GIFT Of No. 1698 INSTRUCTIONS FOR MOUNTING, USING, AND CARING FOR 2-INCH MORTAR CARRIAGES MODEL OF 1891 FOR MOUNTING CAST-IRON MORTARS, MODEL OF 1886 AND STEEL MORTARS, MODEL OF 1890 (SIX PLATES) OFTHJS APRIL 19, 1904 ' REVISED DECEMBER 42,7X909 REVISED APRIL 21, 1917 WASHINGTON GOVERNMENT PRINTING OFFICE 1917 No. 1698 M.S. Orel no no*- e/efT. INSTRUCTIONS FOR MOUNTING, USING, AND CARING FOR 12-INCH MORTAR CARRIAGES MODEL OF 1891 FOR MOUNTING CAST-IRON MORTARS, MODEL OF 1886 AND STEEL MORTARS, MODEL OF 1890 (SIX PLATES) APRIL 19, 1904 REVISED DECEMBER 22, 1909 REVISED APRIL 21, 1917 WASHINGTON GOVERNMENT PRINTING OFFICE 1917 Os WAS DEPABTMENT, OFFICE OF THE CHIEF OF OBDNANCE, Washington, April 21, 1917. This manual is published for the information and government of the Regular Army and National Guard of the United States. By order of the Secretary of War : WILLIAM CBOZIEB, Brigadier General, Chief of Ordnance. (3) 36210o LIST OF PLATES. Plate. Drawing No. I. Side elevation 12-5-1 II. Front elevation .__ 12-5-2 III. Plan 12-5-3 IV. Method of controlling the energy of recoil 15-0-7 V. Shot hoist details___^________ 12-5-16 VI. Shot truck, type 12ME 12-5-34 (4) INSTRUCTIONS FOR MOUNTING, USING, AND CARING FOR 12-INCH MORTAR CARRIAGES, MODEL OF 1891. [The points in italics are of importance or concern the safety of the carriage and should be specially noted. The important changes in this pamphlet are shown in boldface type.] GENERAL DESCRIPTION. Tliis carriage was originally designed to mount the cast-iron, steel- hooped mortar. It is, however, used for mounting both this and the all-steel mortar. This pamphlet describes the carriages for the cast-iron, steel- hooped mortar at this date, including the modifications made subse- quent to their original issue. It applies equally well to those on which the all-steel mortar is mounted, with the exceptions noted in a subsequent paragraph. The principal parts of this carriage are the base ring, racer, azi- muth circle, traversing-roller system, side frames and cross transom, trunnion carriages, recoil and counter recoil system, elevating system, traversing system, loading apparatus, shot truck, and firing apparatus. BASE RING. The base ring is made of cast iron No. 2 in one piece. It is bolted to the concrete foundation by twelve IJ-inch foundation bolts through the interior and twelve through the exterior flange. The outer sur- face is finished to a diameter of 13 feet 3^% inches to form the pintle surface. The lower traversing-roller path is formed on its upper sur- face, and to its inner surface is bolted the traversing rack. RACER. The racer is made of gun iron in one piece 165".5 in diameter. Its lower surface is finished to form the upper path for the traversing rollers; a flange extending down over the base ring is accurately finished inside to form a pintle surface. The diametral pintle clearance is one-sixteenth inch. A dust guard of three-sixteenths inch sheet iron 11 j inches wide is secured to the inner side of the racer by means (5) of bolts, in order to protect the roller paths and traversing rollers from dirt. A removable floor plate of cast iron is bolted across the rear of the opening in the racer to permit ready access to the breech of the mortar. An iron ladder for climbing in and out of the pit is bracketed to the racer in front of this floor plate. AZIMUTH CIRCLE. The azimuth circle is a brass strip one-fourth inch in thickness attached by countersunk screws to an index ring of cast iron made in eight sections. The index ring is supported in place around the racer by means of eight vertical index ring brackets which are bolted to the racer and by sixteen horizontal angle irons, the outer ends of which are embedded in the concrete of the emplacement. These angle irons with the index ring form supports and means of attachment for the sixteen floor plates which, with the concrete floor of the emplacement, constitute the working platform. Four holes are drilled through these floor plates and lifting hooks are provided for lifting them from place. The azimuth circle is graduated to degrees which are numbered after the carriage is mounted. An azimuth pointer graduated to hundredths of one degree is attached to the rear side of the racer by means of two screws. The slots for these screws in the pointer permit of adjustment in orientation. When this has been done, the pointer should then be secured in place by dowel pins. TRAVERSING ROLLER SYSTEM. The racer rests on a circle of twenty- four live conical rollers of forged steel maintained in position by a distance ring. The distance ring is made of two rings of wrought iron bolted to twelve cast-iron separators. These rings are slotted to form bearings for the journals on the ends of the rollers. A few of the first carriages 'made have rollers with double flanges, but most of them have rollers with an inner flange only. SIDE FRAMES AND TRANSOM. To the top of the racer are bolted two side frames as cheeks, about 7 feet high, formed to receive the mortar and recoil apparatus. The side frames are united in front by a cross transom bolted to them and to the racer. A small balata and iron buffer is secured to the center of the cross transom to limit the mortar in its loading position, and a stout hickory stop is secured to a socket in its rear face to limit the mortar in elevation. The limit in elevation is 65 and the system recoils down slides on the side frames placed at an angle of 50 with the horizontal plane. These slides are formed on the inner faces of the spring cylinders cast in the side frames. TRUNNION CARRIAGES. The trunnion carriages of cast steel are so formed as to fit over the guide ribs of the slides and be supported in every direction. They are 3 feet If inches long and are provided with brass bushings for the trunnions. A bronze trunnion cap fits over the mortar trunnion