by means of a thumb lever screw projecting through the bottom of the case. The thermostat can be taken out of its case without any trouble, as.it is not necessary to open any electrical connections. To take it out, it is merely necessary to remove the sliding cover and loosen the set screw on the instrument. The current is brought to the thermostat by means of copper strips and springs which make contact when the instrument is in place. Thus the thermostat, which is by far the mogt sensitive part of the entire searchlight, is readily removed for inspection. The tension on the zinc strip can be ad- justed from the outside, as can the position of the thermostat mirror, so that the position of the positive crater can be regulated without opening anything. The thermostat contacts can be viewed through a small window containing a lens, so that their size is magnified. In this way the attendant can assure himself of the proper operation of the instrument. The contacts of the thermostat are shimted by means of a condenser and resistance, so that arcing is reduced to a minimum. Hence there is little ten- dency towards pyramiding or burning the contacts, and the sensitivity of the thermostat is not impaired. On the thermostat case is mounted a small push button, by means of which the control circuit may be closed independently of the thermostat, so that the positive may be fed by the attendant, if desired. However, after the thermostat is adjusted the lamp will operate automatically.. An ammeter is also mounted on the drum in a weatherproof box. This is so situated that the operator, standing at the instrument box, may easily read 56 THE SEARCHLIGHT. the ammeter scale. A waterproof switch is mounted near the instrument hex which controls the exhaust blower motor at the top of the drum. Two shutters arc furnished with each searchlight, an iris shutter and a Venetian-blind shutter. The iris shutter, which is entirely light-tight, is operated by means of a small handwheel at the side of the drum. The Venetian blind, or signaling shutter, is operated by a handle just above the iris shutter handwheel. The main switch is located in the front part of the lamp compartment, and is operated by a handle on the outside of the lamp compartment. All of these controls are on the same side of the drum, so that the operator at no time has to leave his post to p(nform any operation about the light. Two large doors, one on either side of the drum, afford easj' access to tiio interior for recarboning or cleaning the mirror. BEAM COLOR. The color of the beam of the Sperry high-power searchlight is an intense blue- white, whereas the beam of the low-power searchlight appears a dim yellow by comparison. This blue color is a very important advantage of the Sperry searchlight and has a great military value. As is well known, it is the universal practice of all navies to paint battleships and all other naval vessels a bluish- grav color called battleship gray. The reason for the adoption of this paint is to make the object as inconspicuous as possible by causing it to blend with the background. In the case of ships at sea where the background is blue sky, blue water, or gray mist, the most effective paint color for blending with this is bluish-gray and has been adopted generally as war paint. At night searchlights can pick this color out with more or less success, depending on the color of the beam. It is in this respect that the Sperry light is superior to low- power lights, for its beam contains largely«.just the hght which the blue-gray reflects. A gray ship illuminated with the high-power light glistens with a bluish hue, but with the ordinary yellow-beam searchlights the gray target only reflects a dull colorless light. -Vnother advantage in the blue color is the well-known fact that with very low intensities, such as obtain at the ultimate ranges of the searchlight, blue is the most visible color and can be seen at greater distances than the same intensity of red or yellow. THE SEAKCHLIGHT, Fig. 3S.— Sperry 3R-incli hinh-power searchlitiit. Names of parts. 1= 2 3^ 4^ 5= 6. 1- ,S= 9= 10. 11. 12 13 14= 15. 16- 17- Ventilator hood — housing for ventilator motor. Instrument box. Groimcl glass Qnder. Thermostat pu.sh button— hand feed of positive. Thermostat— automatic positive feed. Arc length regulator. Protecting hood over air inlet. .Vir inlet for coo'in? and ventilating. Mirror dome for protection of mirror. Elevation scale and pointer. Elevation rack. Elevation handwheel. Elevation-handwhee! locking clarap. Focussing screw handle for moving lanip in drum. Sliding door for access to lamp mechanism. Bottom door in lamp compartment for removing dirt. Snap switch for ventilating motor. IS= Baffled slot for air outlet from exhaust fan. 19= Removable Venetian blind shutter unit. 20"= Handle for Venetian blind shutter unit. 21= Handle for jront-door unit. 22= Small lamp container for illuminatin,g ammeter and elevation scales. 23= -Vmmeter seen through gla.ss protecting ttindo\\;. 24= Snap switch for dial-illuminatmg lamp. 25= Positive carbon tube — for protection of exposed end. 26= Handle tor operation of Venetian bimd shutter. 27= Handwheel for operation of iris shutter. 2S= Sliding door and handle for access to drum. 29= Clamp for holding shutter unit. 30= Main switch handle. 31= Snap smtch for lamp-illuminating azimuth scale. 32= Handhole cover in base. 58 THE SEARCHLIGHT. 1» Upper contact shoe— negative head. 2-Smallcup forciitclilng particles from the negative carbon. 3— Lever for pressing upper contact shoe against the carbon. 4— I^ever spring. 5— Spring for holding feed rollers against the carbon. 6— Steel food rollers . 7=» Carbon releasing toggle for spreading apart the feed rollers. 8>" 'joars connecting food shaft to food rollers. 9— Lower contact shoe rigidly mounted on supporting column. 10=- Negative feed rod extending from negative head to voltage control mechanism. 1 1= Supporting strip for negative column. 12- Carbon releasing shaft. 1.3= Negative supporting column of hollow tubing for carrying air to the head. 11— Tray for catching particles dropped from the arc. 15=« Spring and plunger to prevent turning of the nogatlvo head. 16= Counterbalance on the arm of the voltage control mechanism. 17— Rear guide for supporting lamp in drum. 18— Handle for hand operation of positive feeding mechanism. 19— Voltage control spring balancing solenoid pull. 20— Crank for hand feed of the negative electrode. 21— Upper pawl— voltage control mechanism. 22— Clamp for holding brass side plate on the lamp mechanism box. 23— Lower pawl— voltage control mechanism. 21— Tvvo opposed ratchet wheels into which the pawls mesh. 25= Reciprocating member carrying the four pawls. 26— Voltage control solenoid. 27= Reciprocating rod and joint— voltage control mechanism. 23— Centrifugal blower for air cooling of the electrode holders. 29= Motor for driving feeding mechanism and blower fan. 30= Thermostat magnets. 31= Thermostat magnet armature forllftlngfoed rod. 32= Eccentric for reciprocation of tho voltage control mechanism. 33— Worm gear case, reducing motor speed for rotation of positive carbon. 34— Main leads carrying current to the arc. 35— Connection from thermostat magnets to thermostat. 36— Voltage regulator connection from solenoid to variable resistance in tho Instrument box. 37= Front guide for supporting lamp iu drum. 38— Gear train from worm gear shaft to positive rotating shaft. 39= Handle for carrying lamp. 40= Block insulating positive head from the control box. 41-Casting for holding tho supporting stays. 42= Nut for tightening supporting stays and aligning tho heads. 43= Mica insulation on positive column. 44= Positive column supporting stays. 43= Positive column of hollow tubing for carrying air to the positive head. 46- Positive feed rod. 47— Main loads from positive column to silver contacts. 48— Rod for rotating positive carbon. 49— Spring for retaining food rod in tho "out" position. 50— Gear on rotating rod meshing with rotating member of positive head. 51— Point on feed rod raised to hit star wheel. 52— Roller bearing for rotating member of positive head. 53-CircuIar gear on rotating member of head. 54— Food wheels (star wheel not visible in cut). 55— Spring holding brass cap and quartz bushing in place. 56— Brass cap and vanes fitting over cooling chamber. 57— Quartz bushing. 3 2 / Zl 2^ 25 ?6 27 28 29 50 21 52 52. 54- FIG. 39.— SPERRY 36-INCH HIGH POWER SEARCHLIGHT LAMP. NAMES OF PARTS. THE SEABCHLIGHT. 59 The performance of the Sperry high-power searchhght may best be shown by the report of the test made on sample lamp supphed to the Navy Yard, New York. A copy of this report is given below. The searchlight used con- sisted of a low-power 36-inch drum modified to accommodate a Sperry high- power lamp. A searchlight of this type is known as a converted searchlight. Report of Test ok U. S. S. Maine — ^Modified Low-Power 36-inch Se.vrchlight to High Power by the Sperry Gyroscope Co. [JUNE 1, 1917] Tests have been conducted by this dudsion on a Na\'y standard 36-inch low-power searchlight, which was converted by the crew of the Mame to a 36-inch high-power searchlight, the necessary parts being supplied by the Spern,' Gyroscope Co. These tests were conducted to determine the Thermostat KJE.C3.FsLt.oRHC-> E.LtV. 5CAUt \J^M» dM*.t> ^vriT&H Fir,. 40. AvZ.\M\JTV-l 5cA.v.tUhMP ;>!.»*».» ;9WtT^H -Sperr.v 3fi-inoh 'ni;h-nower searchlight 'hand control). Wiring diagram. desirability of placing orders for parts to cover the conversion of a large number of these old lamps and to determine the characteristics, operation, and quality of workmanship performed. DESCRIPTION. (a) The searchlight consists of an old type Xa\-y standard 36-inch searchlight made by the C4eneral Electiic Co., which was part of the equipment of the Maim. The lamp and ventilating hood were removed from this drum and a new ventilating hood, containing a blower, was placed on the drum. Ventilating ducts were supplied and installed on the inside of the drum. These carry the draft from the old ventilating outlets in the base of the drum up to the top of the drum near the ventilating blower. A new lamp housing was supplied, the old housing removed, and the new housing installed in its place. A metal box containing ammeter, thermostat, negative feed- ing rheostat, and finder was also supplied. The drum was pierced for the finder and thermostat and the box mounted on the drum. A mirror for focusing the crater image onto the thermostat strips was furnished and mounted within the drum. The tracks used for holding the old lamp in place were altered to fit the new lamp. 60 THE SEARCHLIGHT. (5) The lamp consists of the standard Sperry mechanism, being of the indirect air-cooled type and similar in every way to that described in machinery division test report Xo. 202, with the exception that the diameter of the positive carbon is J in.stead of J inch, and the operating mechanism is designed for 120 amperes instead of 150 amperes. (c) The front door was altered, having a hole cut in the glaas and a carbon-holder tube mounted out in front for retaining the positive carbon. TESTS. (al Testa were conducted on the lamp to determine the operation, carbon consumption, temperatures, etc., and data taken for the various candlepower determinations and spectrum analysis of the arc and beam. Kl'J. 42. RESULTS. (o) Operation. — The lamp was burned continuously for a period of seven hours and operated perfectly for this period, gi\-ing no trouble and requiring no attention from the operator. (6) Temperature. — Temperature readings were taken on the various parts of the dru.m with the lamp operating under normal conditions. The shutter was then closed for a period of two minutes, at the end of which time temperatures were noted and found as follows: Shutter. Exhaust. Drum sides. Mirror. Room. Shutter. Open 'C. M.5 58.2 •c. 55.0 58.8 'C. 51 57 •c. 28 28 °C. 55.9 THE SEARCHLIGHt. (c) Carbons. — The carbon details for this lamp are as follows: 61 Diameter. Length. Positive.. Negative. MiUimrter. 13 11 India. 36 13 (d) Carbon consumption. — The carbon consumption is about 4 parts of positive to 1 part of negative by length, a trim lasting about 2} hours. Fig. 4.3. («) Candkpower. — The lamp was removed from the drum and readings taken of the total hori- zontal candlepower through an angle of 180°, the results of which are shown in figure 42. (/) Readings were then taken to determine the crater intensity, which was found to be a maximum at 20° (fig. 4.3). The maximum ratio of crater light to total light, however, figures out at 10° and is 73 per cent at this angle and shows 56.5 per cent of the total at the standard 40° angle. The crater and carbon tips comprising the light source within a sphere of a diameter equal to the positive crater diameter shows 79 per cent of the total light at 0° angle and 60.4 per cent of the total light at 40° angle. The results of the above are shown in figures 42, 43, and 44. (g) Intrinsic brilliancy. — The average intrinsic brilliancy of the crater of the positive carbon is equal to the area of the positive crater divided into the mean spherical candlepower of the crater, 62 THE SEABCHLIGHT. which is found from curve 4, inclosure (C), to be 25,000 candlepower. The diameter i>f tlie crator is 10 milliineters. c^\-ing an area of 78.54 square millimeters, which gives- - (M. S. C. P.)<: 25.500 .,.. ,, .... , T ' = .r^-rz=^-'^ candlepower per square iiiilhuieter as the average intrinsic brilliancy of the crater only. (A) Current density. — The current density of the crater only is equal to the total amporo ciir- I 120 rent divided by the area of the crater, which is t" = 70^ = 1-53 amperes per square millimetor as an average current density for the crater. FlQ. 44. (i) Total light on mirror. — The light useful on the mirror expressed in lumins, is equal to the S3lid angle subtended by the mirror, multiplied by the M. S. C. P. of the useful light source The M. S. C. P. is found from figure 4f> to be .S5,500 candlepower which gives Lumins on mirror 2 7r(l-Co8l)X38.500 Lumins on mirror 6.28X0.5f>5X3S.500=137,00O. (j) Efficiency 0/ mirror ani front door. — The average efficiency of the mirror and glass door of the searchlight is about 60 per cent. (t) Lumins in beam outside front of glass. — The total light in the beam just outside the front door is the total lumins on miiTor multiplied by the efficiency of mirror and front door which gives 137,000X0.00=90,500. This total value covers an area equal to the area of front door, which when divided by this area gives^ Lumins 90,500 ,„ _„ A = 7.08 =12,760 lumins per square foot at the front door of the searchlight. THE SEAECHLIGHT. 63 (J) Range. — Considering for Xew York and vicinity an atmospheric absorption of 10 per cent per 3,000 feet for average weather conditions, this gives an illuminant of 81, .500 lumins total on the target at about 3,000 feet. The dispersion of the beam of this light is about 54 each side of the horizontal, giving a total dispersion of 1° 48", which gives a diameter of 100 feet at 3,000 feet from the hght. This gives an area of about 7,850 square feet, gi\lng an average illumination of 10.4 lumins per square foot at 3,000 feet. This figures about 20 lumins per square foot, at 2,400 feet. This checks very closely mth the average illumination on a target 2,400 feet away, using the 150. ampere high-power arc. There is a difference, however, as the 150-ampere arc has a greater dis- persion, thus giving a larger illuminated area at the same distance from the Ught. The effective range of this Ught should therefore be very nearly the same as the 150-ampere searchlights of the same manufacturer, but the area covered by the beam will be less. {m) Color characteristics.— From curves the following distribution of the visible spectrum has been determined: Color. Wave length in micron.s. Per cent in arc. Per cent in beam. Violet and blue tJp to 0.502 0. .502 to .560 ..560 to .592 .59210 .614 .614 to .660 5.1 .15.3 27.0 16.85 15.75 .5.37 42.6 28.2 14.0 9.83 Yellow . Ro.1 The above results show nearly the same characteristics of beam color and arc spectrum dis- tortion as the loO-ampere 36-inch lamp. This arc shows a slightly lower transmission efficiency than the 150-ampere lamp, due probably to a large quantity of red Ught which appears in the arc spectrum, and to the transmission of which the mirror and front door are not very efficient. CO.VCLUSION-. (a) The workmanship on the present converted Ught, although crude, is effective, as the Ught operates properly and steadily. (6) .'Vs compared with the old type of Ught, this remodeled Ught is superior in every way. As compared with the regular 150-ampere high-power Ught, this Ught is sUghtly less effective, o\ving to the smaller area covered by the beam. (c) It is considered that the change of all low-power Ughts can be accompUshed by the ships personnel in the same way as the present conversion was accompUshed, pro\'ided that manufac- turers be required to furnish a complete and detailed instruction sheet, explaining thoroughlj' all the operation, instaUation, and adjustment features of all parts of the searchUght. THE 75-AMPERE .4RC FOR 24.INCH fflGH-INTENSITY SEARCHLIGHTS. In providing a high-intensity arc for use in searchlights of sizes smaller than the 36-inch searchlight, it has been found necessary to develop a high- intensity arc of lower amperage. The behavior of the high-intensity arc changes radically vrith changes in amperage. For instance, it has been foimd that it is practically impossible to obtaia the high-intensity arc phenomena at any current below 65 amperes. This places a limit to the extent to which the arc may be reduced in cur- rent consimiption. At the same time, however, many other characteristics of the arc change at this lower limit of usefulness, which make it necessary to rearrange the electrodes and change the normal burning conditions. The accompanying diagram (fig. 47) of the 75-ampere arc shows the many points of difference between it and the 150-ampero arc. It will be noticed that the arc length is extremely short, the normal length being only about 64 THE SEARCHLIGHT. " ^ r i r g'y- j^ i , : 5 09 ? 09 '-litiiff//hy. 1 ~ 1 = 11 1 j ^miM ~ m p= — = — — 1 — — V — — ^ <>i 1 f^ 'n ^ ^ :5 VJ (V; 1 / Jo'Htwi' -■.. \i v-tv-v-T-v-rn J s t* I's y i / ^r- \ \> \-\-Si-V-^'T^ ^ 1 M - <— — — m h — — "0>r \^P F — ' — — m -^ E = - in -« — -it -_ > \1 ,7 'i!*; 'f' f* o ;• .- .1 / 7 '< T n. ^ «; 1,* ^ 1=^ X^ -ii-i-£ '■ 'iSi - t; g OP ^^ ^4- /' '^ > - -4 — — , — — ■ — -A I^ =r zz — _ „ ___ — — zz ? "' i 1 1 : - — 1 1 i s 1 09 " "^ ^ --^-n\P(\>^ 1 1 I 1 C9 « (>• 1 i- - :^ 09 '■i 1 1 ^ ^* St 1 rJ^ — i—- n .^ H zz: IZ ? 09 Si 8 ^ a k -\ — -V — — — b V) „s^ rill .11 V ^ g '^ K |>;)>. . . . .^^mff a S f ^ s ,5 A^-.-'t V^v \ ■ \ ' \ -" ::--rV- — -c^ — — ^vM^^^" i.rEi: UJ. -^ ■ ' UJ o O 2 n s ^ 8 » S S 09 o 0? -1 >J ^ $ 1 III / •h I? y >^ FIG. 48.- SPERRY 24-INCH HIGH POWER SEARCHLIGHT. RIGHT SIDE. 90° ELEVATION. THE SEARCHLIGHT. 65 one-fourth inch. The negative electrode, however, is tilted at an angle of 45° to the positive and the tip burns slightly below the positive crater, so that even with the short arc the negative casts practically no shadow on the mirror. The reason for the short arc and steep angle of the negative is that the negative arc flame at 75 amperes does not have the same velocity and force that is characteristic of the 150-ampere arc. Consequently, a long arc at 75 amperes is very unsteady and flickers badly. The negative electrode is, therefore, tipped at a steep angle, which causes the arc flame to issue from it vertically. As is well kno^vn, a vertical arc flame is much steadier than a horizontal arc. The positive carbon is, however, Appearance of Arc 75 Amperej ^5 Volts Carhror) Cox mounted on the right- hand side of the barrel. This is fully described under thermostat and arc image sj-stem. All geare are inclosed with covers to prevent injury to operator, and oil holes are provided as described under oihng. The signaUng shutter is of the venetian-blind type and is operated by a handle on tlie side and returned to the closed position by a spring. The shutter may be removed by unscrewing the bolt with handle located at bottom of the shutter and lifting up. A sighting tube is mounted on the right-hand side of the barrel above the thermostat box, and consists of a brass tube with small sighting hole in one end and cross wires in the other end. The ventilator is made of sheet brass and, while light-tight, provides an exit for the air and gases from the barrel. The lamp trough is bolted to the bottom machined surfaces of the front and rear rings and supports the lamp. Bolted to the trough is the fan hous- ing, which contains a fan driven by a motor. The motor is secured in the motor compartment, which is mounted on the rod between the front and rear rings. The fan rotates in the fan housing and delivers air to the barrel, and through the air connection to the lamp, as described under "Air circulation." THE SEAKCHUGHT. 71 Fig. 60.— G. E. 24-iiich higli-po er searclUight. Front view. 72 "FHE SEAHCHLIOHT. Tliis nir connection may be disconnected, when changing the lamp, by pulUng out knurlocf knob and giving it a quarter turn. On the end of the motor sliaf t opposite the fan, a worm and gear, inclosed in gear box, drives through a universal joint, a coupUng which is connected to the lamp and which drives the lamp mechanism. On the outer end of this driving shaft is a handle with latch which releases the motor drive and allows tlie driving shaft to bo rotated by hand. There are two coTmection plugs, one for the main-hne circuit to the lamp and the other for the wires connecting the thermostat to the lamp. These arc arranged so that it is impossible to insert the plugs except in the correct posi- tion. The cables arc brought into the plugs through stuffing tubes. Inside the barrel is a niirror guard, which swings under the arc in all positions of the barrel and protects the mirror from hot particles that may fall from the carbons. This guard is insulated from the barrel. An incandescent carboning lamp is provided on the inside of the barrel. Hush with tlie inner sheet, to provide illumination of the barrel when install- ing new carbons in the lamp or making any adjustments. The iris shutter is operated by a handle and when closed shuts oil all liirht. The shutter is mounted in the same frame as the front door and may be removed with the door by pressing down on latch above the right-hand handle and rotating the shutter ring counterclockwise about 5°. The front door glass strips may bo removed separately, being held in place by retaining strips. The front door is provided with reinforcing strips to prevent injury due to gunfire. A carbon tube with liinged cover provides an entrance for the positive carbon. The focusing screw at rear of lamp trough permits the adjustment of lamp in focus as described under " opek.\tio\." VENTILATION SYSTEM. (See fig. 64.1 The barrel has imier and outer sheets, the lower quadrants on either side of the lamp trough being closed at the top by the inner sheet joining the outer. Air from the fan housing enters between the inner and outer sheets at the front of the barrel. On the right-hand side the air passes between the two sheets, part entering the air connection to the lamp and the remainder pass- ing through small openings in the rear ring to a recess in the mirror frame, which runs on each side approximately 100° from the bottom vertical center line. On the left side the air passes between the inner and outer sheets and through large holes in the rear ring to the same recess in the mirror frame. Slotted air passages connect this recess to the front of the mirror frame and a part of the air flows through these slots and over the face of the mirror, cooling it and preventing the deposit of the combustion products of the car- bons on the mirror. This air is then exhausted through the top ventilator. The remainder of the air flows over the back of the mirror into a recess in the -upper portion of the min-or frame, from which it passes through openings in the upper part of the rear ring to the upper quadrants of the space between the inner and outer sheets of the barrel. The air then flows do\vnward to the center of the barrel and out t»hrough openings between the inner and outer HG. 62.— UNDER SIDE OF BASE FfcOJECIOR. THE BEAKCHLIGHT. 73 sheets on each side to the interior of the barrel, where it is exhausted through the top ventilator. .UlC-IMAGE AND THERMOSTAT SYSTEM. (See fig. 63.) ARC-IMAGE SYSTEM. In the arc-image system light rays from the arc at A are passed through the lenses E, F, and G and reflected on the frosted-glass screen H, which is located on the right-hand side of the barrel toward the rear. ARRANGEMENT or THERMOSTAT ARC image: system. To POilTlve rccp MAGAfer Fig. 6.f. A fuU-size upright image of the arc is produced on the screen H and a black line marked on the glass indicates the correct position for the end of the positive carbon when it is at the focal point of the searchhght mirror. The three lenses E, F, and G are moimted in a lens holder and form a unit known as the lens tube. Over the frosted-glass screen H is a swinging cover which can-ies a dark ruby glass to reduce the intensity of the image of the screen H when operating the searchligiit at night. THERMOSTAT SYSTEM. Light and heat rays from the arc at A pass through the lens B and fall upon the mirror C, where they are reflected and converged on the plane of the thermostat strips D-1 and D-2. 