\ 3 Gr. N,1 » r y S TABLE OF CONTENTS. Page. General description........................................................... 7 The telescope................................................................. 7 The base...................................................................... 9 Tripod....................................................................... 11 Accessories.................................................................. 12 Mounting..................................................................... 12 Adjustments............................................................. 12-14 Operation.................................................................. 14 Care and preservation..................................................... 14-15 Nomenclature.............................................................. 15-18 (5)WARNER AND SWASEY AZIMUTH INSTRUMENT, MODEL OF 1910. GENEBAL DESCBIPTION. 1. The Warner and Swasey Azimuth Instrument, model of 1910, is an instrument for measuring horizontal angles and is used in connection with the finding of ranges and the measurement of deflection errors of fire. The principal parts of the instrument are the telescope, base, tripod, and 'pier mount. THE TELESCOPE. 2. The telescope is of the prism type, and has the usual mechanism for focusing. It has the following optical qualities: Clear aperture of objective, 3 inches; focal length of objective, 24 inches; field of view, 3 degrees; powers, 10 and 15. 3. The telescope tube (6A), a bronze casting, provides seats for the objective (1A), the prism holder (13C), and the eyepiece end. In it are screwed pivots (6M) and (6U) by which the telescope is assembled on the base. 4. The objective (1A) is a doublet, the flint element being assembled so that it receives the incident light. It is held in the objective cell holder (6T) by means of the cell ring (6L), is protected against mechanical injury by the objective shutter (6C), which is operated by the shutter handle (6D), and held in a particular position by means of a shutter plunger spring (2EA) and objective shutter plunger (6F). The two elements of the objective are separated by a paper ring. 5. The prism system is the Porro type, consisting of two 90-degree prisms (2A) and (2B). The prisms are not interchangeable, and in each is a slot for a pin driven in the prism seat of the prism holder. In telescopes of serial numbers 1 to 75, inclusive, the prism holder and cover are one piece, while in telescopes after No. 75 the prism holder (13C) and cover (13A) are separate pieces. In the later telescopes the prism holder is attached to the telescope tube by dowels and screws. The cover in all telescopes is closely fitted to the telescope tube, forming a dust-tight joint, and is secured by screws. On the top surface of the cover (13A) are two lugs in which are cut notches which form an open sight. The prisms are held in their seat by means of prism-retaining spring (13B). 6. The eyepiece end of the telescope provides means for focusing the objective and the eyepiece, and for the measurement of small deflection angles. In the focusing sleeve (7L), screwed in the rear (7) 8 surface of the telescope^ the drawtube (7A) is operated by means of a focusing nut (2Q) attached to it and extending through a slot in f the focusing sleeve. The focusing nut is restrained against rotation by the walls of the slots in the focusing sleeve (7L) and is given a motion of translatuon by the focusing ring (7M), which is free to * rotate but is restrained against translation by a shoulder on the focusing sleeve and a sleeve nut (7T) screwed to the rear end of the focusing sleeve. By means of the focusing nut and the threads on the focusing ring, rotary motion of the focusing ring (7M) produces translation of the drawtube (7A). 7. The drawtube moves in the focusing sleeve and carries the cross wire holder (7B), the splash scale mechanism, and the lamp for the illumination of the reticule. In the rear end of it is secured the eyepiece adapter (8C), which the eyepiece engages. 8. The splash scale mechanism consists of a transparent celluloid splash scale (7N) attached to the cross-wire holder (7B) by means of screws. It is graduated in degrees, with a least reading of .05 degree, and for a total movement of 1.3 degrees in each direction. The normal reading is marked 3 degrees, corresponding to the deflection scales of sights. In the pointer case (7AC), which is assembled in a recess in the drawtube, is held the splash pointer screw (7X), by which the splash-scale pointer (7W) may be given a lateral move- s ment across the field. The splash scale lies in the image plane of the objective and the graduations correspond to angular distances in the field. If the cross wires intersect the target at the instant J of the splash and the pointer is independently moved to the center of the splash, the scale indicates error of deflection. 