74 THE SEARCHLIGHT. When the end of the positive carbon is in the exact focus of the mirror the spot at which the light and heat rays are concentrated is just off the ther- mostat strip D-1. As the carbon burns away this spot moves onto the thermostat strip D-1, causing it to operate and move the contact lever D-3 into contact with D-5. This closes the circuit to the positive feeding magnet. The thermostat strip D-2, contact lever D-4, and contact D-6 are au.xili- arics and are called into operation onlj' upon failure of D-1, D-,3, and D-5 to operate. A switch D-7 permits the thermostat control of the positive feed to' be cut out. The handle of this switch extends th.rough the thermostat ])ox and is operated from the outside, there being off and on indications on the ther- mostat box. The adjustments of the thermostat arc carefully made at the factory and sliould not be disturbed unless there has been some mechanical injury of the thermostat. Flo. 64.— Ventilation diagram of G. E. 24-inch high-pov cr searchlight. CONNECTIONS. DESCRIPTION OF CmCUITS. [Sec fig. Go.] Main lamp circuit. — ^Thc generator is connected to the switch in the base, the positive line being connected to the rheostat so that the current passes througli the rheostat. From the switch in the base, the circuit runs tlirough the contact rings, to the contact plungers, to the switch on the barrel, to the connection i>lug, to the receptacle in lamp, to the carbons, the positive side passing through the striking magnet. The azimuth scale lamp circuit is connected to the contact rings. The altitude scale lamp circuit is conne -ted to the contact plungers. The carboning lamp and ventilating motor circuits are connected to the switch on the barrel through the fuses. One side of the thermostat circuit is connected to the positive main lamp receptacle, and passes through the positive feeding magnet to the thermostat FIG. 65.— LAMP. G. E. 24' H. ?. SEARCHLIGHT THE SEAECHLIGHT. 75 receptacle. The plug which enters this receptacle is connected by one of the conductors of twin conductor cable to one contact on the thermostat. The other contact is connected through the switch in the thermostat box and through the other twin conductor cable to the plug and from the plug to recepta- "^^^'5 ^^^^=^^1 a 8 .1 5 cle in lamp. This receptacle is connected to the negative main lamp receptacle. The common point of the negative feeding clutch coils is connected through the clutch switch to the negative main lamp receptacle. The other ends of the coils are connected through tiie contact points on the relay to the positive side of the circuit at the striking magnet. 76 THE SEARCHLIGHT. OnjNO. Bowen oilers are provided as follows: Four on top of turnta1)lo for oiling the tread rollers. One in the ])racket for pinion mesbing with the turntable, oiling the shaft to the universal coupling. One on gear cover at center of turntable for oiling center pin. TNvo on bearing on turntable for oiling vertical traming shaft. One on bearing on arm for oiling vertical training shaft. One on arm, behind scale lamp, for oiling shaft driving vertical training pinion. One on top of each arm for oiling trunnion pin. Grease cup is placed on end of gear casing on motor compartment for lubricating worm and gear. Two oil tubes leading to the motor bearings are directly under plugs (one largo and one small) on the u])pcr side of the motor compartment. It is necessary to remove these plugs in oihng the motor. The large gear on turntable and the vertical training rack should occasion- ally be lightly coated with vaseline. LAMP. Rating. — The lamp operates at 7.5 amperes and approximately 60 volts at the arc, the difTereiice between the line and arc voltage being absorbed in the supply leads and the rheostat which is in series with the arc. The voltage rating is given appro.Kimately, as the lamp is controlled by a cun-ent relay described later and which tends to maintain a constant current arc. Carbons. — The positive carbon is 11 millimeters (approximately -^ inch) diameter, 24 inches long. The negative is 11 millimeters diameter, 8 J inches long. The positive carbon has a soft core and bums with a deep crater. The nccative carbon has a small core of harder material than the core of the positive carbon. Copfcr-plated carbons should not he used in this lamp. Cai-boning. — Insert the positive carbon so that it projects i inch from the end of the positive carbon nose. The negative carbon should then be inserted to project about J inch from the end of the negative nose. It is not necessary that the negative carbon touch the positive in carboning the lamp. General features. — The ventilating motor, in addition to rotating the fan, drives the lamp mechanism as described above. The positive carbon is rotated and fed toward the mirror. The negative carbon does not rotate but is fed forward and back to maintain essentially a constant current at the arc. When the lamp is not burning, the negative carbon is held against the po3itive by a spring attached to the arm carrying the negative head. ^Vhen the switch is closed, current passes through the starting magnet, which draws the arc down, separating the carbons and establishing the arc. A relay contact arm, attached to one of the yokes of the startmg magnet, as shown on figure 66, operates on leakage flux, and floats between two contacts when the arc current is normal. On an excess arc current the arm makes ill FIG. 67.-LAMP. G. E. 24" H. P. SEARCHLIGHT. FIG. 69— NEGATIVE HEAD G. E. 24" H. P. SEARCHLIGHT. wnub uuuuw ^ '.^m^i^tm 1 r: 0~ t^ ¥ FIG. 71, POSITIVE ROTATING MECHANISM. G. E. 24" H. P. SEARCHLIGHT. THE SEAECHLIGHT. 77 contact with the lowei" contact to one of the negative feed clutch coils, energizing the coU and throwing the clutch into the feed apart position. This moves the negative carbon away from the current to normal, when the relay arm will again float between the two contacts, opening the circuit to the clutch magnet and releasmg the backward feed. If the current is below normal, due to bm-ning away of the carbons, the relay contact arm makes contact with the upper contact, closmg the circuit to the upper contact which is connected to the other negative feed clutch coil. This thi-ows the clutch into the feed-together position and feeds the negative carbon ahead imtil the arc current rises to normal and the relay contact arm again floats. In this connection note that when no current is passing through the starting magnet and carbons, the relay contact arm is against the upper contact in the feed-together position so that when the main switch is closed the negative carbon will feed ahead imtil it touches the positive carbon. The positive carbon is fed in one direction only, toward the mirror, the feeding being regulated by the thermostat, as described xmder the arc image and thermostat system. Levei-s on the rear end of the lamp frame have dial plates marked "A" at the bottom of each plate. This indicates the position of the lever for auto- matic feed. Graduations on these dials mark the position of the levers for hand feed. Moving the lever up the scale increases the rate of feed. The automatic positive feed is cut out by opening the switch on the ther- mostat box. Moving the negative feed lever to the hand feed positions opens a switch to the negative feed clutch coils. The searchlight lamp is shown in figures 66, 67, and 68, and consists essentially of means for supporting positive and negative carbons at the center of the barrel, and mechanism for feeding the carbons in the proper ratio. The positive carbon is rotated to prevent mieven burning of the carbon caused by the rising arc stream. The rotating mechanism is showTi assembled in figure 71 and the parts in figure 72. The carbon is held between two toothed rollers of hardened steel with wide grooves cut in their faces to insure a grip on the carbons for rotating. The roUers are pinned to shafts which have spur gears fastened to the end. These gears engage with one another. A worm gear is pinned to the end of one shaft and is driven by a worm on a shaft par- allel to the axis of the carbon. There is a star wheel fastened to the shaft which engages with a pin on the feeding rod. This star wheel rotates, with the feeding gears and rollers, about the axis of the carbon and during each revo- lution is advanced by coming into contact with the pin on the end of the feeding rod if the rod is in the feed position. Advancing, the star wheel rotates the geai-s and rollers, feeding the carbon ahead. All of the positive rollers, gears, and shafts are moimted in two bearing arms which are pivoted on the shell sliowoi in the lower left-hand corner of figure 72, and are pressed against the carbon by two "U " springs. The shell is rotated on the outer tube by means of the bevel gear on the shell and bevel pinion rotating in the end bearing driven by the positive rotating shaft. This outer tube is clamped in the end bearing by means of a hexagon nut. Inside 78 THE SEAECHUGHT. of the outer tube is the inner tube, which can be pushed forward by means of the lever shown in tlie lo\ver riglU-hand corner of fiojure 72, Hfting the rollers from the carbon by forcing; apart the bearing arms. The end bearing is fastened to one end of the cage shown in figure 72, and the other end is screwed to the casing, being insulated from it. The casing incloses the radiator, which has a slot in the top for the silver contact. The contact is pressed against the carbon by a spring acting on the contact lever pivoted on the shell. The contact is lifted by pressing down the handle on lever at rear. This also spreads the rollers as described above. On the front of the casing is mounted the obdurator, which holds in place the positive nose. The obdurator prevents direct light from the arc passing througli the front door and also acts as a heat shield for the rotating mechanism. The casing has an opening in the bottom, allowing air to pass over the vanes of the radiator and through the rectangular oi)cning in the top, to be exhausted i)y the ventilator in the barrel. The casing is secured to and insidated from tlic support shown in hgure 74, which is hollow, to give passage to the air. The negative head is shown assembled in figure 69 and the parts in figure 70. The carbon is held between toothed rollers of hardened steel, pinned to shafts which have worm gears fastened to one end. On the other end are fas- tened smooth-faced rollers. Meshing with the worm gears are a right and left hand worm, driven by the negative feeding shaft through a universal coupling. The rollers, gears, and shafts are mounted on bearing arms, pivoted on the negative head casting, and the rollers are held against the carbon by means of compression spring at the rear end. The negative nose is held in place by a punching which is screwed to the body casting. The radiator supports the bottonr silver contact and is screwed to the bodj' casting. The upper silver contact is held against the carbon by the contact lever pressed by a spring at the extreme roar end. The lever is lifted by means of a cam on the lever with two handles, and it also forces the tapered pin between the smooth rollers on the roller shafts, forcing the feeding rollers apart to allow entrance of the carbon. The body casting of the negative head is hinged to the lever arm sho\vn in figure 74, and is held in the running position by a latch on the same lever which opens the rollers. The lever arm is hinged to the carbon head support and is held in the starting position b}' a compression spring. When the carbons touch after the main lamj) circuit is closed, the starting rod attached to the striking-magnet armature pulls the lever arm to the running position. The carbon-head support passes over a foot, which is insulated from the top plate of the lamp casing, and is held in position by nuts on four studs. These nuts are raised or lowered on the studs to adjust the heads to the proper position in the barrel. An opening is provided in the foot which communicates with the air inlet inside of top plate of lamp casing. One handle for Ufting is pro- vided on each end of the lamp and winged screws, passing through holes in the clamps, secure the lamp in the lamp trough. The lamp frame is composed of the top, bottom, and end plates and sliding side plates. The frame incloses the negative feeding clutch, striking magnet, positive feeding magnet, and connection plugs. The negative feeding clutch, figures 77 and 78, operates the negative feeding rod. FIG. 72. -PARTS OF POSITIVE ROTATING MECHANISM. G. E. 24" H. P. SEARCHLIGHT. -^^ v^o^ ft db FIG. 73. -PARTS OF CASING FOR POSITIVE HEAD. G. E. 24" H. P. SEARCHLIGHT. FIG. 74. -CARBON HEAD SUPPORTS AND FEEDING RODS. G. E. 24" H. P. SEARCHLIGHT. FIG. 75, TOP PLATE WITH GEARING. G. E. 24" H. P. SEARCHLIGHT. FIG. 76.— PARTS OF TOP PLATE AND GEARING. G. E. 24" H. P. SEARCHLIGHT. FIG. 77. NEGATIVE FEEDING CLUTCH. G. E. 24" H, P. SEARCHLIGHT FIG. 78.— NEGATIVE FEEDING CLUTCH. G. E. 24" H. P. SEARCHLIGHT. THE SEABCHUGHT. 79 (1) In the "A" or automatic position of the negative control lever on the rear end of the lamp the negative carbon is fed forward or back b}- a rotating rod geared to the feed rollers. At the lower end of tliis feed rod is the negative feed clutch, with magnets energized by the relay. When the relay contact floats and neither clutch coil is energized, the feed rod is stationary. It is rotated to feed the carbon ahead by energizing one of the clutch coils, and to feed the carbon back bj^ energizing the other clutch coil. (2) In any of the hand-feed positions of the negative control lever the carbon is moved forward by means of worm and gear driven by the main driv- ing shaft of the lamp, operated by the handle on gear casing on motor compart- ment. When in the hand-feed position, the cam on the contact shaft opens the switch in the clutch-coil circuit. The striking magnet armature, figure 80, operates the negative lever arm through a lever and rod. The full cm-rent taken by the arc passes through the coil. A relay is mounted on one pole of the magnet, and the contact arm is held in a mid-position between two contact points when the current of the arc is of the proper value. The positive feeding magnet armature, figure S2, operates the positive feeding rod, which engages with the star wheel on the rotating mechanism of the positive head. The coil is connected to the main lamp circuit through the thermostat. The connection plugs are mounted on the end plate, as shown in figure 84. OPERATION. PLACING CARBONS IN LAMP. Release rollers in positive carbon head by pressing down the handle at rear of head untU it catches, and insert positive carbon through the carbon tube in the front door, pushing it through the head until it projects i inch past the extreme end of the nose. Push up handle so that rollers close. Release rollers in negative head by raising the handle at rear on negative carbon head to the extreme position which allows the head to swing into a position which \vill allow the carbon to pass the obdurator on the positive head. Insert the negative carbon through the negative nose letting the pointed end project i inch past the end of the nose. Push the head back to r unnin g position and turn handle down to close rollers. STARTING. (a) Turn handle of switch in base to the "on" position. This lights the altitude and azimuth scale lamps and the rccarboning lamp in barrel, and starts the ventilating motor. (b) Turn handle of switch on barrel to the "on" position. This closes the circuit through the carbons and the striking magnet coils, thereby establishing the arc. The positive feeding magnet and negative feeding clutch are now in circuit. Switch lever on thermostat box should be placed at " on " position, putting the thermostat in circuit. 80 THE 6EABCHLI0HT. RUNNING. The end of the positive carbon shoiild show on the line on the arc image screen. The control levers on the end plate should be placed at the position marked "A." STOPPING. Turn handle of switch on baiTcl to the "off" position, which breaks the cir- cuit through the carbons, but allows the ventilating motor to run. Turn handle of switch in base to the "off" position, which stops the venti- lating motor and shuts off the scale lamps and the recarbouing lamp in baiTel. FIG. 79— PARTS OF NEGATIVE FEEDING CLUTCH. G, E. 24" H. P. SEARCHLIGHT FIG. 80.— STRIKING MAGNET FOR G. E. 24" H. P. SEARCHLIGHT. I o _l I o cr < FIG. 82. -POSITIVE FEEDING MAGNET. G. E. 24" H. P. SEARCH- LIGHT. FIG. 83.— PARTS OF POSITIVE FEEDING MAGNET. G. E. 24" H. P. SEARCH- LIGHT. dBn--^ ■M m ^9 £ !^^^^^ t^ ^^^-^T'M J^JMj Br 9H < w ^^^^W"^*''*^^ k^^R^ FIG. 84.— CONTROL END PLATE AND CONNECTION PLUG. G. E. 24" H. P. SEARCHLIGHT. t_J FIG. 85.— G. E. 24-INCH HIGH POWER SEARCHLIGHT. PARTS OF CONNECTION PLUGS. FIG. 86.— PARTS OF FRAME. G. E. 24" H. P. SEARCHLIGHT. CHAPTER 6. ARMA 24-INCH HIGH-POWER SEARCHLIGHT. There has very recently been developed by the Arma Engineering Co. a new type of high-power searchlight for naval use. This lamp was de- veloped particularly for converting present 30-mch low-power searclilights to high-power, and also for making a complete 24-inch high-power searchlight with a drum mounted on a base. Past experience was used to advantage in designing this light and it has been constructed to meet the severe conditions of gunfire shock, spra}', and rough handling to which Navy searchlights are subjected. Simplicity has been empha- sized in the design so that an operator may disregard the operation of his lamp and concern himseK solely with keeping it trained on the target. The great difference between this searchlight and other high-power searchlights is in the method of keeping the positive carbon in focus. This is done by means of a third electrode and uses the arc flame as a conductor, thus doing away with thermostats, mirrors, prisms, etc. Following is a general description of this searchlight: POS. r-£EO A/t/7-.i9 SS-02 The positive-carbon holder will be mounted in a horizontal position and the negative-carbon holder may also be horizontal, orplaf~e:lat an angle with the horizontal center line of the positive- carbon hoUFer so as to give the best burning condition of the carbon and maximum intensity of light flux on miri-or. The lamp will be as light and compact as practicable, consistent with strength. The connections inside the lamp mechanism will be firmly secured in place, and the entire lamp mechanism will withstand a dielectric test of 1,500 volts A. C. applied for one minute. (k) Shullcrs. — .MI shutters will be made of light non-corrosive material. A suitable hand- wheel for operating the iris shutter through gears will be located on the side of the frum, where it is easily accessible for the operator. The Venetian blind shutter will be operated by a handle located on the side. All searchlights will be supplied with iris shutters and Venetian blind shutters. (l) Rheoslal. — The rheostat will be of the unit typo, and must be sufficiently inclosed for pro- tection against injury, and at the same time allow effective ventilation. A suitable insulated board containing resistance contacts and rheostat handle will be mounted on the rheostat. The rheostat will consist of two sections, a variable and fixed resistance. The variable resistance will be divided into at least 10 steps, each step giving when hot approximately a drop of 1 volt when the normal current of the searchlight flows through them. The elements will be thoroughly protected against corrosion in such a manner as not to give off objectionable smoke, and securely fastened in the supporting frame at a sufficient number of points to prevent damage from shocks, and the method of mounting will permit a ready connection of the leads and removal of grids for repairs. A pan will be installed underneath to catch any molten metal or displaced pieces, should the elements become melted or broken at any point. The total resistance from cold to hot shall not exceed 12 per cent of cold resistance. Connections between rear panel and resistance unit will be made with commercial fireproof wire. The temperature rise on frame will not exceed 125° C. The rheostat will withstand an overload of 50 per cent in amperes for a period of 10 min- utes continuously without damage. (m) Carbons. — The carbons will be of the 1 to 1 ratio type, and in strict accordance with Specifications 17C5, latest issue, copies of which may be obtained upon application to the Bureau of Steam Engineering. THE SEARCHLIGHT. 93 4. Types of control. (n) Distant mechanical, type A. — The controller will consist of two separate composition gear boxes, in accordance with Bureau of Steam Enginoeting plan 19S2S32L. Copies of this plan can bo obtained upon application to the Bureau of Steam Engineering, Navy Department, Washington, D. C. (o) Distant mechanical, type B. — The controller will consist of one composition gear box and handwheels, mounted on composition pedestal, and connected by concentrated pipe shafts to searchlight. The searchlight will be controlled by three handwheels mounted on gear box, and connected to shafts. Two handwheels on opposite sides of box will control the angle of train, and the third handwheel will control the angle of elevation and depression. Illuminated dials will be installed in gear box to indicate the number of degrees elevation or depression, and also the angle of train. Means will be provided for disengaging the mechanical control and operating the searchlight by handwheels located thereon. (p) Distant mechanical, typo C. — The controller will consist of gear box, handwheels for con- trol, illuminated dials, and means for disengaging from searchlight, as spocilied under (o), but designed to mount in a single searchlight trestlcwork tower, with handwheels mounted outside of tower sides, and connected to gear box by shafting. (q) Distant mechanical, type D. — The controller will consist of gear box, illuminated dials, and moans for disengaging from searchlight as specified under (o), but designed to mount in a double searchlight trestlework tower with two handwheels, one for control of elevation and de- pression, and one for control of angle of train, mounted outside of tower sides and connected to gear box by shafting. (r) Distant electrical. — The distant electrical controller ^rill consist of two separate composition boxes, mounted on composition pedestals; the design of the electrical controller will be such as to move the searchlight without jerk. The controller will be capable of training the searchlight at a minimum speed of 3° per minute, and a maximum speed of 3G0° per minute. It will also be capable of elevating or depressing the searchlight at minimum speed of 3° per minute, and a maximum speed of 180° per minute. One controller will control elevation and depression, and one vnW control the angle of train. The controller will be as light in weight as possible without sacrificing strength and satisfactory operation. Means mil be provided for disengaging the electrical control and operating searchlight by hand. 5. Material. — All working parts, interior bolts, nuts, pins, screws, springs, brush holders, and studs will be noncorrodible material thoroughly shearadized, heavily copper plated, or other- wise thoroughly coated to prevent corrosion, 6. Insulation. — All insulation shall be of approved insulating material. Hard rubber and porcelain are not approved. 7. Motors and auxiliaries. — All motors and auxiliaries will be in strict accordance with specifications 17A3, latest issue. 8. Wire. — All wire except fireproof and magnet wire will bo in strict accordance with speci- fications 15C1, latest issue, and magnet wire will be in strict accordance with specifications 15W2b unless otherwise specified. 9. Finish. All exterior surfaces of searchlight will be finished in battleship gray. 10. Instructions. — Contractor will furnish with each searchlight a pamphlet containing instructions lor operation and care of searchlight. 14. Drawings. — The vertical dimension of tracings in all cases will be 27 inches. Specifications foe 12-inch Hand-Control Arc Searchlights fob Submarines. [APRIL 11, 1917.] 1. General specifications for the inspection of material issued by the Navy Department, in effect at date of opening of bids, shall form part of those specifications. 2. General. — The material shall be of the best quality and workmanship and consist of a 12-inch searchlight, fitted for use on a submarine boat. The searchlight shall be designed with a special reference to quick striking below decks through hatches 27 inches in diameter. The projector shall consist of a brass drum, Mangin mirror, lamp, rheostat, two sockets, front door with glass strips, signal shutter with operating levers, connecting cable, and tool box. Each searchlight shall be supplied, among others, with spare parts as follows: Twenty-five pairs of carbons In tin box, all to be in accordance with latest specifications issued by the Navy Department. 94 THE SEARCHLIGHT. A diapram of actual connectionB shall be pasted or otherwise securely attached inside the cover of the tool box. This diagram shall be shellacked or otherwise suitably protected against the weather. 3. DnuQ. — The drum shall bo made of low sheet brass at least No. 18 Brown & Sharpe gauge, and shall be supported on trunnions in a manner to permit a movement in the vertical plane of 90° above and 90° below the horizontal, the latter angle to permit the barrel being placed in a safe and secure position for lowering below. The drum shall have ample ventilating facilities. It shall be fitted with cast braes and rings and copper mirror shield. Handles shall be provided at the rear of the dnun for training the beam and a clamp shall be provided for clamping the 8»archlight drum in any position between limits specified above. 4. Anns and base. — The trunnion arms and sub-base may be cast in one piece and cast steel is permitted. The sub-base shall be water-tight and contain a 25-ampere double-pole snap switch and non-turning binding posts for connections. 