9. In the micrometer-lamp sleeve (7C) which is attached to the drawtube is assembled a micrometer-lamp shutter (7H), in which are two slots so arranged that the two apertures to the reticule chamber may be opened or closed, or so that the aperture for the illumination of vertical wire may be opened and the aperture for the horizontal wire closed. The shutter is operated by means of a lamp-shutter handle (7P) working through a slot in the micrometer-lamp sleeve. In order to prevent the access of dust and moisture to the interior of the telescope, the lamp-shutter handle (7P) should be kept in a position halfway between the ends of the slot through which it works. In this position of the handle the shutter is rotated to close both apertures. Light transmitted through the apertures of the shutter is reflected onto the cross wires by platinum mirrors soldered to the back of mirror cover (7Q) (7K). By means of the shutter gradual variations in the intensity of illumination of the cross wires is possible. 10. Two eyepieces are furnished with each instrument, one of 10 power and the other of 15 power. They are similar in construction. » Each has the power engraved on the eyelens cover. The 15-power eyepiece is the shorter one.9 11. The eyepieces are of the modified Karris den type. The field *- lens (IB) (ID) is a-single lens and the eyelens (1C) (IE) an anchro- matic doublet. Both lenses are held in cells, from which they should not be removed except by experienced instrument makers. The > eyepiece is held in the eyepiece adapter (8C) by threads, by means of which the necessary adjustment of the eyepiece on the reticule may be made. An amber-glass holder (8R) is pivoted in the eyelens cover (8T). In it is an amber-glass disk (8V), which may be thrown across the path of the emergent rays by means of the end of the holder which extends through a slot in the eyelens cover. The amber glass is used to diminish the intensity of the emergent pencil of light. 12. An eye protector (8A), composed of soft rubber, is mounted on the holder (8B) and the protector-holder shaft (8H) attached to the drawtube. The eye protector is adjustable in position, and should be so located that when the forehead is brought in contact with it the maximum field of view is visible. Pressure should not be exerted against the eye protector, as it may derange the instrument or interfere with the operation of parts. THE BASE. 13. The base provides means of holding the telescope, of imparting * to it motion in vertical and horizontal planes, and of measuring the horizontal movement. The principal parts of it are the yoke, azi-| muth circle, body, and leveling plate. 14. The leveling plate (10P) is threaded to receive the tripod head (4B) or the base (X35A) of the pier mount, and has seats for the spindle nut (11C) and the leveling screws (11J). 15. The azimuth circle (9B) is attached to the leveling plate by a spindle nut (11C), and is restrained from rotation on the leveling plate by four leveling screws (11J). The slot in upper surface of leveling plate locates one of the leveling screws. The spindle extending from the upper surface of the azimuth circle is tapered and forms a seat for the yoke. In the periphery of the azimuth circle are notched and hobbed worm-wheel teeth threads, which are engaged by the threads of the worm screw (10F). The worm mechanism is used for imparting motion to the body, for measuring horizontal angles, and is machined with great care. In a slot on the periphery of the azimuth circle is inserted a felt strip (IF) for keeping dirt out of the internal working parts of the instrument. 16. The yoke (10A) is a bronze casting with a long, internal, tapered bearing which fits on the spindle of the azimuth circle. The *, ' upper end of the yoke contains bearings for the telescope, and one side is provided with lugs for housing the depression slow-motion ~ mechanism. The base of yoke is machined for two adjusting-level boxes (11L), which contain the adjusting levels (11M) used in level-10000—17---------------210 mg the instrument. The lower end of the yoke is machined for bearings for the body (9A) and for the azimuth slow-motion arm (9D). The yoke is held on the spindle by means of the spindle washer (1 ID). On the forked part are hinged yoke caps (10D), which form the upper bearings for the telescope pivots. 17. The body (9A) is centered on the lower end of the yoke (10A) and is secured to it by the yoke washer (11K). It forms a seat for the worm box and a Cover for the azimuth circle and worm screw. On one side is a window for reading the azimuth scale, graduated in the upper surface of azimuth circle (9B). On the lower surface of the body opposite the worm box is attached an azimuth stop (1 IT) for limiting the movement between the body and the azimuth circle. Four holes are provided in the azimuth circle for the azimuth stop stud (11V), so that it may be set to suit different conditions of field of fire. Over the worm box are seats for the azimuth slow-motion plunger mechanism. 18. The azimuth slow-motion arm (9D) is slotted on one end and provided with an azimuth arm-clamp screw (11 A) for clamping the arm to the yoke. The other end forms a radial arm held between the azimuth slow-motion screw (11H) and the azimuth slow-motion plunger (11B), which is forced against the slow-motion arm by the azimuth slow-motion plunger spring (11KA). Slow motion between the yoke and the body may be imparted by means of the azimuth slow-motion screw when the clamp screw (11 A) is tight, and rapid motion may be obtained by unclamping the azimuth arm-clamp screw (11A). This clamp screw should be kept clamped after the instrument is oriented, so as to prevent motion between the yoke and the body. 19. The worm screw (10F) is mounted in a worm box (10H), which is pivoted on the body. It is forced against the worm teeth of the azimuth circle (9B) by a flat worm-box spring (11U) pressing against the body, and is held from exerting too great pressure against the teeth of the azimuth circle by the worm-box adjusting screw (8AC). The worm may be entirely disengaged from the worm gear by rotating the worm-box crank (10M). This throws the eccentric (11E) against the lug on worm-screw bearing (10Q), thus disengaging the worm from the worm wheel. 20. One end of the worm screw (10F) rests in a bearing in the worm box (10H) and the other in the worm-screw bearing (10Q), which is locked in the worm box by means of a set screw. On the outer end of the worm box is attached the azimuth drum cover (10B) by means of a set screw. The drum-adjusting sleeve (10K) is keyed to the worm screw. The azimuth drum (10G) is clamped to the drumadjusting sleeve (10K) by means of the drum-adjusting clamp (10J). The drum crank (10L) is centered on the worm screw and attached directly to the azimuth drum. By loosening the three drum-clamp screws (10W) the azimuth drum (10G) may be rotated on the worm11 screw and the drum scale adjusted to read 0 when the azimuth circle * scale index is set on a degree graduation line. These drum-clamp screws should habitually be kept tight. Longitudinal play of the worm screw is taken up by drawing the worm screw (10F) through the drum-adjusting sleeve (10K) and drum crank (10L) by means of the worm-shaft screw (10Y). In case backlash develops between the azimuth circle and the worm, the worm screw should be disengaged from the azimuth circle and the worm-shaft screw (10Y) tightened until the worm moves freely in the worm box, but without play. The worm-box adjusting screw (8AC) is then adjusted until there is close contact between the threads of the worm screw and of the azimuth circle. If properly adjusted, the worm should revolve freely and the azimuth circle should respond immediately to reversals of motion of the worm. 21. The depression slow-motion arm (11G) is attached to one pivot of telescope tube and locked thereto by means of the depression-arm clamp screw (8Q); with the arm unclamped the telescope may be rapidly moved in elevation. The lower end of this arm works between the depression slow-motion screw (11F) and the depression slow-motion plunger (11LA). This gives a slow motion adjustment in elevation. For convenience in assembling the telescope, a slow- A motion spring-adjusting screw (11NA) is provided, by means of which the depression-plunger spring (11DA) may be compressed, so that the depression slow-motion arm (11G) may be readily assembled. After % assembling the telescope, the slow-motion spring-adjusting screw (11NA) should be released to bring spring pressure to bear on the depression slow-motion arm. 22. The electrical equipment consists of a combination fuze and resistance-coil block, to be attached to a wall of the station near the instrument, a snap switch with terminal posts, and a set of wiring with receptacles and lamps. Separate lights are provided for the illumination of the reticule, of the azimuth circle, and of the azimuth drum scale. The leads of the lamp for the illumination of the reticule are brought between the forks of the yoke, to allow greater freedom in movement between the yoke and the body. The lamps provided are 2 candlepower, 36 volts. The resistance coil provides a resistance of 125 ohms. The fuzes are for 1-ampere current. The material ordinarily furnished is for 110-volt circuits. In case 220-volt mains only are available, a resistance coil of 280 ohms will be provided. Clips are provided on the fuze block for the two extra fuzes furnished with each instrument. THE TRIPOD. ÿ , 23. The tripod consists of a tripod head (4B), to which is