5. Connections. — Two cables connecting the lamp and sub-baee shall be brought into drum in weatherproof manner and into trunnion base through water-tight stuffing boxes. A flexible type National Electrical Code cable may be used. Stuffing boxes shall be of J-inch size. An 18,000 cm. plain twin conductor cable, conforming to specifications lof'lb, shall be led into sub-base through an anti-kink spring, terminal tube, and securing clamp in a manner such that sub-base will be water-tight and searchlight may be lowered by the cable. It will be 25 feet long and coupling or plug need not be supplied. 6. Socket. — A cast-brass railing socket capable of clamping on niiling stanchion of from 11 to 2i inches diameter shall support the entire searchlight. Two sockets shall be supplied. 7. Mirror. — The mirror shall be of the Mangin type, accurately ground and polished and silvered in a durable manner to withstand the heat of the arc. Silvering shall be protected by one heavy coat of metallic copper, and on this copper plating a coating of heavy enamel shall be applied which shall so seal the backing as to render it absolutely waterproof and air-tight. The mirror shall be flexibly mounted in its supporting ring to allow the expansion and con- traction due to heating and cooling. The mirror shall conform to all requirements of Specifications 17M7, dated 1918. Mirrors shall be of the 12-Lach size, but the mirror frame shall be capable of adjustment, so that dimension "B" may be -^ to 3J inches outside diameter. 8. Front door. — The front door shall contain glass strips conforming to Specifications 17S1, issued by the Navy Department. 9. SigTial shutters. — The signal shutter shall be of the Venetian blind type, in accordance with Bureau of Steam Engineering drawing 19-S-2769-L, easily operated with one liand and held normally closed by a spring, but capable of being locked open. Handle shall bo mounted on right-hand side facing rear of searchlight. It shall be so mounted on the front of searchlight as to prevent possibility of leakage of light. The leaves of the shutter shall be as light as possible consistent with strength. All parts shall be made of noncorrodible material. The signal shutter shall be easily removable from and replaced on the front of searchlight. 10. Lamp.— The lamp shall be of the horizontal carbon type, with the carbons in the axis of the mirror and be designed for operation at approximately 20 amperes. Provision shall be made for the adjustment of the positive carbon in two planes. The feeding magnets shall be so designed that the searchlight may be operated continuously for two hours, on any line voltage from 100 to 160 volts, without automatic cut-outs. Magnet coils shall withstand 160 volts for two hours without injurious heating, with arc circuits uninterrupted. The positive and negative carbons when burned under normal operating conditions shall bum at a suitable ratio. The lamp shall operate satisfactorily on the arc potential of 45 volts after the arc is satisfactorDy established. The carbon feeding mechanism shall be of approved positive screw-feed tj-pe for feeding the carbons together at the proper rates. Arrangement for striking the arc automatically shall be provided, \\1ien the carbons are burned out, the feeding circuit shall be opened by a limit snitch actuated by lamp carriage. Carbons will conform to advance sheet No. 51 of March 8, 1917. 11. Rheostats.— The rheostat shall be suiuble for use on circuits ranging from 100 to 160 volts. THE SEARCHLIGHT. 95 The rheostat shall be sufficiently inclosed for protection against injury and at the same time allow effective ventilation. The elements shall be so supported that they will not become displaced nor fall out in case they should be melted or broken at any point and should be so constructed that each ssction may be readily replaced. A suitable insulated board containing resistance contacts and rheostat handle shall be mounted on the rheostat. All contacts shall be arranged so as to prevent sparking. The rheostat shall consist of two sections, a variable and a fixed resistance. The elements shall be of noncorrosive material and the resistance increase from cold to hot shall not exceed 8 per cent. Connections between rear of panel and resistance unit shall be made with commercial fireproof wire. The temperature rise on any part of frame shall not exceed 125° C. 12. Finish. — The entire searchlight shall be finished in slate gray. 13. Name plates. — A name plate showing manufacturer's name or monogram shall be fitted to the searchlight in a conspicuous place. 14. Material. — With the exception of parts otherwise specified above all parts shall be made of non-corrosive material. Magnetic parts shall be suitably protected against corrosion. 15. Tool box. — With each searchlight a tool box shall be supplied containing, among others, parts as follows: 1 spare set glass front-door strips. 1 spare set of springs for all lamp magnets. 1 spare set carbon clamps. 1 spare set insulation for lamps. 1 spare contact screw. 1 spare shutter spring. 1 chamois skin. 1 dust brush. 1 carbon clamp wrench. 1 small wrench for 8/32-10/32 nuts. 16. Instructions. — ^The contractor shall furnish with each searchlight a pamphlet containing instructions for operation and care of searchlight together with blue prints showing diagrams of elementary and actual connections. These shall be supplied in tool box mentioned above lq paragraph 15. 17. Insulation. — All insulation shall be of approved insulating material. Porcelain is not an approved material for use on searchlights or rheostats. 18. Approval of type. — Searchlights supplied under this specification shall be of a type which has been approved prior to time set for the opening of bids. In the event that type proposed to be furnished has not been approved by the Bureau of Steam Engineering, sample of complete searchlight shall be forwarded to the navy yard, New York, for test. The specifications for 9-inch hand-control searchlights for submarines are almost the same as those for the 12-inch light for submarines. Below are given the points of difl'erences between the two. Specifications for 9-Inch Hand Control Searchlights for Submarines. [february 2, 1916.] general. The material shall be of the best quality and workmanship and consist of a 9-inch searchlight, fitted for use on a submarine boat. The saarchlight shall be designed with a special reference to quick striking below decks through hatches 18 inches in diameter. The projector shall consist of a brass drum, Mangin mirror, lamp, rheostat, two sockets, front door with glass strips, signal shutter with operating levers, connecting cable, and tool box. Each S3irchlight shiU be supplied, among others, with spare parts as follows: Twenty-five pairs of carbons in tin box, all to be in accordance with latest specifications issued by the Navy Department. 96 THE SEARCHLIGHT. A diagram of actual connections shall be pasted or otherwise securely attached inside the cover of the tool box. This diagram shall be shellacked or othenrise suitably protected against the weather. CONNECTIONS. Two cables connecting the lamp and sub-base shall be brought into drum in weatherproof manner and into trunnion base through water-tight stuffing boxes. A flexible type National Elec- trical Code cable may be used. Stufiing boxes shall be of J-g-inch size. An 11,340 c. m. armored twin conductor cable conforming to specifications 15Clb shall be led into sub-base through an anti- kink spring, terminal tube and securing clamp in a manner such that sub-base will be water-tight and searchlight may be lowered by the cable. It will be 10 feet long, and coupling or plug need not be supplied. eiQNAL SHUTTER. The signal shutter shall be of the Venetian-blind tj-pe, easily operated with one hand and held normally closed by a spring, but capable of being locked open. Handle shall be mounted on right-hand side facing rear of searchlight. The effective opening shall be not less than S]/g inches in diameter. It shall be so mounted on the front of searchlight as to prevent possibility of leakage of light. The leaves of the shutter shall be as light as possible consistent with strength. All parts shall be made of non-corrodiblo material. The signal shutter shall be easily removed from and replaced on the front of searchlight. Each searchlight shall be supplied with a signaling shutter unless otherwise specified. SPARE PARTS FOR LOW-POWER SEARCHLIGHTS. The following list of spare parts for low-power searchlights is the one upon which the supply of spare parts to all 24 and 30 inch low-power searchlights is based. Slight departures from this list occur in the different sizes and in lights supplied by different manufacturers. The list as given, however, gives one an excellent idea of what his spare-part searciilight equijimcnt should be. One set of the following spares should be supplied with each searchlight: WHEN BLECTBIC CONTROL IS USED. 1 electric controller. 100 feet controller cable with half couplings attached. 1 canvas cover for projector. 1 rheostat for projector — fixed resistance. 1 rheostat adjustable resistance. 1 tool box. TOOL BOX FOR RATCHET-FEED LAMPS. 1 pair blue go;;gle3. 1 pair carbon tongs. 1 focusing wrench. 1 carbon clamp wrench. 2 small wrenches for 8-32 and 10-32 nuts. 2 small wrenches for 12-24 nuts. 1 spanner wrench. 2 side sight glasses. 1 chamois skin. 1 large dust brush. 1 small dust brush. 1 set positive and negative carbon clamps with clamping screws and washers. 2 feeding magnet contact screws. 2 feeding magnet contact springs. 1 feeding magnet armature spring. THE SEABCHUGHT. 97 2 pilot magnet armature springs. 2 pawl springs. 1 vertical peep sight glass. 1 complete set of mica insulation for lamp. 1 set (4) brushes for elevating motor (when used). 1 set (4j brushes for training motor (when usedV 1 spirit level. 3 rheostat bushings. TOOL BOX FOR MOTOR-FEED LAMPS. 2 sets carbon brushes. 1 brush-holder complete. 3 brush-holder springs. 1 set brush-holder stud bushings. (These in addition to all other parts listed above except those applicable only to ratchet-feed mechanisms). LIST OK SPARE PARTS, HATCHET-FEED LAMPS. 1 complete lamp in box. 1 set (13j contact fingers for elevating and training motor controllers. I set (10) contact plungers and springs for controller contact drums. 1 set (12) armature spools for pilot motor. 1 set (2) field spools for pilot motor. 1 set (2) field coils for elevating and training motors. 1 set plain front door strips in box. 250 positive carbons. 250 negative carbons. LIST OF SPARE PARTS, MOTOR-FEED LAMPS. 1 armature complete with commutator and shaft. 1 field coil of each size and kind. (These in addition to all other parts Listed above except those applicable only to ratchet-feed mechanisms.) DESCRIPTION OF GENERAL ELECTRIC CO. RATCHET FEED FOR CARBONS. The General Electric Co.'s ratchet feed for carbons of searchlights operates as follows : The carbons are fed in both directions; that is, both carbons approach each other or draw away from each other. Regulation is dependant upon the arc voltage. In this lamp the series or striking magnet is dispensed with, and the feed- ing magnet, which actually rotates the feed screws, is connected across the supply circuit to the training motors so as to have a constant supply of power. With this typo of lamp it is necessary to provide full line voltage at the terminals of the feeding magnets, as the arc voltage, when the arc is first established, is about .30 volts, although this is rapidly increased by the feeding- apart mechanism. It will thus be seen that feeding magnets which would operate satisfactorily at the low arc voltage would be injuriously heated by the full line voltage which is present before the arc has been esta1)lished, and the necessity of designing the feeding magnets for the full line voltage is apparent. 66438—18- — 7 98 THE SEAECHUQHT. The feeding magnets are equipped with two armatures rotating the feed screws in opposite directions. These armatures are selectively' operated ami controlled by pilot magnet connected by means of links to steel latches which lock and unlock the feeding magnet armatures. To understand the operation of the lamp and the func- tions of the several parts, let us go through a cycle of operation. After the carbons have been inserted in the clamps and separated a shght amount by means of the hand feed wrench, which may be inserted through an opening at the rear of the projector, to engage with the nut at the end of the positive feeil screw, the main line switch should be thrown in, making sure that the socket wrench for hand feed has first been removed, as if it is left in engagement with the feed screw it causes an umiecessary load on the feeding magnets. Consider the observer to be facing the ratchet end of the lamp and refer to right and left handed parts from tliis point of view. As soon as the main switch has been thrown in, the fuU hne voltage will be thrown across the opening between the carbons, and consequently across the shunt terminals of the pilot magnet, which is connected nci'oss the car- bon holders. This causes maximum flux through the pilot magnet, attract- ing both the right and left handed armatures. The right-hand armature, on being attracted, releases the right-hand feeding magnet armature, causing the carbons to be fed together, the left-hand feedmg magnet armature being locked by the attraction of the left-hand magnet armature. The carbons now feed together until they touch, at which instant current passes through the series coil of the pilot magnet which is connected differentially with respect to the shunt winding and reduces the flux tlirough the pilot magnet to a minimum, the voltage on the shunt winding of the pilot magnet being reduced to about 30 volts when the carbons first touch. Due to the reduced flux through the pilot magnet, both pilot magnet armatures are released. This locks the right- hand or feeding-together armature of the feeding magnet and releases the left- hand or feeding-apart armature, resulting in the separation of the carbons. When the voltage of the arc has reached approximately 60 volts, with normal current of 110 amperes flowing, the flux through the pilot magnet has increased a sufficient amount to attract the left-hand pilot magnet armature, locking the feeding-apart armature of the feeding magnet. Under normal conditions of 60 arc volts and a current of 110 amperes both feeding magnet armatures will be latched and the lamp will cease to feed. When the carbons have l)urned away, reducing the current and increasing the arc voltage, the flux tlirough the pilot magnet becomes sufficiently strong to attract the right-hand armature, thus releasing the right-hand feeding magnet armature, feeding the carbons together until normal conditions of arc voltage and current have been reached. It ^nll thus be seen that an increase in arc voltage above normal increases the flux through the pilot magnet, releasing the feed-together armature of the feeding magnet and restoring normal conditions of arc voltage and current. A decrease in the arc voltage reduces the flux through the pilot magnet, releasing the left-hand armature and also the left- hand feeding magnet armature, feeding the carbons apart and restoring normal conditions at the arc. THE SEAECHUGHT. 99 ^Section A'A •■ a-a " C'C -H " D'Q Fig. 109. — Cormections of pilot motor for type EC projections, Form N. rig.£ FiqNaS fiolaniies ahdPosifu QfriddforPos-NoJl Fig No I A FigNo.lB Teit each Coilas indicated m Fig. No lAffith compass Thugircs North Armature pole fti(h Current flowing as indicated t>y arroivs Connect Coifs on each Pole as shown in Fig No 1 8 giving Norf^/irmature Pole with Current flawing as indicated Fig. 110. — 3&-mch electric coutrol projettor, Form N-2. Wiring of base. 100 THE BEARCHUGHT. ADJUSTMENT. The lamps are carefully tested and adjusted before leaving the factory, and no changes should he made in the adjustment unless the arc voltage is not maintainetl at approxinnitelj' 60 volts. In adjusting the lamp the feed-apart or left-hand armature of the pilot magnet should l^e ailjusted by means of i)ressurc of the spring (Q), so that it will be released when the arc voltage has reached 45 volts, feeduig apart until it is attracted at 52 volts. In adjusting either of these pilot magnet annatures the other should be held in a position where it will lock its feeding magnet armature. The feed-together armature of the pilot magnet should be adjusted by means of pressure on its spring so that it wiU be attracted at 62 volts, feeding together until 54 volts have been reached. The jaws of the latches should be kept clean and occasionally a very small amount of good clock oil should be applied. Current for the feeding magnets enters and leaves the lamp through the small contact shoes while the main arc current, which also passes through the series coil of the pilot mag- net, and the current for the shunt winding rtf the pilot magnet enters and leaves the lamp through the large contact shoes. The mechanism of the lamp should be kept clean and free from carbon dust and the points of the feeding magnet contact screw should be kept clean. DESCRIPTION OF CARLISLE anisinc:i Yfrticairraimnqif'jndW/ieet .[7mpCsiffS Cii/p/inq i'ap FIG. 108.— PARTS OF THE 36-INCH ELECTRIC CONTROL PROJECTOR, FORM N-2. FRONT VIEW. THE SEABCHLIGHT. 101 field to be in one direction or the other, or to completely neutralize each other, destroying the field between ends of poles, thus stopping the motor. At no time during the entire operation are the field circuits broken: instead, cods are short-circuited, and hence no current flows through the winding so shorted. Fig. 111.— Carlisle & Finch Co. motor feed for carbons. General wiring diagram. The operation of this type of feed for carbons may be traced out from the general wu-ing diagram. This, however, is difiicult, and to simplify explana- tion and make it more thorough, additional diagrams are given. Circuits carrying current are shown in solid lines; those not carrying current are shown in dotted lines. Suppose the carbons to be far apart when line switch is closed. It is obvious that to establish the correct length of arc the carbons must first feed 102 THE SEABOHLIGHT. together until they touch to strike the arc, and then feed apart until the arc is drawn to normal length. This operation will now be traced in detail. Referring to the diagram in figure 112, when the line switch is closed the voltage across carbon tips is equal to full line voltage. The solenoids on the solenoid controller are connected directly across the arc, and hence a strong current flows through solenoid coils energizing them strongly and drawing in Via. 112.— Carlisle Si Finch Co. motor feed for carbons, current, flux, and motion. Piagrnm \> ith long arc. the plungers. The plungers are attached to a brass plate carrying a contact at upper end. This plate is drawn toward solenoids against the action of a spring, and contactor on brass plate makes contact with contact (B) (top of solenoid controller). Current then flows from positive line (a) which connects to positive carbon, to motor armature, through armature and to (b). At (b) current divides, flowing partly up through coil 3 on left field, then thiough THE SEABCHLIGHT. 103 coil 3 on right field, then through 2 on right field and on to 2 -on left field, from which coil it returns to the negative line through the collector rings as shown. The other part of current flowing down from (b) goes through contact (B) on solenoid controller and on to coil 1 on right field and then through coil 1 on left field and returns to ne^tive line as shown. Coils 4 right and 4 left carry Fia. U3.— Cdilisle & Finch Co. motor feed for carbons, current, flux, and motion. Diagram with short arc. no current as potential across these coils is zero; that is, they are short-circuited. The direction of magnetic field caused by each individual winding is shown by arrows. On right field there are two Norths and one South, therefore the resultant polarity is North; similarly the resultant field on left is South. The motor, therefore, revolves in the direction shown, feeding the carbons together until they touch. 104 THE SEABCHLIQHT. Refer now tc> figure 113. The carbons have come together, and the poten- tial across the arc is therefore zero and tlie solenoids on solenoid controller are no longer energized. The sjjriiig on brass plate pidls plate to right, drawing plungers out of solenoids and brhiging contact point on end of plate in contact with contact point A. The current then Ho^^'s thrtiugh coils as follows: First, Normot Afc e t^a © finushes .vlovab'a Bms* Rings in Fik'pe A searchlight and sheet steel for type B search- light. It will be supported in an approved manner by clamps as boreinafter described. It will LAMt rOi B w ic? ifM a Fio. 119. — 12-inch incaodcscent signal searchlight, showing mounting and wiring diagram. be sufficiently ventilated to prevent injury to the mirror from heat when operated continuously for four hours indoors. A suitable handle at back of barrel will be provided. The barrel will be capable of free movement of at least 45° above and below horizontal, and a free movement of the entire circle in the horizontal plane. Suitable means mil be pro\'ided for locking the barrel in any desired position in the vertical and horizontal planes. The barrel will contain an incandes- cent lamp socket and parabolic reflecting mirror, in accordance with paragraph 5 of these specifica- tions, and will be fitted with a glass weatherproof front door, hinged on one side and secured on the other side by a suitable clamp to provide easy access for removal of lamp. Heat-resisting glass will be installed in front door. Arrangements will be made for the adjustment of lamp in focus by means of a thumb screw or other suitable method from the e.xterior of barrel. A sighting arrangement consisting of two suitable gun sights mounted on right-hand side of barrel facing mirror will be provided. THE SEARCHLIGHT. 109 5. Mirror. — The mirror will be parabolic and in strict accordance with specifications 17-M-3a of February 1, 1917. ^Miere mirror is not manufactured by bidder, the bureau will be informed in bid the name of the firm manufacturing same and also supplied with a copy of contract. 6. Securing clamps. — The securing clamps will be in the form of a socket and pivot. The socket will be provided with a nonremovable thumb screw which will easily and effectually clamp the searchlight by friction in any desired position. The stanchion clamping arrangement will be adjustable for stanchions varying from 1} to SJ inches in diameter. The pivot will operate freely and be mechanically secured by a quick releasing arrangement in the socket so arranged that the searchlight can be lifted from the socket. Two sockets w ill be supplied for each search- light. The clamps for type A searchlight will be of uormiagnetic material. The clamps for type B searchlight will be of cast steel or other approved material. 7. Operating key. — Means \rtll be pro\ ided for the operation of searchlight with an approved blinker key and condenser which will be inclosed in a light splash-proof key box, secured to the TZLLGftfiPH KEY AND CONSlfiitR IN CASe Fig. 129. — Crouse-Hinds 12-inch incandescent signal searchlight, showing method of mounting on rail. searchlight support. Material for type A searchlight will be non-magnetic. Material for type B searchlight will be steel or other approved material. 8. Bushings. — Each searchlight and key box will be equipped with bushings capable of talking a No. 10 B. & S. gage N. E. code, plain braided cable 9. Lamp socket. — Lamp socket will be for Edison medium screw base, and if of suitable design may be of porcelain. 10. Material. — All material of searchlight type B will be thoroughly sheradized to prevent corrosion. 11. Approval of type. — The searchlight will be constructed throughout with a view to lightness without sacrificing strength and ruggedness. It shall be of a type which has been demon- strated by test to be satisfactory for the service intended. In the event that the type proposed to be furnished has not been tested by the Bureau of Steam Engineering, a sample of searchlight will be forwarded to the navy yard, New York, for test The sample submitted need not be com- 110 THE ftBABCHUQHT. FiQ. 121.— The Carlisle & Finch Co. 13-lnoh incandescent signal searohUght. Pedestal mounting tus used on UO-foot putrol bonis. WEIGHT OF SEARCHUeHT ... 42 LBS. APPfiOX)tMT£LY Fig. 122.— National X-Ray Heflector Co. 12-lnch Incandescent signal searchllgbt. Stanchion mounting. THE SEABCHUGHT. Ill plete in all respects to the requirements of these specifications. Searchlight as conamercially constructed will suffice for material for test, pro\'ided assembly and detailed plans of outfit to specification requirements as proposed are submitted with samples. Plans will be in detail as called for under paragraph 14. 12. Finish. — The exterior surfaces of searchlight will be finished in slate gray. The interior surfaces of barrel and back of mirror \vill be finished dull black. 13. Name plates. — A name plate showing manufacturer's name or monogram, serial munber of searchlight, requisition and contract number and date will be fitted to the searchlight in a conspicuous place. 14. Plans. — Prior to placing contract. — Unless already on file at the bureau, there wiU be furnished, in triplicate, with each proposal, blue print plans covering the apparatus proposed. Fig. 123.— General Electric Co. 12-iiich incandescent signal searchlight. Pedestal mounting'. These plans will include assembly and details of all parts, weight of each part, materials used , mirror manufacturer's name, method of securing'mirror, method of securing and adjusting lamp socket, actual construction and connections, etc. No PKOEOSAL WILL BE CONSIDERED UNLESS THESE PLANS REFERRED TO ABOVE ARE INCLUDED AS PART OF THE BID. After placing contract. — Unless already on file at the bureau prior to date for final delivery there will be forwarded to the Bureau of Steam Engineering, Navy Department, Washington, D. C, via the inspection officer, one set of assembly and detailed tracings of the complete outfit. Finished plans will conform to the following sizes: 27 by 20 inches. 27 by 40 inches. 27 by 60 inches. 27 by 80 inches. 27 by 84 inches. The vertical dimension of tracing will, in all cases, be 27 inches. 112 THE SEABCHUQHT. 15. Spare parts. — The following spare parts will be furnished with each searchliglit: One lamp socket, if of porcelain. 16. Weight. — The net weight of the apparatus as a whole and the principal parts will be stated Lu the proposal. Copies of this advance sheet can be obtained upon application tfazda "C" stereepticon-type lamp was mounted in the searchlight and the beam focused as nearly parallel as possible, and readings taken of the intensity of the- beam in foot candles at 80 feet from the searchlight. The results are shown plotted in fig. 125. A beam candlepower reading was then taken at the beam center. THE SEAHCHUGHT. 113 4. The mirror was then removed from the light and tested in accordance with specifications 17-M-3a, w-ith the omission of the backing test, which was not conducted as the contractor objected to this mirror being subjected to the complete backing test, as his understanding when he accepted the contract was that any mirror, so long as it approached a parabolic shape would be accepted by the Navy Department. Under those circumstances it was not thought advisable to apply the backing test of specifications 17-ll-3a, as it is thought probable that this mirror, which is very cheaply made and poorly annealed, will check and break if subjected to any high temperatures. 5. Res^dts. — The drum and lamp moimting are considered up to specified requirements and satisfactory for naval 8er\'ice. /^ n / \ 1 \ /' \ „ 1 \ y \ 1 ^ / N ^, 1 \J /' \ \ JC 1 \ / s, 9 ' V, 1 \ 6 1 K f \ 7 / \ / \ ? 6 J \ § / 5 < / k / i; 4 / -a TA^ ■t 1 Wtv? 'Bl 'T> OA / fl f= 3 / ? /£ "/A bifcfj :» 7- ■^ IP S& \ffC fli Viff r ^ y § ' M tiffi e y ? ^ 'Af •OA U 1--/ ^^ Rk n sr VOA C ■> Si OM / ^ CO) vr 79 7.- ?.£« /} \t. 7 b 1 1 1 1 1 1 1 ,. / 4 i 6 S ^ACH £//w/s/ i In both types there are two classes— self-contained and "plug-m classes. The self-contained class (shown in fig. 123) has a battery in the base of the tube wliich suppUes power for the light, while the "plug-in" class has attached a w — P Li! dT ^C FIG. 127a. ALOIS SIGNAL LIGHT WITH STORAGE BATTERY ANU iPAhE BULBS FIG. 12713. —FRONT VIEW OF ALOIS LIGHT. FIG. 127c.— METHOD OF USING ALOIS SIGNAL LIGHT TO SIGNAL AN AEROPLANE. THE SEAKCHLIGHT. 115 cord and plug by means of which the lamp is plugged in on the ships' circuit and gets its power supply from a source external to itself. The Navy standard portable tube blinker has on the tube two rests on which an officer-of-the-deck spyglass may be laid and strapped in place by using the strap attached to the spyglass. This provides the means of sighting. The commercial type portable tube blinker is supplied with gun sights for the same purpose. The range of this blinker is very short (about 2^ miles). It can be used only at night. THE 21-INCH HIGH POWER SIGNAL SEARCHLIGHT. Recent developments in naval warfare have necessitated the supply of searchhghts for signaling which have far greater range of visibility, and there- fore a greater signahng range, than any signaling searchlights the past. Ships on patrol duty against submarines, and in convoy, and fleets of large size in very extended formation require visible signaling apparatus with long range, inasmuch as it has been found unsafe to use radio for signaling while at sea. The 24-inch high-power searchlight, specially designed for signaling, seems to be the most suitable searchlight for use imder the conditions imposed by present circumstances at sea. The first searchlights of this type are manufactured by the Arma Engineering Co. They wiU be arranged especially for signal use, having one- man control, a suitable signaling shutter, and telescope for sighting. The telescope wUl be arranged so that it may be "bore-sighted" with the beam of the searchlight. The control will be operated by two handwheels connected bj" suitable gearing to the turntable and to the trunnion arms. One handwheel will operate the searchhght ui train, the other in elevation. Tlie rate of train will be 10° in azimuth per revolution of the training handwheel; rate of eleva- tion will not exceed 2^° per revolution of elevating handwheel. The lamp mechanism will be similar to that described in chapter 2, Arma high-power searchhght. ALPIS SIGNAL LIGHT. ' The Aldis signal light is a hand signal light with a pistol grip. The dots and dashes are produced by pulUng a trigger which tilts a parabohc mirror and brings the searchhght beam to coincide with the line of sight through the sighting telescope or tube, which is mounted on the barrel. When trigger is not pulled the beam is much higher than the line of sight and hence not visible to anyone on whom the telescope is sighted. An incandescent lamp of special design is used in the hght. It bums continuously when light is held by grip, the circuit being closed by the pressure of the hand on a second trigger on the grip. A small storage battery supplies the power to nm the lamps. This piece Of apparatus is small, hght, and efficient, and very useful for daylight signaling between vessels operating near each other, and between aeroplanes and ships or ground. The weight of lamp is about 5J poimds. The illustration will serve to give a general idea of the light. (Fig. 127.) These lights will be supphed to seaplanes, naval air stations, battleships, cruisers, destroyers, etc. CHAPTER 10. TYPES OF OPERATING GEARS. DISTANT MECHANICAL. The earliest types of distant operating systems were crude and inaccurate, though rather interesting. One of the very earliest emploj-ed two drums at the control station; around them was wound a rope drive. This drive went to other drums on the searchlight which turned when the drums at the control station were turned, thus forming a pulley sj-stem for elevating or depressuig the light, or for training it. Fia. 12j.— Searchlight operating gear. I'ump-haml.e type. f Shortly after this type was used, there was developed the pump-handle type shown in sketch. (Fig. 128.) The light was supposed to follow exactly the motions of the controller, training as the lever was turned and elevating or depressing as the lever was raised or lowered. This, however, it never did very well, and though used to some extent was never very satisfactory. The pilot-house type of control was found satisfactory for small lights so mounted that this type of control could be used. One form of pilot-house type of control is shown in figure 129. The systems of gearing in the bases of scarclilights are interesting and are of many types. A few are shown in diagrams and brief descriptions given. The system shown in figure 130 is a development of the pilot-house type of control for application to large searchlights. Two shafts are used, being connected to the operating handwheels by universal joints. 116 THE SEABCHUGHT. 117 The light is elevated and depressed by a gear fixed in space turning about a screw shaft; this shaft moves a crosshead bar which, by means of connecting rods and cranks, tilts the light on its trunnions. The training gear is very simple and the sketch needs no explanation. It wiU be noted that as the lamp is moved in train the elevation changes, due to the screw shaft screwing in or Fio. 129.— Pilot-house type of searchlight operating gear. out of the surrounding gear. This type of control was used on old General Electric Company's searchlights. Another type of operating gear used on the General Electric Co.'s old searchliglits is shown in figure 131. The training gear is practically the same as that shown in preceding sketch. The elevating gear employs a worm and wheel, the worm wheel being at one end of a short shaft and a pinion at the other end. The pinion engages an arc rack and rolls the hght about its trunnions. 118 THE SEAHCHLIOHT. Afic ElLSiVATiNG Rack '/ /j^/////////////////////M ^ NoT^ . Error in £l£YATION due To Tr/]i/V Pio. 130. — Old arc rack and pinjon type of searchlight operating gcai'. Arrangement of geart In base. NOT£. ERROn i/i EL£VAT/ON DUE TO Training. EiLEVATIOt^- TRAIN Fio. 131.—" Push type" searchlight operating gear. THE 6EABCHLIGHT. 119 In this light there is also a change in elevation due to training, caused by the worm wheel revolving about the worm when the turntable is revolved. Concentric shafts are used in this type of operating gear. These shafts carry horizontal handwheels on their lower ends, one for training and one for elevating. This type of gear is now in use on the Wisconsin and other ships. In figure 132 is shown the type of operating gear now in use on many Beck (General Electric Co. high power) searchlights. Concentric shafts aro used in this type of operating gear, the outer shaft being for training and the inner for elevating. The gear for elevating is in a general way similar to the last gear described, except that bevel gears are used in place of worm and wheel gear. Note. - ERROR iN EuevfijioN Due TO TR/\lf/. H/\No Operating S£>ja (pdovioEo wm lock} EuevfiijioN TRfKlN Fia. 132. — Arrangement of gears in base of Beck distant mechanical control. High-powerscarchllght. The training gear is supplied with distant mechanical control and also hand control at the light. Gears A and B are provided with locks which may be used to keep the wheels fixed against revolving. Gears B and D, and A and C are on separate shafts. Gear E is an idler, loose on the elevating shaft, fixed in space, and meshing with C and D. To use hand control at the light, gear A is unlocked and gear B is locked; this locks gear E as well, so that when A is turned, C, being on the same shaft, also turns and rolls around E, revolving the turntable. To use distant mechanical control, gear B is unlocked and gear A is locked, so that there is possible no relative motion between E and C. Thou, when training shaft is turned, D turns E, and as E turns, C is carried around with it, revolving the tiu-ntable. 120 THE SEARCH LlGHt. In this light there is a change in elevation due to training, caused by the vertical bevel gear rolling around on the horizontal gear when turntable is revolved. The Pennsylvania is equipped with this type of operating gear. This type of gearing may be arranged to operate by separate shafts by omitting gear B, providing a lock on gear D, and extending shaft carrying D and B through base of searchlight. Some lights are arranged this way. The General Electric Co. is now developing a standard type of base for use with nil operating stands. Separate shafts lead from the base to the stands. No drawings of this base are available at present, but no new principles are involved. Tliere are at present installed on ships six old types of distant mechanical controller gears for scarclilights, knowTi respectively as A, B, C, D, E, and General Electric Co.'s. TYPE "A" OPERATING GEAR. Tliis system is designed to operate the light from a point about twelve feet below the base of the light. It provides a simple and reliable method of training and elevating the light from a short distance. Tlie light is operated by turning a pair of handwheels connected to the drum b}' means of gears and shaftings. There are two such pairs of handwheels, one serves to elevate the drum and the other to train it. Tlie construction of the elevating controller is identical with that of the training controller. The handwheel transmits its rotation to a vertical shaft in the box through a beveled gear. This operating gear is connected to the operating mechanism in the base of the lamp by means of a shaft and two universal joints. This mechanism will be described later. The shaft in the control box also carries a worm which engages a gear wheel carrying a brass disk. The edge of the disk carries a scale of degrees of arc which may be viewed througli a small window. A small electric lamp is placed above the scale so that i t may be illuminated and the scale read at all times. The scale is geared to the shaft in the same ratio that the drum is, so that the scale readings iu the controller box correspond to those on the drum at all times. The mechanism in the base of the lamp consists of gears and shafting to transmit the motion of the handwheel to the drum. ITie two operating shafts come up through the base of the lamp. The training shaft is connected to the rack on the rotating part of thebasetlirougha train of gears and a short shaft. One pair of gears may be disengaged by means of the pedal on the side of the base, so that the light may bo trained at the lamp. The handwheel for this purpose is geared to the training rack at a point diagonally opposite to the remote operating gear. . The elevating shaft passes through the axis of the base and is geared to a small horizontal shaft on the rotating part of the base. The other end of the shaft is under one of the ti-unnion arms supporting the drum, where it is geared to another shaft running along the trunnion arm to a point just under the drum bearing. Here it is geared to the elevating rack on the side of the drum. This gear may be made to enage or disengage the rack by the small liandle on the standard. The whole mechanism is easily seen by removing one of the handhole covers from the base. 4H i nJin @=I M '^i o y-^pZ' E. S.TfPt 6G438— ~rvpE-A o^ TvPE-B Type-<1 TvPt-D 5EARdHU<&HT ^OKJTRO\.£ ^-G TYPE- E . Fio. 13».— Type I> searchllRht opcratinRgcar (aitachcd to necV Jfi-inch hlch-powcr searchH^hls). TYPE "C" OPERATING GEAR. Type C gearing itself is almost identical with that of type B, the only difference in the two types being extended handwheel shafts. This is used on THE SEABCHUGHT. 123 some destroyers and on any other ships where it is necessary to extend the shafts to clear the searchUght tower or other obstruction. The general plan is shown in figure 134. WtlOKT OF Jearchusht V/EI5HT OF CotiTttOL Fig. 139.— Type C searchlight operating gear ^attached to 3e-inch low-power seareh|isiit , TYPE "D" OPERATING GEAR. Type D operating gear consists of two control pedestals used in pairs, one right hand and one left hand. The gearing is similar to that of types B and C. Only one training handwheel shaft extends through side of box. The shafts to hght are concentric. Figure 134 shows the general arrangement. This type of gearing is used where two searchlights are mounted close together on a tower or on twin towers. 126 THB BBASCHUOHT. S"Z?.- Fio. iw.-OenermI Electric Co.s type of searchUjht operating ge«r (attached to Beck 36-incb Usb-power saarcbUght J. THE SEABCHLIGHT. 127 TYPE "E" OPERATING GEAR. Type E operating gear has very recently been designed for use on certain new destroyers. The diagram is self-explanatory. "G. E." TYPE OPERATING GEAR. The General Electric Co.'s type of operating gear is somewhat similar to type B gear, except that only two handwheels are employed, one controlling elevation on one side of pedestal controUing elevation, and one controlling train on the other side controlling train. Eight of these operating gear sets are used on the Pennsylvania, and have given very satisfactory service. Figure 134 shows general arrangement. T\TES OF OPERATING GEAR, DISTANT ELECTRICAL. There are two fairlj- satisfactory types of distant electric control in use, the Sperry and the General Electric , neither of which is on the follow-up principle, but operate as long as the controller is on the "on" position. ITie motion is in all cases transmitted by worms and worm wheels and spur or bevel gears. REMOTE ELECTRICAL OPERATING GEAR SYSTEM FOR SG-INCH SEAKCHLIOHT. SPERRY TYPE. The Sperry remote control system is imique in that it contains no moving parts except the two motors which serve to train and elevate the light. Tlie entire mechanism is inclosed in the base of the light, protecting all parts from the weather. Access may quickly and easily be had to each and eveiy part of the system by removing a handhole cover. The construction is rugged, so that the system vnR stand rough usuage without getting out of order. It will operate successfully under all ordinary conditions. The purpose of the system, to find the target and keep it illuminated from any point within 500 feet of the 'light itself, is accomplished by a reversible, variable speed motor control system. There are two motors, one to rotate the light in its azimuth and the other to rotate it in elevation. The location of the working parts of the training system is on the lower half of the base, and the elevating motor is on the upper half. Tlie training motor is geared to the vertical axis of the light by means of a worm and set of gears, which are shown in the cut. The motor can be disconnected from the drum by means of a clutch which engages or disengages one pair of the gears in the train. When the clutch is out, the light must be trained by hand ; when it is in, the light is trained by the remote control system. The elevating motor is moimted on the rotating part of the base. It is geared to a shaft that runs up along one of the trunnion arms through a worm and gear train, which is shown in the cut (fig. 141). This shaft is geared to the elevating rack on the side of tl:e drum. A clutch is provided at the standard so that the gear can be made to engage or disengage the rack. Thus the light can be elevated either by hand or by the motor. Since this motor is moimted on the rotating part of the base, current for its armature and field is led to it through three slip rings, shown in figirre 141. The brushes which ride on these rings can be seen on the upper half of the base. The two wide slip rings shown 128 THE SEAECHLIGHT. carry the current for the arc. The speed and direction of the motors is varied by the two control boxes shown in the cut. One of tlicsc regulates the eleva- tion, and the other the training of the light. It is seen that the axes of the controlling wheels correspond to that axis of rotation of the light which it con- trols; also that the direction of rotation of the controller wheel indicates the direction of rotation of the light. This, coupled with the fact that the con- trollere can be so placed that the pair may be operated satisfactorily either by one or two men, as the occasion calls for, is one of the advantages of this S3'stem. Each of these control boxes contains a multiple point switch. The points on these switches are connected to taps on the potentiometer, located on the base of the light. The potentiometer is connected across the 120-volt line abend of the arc rheostat, so that the potentiometer voltage is constantly 120. The simplicity of the system is due to the use of potentiometer control of the motors. It operates as follows: The field of each motor is connected across one-half of the potentiometer which makes the field constant in magnitude and direction. One side of each armature is connected to the middle or neutral point of the potentiometer. The other side of the training motor is connected to the switch blade in the training control box, and the other side of the elevating motor is connected to the blade in the elevating controller. The connections are plainly shown on the accompanying wiring diagram (figure 143). Consider first the training motor. If the switch is on the middle point of the controller, the motor is short-circuited, has no voltage across it, and hence will not rotate. If the controller is moved one point to the left, then the motor armature is connected across a few turns of the potentiometer. There will then be a small voltage across the armature, causing it to revolve slowly. If the controller is moved farther from point to point, more and more turns are included in the armature circuit, causing the voltage to rise and its speed to increase. When the last point is reached, the annature has the maximum voltage across it, and the motor is ininning at maximum speed. If the controller handle is moved in the other direction from the neutral point, the armature polarity is reversed. Since the polarity of the field remains unchanged, the motor will reverse its direction and increase its speed as the controller is moved farther and farther from the neutral position. When it is on the middle point, which is its nonnal position, it being held there by springs, the armature is short-circuited, which applies a large braking efi'ect to the motor and causes it to stop quickly. In fact the drum can be brought to rest from full speed in any direction in less than 2° of arc. A glance at the wiring diagram wiU show the extreme flcxibihty of the system. On the present type of this control there are 17 taps on the poten- tiometer, giving 8 different speeds in either direction, varying from 6° to 360° of arc per minute. Both motors will run at full speed in either direction, and changing the speed of one motor when the other is running will not affect the speed of the other for more than one-half to one second. The potentiometer is of such resistance that it draws about four amperes from the line continuously, but can safely carry considerably more than this. Thus either or both motors may draw sufficient current to provide enough start- ing torque to bring the drum from rest up to speed in less than 5° of arc. < {/I m — z I- < I X O U i^ 5 o Q. I o I I o I o 5 o I o NE.C FUSRki VJLT- AMMtTtl? TIUATtON f Af« ' ( ^Sil. T'' LA MP CowiPARTMeNT KTEfc=?Sl LC'Voi.TMCTtK \_6«oiToe I* fH.^»sS Be. HooKfo Ah.Cho o*' H"EOS,T*T iM^AtC OtVT. FIG. I43.-SPERRY DISTANT ELECTRICAL CONTROL FOR SEARCHLIGHTS WIRING DIAGRAM 66438—18 9 FIG, U4 SPERRf DISTAtlT ELECTRICAL CONTROL FOR SEARCHLIGHT CONTROLLERS. BOXES OPEN. FIG. 145. SPERRY DISTANT ELECTRIC CONTROL FOR SEARCHLIGHT CONTROLLERS. CABLES, PLUGS, AND JUNCTION BOX, FIG. 146.— SPERRY DISTANT ELECTRICAL CONTROL FOR SEARCHLIGHT CONTROLLERS. BOXES CLOSED. THE SEAKCHLIGHT. 129 This system provides a method of following up the target smoothly and continuously, not in the jerky manner which was formerly necessary. The range of speeds at which the drum can be rotated is wide enough to satisfy all con- ditions met with in practice. Moreover, the system is by far the simplest which has yet been devised, in addition to which it is of such rugged con- struction that it will not get out of order except under extreme conditions. If it should break down, repairs can be made with extreme faciUty as every part of the system is easily accessible. The system of remote electrical operating gear supplied by the General Electric Co., is very similar to the Sperry system. THE GKNEKAL ELECTRIC CO. SYSTEM. The system of training these projectors in altitude and azimuth diflfers from previous methods employed, a synchronous training arrangement being provided between the controller and the projector. Fro. 147.— Assembly of horizontal training mechanism. On the controller, figure 149, there are two separate handwheels, one for each plane of control. These handwheels rotate by means of shafts and simple commutating devices, which commutate the direct current to currents having three-phase relation. This causes to rotate, in the base and on the turntable of the projector, pilot motors which have the same direction, speed, and relative magnitude of rotation as that of the commutating devices or the handwheels rotating the same. Referring to figure 147, it will be seen that the pilot motor (D) consists of 6-pole pieces, on each of which are moimted two stationary coils which will be referred to as the armature coils. These pole pieces are arranged on the cir- ciimference of a circle, inside of which is placed a movable field excited by two stationary coUs connected in series across the training circuit, as shown in figure 151. 130 THE SEARCHLIGHT. Tho armature coils on each pole piece aro connected in series, the coils on tho different pole pieces being so interconnected as to leave three leads which run back to the controller. The field of this motor is so constructed as to take up 12 definite equidis- tant positions for one complete revolution; each position depending on the combination of current through leads 3, which run back to the controller. It will thus be seen that diflereut current combinations through tho pilot motor, caused by rotating the handwheel of tho cohtrollcr, will cause the field of the pilot motor to rotate. Rotating tho horizontal training handwheel on the controller through half a revolution causes the revolving field of the pilot motor (D), fig. 147, in tho projector to rotate one-fourth of a revolution or 90°. The rotation of this motor field causes the cam cjdinder (E) to rotate, for example, through l.'j°, by moans of the spiir gears (F), (G), (H), and (I), and the bevel box gearing (J), (K,) and (Tj) ; (K) not being visible in the upper view on account of its not occurring on the section, but engaging with (J) and (L). The operation of the cam cylinder (E) operates the contact fingers (M), connecting tho training motor (N) to tlio circuit for tho proper direc- tion of rotation. Tho projector then begins to rotate by moans of the worm (O) attached to the motor, the worm gear (P) and spur gearing (K) and (S) which is connected by means of the spur gear (T) to tho main training gear rinf which is fastened to the turntable. Connected to the shaft (U) is the bevel fear (V) whicU, through tho diff'erential gears (L) and (K) , also drives the cam cylinder (E), but in a direction opposite to the rotation induced by the pilot motor, so that wlien tlae turntable has rotated through 1° it will have turned (E) back to its off position, stopping the training motor. To sum up, the cam cylinder (E) has a motion equivalent to the alge- braic sum of the motions derived from the pilot motor and tho training shaft (U) and is always equal to zero. The explanation of these movements has been made as if they occurred separately; but, as a matter of fact, as soon as the cam cylinder (E) is rotated by the rotation of tho pilot motor, the pro- jector begins to revolve and in so doing tends to rotate the cam cyhndor back to its original off position. As long as the controller handwheel is rotated the projector will continue to rotate. From this description it will be gathered that a half turn of the controller handle corresponds to 1° movement of the projector beam, and that if tlie controller handle bo turned through 10 one-half revolutions the beam will travel through 10° at tho same relative speed of rotation as the handle. It will thus bo seen that a slow movement of tho controller handle results in a slow movement of the beam, and a rapid movement of the controller handle will produce a rapid movement of tho beam. For slow movements of tho con- troller handle the training motor (N) is connected to the circuit through re- sistances; for greater speed the resistance are short circuited by one of tho contact finders (M) for faster speeds of training. If the speed of rotation of the handwheel is relatively faster than the rotation of the turntable, there will be a sU<^ht lag in tho beam but the projector will catch up and stop at the proper angle. The vertical training gear, shown on figure 148, is the same as the hori- zontal except for the difference in the mechanical connection between the training motor and the projector barrel. FIG. 143.