pivoted three adjustable legs. A brace rod (oA), which telescopes in a brace tube (5F'), provided with a clamp (oG), is furnished for holding the12 legs in. a given, position, providing greater stability of the tripod. A-plumb bob is furnished with each instrument and is contained in the £ chest. In the tripod head is mounted a circular level for roughly setting the tripod before mounting the instrument. The level consists of a small glass cup and a cap with a spherical interior face. The- % level cup is secured in a level support by means of a screw plug, disk spring, and washer. The level is designed for disassembling only in case filling of the cup is necessary. The filling is a solution of 60 per cent ether and 40 per cent alcohol. A leather strap is provided for carrying the tripod. . ACCESSORIES. 24. The carrying case furnished with each, telescope provides seats for the telescope, the second eyepiece, and the eye protector. The telescope should always be kept in the case while not assembled on the instrument. 25. A chest is provided for transportation and storage of the base of the instrument and contains holders for the plumb bob, the screw driver, and the adjusting pin furnished with each instrument. 26. The pier mount is the same as that which has heretofore been issued with azimuth instrument, models of 1900 and 1900 Mi. The azimuth instruments, models of 1900, 1900 Mi, and 1910, may be used interchangeably on tripods and pier mounts furnished with * either instrument. MOUNTING. | 27. The instrument is shipped by the manufacturer in three boxes, one containing the telescope and its carrying case, another containing the base of the instrument and its chest and combination fuze and resistance coil, and the other containing the tripod and pier mount. Each unit is complete, ready for mounting, and has been adjusted by shop tests. In setting the pier mount care should be taken that the telescope points approximately south when the azimuth circle reads zero, and that the yoke and the body are in their normal positions. In dismantling instruments for storage or for shipment, care should be taken to pack them in the same manner as received from the manufacturer. 28. Before the telescope is assembled in the yoke the telescope pivots should be carefully wiped off and covered with a light coating of dock oil. Similarly the bearings of yoke should be cleaned and lightly oiled.. ADJUSTMENTS. 29. The adjustments of the telescope are the focusing of the eyepiece on the cross wires, the. removal of parallax by rotation of the focusing ring (7M), and the variation of intensity of illuminatioh of the reticule by means of the shutter described above. 13 30. In adjusting the telescope, first focus the eyepiece on the cross wires so as to bring out most distinctly the roughness of the wire. Ik Then remove parallax by rotating the focusing ring (7M). After W this preliminary focusing remove the eye from the eyepiece and look at some distant object in order to allow the muscles of the eye to relax; then refocus the eyepiece on the cross wires if necessary. It may be noted that for a given observer the adjustment of the eyepiece should not change and that the adjustment of the reticule for removal of parallax changes with the range. The telescopes are constructed for the removal of parallax for all distances between a comparatively short range and infinity. It is often impossible to remove parallax completely from both horizontal and vertical wire. In azimuth instruments total removal of parallax should be made for the vertical wire. 31. The adjusting level boxes (11L) are attached to the yoke by means of two short level screws and two long level screws. The long level screws are seated in holes tapped in yoke and the short level screws rest against the surface of the yoke. To adjust the-levels proceed as follows: Turn the instrument so that the axes of the levels are parallel to the line joining diagonally opposite leveling screws. Level the instrument by means of leveling screws, making the bubbles of both levels central. Release the worm, rotate the body, > including the yoke and telescope, through 180 degrees. In case the bubbles do not remain central, correct half the error by change in leveling screws, and half the error by readjusting the screws of the ' level boxes. In adjusting the screws of the level box, the long screws must be released before the short screws can be set up. In the final adjustment care should be taken that all screws in the level boxes are set up, but not overstrained. The whole operation should be repeated until both levels are properly adjusted. In the levels 0.1-inch movement of the bubble corresponds to a difference of 30 seconds in the plane of the axis of the level. The levels are assembled in glass tubes packed with paper, and the tubes are sealed in the bronze level boxes by plaster of Paris. Except in case of breakage the levels should not be disturbed. 