—ASSEMBLY OF VERTICAL TRAINING MECHANISM. FIG. 149. —PARTS OF THE FORM N-I PROJECTOR CONTROLLER. A= Vertical adjust iiif; Ihumbscrew. B= Horizontal adjust iii^' t Immbscrew. C=SiL''it h:ir o[)pr;iliii,Lr scri'W. D^ I Im I niii il h ;iiTiin^ liandwlieel. ■£=- \ el 1 !'■ >| I i.iining luuidwheel. F= J-iRkiu^ ii»d armature spring. G = Locking; coil armature. H= Vertical control contact drum. 1= Sight bar. J= Sight bar standard. K= Top plate. L= Frame. M= Bottom plate. N= Receptacle shell. <)= Receptacle contacts. P= Locking coil. 0=Horizontal control contact drum. R= Frame for horisontal control con- tact drum. S=Contact finger for vertical control contact drum. T=Stop plate for vertical control handwlioel worm gear. U=\Vorm gear for vertical control handwheel. V= Bevel gear for sight bar operatiJig screw. W=- Worm gear for horizontal control . X= Worm for horizontal control hand- wliee. . Y=^Tvnob for horizontal training hand- wheel . Z=Knob for vertical training hand- wheel. Aa=Cap for cable receptacle. Ba= Chain for caltle receptacle cap. Ca= Contact plunger. Da= Shaft for vertical control hand- wheel. Ea=Oear for sight bar operating screw. Fa=Collar for vertical control hand- shaft. In ordering, give niinie of pari . reference letter, and figure number. THE SEARCHLIGHT. THE CONTROLLER. 1^1 The controller is provided with a sight bar which moves synchronously with the projector beam; this is shown in figures 149 and 150. The operating handwheels which train the projector are geared to the sight bar so that the movements of the sight bar in altitude and azimuth correspond to the move- ments of the projector beam. It will be seen that if the controller sight bar and the projector beam are in orientation, the projector will be pointed at the target, if the Hne of sight of the sight bar is on the target. 182 THE SEAHCHUQHT. A convenient method of orienting is to bring the projector beam and the line of sight of the sight bar together on a common object at some distance, after which the projector is clamped to the electric control. A clutch is pro- vided for this purpose on the handwheels, and any slight variation in aligiunent may be corrected by adjustments on the controller, the thumbscrews (A) and (B) (fig. 149). being ])rovided for this purpose. Referring to figure 149, the locking coil (P) locks the horizontal and vertical handwheels when the voltage on the training motors fails or is cut off, thus preventing the sight bar from becoming out of orientation with the pro- jector. Another function of this coil is to lock the handwheels in case the speed of rotation of the controller handwheels is greater than the relative speed of the beam, thus allowing the beam to catch up and preserv^ing the orientation. In this case the operation of the coil is effected by opening its circuit through one of the cam fingers (M) operated by the pilot motor. ^22li Fig. 150.— Assembly of Form N projector oontroUer. Electric o])erating gears are used to only a hmited e.xtent aboard ship because, though they are rugged and operate successfully at fii-st, they deterior- ate rapidly. They are necessarily more complicated than mechanical operating gears; repairs are more difficult to make and require a higher grade of work- manship than is usuallj- obtainable on board ships of the Navy. Mechanical operating gears are preferred because they are simpler, less liable to require repairs, and more easily repaired. Moreover, with mechanical gear systems, the operator feels that he is in tangible connection with the searchlight and is more conscious of absolute control of the movements of the light. CHAPTER 11. TABLES OF GENERAL DATA ON SEARCHLIGHTS AND BLINKERS. INDEX TO TABLES. Table. 1. Signaling distance (miles) of searchlights and blinkers. 2. Target illuminating distance (yards). 3. Searchlight currents, voltages, and wattages. 4. Depression angles to bring searchlight beam on targets (degrees). 5. Deflection of beam (feet) at various ranges, corresponding to training searchlight through an angle of 1 degree. 6. Beam-spread angles (degrees). 7. Beam diameters (feet) at various ranges. 8. Weights of searchlights, rheostats, etc. (pounds). TABLES OF GENERAL SEARCHUGHT DATA. Following are tables which ^re of some interest in connection with search- light and signal equipment: TABLE 1. SIGNALING DISTANCES (iN MILES) OF SEARCHLIGHTS AND BLINKERS. The distances given in this table are the average values of signaling dis- tances, the average being computed from a number of reports on distances at which signals could be read in clear weather. Signaling distances {in miles) of searchlights and blinkers. 36-inch low-power searchlight. 30-inch low-po^er searchlight. 12-inch arc signal searchlight. Day. Night. Day. Night. Day. Night. 15 30-35 12 30 9 16 12-inch incandescent sig- nal searchlight. Yardarm blinker. Portable tube blinker. Day. Night. Day. Night. Day. Night. 2.5-3 7-10 1 5 ' 2.5-3 No data is available on the distance at which signals by high-power searchlight may be read, but as the beam is so much more powerful than the beam of a low-power searchlight the distances are probably very much greater. 133 134 THE BEABCHUGHT. It is expoctod that the range and speed of incandescent signal searchhghts and of bUnkers will be increased considerably by using high-speed, concen- trated filament lamps. T.\ROET-lLLUMlNATINQ DISTANCES (yARDS). I The information about ranges at which targets can bo illuminated is very meager owng to the fact that but few tests have been made idong this line. The vtUues given are appro.xiiuato and are for clear weather. TABLE 2. Target-illuminalion ranges (yaMi). I Range-finder Target plain readings. (nated eyeV Target plain ,,ig-ihiV(,^i-„o,,. ibinorularsl. ,.,„!, Target just 'ble (bii ularsK 36-inch low-power searchhght j 2,000-2,500 3. 500 4, 000 6, 000 36-inch high-power searclilight . 4, 500 6, 000 8, 000 10.000-12,000 24-inch high-power searchhght 2,500 | 4,000-4,500 | 5,500-6,000 8,000 i I ' TABLE 3. SEARCHLIGUT CURRENTS, VOLTAGES, AND WATTAOE8. The values in Table 3 are given as an aid in selecting searchlight material suitable to the generator capacity available. Searchlight currenU. voltage*, and wattages. • ' Arc volt- age (volts>. .Miuimum supply vo tage recom- mended.* Average power (kilowatts). Sizeofeearchlighl. (f^,",",^) 1 In arc. Consumed in rheo- Btat.t Total. 9-inch arc. 10 12-inch arc 20 18-inch 35 24-inch low power... 50 30-inch low power... 80 36-inch low power... 120 24-inch high power. . 75 30-inch high power. . 120 36-inch high power. . 150 45 45 50-54 50-54 55-59 58-62 45 72 75 70 70 80 80 90 100 70 110 110 0.45 .9 1.82 2.6 4.54 7.2 3. 375 8.64 11.25 0.25 .5 .98 1.4 2.46 4.8 1.875 4.56 5.25 0.7 1.4 2.8 4.0 7.0 12.0 5.25 13.20 16.50 • To obtain the proper balance for steady burning the supply voltaEe should be not less than 1.5 times arc voltage t Based on a drop across rheostat equal to difference between " Minimum Supply Voltace Recommended and "Arc Voltage." THE SEABCHLIGHT. 135 TABLE 4. DEPRESSION ANGLES TO BRING SEARCHLIGHT BEAM ON TARGETS. The following table shows angle of depression of searchlight required to bring the center of the beam on the water line of the target at different ranges from different searchlight mounting heights measured from the water line to the searchlight trunnions. '. Height of searchlight trunnions above water line (feet). Range (yards). | 40 45 -f- 50 55 60 65 68' 5'' Depression angles. O / ft O ! 2,400. 4,000. 8,000. 19 6 11 28 5 44 // 'O / ff O f // / f f \ O t tl 21 29 10 23 16 :0 26 16 12 53 14 19 15 45 6 27 :0 7 10 7 53 28 39 lO 31 2 I 32 40 17 11 lO 18 37 I 19 36 8 36 9 19 : 9 4S The trunnion of the searchlight on the forward mast of the OMahoma is 68 feet 5 inches above water hne, therefore the angle of depression required to put the center line of beam on the water line of target at 8,000 yards range is 0° 9' 48". Note.— The curvature of the earth was not considered in calculating above table. The difference would be slight at the shorter ranges and not important at the longer range of 8.000 yards. TABLE 5. Deflection of beam at various ranges corresponding to training searchlight through an angle of one degree. Range (yards). ' I I 2,000 ' 4,000 I 6,000 ' 8,000 i- ^1 Training searchlight 1 degree moves beam ..feet. J 104 208 312 416 10.000 12,000 520 i 624 TABLE 6. Beam -spread angles of high-power searchlights. Size of light. Beam-spread air- cooled searchlights. Beam-spread Beck searchlights. 60 inches 36 inches 30 inches . . . 1° 15' 2° 0' None made. 2° 20' 2° 20' 24 inches 2° 0' No data is available on the beam spread of low-power searchlights. 136 THE gEAHCHLIOHT. TABLE 7. BEAM DIAMETERS AT VARIOUS RANGES — HIOH-POWER SEARCHLIGHTS. This table shows the importance of having accurate mirrors and of keeping the positive carbon crater exactly in the focus of the mirror, inasmuch as the target illumination in foot candles varies inversely as the square of the diameter of the beam at that point, if atmospheric absorption be neglected. Atmospheric absorption is approximately 10 per cent for 1,000-yards range i. e., only 90 per cent of the total light in the beam outside of the front door strips. If the beam-spread angle could be reduced to one-half its original angle the illumination on the target would be four times its original value, hence the neces- sity of keeping the beam as concentrated as possible. The beam-spread angles increase very rapidly as crater of positive carbon is moved out of focus of the mirror. BEAM DIAMETERS .\T VARIOUS RANGES HIGH-POWER SEARCHLIGHTS. 60-inch air-cooled high-power searchlight — Beam spread 1° 15'. Range (yards) 2,000 4,000 6,000 8,000 10, 000 12, 000 Beam diameter (feet).. 131 262 393 524 655 786 36 and 24 inch air -cooled high-power searchlight — Beam spread 2° V . Range (yards) Beam diameter (feet) . . 2,000 4,000 6,000 8,000 10, 000 12,000 1 1, 260 ' 210 420 630 840 1,050 so and 36 inch Beck {alcohol "cooled*') high-power searchlight — Beam spread 2° 20". Range (yards) 2,000 4,000 6,000 8,000 10, 000 12, 000 Beam diameter (feet) . . 251 502 753 1,004 1,255 1,506 TABLE 8. WEIGHTS OF SEARCHLIGHTS, RHEOSTATS, ETC. HIGH-POWER SEARCHLIOHTS. 36-INCH BECK (GENERAL ELECTBIC CO.) HIGH POWER. Pounds. Searchhght 1,670 Rheostat (125-volt circuit) .- 490 30-INCH BECK (general ELECTRIC CO.) HIGH POWER Searchhght 1,490 Rheostat (125-volt CHCuit) 429 24-INCH GENERAL ELECTRIC CO. AIB-COOLED HIGH POWER. Searchhght 1,045 Rheostat (125-volt circuit) 360 TBTE SEABOHLIOHT. 137 36-INCH 8FERBT HIOH FOWBB. Ponnds Searchlight 1 , 628 Rheostat (125-volt circuit) 210 36-INCH 8PEBRT-OENERAI. ELECTHIC HIGH-PO WEB CONVERTED. General Electric Co., drum before fitting 1, 100 Conversion parts: Sp«ny high-power lamp for conversion 70 All conversion parts 385 36-inch Sperry-General Electric converted searchlight 1 1 , 485 Eheostat (125-volt circuit) 210 24-INCH 3PERRY HIOH FOWKK. Searchlight 975 Rheostat (125-volt circuit) 120 24-INCH ABMA HIOH POWER. Searchhght 791 Lamp 70 Rheostat (125-volt circuit) 125 Rheostat (80-volt circuit) 120 LOW-POWER SEARCHLIGHTS. 36-INCH GENERAL ELECTRIC, >fAVT STANDARD, LOW POWER. Searchlight _ 1, 800 Rheostat (125-volt circuit) 315 Signal shutter 72 125 pairs carbons ._ 138 Spare lamp in box 59 30-INCH GENERAL ELECTRIC, NAVY STANDARD, LOW POWER. Searciilight 910 Rheostat (80-volt circuit) 225 24-INCH GENERAL ELECTRIC, COHMBRCLAL, LOW POWER. Searchhght. 725 Rheostat (125-volt circuit) 135 18-INCH GB.VERAL ELECTRIC, COMMERCIAL, LOW POWER. Searchhght. 230 Rheostat (125-volt circuit) 125 12-INCH GENERAL ELECTRIC, NAVY STANDARD, ARC SIGNAL. Searchlight 93.5 Rheostat (r25-volt circuit) 96. 9-INCH GENERAL ELECTRIC, NAVY STANDARD, SUBMARINE ABC. Searchhght 83 Rheostat (110-volt circuit) ._ 60 138 THE SEAHCHLIGHT. 12-IKCH CARLISLE i FINCH, NAVV STANDARD, ARC BIONAL. Poonds. Searchlight - - - - 110 Rheostat (r25-volt circuit), approximately 95 12-INCH INCANDESCENT SIGNAL SEARCHLIGHT. Searchlight • - 30-45 (Weights vary for different manufacturers' lights.) CHAPTER 12. CARBONS FOR SEARCHLIGHTS. CARBONS FOR SEARCHIJGHTS. Searchlight carbons are of great importance in the efficient operation of any arc searchlight. They must be so made as to feed smoothly. burn evenly, not crack or flake, and not sputter. Dampness is injurious to all carbons, in that it causes them to sputter and burn unevenly and with a flickering light. This is particularly true in the case of high-power searchlight carbons which have a special core. Not only does dampness cause flickering and sputtering, but it may also loosen the core and cause parts of it to break oft, destroying the shape of the crater and seriously impairing the illuminating power of the searclalight. It is of prime importance to keep in mind the fact that carhons are ■porous and absorb moisture from the atmosphere. They are more absorbent of salt water than of fresh water. It is imperative therefore that the containers of carbons be kept tightly closed and sealed, if best results are to be obtained. Tlie chief difference between the illumination given by "low-power" carbon arcs and "high-power" cored carbon arcs, is due to the higher intrinsic brilliancy of the surface of the high-power positive carbon crater and to the smaller crater diameter. The high intrinsic brilliancy is caused by the higher current density in the arc and the higher temperature produced thereby, and by the mass of highly incandescent gases in the positive crater produced by the volatilization of the salts composing the positive and negative cores. The following table taken from an article printed in the Aerial Age, Sep- tember 4, 1916, on the Sperry air-cooled, high-power searchlight shows some- what the improvement made over the old low-power searchlight illuminating power in brilliancy. Tlie figures are for specific brilliancies in candlepower per square millimeter. (1) Candleflame 0.01 (2) Acetylene flame - . 0. 08 (3) Carbon-filament lamp . 1 . 00 (4) Ordinary tungsten lamp 2. to 4. (5) Gas-fiUed tungsten lamp 10. to 20. (6) Tungsten at the melting point (3,500° C.) 72. (7) Arc flame, ordinary white flame arc 7. to 20. (8) Crater of carbon arc 110.0 to 160.0 (9) Crater of Sperry arc 550. to 800. (10) Sun at 30 degrees elevation 775. (11) Sun at noon 930. Not only is there a vast increase in brOliancy but there is abo a great improvement in the character of the light. The low-power searclilight beam appears foggy and yellow when compared to the clear bluish beam of the high- 139 140 THE SEABCHUGHT. power searchlight. The beam is a pale blue, particularly at twilight or dawn, although the spectroscope analysis of the light shows it to be of a greenish hue. Spectrophotometer analysis of the beam of a low-power searchlight shows it to have its greatest intensity at a wave length of 0.58 microns (a micron = 0.001 millimeter), which is in the yellow part of the spectrum. The high-power hght has its greatest intensity at 0.55 microns, which is in the green part of the spectrum. Light of this particular wave length reflects better from a mirror than hght of a wave length of 0.58 micron, and has a greater illuminating power of objects of gray, blue, black, or green colors, such as are most frequently met with at sea; i. e., it reflects better from surfaces of those colors. Battle gray Ls no protection against the light of the high-power searclilight, while in the light of a low-power searchliglit it shows dull and dead. Specifications for liigh-power carbons must be based on spectrophotometer analysis of the hght given off, inasmuch as the composition of the cores are knoA^Ti only to the manufacturers, and hence can not be specified. Specifications for searchhght carbons are given below. It will be noted that Sperry searchhght negative carbons are copper coated, while the other high-power searchlight carbons are not. This copper coating is an undesirable featme, inasmuch as lumps of molten copper may drop on the mirror and cause breakage when operated in the antiaircraft position; also, the coating may melt and "spot-weld" the carbon into the negative head, preventing feeding. The Sperry lamp negative head will be altered in construction in the future so that imcoated liigh-power carbons may be used, thus providing a standard carbon for all liigh-power searchhghts of the same size. Two sets of specifications are given for low-power searchhght carbons, as man^' of the older type of carbons are in use and are being supphcd, while improvements have necessitated a change of specifications for carbons used in later low-power lamps. 17C5a. Superseded by 17C5b. Navy Department Specifications. LOW-POWER 8EAECHLIGHT CARBONS FOB USE IN THE tTNirED STATES NAVT. June 1, 1917. General specifications. 1 . General Specifications for Inspection of Material, issued by the Navy Department, in effect at date of opening of bids, shall form part of these specifications. Gteneral description. 2. Carbons shall be circular in cross section, uniform in diameter for the entire length, homogeneoiLs in texture, and free from all flaws, cracks, or im- purities which may cause unsteady burning. The carbons covered by these specifications are of two classes, known as the 3-to-2-ratio and the 1 -to- 1 -ratio carbons. These terms refer to the rate of burning of positive with reference to negative. Dimensions, current, and arc voltage. 3. The tables following give the general dimensions, current, and arc volt- age of the two types of searchhght carbons. THE SEAKCHLIGHT. (a) JHmensions for the l-to-1-ratio carbons. 141 Bizeof search- light. Current amperes. Arc voltage. Dimensions in millimeters. Positive Positive diameter. length. 1 Negative diameter. Negative length. India. 9 12 18 24 30 36 10 20 35 50 SO 120 48-51 50-54 50-54 55-59 oS-«2 13 16 16 19 25 28. S 120 140 180 250 250 250 I 9 10 11.5 13 110 130 160 230 230 230 (6) Dimensions for the S-to-2-ratio carbons. 1 ^t 1 »'"p^'*^- 1 Arc voltage. Dimensions in inche-s. Positive diameter. Positive length. Negative j Negative diameter. length. t India. 9 10 12 20 18 35 24 50 30 80 1 36 110 1 1 • 45 45 45 45 45 60 t 1 li 6 8i 12 12 12 i r 1 " Negative carbons. 4. (a) For 1-to-l ratio. The negative carbon for the 1-to-l-ratio carbons shall consist of a solid carbon, heavily copper coated over its entire length. It shall be uniform in diameter, and one end shall be tapered to a point at an angle of about 70 degrees. The carbon shall be hard, homogeneous in texture, thoroughly baked, and straight. It shall be free from any imperfection which may cause the arc to hiss or fhcker. The dimensions for carbons for various sizes of searchlights can be found in table forming part of these specifications. (6) For S-to-2 ratio. The negative carbons for the 3-to-2-ratio carbons shall consist of a shell and core, the shell being a hard, homogeneous carbon, and the core shall be soft carbon. The negatives for the 36 and 30 inch searchhghts shall be copper coated for their entire length, while those for all other sizes of searchhghts shall be plain. The dimensions of carbons for various sizes of searchlights can be found under table forming part of these specifications. Positive carbons. 5. The positive carbon shall consist of two parts, namely, the shell and the core. (a) The shell. The shell shall be homogeneous in texture, free from injurious imperfec- tions, thoroughly baked, and one end slightly tapered, with a crater formed. (6) The core. The core of the positive carbon shall be composed of a hard white flame material, of uniform circular cross section, shall run evenly in the center of the shell, and shall be so fitted in the shell as to eliminate any spaces between it and the shell which may tend to cause flickering of the arc. The structure of 142 THE SEAECHLIQHT. the core shall be such that it shall not crumble or loosen from the shell without the actual breaking of the shell from the core. The dimensions for various sizes of searchlijrhts are shown under a table formini; part of these specifications. Ratios of burning. 6. (a) The ratio of burning of the carbons known as the 1-to-l ratio shall be 1 part by length and by weight of positive to 1 part by length and by weight of negative. (b) The ratio of burning of the carbons known as the 3-to-2 ratio shall be 3 parts by length and weight of positive to 2 parts by length and weight of negative. Performance when burning under normal conditions. 7. The carbons, when burning under normal conditions, shall burn without dickering or sputtering, shall not crack and throw off chips, and shall give ofT a small quantity of ash. The liame shall not l)e excessive and the composition of the flaming material shall be such that the combustion shall be complete, no soot being formed which will deposit on the mirror or finders, thus impairing the range of the light. Minimum candlepower. 8. The following table gives values of the candlepower of tlie arc, l)urning under normal conditions, which will be considered a minimum acceptable maximum value, for the carbons for different sizes of searchlights. size of searchlight. 3-to-2 ratia 1-to-l ratio. 1 1 India. Canilf Candle- power. power. 1 » 900 I, MO , 12 2,200 3,.tOO 18 .■i.Oflfl 7,500 24 9,000 11,500 30 15,000 20,000 36 1 25,000 .•12,000 General characteristics of light from arc. 9. (a) Color of crater luild. The light from the arc formed on these carbons shall be decidedly blue in color, and upon spectnim anah-sis shall show at least 5 per cent of the total energy below wave length 0.002 micron, 30 per cent of total energy between wave length 0.502 and 0.560 micron, and shall show a maximum value of intensity of the spectiiim at wave length 0.55 micron. The above values are obtained by test of samples at the nav}-^ yard, New York, from standards made at that yard. All comparisons and verifications of these values and testing of samples will be conducted at the navy yard, New York, by a Government representative. The above values of percentages are a minimum and any increase in the total energy below wave length 0.560 micron wiU be considered satisfactory and advantageous. (6) Color ofjlame. The color of flame shall show general characteristics somewhat similar to that of the an;, except that the maximum point of intensity shall be at 0.580 micron, and the per cent of energy in the flame shall not show more than 10 THE SEARCHLIGHT. 143 per cent of the energy of the total, which includes the crater, flame, and carbon tips. (c) Height of flame. The height of this flame should not exceed six times the diameter of the positive carbon. Samples. 10. Before shipment of carbons samples must be submitted for test to the material officer, navy yard. New York. The package containing these samples shall be plamly marked, stating the size of carbons, and all data necessary for identification. Failure of the samples to meet any of the above requirements shall be deemed sufiicient cause for rejection of all carbons represented by samples. Packing. 11. Carbons shall be packed for shipment in tin cans, 10 in each can, positives and negatives separate. They will be so -vvrapped in paraffined paper or other waterproof material as to prevent the absorption of moisture by the carbons. Cans will be sealed waterproof and in such a manner as to be easily opened and resealed at will. Each can will be plamly and completely marked with sufficient data to facfiitate the identification of. the contents. Specifications for 60-inch searchlight carbons are not given, but the above specifications in general apply to this size of low-power carbons. The dimensions of 60-inch low-power carbons are as follows: Diameter. Length. Po'!itive Negative Inches. 2 IS Imlies. 15 12 Navy Department Specifications. SEARCHLIGHT CARBONS FOR USE IN THE UNITED STATES NAVY. Janvary 8, 1918. General specifications. 1. General Specifications for Inspection of Material, issued by the Navy Department, in effect at date of opening of bids, shall form part of these speci- fications. General description. 2. Carbons shall be circular in cross section, uniform in diameter for the entire length, homogeneous in texture, and free from all flaws, cracks, or impurities which may cause unsteady burning. The carbons covered b}' these specifications are of two classes, known as the 3-to-2-ratio and the 1-to-l-ratio carbons. These terms refer to the rate of burning of positive with reference to negative. Dimensions, current, and arc voltage. 3. The tables following give the general dimensions, current, and arc volt- age of the two types of searchlight carbons. C(U3S— IS 10 144 THE SEAKCHUGHT. (a) Dimension* for the l-to-l-ralio carbon*. PI'eof .teirch- Ught. Current amperes. Arc volt- oge. Dimensions in millimeters. Positive diameter. Positive length. Neratlve diameter. Neeatlve length. Inclttt. 9 12 18 24 30 3« 10 20 35 50 80 120 4ft-49 48-51 50-54 £0-54 5.5-59 58-82 13 16 16 19 25 28.5 105 140 ISO 230 2,'0 2i0 8 9 9 10 11.5 13 CO 130 ICO 210 230 230 (6) Dimensions for the 3-to-S-ratio carbons. Size of search- light. Current amperes. Arc volt- age. Dimensions in inches. Positive diameter. Positive Negative Neiative length. diameter. length. Incha. 1^ 18 24 30 36 10 20 35 50 SO 110 40-t5 4(M5 40-45 43-48 4.>-S0 55-60 1 5 6 m 12 12 12 1 7 Negative carbon. 4. (a) For 1-to-l ratio. The negative carbon for the 1-to-l-ratio carbons sliall consist of a cored carbon, heavily copper coated to within 1\ inches from the tip. It shall be uniform in diameter and one end shall be tajiered to a point at an angle of about 45 degrees. The <'arbon shall be hard, homogeneous in texture, thor- oughly baked, and straight. It shall be free from any imperfection which may cause the arc to hiss or flicker. The dimensions for carbons for various sizes of searchlights can be found in table forming part of these specifications. (b) Ftw 3-to-2 ratio. The negative carbons for the 3-to-2-ratio carbons shall consist of a shell and core, the shell being a hard, homogeneous carbon and the core shall be soft carbon. The negatives shall be copper coated to within 1^ inches of end. The dunensions of carbons for various sizes of searchlights can be found under the table forming part of these si)ecifications. Positive carbon. 5. The positive carbon shall consist of two parts, namely the shell and the core. (a) Tie shell. * The shell shall be homogeneous in texture, free from injurious imper- fections, thoroughly baked, and one end slightly tapered, with a crater formed. The composition of shell must be such that combustion shall be complete under normal conditions of operation. (b) Tie core. The core of the positive carbon shall be composed of a hard, white flame, material, of uniform circular cross section, shall run evenly in the center of the shell, and shall be so fitted in the shell as to eliminate any spaces between THE SEARCHLIGHT. 145 it and the shell which may tend to cause flickering of the arc. The structure of the core shall be such that it shall not crumble or loosen from the shell without the actual breaking of the shell from the core. The dimensions for various sizes of searchlights are shown under table forming part of these specifications. Ratios of burning. 6. (a) The ratio of burning of the carbons known as the 1-to-l ratio shall be approximately 1 part by length of positive to 1 part by length of negative. (b) The ratio burning of the carbons known as the 3-to-2 ratio shall be approximately 3 parts by length of positive to 2 parts by lengths of negative. Performance when burning under normal conditions. 7. The carbons when burning under normal operating conditions shall burn with a minimum of flickering or sputtering and shall not crack or throw off chips. The iiame shall not be excessive and the composition of the flaming material shall be such that the ash deposit wiU not impair the mechanical operation of the lamp. The amount of soot deposited on the mirror and finders shall not be great enough to seriousl}' impair the range of the searchUght during a 4-hour period of continuous operation. Minimum candlepower. 8. The foUowing table gives values of the candlepower of the arc, burning under normal conditions, which wiU be considered a minimum acceptable value at maximum point of distribution curve for the carbons of different sizes of searchhghts. Size of sparch- 3-to-2 ratio. 1-to-l ratio. ILSht. Candle- Candle- Ituhtt. power. power. 9 900 1,500 12 2,200 3,500 18 5,000 7,500 24 9,000 11,500 30 IS, 000 20,000 36 25,000 32,000 General characteristics of light from arc. 9. (a) Color of crater light and general cJiaracteristics of beam. The color of the light from the arc when operating under normal condi- tions shall appear bluish white to the eye, and shall show color characteristics and distribution of intensity identical with samples previously tested at the New York Navy Yard, records of which can be had by apphcation for report No. 289 on file at Navy Department, Bureau of Steam Engineering, Washing- ton, D. C, or at the testing laboratory, machinery division, navy yard, New York. (6) The height of the flame above the positive tips shall not exceed six times the positive-carbon diameter. Samples. 10. Before shipment of carbons samples must be submitted for test to the engineer officer, navy yard, New York. The package containing these samples 146 THE SEARCHLIGHT. shall be plainly' marked, stating the size of carbons and all data necessary for identification. Failure of the samples to meet any of the above requirements shall be deemed sufRcient cause for rejection of all carbons represented by samples. Packing. 11. Carbons shall be packed for shipment in tin cans, 20 in each can, positives and negatives separate. The}' will be so wTapped in parairined paper or other waterproof material as to prevent the absorption of moisture by the carbons. Cans will be scaled waterproof and in such a manner as to be easily opened and resealed at will. Each can will l)e plainly and complctel}' marked with sufficient data to facilitate the identification of the contents. SPECIFICATIONS FOR CARBONS FOR HIGH-INTENSITY SEARCHLIGHTS. January 1, 1918. General. 1 . General specifications for the Inspection of Material issued by the Navy Department, in effect at the date of opening of bids, shall form a part of these specifications. Description. 2. The carbons covered by these specifications shall be classed under two headings, one for the carbons for the two tj'pcs of lamps manufactured by General Electric Co., and one for the type manufactured by the Sperry G3'roscope Co. The general characteristics of the carbons are identical, the positive to consist of a hard plain carbon sheel, uncoatcd, with a core of flaming material, and the negative to consist of a hard cai'bon shell and soft neutral carbon core. Dimensions. 3. The dimensions of the positive and negative carbons for each type of lamp as noted above shall conform to the following tables: (a) General Electrk Co. {Beck) alcohol and air-cooled lamps. Size of search- light. Positive. Nceativo. l-iianieter of shell (outside). Length. Pia meter ol shell (out.'-idc). Length. Inches. 36 30 24 IS Ivch. 0.630 .53.1 .433 Inches. 44 36 IR Ircfi. «3 .413 .433 Inches. 13} 12 7 (6) Sperry Gyroscope Co. lamps. Pi-e ct search- light. Positive. Negati e. Diameter ol «hell (outside). Length. Diameter ofshrll (outside.). Length. Inches. 36 30 24 18 Inch. 630 Inches. 36 Inch. 4.^3 Inches. 12 .433 io .«3 ' THE SEARCHLIGHT. (c) Limits of allowance for positive and negative diameter. 147 size nf .searchlight. Positive diameter. Negative diameter. Negati\ e coppered. Minimum. Maximum. Minimum. Maximum. Minimum, Maximum. Inches. 36 30 24 Inches. 620 .527 .425 Inches. 0.r.40 .547 .433 Inches. 423 .42i .423 Inches. 0.443 .443 .443 Inches. 0.428 Inches. 453 .42S .453 {d) Core diameters. Tlie diameter of the negative core shall be approximately 0.05 inch and the diameter of the positive core shall be in all cases one-half the outside diameter of the positive shell. The positive carbon. 4. (a) SleU. The positive carbon shell for both tj'pes of lamps shall be identical and shall consist of a hard, homogeneous shell of neutral carbon, fine in texture, free from any flaws, cracks, holes, or irregularities in roundness, to be sufliciently , straight over its enthe length to pass through a tube 12 inches long, and having an internal diameter of 0.031 inch greater than the maximum allowed diameter of the positive shell. The rise from a plane surface at its highest point shall not exceed 0.25 inch. The shell shall be circular in cross section, uniform in thickness for its entire length, and the core centrally located. One end shall be chamfered 3^ inch deep. The positive core. (6) The core shall consist of a hard flaming material and shall run central in the shell for its entire length. It shall be of uniform diameter, homogeneous in texture, and shall contain no air holes or spaces, cracks or injurious flaws, and shall be so applied within the shell as to be secure and hard enough to with- stand all shocks to which the caibon may be normally subjected, without crumbling or disintegrating. The negative carbon. 5. The negative carbons to be of two types described and specified as follows : (a) For General Electric Co.'s (BecJc) alcolol and air cooled lamps. The negative carbon shall consist of a hard, homogeneous shell of neutral carbon, uncoated, free from flaws, cracks, or other injurious defects, sufficiently straight so that when laid on a plane surface with one end held do\^^l the other end will not rise more than 0.08 inch from the plane surface. Both ends of the carbon shall be beveled about 70 degrees. This carbon shall be cored for the entire length with neutral material, applied in such a way as will prevent crumbling or detachmg from shell. (6) For Sperry Gyroscope Co.'s lavips. The negative carbon shall consist of a hard, homogeneous shell, or neutral carbon, free from flaws, cracks, or other injurious defects, sufficientlj- straight so that when laid on a plane surface with one end held down the other end will not rise more than 0.08 inch from the plane surface. One end of the car- 148 THE SEABCHUGHT. bon shall be beveled about 70 degrees. The carbon shall be cored for the entire length with neutral material applied in such a way as will prevent crumbling or detaching from the shell. Tlic carbon shall be copper coated to within H inches from the tapered end with a heavy copper plate, uniform in thickness, smooth of surface, and of such thickness as to show an ohmic resist- ance of 0.0003 to 0.000.') ohm per inch of length of the finished carbon. Performance when burning. G. Tlie carbuns, when ))urning under noniiiil conditions, shall maintain a dcej), well-formed crater. The arc formctl on these carbons under normal conditions shall be steady and shall not emit any excessive amount of soot or other substance which will seriously impair the reflective qualities of the miiTor or the transmission qualities of the front door strips during a period of eight hours' continuous operation with the ventilation of drum normal. AMieu l)urniiig under normal conditions the carbons shall burn with very little asli anil shall not throw olT chips. The candlepower of the arc for the normal sjiecified operatuig cunent for the two types of arcs shall show a minimum value of crater light and a minimum horizontal intensity at the maximum point of the distribution curve, conforming to the following table: .VLC0H0L-C00LEi> LA.\I1'S. Size or searcblight. Operating cnrront. .r^riii^'Si-"' Ma'-imiim Ilamf and tip in- tenMtv. at 30'. Inehrt. 315 30 ISO 120 100,000 70,000 70 000 .30,000 1 AIR-COOLED LAMPS. Size of searchlight. Operating current. Vinimum total hori- zontal can- dlepower 8120°. Minimum crater inteiL^itv at 30=.' Maximum flame and tip in- tensity ai 20'. Inehet. 30 24 150 115 75 100,000 70,000 45,000 50,000 50,000 27,000 1 IR.OOO Life per trim. 7. The life per trim of a single pair of carbons shall be in accordance with the following table. After the prescribed time there shall be sufficient length of both positive and negative so that stubs still are in electrical contact with conducting fingers. 3G-inch searchlight. 30-lnch searchlight. 24-inch searchlight. 2} hours. 2i hours. IJ hours. General characteristics of light from arc. 8. The color of the beam from a standard searchlight workhig under normal conditions shall appear bluish white to the eye and shall show color THE SEARCHLIGHT. 149 characteristics and distribution of intensity identical with samples previously tested at the New York Navy Yard, records of which can be had by application for report No. 289 on file at the Na\y Department, Bureau of Steam Engineering, Washington, D. C. Samples. 9. Before shipment, samples of material to be supplied on the contract must be submitted to the engineer officer, navy yard. New York, for test. The packages containing these samples shall be plainly marked with all data necessary for identification of contents. Packing. 10. Carbons shall be packed for shipment in tin cans, 25 pairs per can, and the can sealed waterproof in such a manner that it can be opened and resealed easily. Each can shall be plainly labeled with all data necessary for identification, stating whether for General Electric Co.'s alcohol and air-cooled lamps or for Sperry Gyroscope Co.'s lamps. Note. — The General Electric Co., 24 inch, high-power, air-cooled searchlights will use car- bons as follows: Positive, 24 inches lon^, NeLrative. 8J inches long, instead of lengths of IG inches for positive and 7 inches for negative carbons as given in speci- tlcations. The time of burning per trim is greatly increased by using the longer carbons. The navy yard, New York, has tested all types of carbons u^ed in the United States Nav3% determining, bj"^ spectrophotometer analysis of the beams, the intensity of each beam in each part of the spectrum. The results are shown in a series of curves which follow th? report of the test given below. These curves form a basis on which are founded specifications governing light characteristics of carbons. TEST Xo. 289. TEST OF HIGH-POWER AXU LOW-P()WEI£ SEAKCHLIGIIT CARBONS TO DETERMINE SPECTRUM CHARACTERISTICS OF ARC AND RESULTANT BEAM. March 14. 1917. 1. Tests have been conducted by this division on all types of searchlight carbons in use in the Navy to determine the spectrum characteristics of each ty])e, and also the effect of the color of the arc on the visibility of the beam, the arc being protected tlu-ough a Navy standard silver-backed glass parabohc mirror. 2. Method. All data taken was calculated from results obtained from a Hilger spectro- photometer. Before starting to obtain any data on the arcs it was found necessary to have standards of a known emission curve with ordinates in such convenient units that a direct comparison between the total visible intensity, and the intensity at each wave length of the spectrum could be easily found. 150 THE SEAIiCHLIGnT. 3. A brief description of the spectrophotometer Is as follows: The apparatus consists of a base, fitted with two colimeters, placed at 90- dcgrec an<;lcs, and at the apex is mounted a standard Lummer Brodhum prism. Each colimeter Ls fitted with a graduated slot at its outer end for var^-ing the intensity of the light on the prisms, and also for proper concentration of the light on the prisms. Tliorc is also fitted a four-sided prism termed a constant- deviation prism, mounted on a revolving table, which is controlled by means of a micrometer screw, calibrated to read directly in micron-. In front of this prism is mounted a telescope, through which the spectrum is viewed. This telescope is also fitted with symmetrical slit, whicli forms the second slot of a nonchromatic illuminator for use when comparing single colors of the spectrum. When used as a spectropho- tometer, thcimage seen through the telescope is identical with that seen tlirough the eyepiece of a Lummer Brodhum sight box, the light from the one colimeter being thrown on the outer field and that from the other being throMn on the in- ner field. By varying the in- tensity of the standard lamp in the usual way of moving same along the j)hotometer bench until the fields match in intensity, the actual inten- sity of the unkno\\'n light, the intensity of the standard of course being kno^vn for this color, can be calculated directly for the law of squares. The constant deviation prism, when once calibrated and thecc)hme- ter.s properly set, automatically throws the same color on both fields of the Lummer Brodhum prism, so that the comparison of any or all parts of the complete spectrum can be ea'^ily made by simi)ly turn- ing the calibrated micrometer screw to the wave length desired and balancing the standard lamp till the fields are of the same intensity. 4. Great difiiculty was experienced in getting a standard calibrated in convenient units for practical use in the comparing of the arcs, so after many attempts to have this work done outside, an attempt which finally proved successful was made at this yard. 5. The standard used in all curves and data submitted are calibrated so that the ordinates read directly in international candlepower and the abscissa in microns. The candlepower is only comparative, no compensation being made for absorption of the lenses, prisms, diffusing screens, etc., used in the ^*i9f*^mry Sfa^darJ 6* H/L6£fr 5P£CT/fOPH0rOMCT£fl 5PeCTRUM COMPAR/SOMoflAMn Fio. 151. THE SEARCHLIGHT. 151 photometer, but as all data was taken under the same conditions, the values of the ordinates are all in the same ratio to the absolute, it only being neces- sary to multiply by the absorption factor of the apparatus to obtain absolute values in international candlepower for each wave length. However, compara- tive values are considered ample for the results required, so no attempt was made to correct to absolute units. 6. In order to calibrate the standard lamp, the spectrophotometer was removed from its mount, and one colimeter and the Lummer-Brodhum prism removed, allowing the light admitted through the slit in the one colimeter to pass directly into the constant-deviation prism. This light was then viewed through the telescope and the nonchromatic adjusting slots in the telescope calibrated to correspond to the wave length drum on the constant-deviation prism. Comparatively small slots were used, both on the colimeter and the telescope. This arrangement was found to project a single color, controlled directly by the constant-deviation prism adjusting drum, out from the eye- piece of the telescope. The arrangement of the spectrophotometer was then mounted on end of a standard photometer bench, the slot of the eyepiece of the telescope being located directlj" over the standard setting for the test lamp. 7. A Schmitt and Haensch flicker photometer was then located on the bench in a stationary mounting, with its liitchie wedge just 2 inches distant from the telescope eyepiece, the eyepiece being considered tlie source of light, and no account being taken of the distance from this e3'epiece to the lamp through the photometer. As only comparative results were sought, this arrangement was considered satisfactory. 8. A movable carriage was then arranged on the photometer, upon which was mounted a 32-candlepower horseshoe-filament standard carbon-filament lamp, this lamp being considered as the standard by which all intensities were to be compared. 9. This gave an arrangement whereby there was a light representing the 32-candlepower standard lamp on one side of the Ritchie wedge of the flicker photometer, which was not selective for any particular color, but gave the full spectrum of the lamp and could be used as 32 international candles from which all intensities could be figured, and a small beam rectangular in shape on the other side of the wedge which represented the intensity of the slot in the tele- scope the color of which, and consequently the wave length, was controlled by the constant deviation prism. 10. It was found that the flicker photometer furnished an ideal instiument for the comparison of these two different-colored lights, from wave length 0.71 micron to about 0.53 micron, which runs from the red through the yellow and partly into the green. Below 0.53 micron the difference in intensity, due to the fact that the carbon lamp is essentialh' an orange light, and consecjuently the intensity in the green and blue part of the spectrum being low, it was found necessary to interpose a blue screen between the standard lamp and the photo- meter. This screen was calibrated for the transmission factor of the entu'e spectrum of the carbon lamp without any regard to coloration and the factor was foimd to be about 0.1, so that below wave length 0.53 micron the standard intensity was taken as 32 X 0.1 =3.2 international candlepower. 152 THE SEARCHLIGHT. 11. It was desired to use as standards, 250-watt tungsten lamp, rating at about 200 international candles. Owing to this comparatively low intensity, and the color cliaractoristics of the tungsten lamp, which is decidedly a yellow light, it was found very difficult to obtain an}' reliable readings below wave length 0.56 micron. In order to overcome this difficulty, a 65-volt, 600-watt, nitrngen-iill(>d tniiasten lamp, with a highly concentrated filament wa^ used as a primary standard and was calibrated by the comparison of each part of the spectrum with the standard carbon lamp, with and without the color screen, as required, and tl.e curve fif this lamp, when computed and drawn, was the primary standard by wliich the secondary working standards were calilirated. 12. After the a])ove procedure had been tried and the results carefully checked, tlie spectropliotometer was remounted in its permanent sotting and the secondary standanls calibrated direct through the photometer, using diffus- ing blocks before each colimeter, with the primary standard at one slot and tlie secondary standard to be at the other slut with all prisms in place, and each wave length of the standard nitrogen-filled lamj) compared with the 250-watt tungsten lamp, and from this data a curve was computed showing the value in intematioiial candlepower, neglecting all absorption corrections, for each part of the spectrum of the 250-watt Mazda lamps. The 250-watt Mazda lamjjs are used as the working comparison standards for all data represented by the curves. 13. Although the inclosed curves show nothing absolute as far as intensities or energy characteristics go, and are probably inaccurate and useless from any research standpoint, due to the necessarily large unknown absorption prop- erties of the different materials used in the diffusing blocks and prisms, the curves thus obtained give a vcrj' good base for comparative data on all spec- trums. This also necessitates the taking of any future comparative data which the bureau maj' desire on this particular photometer, using this method and the standards which are here, or are made in this yard. However, it is considered that some very interesting and instructive results can be obtained in this way, whereby a method is furnished of comparing the present product of the manufacturers of carbons for high and low power searchlights with those carbons which may be furnished in the future. 14. Havuig had the two 250-watt tungsten standards previously cali- brated at the Bureau of Standards for total international candlepower and total watts, it was found by comparing the areas of the spectrum curves of these two standard lamps that the ratio of the area covered by the two curves when compared with the ratio of the total intensity of the lamps was almost identical, thus giving ground for stating that the ar(>a of the curve of a lamp taken by this method is du-ectly propoitional to the total visible intensity of the lamp in inteniational candlepower. Thus, in the data taken for the arcs, a direct method is supplied of comparing the total visible intensities of the respective arcs when burned on certain carbon. These curves, for convenience, may be called emission curves of the arcs formed on the different types of carbons. 15. This outlines the method of calibrations of standards from which all comparisons are taken, and which gives a base for all discussions and formed THE SEARCHLIGHT. 153 in this report. The setting of the apparatus for caUbrations of standards and comparison of arcs are showm. 16. After a satisfactory working standard had been obtained, the next step was to apply the comparison of each separate wave length of light from the standard with that of the arcs. 17. The arcs were set up at a distance of 10 feet from the test colimeter, with a slot opening of 0.004 inch and the slot at the standard opening set at 0.050, giving a reduction ratio of 12.5 to 1. This ratio of reduction was found adequate for the low-power arc, but the high-intensity arcs required the inter- position of a sectored disk with a 4-to-l ratio in the path between the arc and the coHmeter in order that a balance could be obtained with this light from the standard. IS. Readings were then taken for the intensity of each 0.005 wave length starting at 0.44 micron and reading as high as possible in the visible spectrum. No successful attempt was made to take any data outside the visible spectrum, as the only part to which interest is attached is the useful visible spectrum. Data was taken on all types of 36-inch carbons at present in the service, but no data was taken on any other sizes as this data really only gives a comparison between the light from the new high-power lamps and those of the old low- intensity type, and as there are no lamps at present developed smaller than 36 inches in the high-power type no tune was spent on taking the data on smaller low-power lamps, although all this will be accomplished hi the future. 19. It is an established law that the light from the part of the spectrum represented by wave lengths 0.54 to 0.56 micron, inclusive, is the light which the retina of the eye is most sensitive to, therefore the arc most desirable for long ranges is that arc which shows the greatest intensity in this part of the spectrum; but from experiment it has been found that when the light from the arc is projected by means of a reflector, this reflector has absorbing qualities for certain coloi-s. In the Na%'3' standard searclilights a glass parabolic mirror is used. This mirror is backed with silver and the combination has been found to have selective quaUties for the light of wave lengths higher than 0.57 micron and the greatest efficiency of transmission at the green part of the spectrum between 0.54 and 0.56 micron wave length. This fact accoimts for the high efficiency of transmission of the visible spectrum by the silver mirror, and this fact also brings out the reason why the gold-backed mirror is so inefficient when used with the electric arc as the light source. 