32. To orient the instrument, set the azimuth circle and azimuth drum at the given azimuth, then unclamp the azimuth slow-motion arm, sight the telescope approximately on the object on which the instrument is to be oriented, clamp the azimuth-arm clamp screw (11A), and make the final adjustment of the telescope by means of the azimuth slow-motion screw (11II) so that eross wires intersect with the object. The slow-motion screw clamp screw (8Z) should ; then be tightened. 33. The adjustment of the elevation mechanism of the telescope is similar, except that no scales are provided for measuring vertical angles. \14 34. The method of adjusting the worm for removing backlash is described above under description of that part. (Paragraph 20.) 35. The telescope is properly adjusted for verticality of cross wire and for collimation by the manufacturer. In case a cross wire is replaced in service, it should be noted that the holes through draw-tube for the cross-wire adjusting screws (8AA) are elongated, and care should be taken to make vertical wire parallel to a plumb line after first leveling the instrument. The diameter of platinum wire used is 0.0005 inch. Wire of this size can be obtained by requisition on the armament officer. 36. The telescope should be collimated in its own yoke in a manner similar to that described in paragraphs 51 to 56, Pamphlet No. 1795, Instructions for the Care, Preservation, Repair, and Adjustment of Instruments for the Fire Control Systems. OPERATION. 37. After adjustment and orientation of the instrument, azimuth angles are read directly from the azimuth circle scale and the azimuth drum scale. During operation care should be taken not to disturb the azimuth clamp or slow-motion clamp. The worm may be disengaged and the telescope moved rapidly through any part of the field by throwing the worm-box crank (10M), but the final setting and reading should be made with the worm in mesh. CARE AND PRESERVATION. 38. The Azimuth Instrument, model of 1910, is a delicate instrument, and special care is required to keep it in good condition. An oil hole in the base of the yoke closed by an oiler (10S) provides for lubrication of an internal bearing. Clock oil only should be used for the purpose. , For lubrication of worm and worm gear, vaseline is suitable. The opening covered by the spring cover (9H) in the rear surface of body is for the insertion of a screw driver to adjust the worm-box adjusting screw. Keep this opening closed. 39. The instrument should be stored in a dry place, free from dust and dirt. Both dust and moisture cause deterioration of optical surfaces. 40. In packing the instrument for shipment, place the base in its chest, taking special care to see that there is no liability of movement of the base in its chest. Place the telescope in its carrying case, taking care to see that no parts are free to move. Then place the carrying case and chest in separate boxes which are made large enough to permit a layer of excelsior or other packing material between the chest or carrying case and the inside of the packing box.15 41. In making requisitions for parts for repair or in requesting return of instrument to an arsenal for repairs, always state the serial number of the instrument. Use the nomenclature given below. 42. General instructions for the care, disassembling, and cleaning of this instrument are given in Pamphlet No. 1795, Instructions for the Care, Preservation, Repair, and Adjustment of Instruments for the Fire Control Systems for the Coast Artillery. 43. The following notes for this particular instrument are added: The interior parts of telescope will seldom require disassembling for .cleaning. One of the eyepieces should always be assembled in the telescope. Less frequent cleaning of the interior parts will be necessary if the micrometer lamp shutter is kept in a position to close the aperture between the lamp seat and the reticule chamber— when the lamp shutter handle (7P) is halfway between the ends of the slot in which it moves. 44. In cleaning, observe the following precautions: Do not remove the objective from its cell unless dust or moisture is visible in considerably quantity on the interior surfaces of the lenses, and always assemble the 'payer ring between the component lenses. The objective is easily broken. Under no circumstances remove the eye or field lenses from their cells. Do not disassemble the prisms from the prism holder unless they plainly require it. This should seldom be necessary. Leave no finger marks on optical surfaces. Keep exposed optical surfaces free from dirt and moisture. Use only the cleaning material issued for that purpose. To examine the interior optical surfaces of a telescope, hold the extra eyepiece in rear of the assembled eyepiece, moving it back or forth to bring the image of the interior surfaces formed by the assembled eyepiece successively into the focal plane of the extra eyepiece. NOMENCLATURE. 