20. With the above facts established, it is evident that the aim should be to adopt the color of the arc to give its highest intensity at a wave length of about 0.55 micron, this being about the center of the green spectrum. 21. The material used in the mirrore is the best obtainable at the present time for efficient light transmission at the point of highest visibility, so that the miiTor question can be left for the present time as satisfactory. 22. Results from the experiments show that the low-power arc, although showing a fairly high candiepower on the photometer, is very rich, in the wave length greater than 0.57 micron, which represents colors ranging from the yellow up to the red and shows a minimum of Ught in the visible spectmm below 0.57 micron, which runs from the yellow through the violet. 23. This arc, which in itself does not give the maximum Ught at the most efficient point, when pi-ojected thi-ough the mirror which is selective 154 THE SEARCHLIGHT. above wave length 0.56 micron, will naturally be very inefficient and necessarily have a short range, due to the comparatively small amount of light emitted below wave length 0.50 micron. 24. On the other hand, with the high-power searchlight lamp, the arc shows its greatest intensitj' at wave length 0.55. Tliis seems to be a particu- larly well-(le-;igncd s))cctrum for use with the Navy standard min-on-, as the higho-^t i)oint of light transnii.-^sion of the mirror and that of the spectrum of the arc practically coincide, thus making the transmission of (he light of the arc by the mirror in the most efficient possible waj-, in addition to having this light tran.^mitted at the point of ma.ximum emis,-ion, that is, the gi-eatest amount of light generated by the arc, and that transmitted bj- the mirror is at such a color as to give a beam with its highest intensit}- at the color to which the retina of the eye is most sensitive, 'lliis fact has much to do with the gi'eatly increased range of the high-power light over the old t}^)e of low-power arc. 25. The values given in the following table are computed from the areas of the curA'es of emission of the spectrums of the different t3-pes of arcs and show the percentages of emission and different-colored light in different parts of the spectrum, and also the eliiciency of the mirror for different parts of the spectrum and for the total beam. In order to compare the beam spec- trum with the arc, it was necessary to reduce the intensity of the beam spectrum to a scale con-esponding to the arc s|:ectrum. The intensity can not be com- pared by the area of these curves, but the percentages of the colors transmitted can, thus giving the efficiency of transmission of color by the mirror. Tor con- venience, a point was chosen in the spectrum, which showed the highest efliciency of transmission by the mirror, and the mirror at this point was considered to have an efliciency of 100 per cent. This accounts for the curve of the beam touching at one jioint on the curve of the arc. Tlien con- sidering this point 100 per cent efficient, the other colors at various wave lengths are compared, the efficiency being figured from the ratio of the ordinates at the various wave lengths. Of course the assumption of the 100 per cent trans- mission at one point is only comparative, because the efficiency wUl not be near as good as this, due to the energy and light ab.^orption by the glass and silver and also the front-door lens, but the results give a very good comparison between the transmission efficiencies at different parts of the spectrum of the beam, when using the low and high power arcs as a source of light, and trans- mitting the light through the glass mirror and front door of a Navy standard searchlight. The same miri'or was used in all cases. 26. Upon investigating the emission cur^-es for (he s])ectrum oi the differ- ent type of arcs and their resultant beams, the following values representing the percentage of the total fight in the visible spectrum were found: Color. Wave length. Beck. Spcrry. Navy standard, plain. Navy standard, white flame. Per cent in ate. Per cent in Ixsam. Per cent in arc. Per cent in beam. Per cent Per cent in arc. { in beam. Per cent in arc. Per cent in beam. Vi lot and blue Green 0.44-0.5')2 .512- .ofi .56- .512 .592- .014 . Cl-t- . 70 5.5 36.5 26.9 16.0 15.1 5.5 42.6 20.7 12.8 12.4 6.0 36.2 27.4 15.4 14.4 6.0 40.0 26.2 15.5 12.3 l.S 3.3 30.0 35.8 30.0 28.9 20.0 17.3 18.5 14.7 3.3 33.3 29.0 17.5 16.9 4.25 38.3 Ydhw 0ran'.;e Red.: 27.8 16.0 13.05 THE SEARCHLIGHT. 155 27. From the foregoing table, it is apparent that the high-power type of lamp and the white-flame tj^pe carbon for the old-type lamps are much more efficient than the old-type carbon. 28. The greatest efficiency is obtained in the transmission of the light from the arc, when the intensity characteristics of the beam conform to those of the arc. This condition is reached when the characteristics of the muTor for the transmission of hght at different wave lengths are such that the emission curve of the beam would follow the curve of the light source. In order to accomphsh this, the curve of the transmission of light by the miiror would have to be a straight hne. As the mirroi-s are selective for color, the greatest efficiency is obtained by having the light from the arc at its gi-eatest intensities at points where the transmission by the mirror for these colors is gi-eatest. With the new type of flame carbons, both for the high and low power arcs, this condition is very closely approached, the highest intensity points of the arc spectrum being at the point of greatest efficiency of the miri'or, whereas with the old type of carbons, the gi-eatest amoimt on intensity and emission of light is on the points of diminishing efficiency of the miiTor for transmission. ITius the emission curve of the beam from the new-tj-pe carbons, both high and low power conform fairly close to the emission curve of the arc, while with the low-power arcs, the beam is considerably distorted. 29. The results given in the table are an average of several observations and are considered fairly representative of what may be expected from future carbons of the same composition and characteristics. The results in the blue and violet part of the spectrum vary considerably, and this is due probably to unknown absorptions of the various parts of the apparatus. The intensity of the blue part of the spectrum Ls very low compared with that of the rest of the spectrum so that eiTore may also be introduced due to the difficulty of balanc- ing these very low intensities. 30. The intensity distiibution of the Beck beam is not quite so desirable as the Sperry beam for the highest efficiency of transmission by the mirror. The intensity distribution of the Sperry beam coincides very closely to that of the arc in intensity at the points of highest visibihty, while the Beck beam shows slight distortion at the gi-een part of the spectrum. This is probably due to the color of the flame of the Beck lamp which is decidedly orange in color, and this intensity is taken as part of the totals of the foregoing table. The Sperry flame shows a color nearly approaching the arc so that the distor- tion in the Beck beam may be due to the flame and cool carbon tops. 31. Regarding the percentage of total intensity emitted by the crater and the carbons, the following table shows these values, expressed in percentage of total emission: Searchlight arc. Percentage flame. Percentage crater light. Navy standard, plain Nav'v standard, white Qame. Sperrv (at 30°) 2 6 49 28.8 98 94 .■il 71.2 Beck (at 30°) 32. Although the Sperry arc shows a much smaller percentage of crater Ught than the Beck arc, this is not considered a disadvantage, as it has been 156 THE SEAnCHLIGHT. found by actual experiment that the hot carbon tips of the Sperry arc are u?e- ful and enter into the beam. With the Beck arc, the tips are fairh' cool and thuri do not radiate nmch light. A\Tien the Sperry arc is measured -svith con- sideration for the hot tips, the arc s-hows about 72 per cent useful illumination. This is true if the following con>iderations are taken. Consider the s) here of aberrations from which useful light emanates as being 3^ inch in diameter. Then all light falling within this sphere is ui-eful. Much of the hght from the crater and carbon tips of the Sperry arc wUl fall within a sphere of this ; ize so that it is feasible to coa^ider these carbon tips as a useful source of illumination. 33. There are 20 plates showing the general characteristics of the arcs, beams and parabolic inirroi-s used with naval searchlights, both high and low power. From these plates, with the addition of several others, used to check these, all the results given in this report have been calculated and con- clusions drawn accordingly. 'U ir,r Sm\ 1 Tffkcaf m Co *afl fofCY.Cc.f' '^Ufh i¥er^ r ni A p . 77 Ma ifesa /'On ■"* /\ 1 \ ^^ 'ffms itomi r=,;/Si WrfiX jfj \ »A \ cr-f \ fSi !~ \ L ,; \ f \ If { \ iijt y -\ \ It' r y \ S \ ri / / y N \ 1,' / J \ \ !l 1 A/ / / — ^ \ v> .•"^ r VliHI M 1 Jv 1 Crrf: 'V^ %' }6" i h i^ "^ 1 .. . 1 THE SEAECHLIGHT. 157 ^S.3^ PUr ■N92 M! _^ r \ Arc Vorma Arc OAntp 1 2.?( 7SVai .M. ^, M^ A 1 \ ^ VJ9C r»esl$ ■ye jAc owsva fu€ifc. aitd a»M 1 e are na/ to undt curv \JiU£B. S^_ nst \\ ' CJ. fnvat a/ !S '>eArc ma ,1 fi-np- jecfrt * Arc \ \ to \ A, 'rJ? 1 ..„/, esof ■3tul ^ yes u :vaJu ti/or f/OiHg £I£3 1 1 [/'U/// '^//a^ ofaTl 'A car rettSf •r- h,~^h , cwc- /arffi ""*" jpert OOff. \ y \ ^ '".T.fi / \ 1 \ /T^ \ "" / N s \ \ / ^ / '"^ / \ \ .-. f 1 \ \\ s. /^u J /^ ' \ 3ai pleN ! \_ _ /^ 1 \ Bo*' H ^/^«r 1 -,.'. •s — ^ 9 •« \/fi-d w— 1 y - ' ~1 1 1 CSif 1 158 THE SEARCHLIGHT. 1 — - plAkM-} , 4U 1 .^p»\f^u- tmtmX^h^ 1 "cjr^A^ yjj i ! U — TU. i a#^ k.^o/^Trfl ^'i^TtSlct ^-t-t/. f^-o I !■• . . , . . . . -iW ^*i*Ji /?- iV(M «^//0i i ^r^^yiWit. v ; A . i i 1 1 r ^ I'J \ i ■I; u ; .Mf IT' — — \ ^ \; / \V / '^ i \ ^1 k i ■ / \ A i ' N // / ' 1 V 1 1 1 I _ J r // 1 .__ I 1 \ ! 1 \ ' 1 ' fr / ! ^ S~Lt ^ 1 1 M ^\:N ! i y'ff'e/ 1 < ; " r 1 1 1 1 ^v k , 1 1 1 1 ..... .1 PL. \Tt,*ies ^riM- 1 i »t 1 >— i— 1 »....,-tv m 1 i''*-^ Hi 7Ji€ ^tiw^/Ccr fij A 6 fltmi- f" SC'Af^-^f I /\ ^A ' A 1 ^ :? A \ < k ^^ \ \ r / \\ 1 1 A \ \ \ / \ \ \l 1 k\ /■ \ V h r \ \\ V f\ < KaV H F*^ 1 !»«. '- m W ' •t< 1 THE SEARCHLIGHT. 159 Pla) £yv? 5^ light Ji^^r ~ar6o lArc JU ^eSf oeCot '/»"> v,»r atj 7 /4 rcAcD 'anal "^ofda leeah 10. £ZMm. 3?J / \ /?, TTtast fwTo fori be ft. •^Ufyi AW / / L > ? ISA ' V L V \ ! •jr., A ^ \ k'" / / \ \. // \ \ \ ,,^ y \ \ f \ \ I \ ^ (/ Z' \ \ e.s 1 \\ ^. V v^ V ' J A V.e/t* H B/u« 1 C/^^* nihi •^ t t.n< •./ fa «9 t,„ \ 1 \ fm \ jj.n-r ;, ^^ /■ \ \ // \ \ / 7 \ \ \ f / \ \ x.f / ' \ \\ /■ y \ \ t.j ^ / > \\ 5^ //c / ^ 7 !'.•** H at^t 1 f^M mv . 1 Xt' '' *«i aJ^ Pla i-^< tf ,^ At- tf.l/.^^ /or , •e A '—'9 tofal fame- CSfo lira rnoft ■Jff".. tkJ2£ Mm* 5« C in J«> fTJ »v 1 ■^2ZS > ^n^ } \ ISO / 1 \ «i 1 \ i \ \ 7S / \ la / J \ \ It / / \ _j / ^ •^ k'«)-rn M BliAt Off '•It H L . ."- 1 THE SEAECHUGHT. 161 PL A TEf, ?3 Lo fCa in^cfJ ■jfy rcfo Nav il ^ Tips andf ffead 9fArt Oaf< ktnor rCar 30 'A ■h c '.X' by/Va 5va cU)q from ! \fs Oft Cq 7~C- XJI ni ■>ii«.( |,„ r \ !- I \ L A \ IM \ -Jtl - \ \ ../f.' / \ rt y \ -^1 / / \ ej / \ S^p. tmi r -^ Vhhf M W -J aw 1 a .s •J .J ^IfS B — -3 15—3 K — - W .7 to ' 1 Pi ^T£f\ 9/0 "T/wrV Typict 1 Lo* fh^ft) CarU 5ea.rcf nArc h'ghts orN>n I S/7 f otaHn ',d F!a sfaKe cffAn Cratt, "Angh Carte 21 A Arc Vorma. ai-llO Amp.$pV/v e yf'th pla!" ZS.L Curve 1 ftame *iardc oi^fSt "jt/ari3 Pbsir,. -mM wh'fe t, f \ 1 \ \ (t\ ^/ N V rt.S H — s V \ / \ \ J \\ /. 7 V V // V ^^ / A v!airf M ■0 .J 1 Si^f "'" 1 Lertf '\l Vfl « .» ' tsls:. 162 THE SEABCHUOHT. Pl, r£^ »// \^PC< '"n 'trfwfi ufy 3e 1 fa *^ re y. G^trat i/s;' n'cCo m^fj «Ci LtK rM /.lir/..c ■ SDH /)*.-« nc /N -/tf ./»rt k^« { /^ \ T^f: »# ' L6r^ tmnn/. I untie nd.i 0./7- 1"" ^ \ fM, .5 1 \ 4" \ • \ 1 \ / \ IM / 1 y V / / \ V, — / _^ -P *^ A ■-* tr-ote* 1 M-'-w. h'^K 1 3: T t r ; n 1 1 1 »/-"" 1 -^ /'i *T£A ?ts I Itrrtf/ A Sfc... Samd Ca l^oif'c W ^Ji \ . \ « t t- 1 — N \ 1 \ tfj \ A».* / \ y ^ / / \ / \ .S«^ lf*f/ ^ ■^ ¥K,f _M_ ^^' ii <>w. ■•J '"(t 5r ^ -J- ' " ^ i 1 1 1 ■" THE SEABCHLIGHT. 163 1 PiJTENiia I Coi^:L 30J ^0 energy fff/c*™/ Gt^ssPaJ^aboh'c MJfro\ajiti F. vntU is M4 ?<4 n, ;nase<. undej^Sc^c. 7'C-S n* Not Curve \sMo» fSptc. -umo Arc / \ f,., \ A \ s, M N \ *fl A \ IO.Q [ ^\ / \ \ / / \ s \ «0 // X \ \ .i ^ \ \ / \ ^ \a • r-5 ; — 3 ^ 1 7rcefT ■*>KnS reify. — y 7«M 1 Fed - ' J ft/ r 1 1 PL <\TE 1/m Sp^ trwnl t. ki soy/a> fMazc iLmo / \, C /or St / \ G/tns %ra6c 'ic Mi. rcr & 'rvfrfi OCT Li ns .H / \ [^ Max, Waff Cjr,ce yfCart menf Of Arc 1 \ h '/ \ 1 Nnfe i. / V V \ L o c irv«A ■ Lauf trveB showi O sfiow. Sped 4im i / \ \ o ■i 1 \ r~ I \ \ \ .as / \ // \ \ ■OJ '/ \ 1 ^ y Xb .0/ / r"^ / KVt f 3 H > -J 1 — = '^ h^ r-..| '"- i;J ^ f""j 1 I 1 1 1 <;i/or 1 1 1 . L. 1. ,1, '■ 164 THE BEABCHLIQHT. Plated '?«• Camoi 5p«ft •1 ;r*/r •fArc J ffryt ■.j*/t A fx •cy / A ttltit 'ons 1 1 Erei^yefffcief^cy dhi-af^rabo/KT Mirror ant/ '^ront-t/^s MJt ^ V^,!te Ftainc Na^d Co"^Pa3i*i e I lS.9 t / 1 / V i 1 1/ i L- r l\ /nfvns/fy r fat: >z fS iH 1 l„ / i 1 U \ i \ 1 i / \ \ / , rf/ ; ' \ 7^/1 ^ V^ ^ L J J \ 1 4 Vcrrfc '/ \ Ns ■^fvin aC^a \ Cur,t 'iSf^^ J^CI 1-umei, S«A, A \ / \ \ 1 \ \ 1 / / \ •~, \ / i \ j \ ^ ' \ \ \ ^ / \ \ \ ,^ \ \ 1 1/ K \. :b^^ NS j ^tak r ■vA- ; A ff .T 166 THE SEARCHLIGHT. /=-. AT£ M: / /» -«MT I H U N t^ 5:„ \ j L j^ N ,a , \/ 5 L / \ it™ V J \ K i \ [- I ^-'.L-^^'-l. 1 <: Ur .^ ) ^n^f- aft tMxW U^St^p^ktm-BbSH, U \ /U r*^ 0.<^ti -fcft-tj-i-fcjff/ta-y i i \ r-*«A. ^ m^ -•H ? / \ l^ ll .1^ / \' r Bin 1 o. r» Ymfli»y XOr •f" 'L&^tf u -' (M "^o^l A !«/ ''"■i 1 -T -*1 1 j5 ■*« i , 1 \ In, y I . .M / <' 5 i V / / V. 1 / 1 / N L / 1". i \ \ \ y ] \ i; 1 \ I f — ' I •-f^i iP-f' SA.A c k/«r« \ 'V- /WiVn 1'. V -ftVM • ^ ntfrr />* \ acfu'ttet b^ "Vffr^ 1. N D^H «(m!-^ ^*-/ »«^i! (V»r*- ■s- J If ^^y.tf *r#. ■fit* 1 Hj ■»» ll^ / ^^ y ^ S^.-i ,^ i. " - 1« '^ K^ m i V •» * Spr. r THE SEAECHLIGHT. 167 PLAT r/VP ?^ f^ ■,>lf>r fv s rcta, arOili rtr. F///a or , s * 1 • 1- * .5™ --^ — > ^. / ' "^ V y cf ■^ i ?* te 1 1 1 __ ■ ' I'^t'l M 1 I.--.-" ) ■ . s% ?;-,-.£ ?■ -"^ »,rf 1 1 1 1 1 1 |C.-,o,J 1 1 CHAPTER 13. MffiRORS FOR SEARCHLIGHTS. focue ANO OOORCI Of \-ic»MT Rao-I Rad-Z Fia. 152. SEARCHUGHT AHRRORS. The United States Navy cmplo}-s two types of niirrore for use in search- lights, namely, Mangin minors and parabohc mirrors. The former are used only in small searclilights of 9 and 12 inch diameters. Mangin mirrors are much more easily manufactured than are parabolic mirrors, and hence are cheaper. For small search- lights they are excellent, but in large sizes they are not nearly as satisfactory. The principle of the Mangin mirror is as follows: the curvature of the surfaces are such as to correct for refrac- tion, caused by the glass, of light rays emanating from the focal point, and to finally effect the approximate paralleling of all light striking the mirror and emanating from the focus. Figure 152 shows path of light rays with such a reflector. * Tlie Mangin mirror gives a beam of small spread and fairly good results are obtained from this type of mirror even with a comjmrativcly large light source. The parabolic mirror uses the principle of the Jparabola.'^ Any Inline drawn from the focus of a parabola to the curve makes an angle with the normal equal to the angle made by the nor- mal \vith a line parallel to the axis of abscissiE. This is shown in the dia- gram (fig. 153). In small sizes, up to about 7 inches, the parabolic mirror is not as satisfactory as the Mangin mirror, though it is lighter. In grinding glass for mir- rors it is of importance that glass used be free from stria- tions or tear drops, as these seriously affect the optical properties of the mirror. The explanation for these striations seems to be that they are caused by particles of the crucible in which the glass is melted dissolving in the molten glass. When poured, they produce the striae, and, being optically verj- different from the glass, produce absorption and refraction of hght which impairs the efficiency of the mirror when present in large quantities. More- 168 ■' RSi.'iS-'-'*-' '.- ''r-''hyf^-*^i'°^ff^ Or Uk^mt Fio. 1S3. THE SEABCHLIGHT. 169 over, they weaken a mirror mechanically because, being of a different substance and having a different coefficient of expansion, they set up internal stresses during the heating or cooliug of the glass. Bubbles in the mirrors are not very serious as they have little effect on either the mechanical or optical properties of the glass. The most desirable glass for searchlights is one which would have the optical properties of the white glass now used and the mechanical properties of "Pyrex" glass so much used for cooking utensils. "Pyrex" has a very low coefficient of thermal expansion, so low, in fact that it may be heated quite hot and plunged into cold water without causing it to shatter. "Pyrex,'' however, is not a good optical glass. Work is being done to produce a glass equally as good optically as any glass used at present, with a coefficient of expansion approaching that of "Pyrex." Searchhght mirrors require constant care to keep them up to the required point of efficiency. They should be wiped and dusted frequently, particularly where particles deposited are on the surface of the glass which, if allowed to remain, would destroy the accuracy of the surface. Following are specifications for Navy searchlight mirrors: 17M7 1918 Navt Department SPEcmcATioNs. MANGIN MIRRORS FOR SEARCHLIGHTS IN THE UNITED STATES NAVT. General specifications. 1. General Specifications for Inspection of Material, issued by the Navy Department, in effect at the date of opening of bid, shall form a part of these specifications. Description. 2. The mirror shall consist of a glass plate, the respective radius of the faces of which shall conform to Mangin's determinations of same, a reflective backing, and a protective backing. Dimensions. 3. The over-aU dimensions, thickness of glass plate, focal length, etc., of mirror for various sized searchlights shall conform to this table and sketch, forming a part of these specifications: [Ail dimensions in inches.] SiMof minor. A. 1 B. c. D. E. F. 9 8^' m 9 lA H 4.125 12 11^ 12H 12 2H H 6.10 ' 18 I 19A 18 % lA 8.625 Glass plate. 4. The glass plate shall be made of the finest grade of clear glass without perceptible tint, free from flaws, bubbles, and other defects, and shall be gromid 170 THE SEABCHLIQHT. to a true surface, highly polished, front and back. The ratio of the radii of the front and back surfaces shall be such as to give a minimum beam dispersion. Reflective backing. 5. The reflective backing shall consist of a heavy coat of metallic silver. It shall be homogeneous, evenly applied to the surface of the glass, and be so fitted as to form an air-tight joint between it and the glass. The backing shall be such that it will prevent the admission of air or any foreign substance between it and the glass which will cause oxidization of the reflective surface. Protective backing. 6. Over the reflective backing shall be placed a protective backing con- sisting of one heavy coat of metallic copper, and over this copper plate a coat- ing of heavy enamel which shall so seal the backing as to render it absolutely waterproof and air-tight. Focoo Ra.d-1 Rao-Z Fio. 154.— Dimension diagram. ifaii?ln mirrors. Tests. 7. The mirror shall be required to meet all of the following tests : (a) BacHng. — The backing shall not be afl"ectcd by either sea water, boiling fresh water, or a dry temperature of 65° C. (150° F.). The backing shall be subjected to each of these consecutively for a period of 72 hours. The enamel paint shall be of such material as not to be readily rubbed off at a dry temperature of 65° C, or when moistened with sea water. In the event that the backing proposed has not previously been approved by the Bureau of Steam Engineering, the contractor will be required to submit, prior to delivery, a sample mirror, approximately 8 by 8 inches, to the New York Navy Yard for test, this sample to be backed with the material which he proposes to furnish. (6) Line or screen test. — The reflection from the mirror of straight, hori- zontal, and vertical intersecting lines, forming 1-inch squares on a screen, shall THE SKAECHUGHT. 171 be photographed and this photograph shall show the mirror to be free from any irregularities of grinding or polishing. (c) Sun or zone test. — A photograph of the reflected rays of the sun, when the mirror is placed at right angles to the rays of the sun, shall show a cone of sharp outline and weU-defined apex. The diameter of the sphere of aberra- tions shall not exceed }4 inch. (d) Beam.— -The reflected beam from the mirror when a concentrated filament lamp is placed at its focal center shall be round, free from zones, and the quantity of useless dispersed rays shall be negligible. (e) NigJd illuminating tests. — The tests for the acceptance of the mirror shall, at the Government's option, include a night illumination test, consisting of placing the muTor in a searchlight and using the searchlight arc lamp for the som-ce of light. Tliis test shall show the beam to be of a uniform intensity, decreasing from center to outer edge and free from light zones. The shape of the projected beam shall be a true circle and its edges clearly defined. (/) All of the above tests shall be conducted by a Government representa- tive and the failure of the mirror to meet any one of the above tests or require- ments shall be deemed sufiicient cause for its rejection. Shipments. 8. Each mirror shaU be secm'ely packed in a separate case and case shall be plainly marked with all data necessary to give complete information as to its contents. Specifications, where obtainable. Note. — Copies of the above specifications may be obtained upon application to the Bureau of Supplies and Accounts, Navy Department, Washington, D. C. Navy Department Specitications. PABABOLIO SEAKCHLIGHT MIRKOR3 FOB USB IN THE UNITED STATES NAVY. June 1, 1917. General specifications. 1. General Specifications for Inspection of Material, issued by the Navy Department, in effect at date of openmg of bids, shall form part of these speci- fications. Description. 2. The mirror shall consist of a glass parabolic plate, a reflective backing, and a protective backing. Dimensions. 3. The over-all dimensions, thickness of plate, focal length, etc., of mirrors for various sizes of searchlights, shall conform to this table and sketch, forming a part of these specifications: Size of search- light (Inches). 11>. 18... 24.. 30... 36... Uirror dimensions In Inches. F Q H I J WH 11 H 2H 4 19A 19A ^ ■■w. m 25!^ 25ii Vf 4A 10 31A 31H rt 6H ua 37 * BM UH > The 11-inch mirror is for installation in incandescent lamp searchlight. This mirror shall be of best commercial type. Slight Taraltions from the dimensions specified will be permitted. 172 THE SEABCHLIGHT. Parabolic plate. 4. The parabolic plate shall bo niado of the finest grade of clear plate glass, without perceptible tint, free from all flaws, bubbles, striae, and other defects. It shall be ground to a true parabolic surface on both front and back, the focal center specified being made the focus of the convex surface and the concave surface being ground parallel to the convex surface. The thickness of glass shall be uniform over the entire surface, and all dimensions shall con- form to those set forth in table forming part of these specifications. Reflective backing. 5. The reflective backing shall consist of a heavy coat of metaUic silver. It shall be homogeneous and evenly applied. The backing shall be such that it will prevent the admission of any foreign substance between it and the glass which will cause oxidization of the reflecting surface. FiQ. 155.— Dimension diagram, parabolic mirrors. Protective backing. 6. (a) Over the reflective backing shall be placed, electrolytically, a heavy coat of motaUic copper of such a thickness as to reinforce the reflective backing and protect same from mechanical injury. (6) Over this copper backing shall be placed one or more coats of a paint or enamel of such quaUty as to render the greatest resistance possible to the admission of any moisture or gases which may injure either the copper or silver backing. The gases encountered wUl be the usual flue gases given off from soft coal and fuel oil purchased under naval specifications for use aboard ships of the Navy. Tests. 7. (a) Before acceptance, and at the discretion of the Bureau of Steam Engineering, the mirror will be submitted to the following tests : (6) Backing. — The backing shall not be affected by either sea water, boiUng fresh water, or a dry heat of 90° C. The backing shall be subjected to each of these consecutively for a period of 72 hours. In addition to this, THE SEAECHUGHT. 173 the protective backing will be subjected to the appUcation of hydrogen sulphide gas, washed and dried, appUed over the entire surface of the mirror for a period of 6 hours. At the end of this period the reflective backing must not show the least signs of sulphiding, the copper must not show any signs of discolora- tion, or the paint must not be affected beyond the surface. (c) In the event that the backing has not been previously approved by the Bureau of Steam Engineering, the contractor will be required to submit to the New York Navy Yard for test and approval, prior to opening of bids, a sample parabolic mirror, 12 inches or more in diameter, backed with the material which he proposes to furnish. (d) Line test. — The reflection from the mirror of straight horizontal and vertical intersecting hnes forming 1 inch square on a screen shall be photo- graphed and this photograph shall show the mir ror to be of uniform thickness of glass, free from aU irregularities in grinding, striaj, and bubbles. (e) Focal center. — The reflection of a beam of Ught 1 inch in diameter, projected perpendicular to the directrix of the parabola and reflected through center of the mirror when moved across the mirror of any diameter, shall indicate a spherical aberration of not greater than ^ inch. This shall be determined photographically, and shall be taken on each mirror. Tests will be made on not less than two diameters, 90° apart. (/) Efficiency. — The efficiency of transmission of the Ught from a 250- watt concentrated filament incandescent lamp, with filament on focal center of mirror, shall show not less than 70 per cent of the entire energy of the fight of the lamp falling on the mirror, and shall show a transmission of not less than 70 per cent for fight at a wave-length of 0.510 micron (green fight) and an efliciency of not less than 76 per cent for Ught on wave-length 0.540 micron (green fight). (g) Night illumination. — The tests for the acceptance of the mirrors shall, at the Government's option, include a night Ulumination test, consisting of placing the mirror in a searchfight and using the searchlight arc lamp for the source of fight. This test shall show the beam to be of a uniform intensity decreasing from center to outer edge and free from fight zones. The shape of the projected beam shaU be a true circle and its edges clearly defined. Eejection. 8. All of the above tests shaU be conducted by a Government repre- sentative, and the failure of the mirror to meet any one of the above tests or requirements shaU be deemed sufficient cause for its rejection. Shipment. 9. Each mirror shall be securely packed in a separate case and case shall be plainly marked with all data necessary to give complete information as to its contents. Mirrors whose backing is damaged, but whose sTirfaces and cm-ves are not impaired, may be resdvered and made equal to new mirrors by the process given below. EESILVERING PARABOLIC SEARCHLIGHT MIRRORS. 1. The backing paint is first removed by immersing the back of mirror in solution of potash and water. (Three pounds of potash to 8 gaUons of water, approximately; time, 3 hours; is usuaUy found to be sufficient.) 174 THE SEABCUUQHT. 2. Rinse with water. 3. Place mirror in trough for cleansing and silvering. 4. Remove old silver with nitric acid, use absorbent cotton on wood Btick, rubbing carefully over surface. 5. Cleanse thoroughly with water. 6. Wash the surface with ammonia and water mixed, to remove grease from surface to be silvered. Use absorbent cotton. 7. iVgain cleanse thoroughly with distilled water. 8. Cleanse surface with absorbent cotton dipped in nitric acid; rinse with distilled water. 9. Apply sUver and reducing solutions. Special fixtures are fitted to place bottles of silver and reducing solution above mirror to be silvered. These bottles are furnished with stop cocks to regulate flow through glass fumiel. Distilled water is run through rubber tube into funnel to mix with silver solution in order to give better How over parabohc surface. 10. Should brownish streaks appear, stop flow of silver and reducing solutions. ^Vllow water to run, rub surfaces carefully with absorbent cotton. Start silver solution again, as soon as the dirt has been removed. Note. — Care must be takeu that the cotton used is perfectly clean. 11. As soon as the silver solution is appUed, the mirror should be placed in copper bath to receive the necessary coating of copper. Note. — Surface to be silvered should be kept wet constantly, until silvering and copper plating is completed. 12. For 30 and 36 inch mirrors about 30 minutes is usually the time given for copper plating the silvered surface. 13. Mirror removed from plating bath should be washed thoroughly with clean water. 14. Use filter paper to dry mirror surface as soon as removed from water bath. The paper must be used as a blotter, and is not to be rubbed over the surface. 15. The first coat of backing paint is sprayed on and baked in a tem- perature of about 250° F. for about three hours. For the first coating, red mirror hack paste is used with good result, followed with three coats of Valspar varnish, each coat baked on as given above. 16. Any paint spots on concave side can be removed with xylol or ben- zine. Use absorbent cotton and clean linen cloth to dry. Rub surface with absorbent cotton and nitric acid. Wash with soapy water. Dry thoroughly with clean linen cloth. Note. — It is important that no other than distilled water is used at any time during entire process. TBAY METHOD FOE SILVEEING jnEBOBS. 1. Dissolve 4 ounces silver nitrate crystals in 150 cubic centimeters of distilled water. 2. Take 4 gallons of distilled water, add 125 cubic centimeters silver nitrate solution given in paragraph 1. This solution will turn muddy in color. Remaining portion of silver nitrate is kept in reserve. THE SEABCHLIGHT. 175 3. To the above solution add C. P. ammonia until precipitate which first forms redissolves. Stir well with glass rod. Stop adding ammonia as soon as solution begins to turn clear. 4. Add a solution of 2 ounces (dissolved in water) of potassium hydroxide C. P. alcohol sticks. The solution will again turn muddy in color. 5. Again add C. P. ammonia to redissolve the precipitate. As soon as solution begins to turn clear stop adding ammonia. Stir weU with glass rod. 6 . A silver kept in reserve until solution turns straw color. Stu- well while mbdng. Add distilled water to this reserve solution before pouring into solution in paragraph 5. 7. The above quantity of solution wiE silver sui'face of approximately 6,270 square cubic meters. 8. The silver crystals and potassium hydroxide must be dissolved in water in separate vessels. <=l-/\€>6 Stop Cocks 30TTUE. doNTAlMlKIO. — BciTTUe - Dl £>T>V,V.E.O WATER - Mirror — Rvj&BER Tube. — Wood TroooW DrfxikI FiQ. 155.— Arrangomeat of apparatus for resUvering mirrors. REDUCING SOLUTION FOR SILVERING MIRRORS. 1. Mix 4^ pounds of granulated sugar. Eight gallons hot distilled water, 110° to 130° F. 80 cubic centimeters C. P. nitric acid. Stu* well while mixing. This solution must be kept in weH-corked bottles. 2. If this solution is made up with cold instead of hot water it must stand 10 days before using. 3. The solution made up as in paragraph 1 can be used immediately. TO CLEAN SURFACES OF SEARCHLIGHT MIRRORS. 1. To prevent scratching use absorbent cotton saturated with wood alcohol; dry with clean hnen cloth. 2. At the factory ammonia is used a great deal, although wood alcohol will do as well. 66438—18 12 CHAPTER 14. CARE OF MODERN HIGH-POWER SEARCHLIGHTS AND CONTROL GEAR. CARE OF MODERN fflGH-POWER SEARCHUGHTS. Tlie advent of the high-power searchlight has materially increased the importance of the application of searchlights to naval work. The low-power scarchliglit, while excellent for navigational purposes, was of comparatively little use as an aid to gunnery except at very short ranges. It is hclievcd, however, that high-power searchlights, when properly used in connection with broadside guns, will materially increase the efTcctivcness of these guns, and it is quite possible that they will be called upon for use during the firing of main- battery guns. Low-power searchlights did not require nor receive very carefid use or attention. High-power scarchliglits, with their many comparatively delicate parts and additional refinements, when instaUcd on naval vessels received no more care than the old low-power lights. Conse(|Ucntly gears became damaged and stuck with paint, pins holding gears to shafts have frequently been sheared off, and the broken pins replaced by nails. These pins were sheared off by operators attempting to forcibly turn the searchlight when the control shafts were locked in position. An operator trying to turn a search- light and finding he can not do it all too often docs not look for the reason, but gets some one else to help him turn it. Together they turn the light, but it turns only at the expense of pins, gears, shafts, and bearings. Something had to break before the searchlight would turn. Carelessness in details, such as cleaning, painting, oiling, and operation, has resulted in the dcvelopnjent of much backlash and lost motion in con- trol of mechanism, grounds and short circuits became frequent occurrences, and lights did not operate satisfactorily and deteriorated rapidly. Present high-power searchlights are entirel)' diflcrent from the old search- lights, which, by comparison, are Icnown as "low-power searchlights." Their mechanisms are more complicated and their construction and design carried out vnth much greater accuracy throughout. So, too, are the newer types of control gears, designed especially to ojjerate with the greatest smoothness and accuracy. They are made with a care commensurate with the refinements of the machines to which they are to be applied. There is now being developed in this country for the Navy a system of control of searchlights on battleships and destroyers similar to the foUow-the-pointer sj-stem of control of guns. Other s}-stems of follow-the pointer control of searchlights are in use in the navies of foreign countries and are developed to a high point of efficiency. Experience has shown that the belligerent nations on both sides have for some- time controlled their searchhghts with great accuracy by some S3stem of this kind. Particular care is therefore necessan,- to keep searclilights and their control sj'stems at the highest obtainable point of efficiency. 176 THE SEAKCHLIGHT. 177 Following are a number of items which, if observed, will aid greatly in obtaining efficient cooperation between guns and searchlights at night and the maximum efficiency of the searchlights at all times: 1. Trained men. Men shoidd be trained thoroughly in the care and operation of searchlights. 2. Frequent drills. Use of searchlights in connection with the follow-the-pointer system, opening shutters only after searchlights are trained on target. 3. Study. The men in charge should thoroughly know their equipment. If the}^ do, they win appreciate its refinements and the necessary care in operation will be easy to obtain. The instruction booklets furnished with searchlights should be carefidly studied by men charged with the care of searchlights. 4. Backlash and lost motion. When these develop it is important that immediate steps be taken to carefully align and adjust gearing to remove them. 5. Paint. A frequent cause of lost motion when applied to wearing surfaces, particu- larly to the teeth of gears. Occasionally oil holes have been painted over, paint even being put into the holes. 6. Lubrication. Some gear boxes and searchlight bases are packed in grease. These should occasionally be examined and repacked where necessary. Where oil is used it should be used liberally and frequently. Graphite should be used frequently on exposed gears. 7. Grit, sand, dirt, etc. In oil or gi'case these quickly destroy accuracy of gears, bearings, and wearmg surfaces. Great care should be taken to keep searchlight gears and electric apparatus free of abrasives. 8. Dampness. Electric gear should be kept as nearly dry as possible to prevent "grounds" and "shorts." The mechanism in base of lamp and base of searchlight should be exposed to the sun on hot, sumiy days m order that the sun may help dry out any moisture that may have accumulated. 9. Oil and grease on electric contacts. All contact points should be kept free of oil and grease, as these substances are insulators and prevent good contact between cuiTcnt-carrying surfaces. 10. Electric connections. Should be kept tight. An occasional examination and tightening of loose connections caused by vibration will take care of this item. 11. Synchronizing. It will occasionally be required to sj^nchronize searchlights with the follow- the-pointer mechanism. This is done by locking the searchlight in position and making electrical and mechanical pointers both indicate this position. The zero position is most convenient. 178 THE SEAnCHLIGHT. 12. Use of undue force. Searchlights and control geare work casil}' and smoothly. They will not stick. If the £carchli<;ht sticks, it should not be forced to move as it will move easily after l)ein£:; unlocked. 13. Frequent use. Manufacturers of high-power searchlights recommend the frequent use of their product, for two reasons: First, it familiarizes the personnel with the operation of the searchlight; and, second, a mechanism of this kind deteriorates more rapidly when unused than when in frequent operation. Troubles develop, due to sticking of parts and change of adjustments due to vibration when searchlights stand idle for a long time. 14. In general, searchlights and control gears shouM be as carefully cared for as ordnance gear, for if their accuracy fails, in battle they will be a menace rather than an aid to the safety of the ship. CHAPTER 15. VICKERS "FOLLOW-THE-POINTER" SYSTEM OF SEARCHLIGHT CONTROL. VICKERS SYSTEM. An important recent development is the control of searchlights by director in a similar manner as broadside guns are controlled. This is efifected as foUows: Leads are run from the director tower for a training indicator at each searchlight. Each searchlight has mounted on its control pedestal a control indicator. The director tower contains a dummy-gun sight with telescope. This sight is mounted on a turntable and geared to a transmitter described later. This transmitter is connected electrically to an indicator on a searchlight pedestal and moves there, which indicates the angle to which the searchhghts are to be trained. Connected by gears to the searchlight training control rod is another pointer on the same dial. When control handles are turned until a mechanically operated pointer coincides with an electrically operated pointer, the searchlight is trained on the same target as the telescope in the director tower, except for errors of drift and deflection which is applied to guns and not corrected for in searchlight mechanism. On the training indicator there are two dials, each with electrical and mechanical pointers. The upper dial indicates training angles of 360 degrees per revolution of pointer. The lower dial pointers are geared to upper dial pointers in a ratio of 60 to 1, so that lower dial shows training angle of 6 degrees per revolution of pointer. The upper dial is used to bring guns and searchlights approximately on the target, and the lower dial, which is then thrown into gear, is used to train accurately on the target. The first battleship installation will be made on the North Dakota. A general description of this system is given below. "NORTH DAKOTA'S" SYSTEM OF SEARCHLIGHT CONTROL. The North, Dakota is to retain the original lights on board when changed over, but the base-gearing arrangements and lamp will be changed. The searchhghts will be made high power by removing old lamps, altering drum, and supplying Sperry high-power lamps. Shock-resisting glass front doors will be provided. The greatest change will be made in the searchlight base, where practically all old gearing, etc., wdU be removed and new gearing with different ratios will be put in. Every precaution possible will be taken to eUminate and prevent lost motion, backlash, incorrect alignment, and wrong indication. This is done by using only very carefully cut gears, spht pinions of Ordnance design. 179 180 THE SEARCHLIGHT. THE SEAKCHLIGHT. 181 - 0- is 11. IN si"! iiii mil 182 THE SEARCHLIGHT. 1^ pf Ipi Hit iliki 1 n!ii THE SEAECHLIGHT. 183 i,° Hi illll p-* • ' ''•■■'?.sv^^;^;-i"3c, .: ......,.,.,,,.,^^ -- I mr-^^B^ ill s ii3nr~i 184 THE SEABCHLIGHT. THE SEAHCHLIGHT. 185 :5i? II i 1? . 5 ^ i :':■■ i^ 186 THE SEARCHLIGHT, I I'H .iiiiili \^ ?> «;S THE SEAECHLIGHT. 187 roller bearings, ball thrust bearings, expansion joints in shafts, and special universal joints. The searchlight control mechanism must worii with mathe- matical accuracy to be of practical use. New control pedestals were designed, and the gears and bearings in the control box are also of same refinement as in the searchlight. The entire installation must be as accurate as possible. Illustrations show sections of gears in the searchlight base, control pedes- tals, sections of control boxes, and general arrangement. The speed of training will be 10 degrees in azimuth for each revolution of the handwheel. The speed of elevation will be 2 degrees for each revolution of the handwheel. The entire searchhght installation will be overhauled and when finished should be a marked improvement over present control systems. The search- fights with the shutters closed may be trained on the target. ^^r -6 M.'i i-rn "PT -D- -n \^ Arntaftii-a jrAo^-wrf /<» jftt/'C^cr~ Dial of- Sto r-c A/^y^f C/j^rarrngSrontt tr/CA'£/i5 fOLLCt^-T^JC'/'O/NTER rffyi^^/^/TTeFt AND f/V0ICA70f< f^OTQf^ Fig. IGl. SEARCHLIGHT CONTROL ON DESTROYERS. All destroyers will be fitted with follow-the-pointer system of control somewhat similar to that used on Noiih Dakota. Some modifications are necessary, but the general scheme is the same. Illusti-ations showing sections of different types of gear boxes and general arrangement will serve to present a general idea of the installations on destroyers. These, too, require great accuracy of manufacture and installation for a successful installation. ELECTRICAL PRINCIPLES. The general electrical arrangement is as shown in figure 164, the transmitter having six steps or segments laid out in four circles on a disk and arranged and connected as sliown. The disk is geared to the director-scope turntable, so that when the turntable revolves the disk rotates under contact fingers and various circuits are closed or opened. The contact fingers are connected to the poles of the indicator motor as shown. The indicator motor consists of a cross-shaped armature of soft iron 188 THE SEABCHLIGHT. mounted on a shaft. The shaft is geared to the slowing pointer on the indicator dial. Around the four-pole armature are arranged six fixed poles, connected as sho\vn. The motor has 24 positions for one revolution of armature and 6 positions for one revolution of transmitter contact disk. Table A shows the various positions taken by armature of the indicator motor as transmitter contact disk is revolved. Table A. Revolutions of transmitter. Contractors on transmitter point No. Degrees of Rcv(ilutl)nof indicatir-mjtor armature. 1 2 3 4 S 6 1 2 3 4 s 6 1 2 3 4 5 6 1 2 3 4 6 6 15 30 45 60 76 SO 105 120 1.15 ISO ins ISO 195 210 225 240 255 270 285 300 315 3.10 345 Second revolution Third revolution... Fourth revolution The polarity of poles of motor for different positions of contact disk in transmitter is shown in table following: Table B. — Field pole polarity as Iransmitlcr revolves. Contactors on pjint No.-. Rcvolu- tl ms of trans- mitter. Pole No. -. 1 2 3 1' 2' 3' 1 First ^Second... S s Not excited. ....do ....do S S \3 Not excited.. S S S Not excited.. d. do S Not excited.. do do S 8 S ... N N Not excited.. do do N Not excited.. N N Not excited. Do. Do. N. N. N. Not excited. Do. 2 3 4 N 5 NotexclUd.. do 1 Not excited.. do N do 2 N N Before explaining the operation of indicator motor, the electric principles involved will be reviewed. When two magnetic poles near each other arc excited with opposite polarity, one north and one south, there is a magnetic force between them. Magnetic "lines of force" are said to flow from the north pole to the south pole. These lines of torce follow the path having the least magnetic resistance. Magnetic resistance is known as reluctance and reluctance of a magnetic circuit corre- sponds to the resistance of an electric circuit. If some material of smaller reluctance than air is introduced into an air gap of a magnetic circuit, this material is acted upon by the magnetic force in THE SEABCHLIGHT. 189 such a way that it tends to move so that it would, if free to move, take a posi- tion wliich would make the reluctance of the magnetic path a minimimi. The reluctance of soft iron is about 7^ to 3-^ that of air, therefore a piece of soft iron in an air gap in a magnetic circuit wUl tend to move so as to offer the path of least resistance to the magnetic lines of force. Suppose the motor to start at 0° and that transmitter is at point 1. Referring to Table II and figure — it is seen that poles 1 and 1' are excited as sho^vn. The dotted hues through armatiire show path of lines of force and arrows show direction of lines. Suppose, now, that transmitter be moved to point 2, poles 1, 1', 2 and 2' are excited as shown and the armature moves so that lines of force may travel ^^ i,_i CCNTflCTOR30NP0i«T6 OMgFMMS SHOWIhC P-£^CLUTlC^^ Or INOtCrtTOR MOTOA Fig. 165. through as Uttle air and as much iron as possible. This point is seen to be when the armature revolves 15 degrees. Then suppose transmitter to move to point 3. Poles 2 and 2' are excited and path of least reluctance occurs when armature moves 15 degrees more or advances to 30 degrees from 0° position. It is seen that for each point that transmitter moves, the armature rotates 15 degrees, or that one complete revolution is made in 24 steps or four revolu- tions of transmitter. There is sho%vn in figure 165 the successive steps of motor for eight points (1§ revolutions of transmitter). By suitable gearing this apparatus may be made to indicate to any desired degree of accuracy. CHAPTER 16. CURRENT DEVELOPMENTS. FRONT-DOOR STRIPS. Considorablo trouble has boon experienced caused by the breaking of front-door strips by the shock of gunfire when the front doors are in place during firing. It is probable that the main battery will be used in an action at night. Front-door glasses that will withstand the shock of gun filing are accordingly an essential part of the modern searclilight. The British Navy has had some success in using old mirrors, having the sil- vering removed, as front doors. On account of their dome shape, they are very strong and stand great shock before breaking. So far all attempts to use full- width strips supported by springs have failed to prevent breaking, the inertia of the strips being so great that the glass is shattered before the springs have time to absorb the shock. It is proposed to try out radial front-door strips which will bo only half as long as the long center strips now used, and therefore more compact. Also by having considorablo spring and no rigidly fixed center point, they should give at each impact and not shatter as easily as our present type of strips. Difficulties are presented, but they may bo overcome by accurate manufacture. The greatest one is that a very slight difi"orcnce in angle of edges is additive around the entire circumference, and when all pieces are placed in position a gap would bo left, and the space left for a radial strip would bo larger than the strip, or, if the other strips were slightly larger than they should be, the last strip would not go into place at all. A great advantage is gained, however, in that all strips would be the same. No radial front-door strips have been tried out as yet, but tests are expected in the near future. The dome-shaped front doors will also be tested, and should they withstand the shock of main battery firing the searchhghts, will be adapted for their use. fflGH-SPEED BLINKER LAMPS. For a long time blinker signaling with incandescent searchlights was ham- pered by the slow heating and cooling of the filament of the lamp used. A decided afterglow was visible, and unless great care and slow sending were used, the dots and dashes merged into each other, particular^ at the longer ranges. The speed was limited to only a few words a minute and signaling with incan- descent searchlights was very unsatisfactory. Recently tw.o companies have been working on lamps which will be of such speed as to allow a signalman to work to the limit of his speed of send- ng or receiving, except at very long range. These companies have succeeded in producing a lamp which is so fast that the separate flashes can be distin- guished as rapidly as an operator can work the key. Signaling with either of 190 THE SEARCHLIGHT. 191 these lamps may be done at a rats of 25 words a minuts, which is sufficient for all purposes. One type of lamp has a far less concentrated filament than the lamp developed by the other company. It is not very good in front of a parabolic mirror, for the effect of a parabolic mirror in concentrating the light depends on the light rays emanating from a source as concentrated as possible at the focal point of the mirror. The lamp with the more concentrated fila- ment is quite compact and is of equally high speed as any other type of lamp, making it the logical lamp for use in incandescent signaling searchlights at the present time. High-speed, 250-watt signal lamps have been put on the allowance lists of first-line battleships, armored cruisers, and 110-foot submarine chasers. CONVERSION OF LOW-POWER SEARCHLIGHTS TO fflGH POWER. Since high-power searchlights have been developed to such a point that low-power searchlights, in comparison, are practically obsolete for use at sea, it has been necessary to provide a means of convertmg the greater number of Navj" low-power searchlights to high power. This may be done in general as follows : A high-power lamp is substituted for the low-power lamp, an inner drum is built to provide for ventilatmg air currents, and a ventilating motor is in- stalled. A number of low-power searchlights are now being converted to high power m this way, and it is intended to convert to high power the great majority of 36 and 30-mch low-power searchlights on battleships and eruisei-s. A full description of method of convertmg low-power searchlights to high power is given in Chapter 7. 66438—18 13 o UNIVERSITY OF CALIFORNIA LIBRARY Los Angeles This book is DUE on the last date stamped below. Form L9-32»i-8,'57(,C8680s4)444 iiiai TT^S, Finrpan of 1x93 Engineering - AS SearchlightR and 1918 signal lights for the instruc- tion of officers and h93 1918 UC SOLrmERN HEGtONAL UBftARy FACIUT/ D 000 326 588