45. Spare parts should be ordered by the nomenclature given below. The symbols refer to the plates following. Symbols. Name of piece 1A Objective.................-........... IB Low-power field lens................ 10 Low-power eyelens..................... II) High-power field lens............. IE High-power eyelens.................... IF Felt strip............................ 2A Prism................................. 2B Prism............................. 2H Shutter shaft.......................- - - 2Q Focusing nut.......................... 2EA Shutter plunger spring............... 3A Azimuth pointer window............ 3B Azimuth pointer................... 3C Azimuth pointer screw............. Plate. Fig. . I I . I I . I I . I III . I III . II VI . I I . I I . II V . I I . II V . II VI . II VI . II VIShort prism stud}N°Î sh.own' ,For instruments Nos. 1 to 75, in- Plate. Fig. . i I J . i I % i I . i I . i IV I i I . i IV . i IV . i . i I . i IV . i IV . i . IV . i IV . i IV . i IV . i IV . i IV . i IV . i IV . i IV . i IV . i IV . i IV . i IV . i IV . i IV . i IV . i I . il V . il V * . il V . il V Ì? Ì . i I I . i I . il V i L- I . I I . I I . I II . I I . I I . I I . I I . II VIII . II VIII . II VIII . II VIII . II VI IT . II VIII . II VIII . II VIII . I I . I I . II VIII . II VIII . II VIII . I I . II VIII . II VIII Symbols. Name oi piece. Plate. Fig. 7Y Pointer screw nut............................................ II VIII 7Z Focusing nut screw............................................ I I 7AA Mirror cover screw............................................ 11 VIII 7AB ' Pointer case screw........................................... I I 7AC Pointer case................................................. II VIII 8A Eye protector................................................. I II 8B Protector holder............................................. II V 80 Eye piece adapter.......................................... I I 8D Eye piece draw tube, long..................................... I I 8E Eye piece draw tube, short.................................... I III 8F Protector clamp screw....................................... II VIII 8G Eye protector screws.......................................... I II 8H Protector bolder shaft........................................ I I 8L Field lens cell............................................... I III 8M Eyelens cell (x 15)........................................... I III 8N Eyelens cell (x 10)........................................... I I 8Q Depression arm clamp screw.................................... I I 8R Amber glass bolder............................................ I I 8S Amber glass holder screw...................................... I I 8T Eyelens cover (x 10).......................................... I I 8U Amber glass holder washer..................................... I I 8V Amber glass disk.............................................. I I 8W Draw tube washer.............................................. I I 8X Worm box pivot.............................................. II VII 8Y Azimuth plunger spring plug................................... I II 8Z Slow motion screw-clamp screw................................. I II 8AA Cross wire adjusting screw.................................... I I 8AO Worm box adjusting screw...................................... 8AD Eye protector screws.......................................... I II 8AE Eyelens cover (x 15).......................................... I III 9A Body........................................................ II V 9B Azimuth circle............................................ II VI 90 Worm box cover.............................................. II VII 9D Azimutb slow-motion arm...................................... I I 9E Crank stop pin................................................ I ' 9F Spindle washer screw.......................................... I 9G Spring cover screw............................................ I II 9H Spring cover.................................................. I II 9J Worm box cover screw......................................... II VII 10A Yoke.......................................................... I II 10B Azimuth drum cover........................................... II VII IOC Azimuth drum lamp shield..................................... I II 10D Yoke cap...................................................... I I 10E Azimuth circle lamp bolder................................... II V 10F Worm screw................................................... II VII 10G Azimuth drum................................................. II VII 10H Worm box..................................................... II VII 10J Drum adjusting clamp......................................... II VII 10K Drum adjusting sleeve........................................ II VII 10L Drum crank................................................... II VII 10M Worm box crank............................................... II V ION Drum crank handle............................................ II VII 10P Leveling plate................................................ I I 10Q Worm screw bearing........................................... II VII 10R Worm box support............................................ II VII 10S Oiler......................................................... I I 10T Yoke washer screw............................................. I I 101) Lamp shield screw............................................ II V 10V Worm shaft screw............................................. II VII 10W Drum clamp screw............................................. II VII 10X Drum crank screw............................................. II VII 10Y Azimuth drum cover set screw................................ II VII 10Z Worm box support screw........................................- II VII 10AA Worm screw bearing screw.................................... II VII 10BA Azimuth circle lamp holder screw............................ II V LOCA Worm box crank taper pin..................................... I I18 Symbols. Name of piece. 10DA Yoke cap pin............................... 11A Azimuth arm clamp screw.................. 11B Azimuth slow-motion plunger.................... 110 Spindle nut.................................... 11D Spindle washer................................. HE Eccentric................................ 11F Depression slow-motion screw............. 11G Depression slow-motion arm............... 11H Azimuth slow-motion screw...................... 11J Leveling screw........................... 11K Yoke washer.................................... 11L Adjusting level box............................ 11M Adjusting level............................. 11N Adjusting level tube........................... 11Q Drum crank shaft............................ 11R Level shoe (with tongue).................... IIS Level shoe (plain)....................... 11T Azimuth stop............................. 11U Worm box spring............................. 11Y Azimuth stop stud........................ 11W Yoke cap clamp screw........................ 11AA Spindle nut lock screw..................... 11BA Depression plunger spring plug............. IICA Level screw, short......................... 11DA Depression plunger spring....'............. 11EA Drum crank shaft screw..................... 11FA Level screw, long.......................... 11GA Azimuth stop screw......................... 11HA Drum crank shaft nut....................... 11JA Worm box spring screw...................... 11KA Azimuth slow-motion plunger spring......... llLA Depression slow-motion plunger............. 11MA Slow-motion spring adjusting screw knob____ 11NA Slow-motion spring adjusting screw......... 12E Azimuth drum pointer........................ 12F Azimuth drum pointer screw.................. 13 A Cover...................................... 13B Prism retaining spring...................... 13C Prism holder................................ 13D Prism holder screw.......................... 14A Switch binding post......................... 14B Binding screw............................... 14C Binding post screw.......................... 14H Auxiliary binding post...................... 14J Hart surface switch......................... 14K Switch screw................................ Base.................................... 1-ampere fuze........................... Resistance coil......................... X27C Plumb bob hook............................. X27V Leg clamp stud............................. X35A Base....................................... X35B Cap........................................ X35C Bolt....................................... X35D Nut........................................ E9B Lamp holder............................■____ E9F Electric lamp............................... E9G Lamp holder spring.......................... E13AJ Candelabra receptacle..................... War Department, Office of the Chief of Ordnance, Washington, December 14, 1911. Plate. Fig. . i I . i II . i II . i I . i I . i I . i I . i II . i II . i I . i I . n Y . i II . i II . ii VII . i I . i I . i I . i I . i I . i I . i I . ii V . i I . ii VII . ii V i I . ii VII . i II . i I . i I . i I . ii VII . ii VII . i 1 . i I i I . ii V . ii V . ii V . i I . ii V . ii V . ii V . ii V i I i IV . ii X . ii X . ii X . ii X . n V . ii V . ii V . ii V 1 Form No. 1656. 35523/459-1. Ed. Aug. 24-17—1,000. oPUTTE J 2362£3££1" tri