and an elastic buffer of balata and iron plates is placed between this cap and the cap square bolted in the top of this trunnion carriage. The upper ends of the trunnion carriages have brackets projecting right and left, respectively, into the spring cylinders. Spring com- pression screws are screwed into each of these brackets. These bear on hard steel washers and thus transfer the weight of the mortar to the spring columns. RECOIL AND COUNTER RECOIL SYSTEM. The spring cylinders cast in the side frames are 9.6 inches in interior diameter and have the same inclination as the slides. They are slotted on the inside between the guide ribs to allow the trunnion carriage brackets to move the full length of possible recoil, which is 2 feet 6 inches. Although the above slots permit it, the recoil should not be more than 20 inches for the cast-iron mortar and 22f inches for the steel mortar when full service charges are used. Small buffers of balata and iron are secured in each slide at the limit of recoil of the trunnion carriages. The spring cylinders cast in the side frames are not sufficiently long to accommodate the requisite number of springs; they are therefore extended downward by means of gun-iron cylinders secured to the side frame by flanges and bolts. Supporting brackets bolted to the racer are provided to prevent lateral vibration. Each column of the counter recoil springs for the cast-iron mortar consists of 11 double-coil spiral springs separated from each other by sheet-iron disks. The inner and outer coils are oppositely wound. The springs for the steel mortar are similar to the above except that the upper double coil in each column is replaced by a short column of 8J pairs of Belleville springs. The work required to compress the springs is not nearly so great as the energy of recoil of the mortar down the slides; therefore two recoil cylinders are secured to the side frames and to the exterior of the spring cylinders. The recoil cylinders are of cast steel, T| inches in interior diameter, and are fitted with 3J-inch steel piston rods working through stuffing boxes at each end of the cylinder. The upper end of each rod is keyed to a socket in the trunnion carriage directly below the trun- nions, while about the middle of the rod a piston head is formed, forged out of the solid. This piston has a bronze bushing and is an easy fit in the cylinder. 8 A connecting passage is formed between the ends of each cylinder, entering the upper end immediately below the stuffing box, and holes 0.7 inch in diameter are bored at proper intervals connecting this passage with the cylinder. When the mortar is fired, it, together with the trunnion carriages, recoils down the slides, forces the pistons through their cylinders and compresses the spiral springs. Part of the energy of recoil is absorbed by the resistance of these springs, but the greater portion is absorbed by the resistance which the oil in the cylinders offers when it is forced, from below to above the piston head through the holes joining the connecting passage and the large cylinder. The general movement of the piston and the oil is shown on PI. IV. In any hydraulic brake the resistance is greater as the velocity of the piston is greater and as the openings for the passage of the liquid are less. The velocity of retarded recoil of the mortar being variable and a constant resistance being desired, the orifices are varied in such a manner that the relation between the velocity and the area of the orifices is at all points such as to give a nearly constant resistance. Th'ese cylinders are provided with an arrangement of throttling plugs which partially close the holes connecting the recoil cylinders with their connecting passages. The amount of closure produced by each plug is stamped on its end. The effective area of orifice at any point of recoil is the clearance around the piston head plus the ef- fective area of all the holes not passed over by the piston in its recoil. PI. IV shows how these orifices are successively cut off by the piston in its movement. By this arrangement the area of the orifice of flow at any point of recoil has such a relation to the veloc- ity of recoil at that point as to give a nearly constant resistance to the motion of the piston. This results in a nearly constant fluid pres- sure. The areas of orifices have to be calculated for a particular set of loading conditions. The conditions used are those that obtain with the maximum service charges. Smaller charges will result in somewhat shorter recoils than with full charges. The upper face of the piston is recessed, and into this recess fits an annular projection from the upper bronze cylinder head. When the pistons have reached the limit of recoil, the springs return the mortar to the firing position. Near the end of this return to the firing posi- tion the annular projection of the cylinder head enters the recess in the piston head. The oil caught in this recess can escape but slowly through the small clearance, and thus the recoiling parts are brought gradually to rest. The lower or pressure ends of the recoil cylinders are connected by an equalizing pipe so that the pressure in both cylinders is always the same. Should the equalizing pipes break or become unserviceable they may be removed and the carriage continued in service, the holes tapped in the lower ends of the cylinders for the equalizing pipes being filled by bronze plugs kept on hand for this purpose. Lateral guides of gun iron are secured to the side frames and adjusted so as to bear against the body of the mortar at its breech end. By this means any tendency to move out of the vertical plane is counteracted. Each cylinder is provided with a filling plug, and an emptying plug is placed in the coupling of the equalizing pipe. In -filling the filing plugs should be removed from both cylinders so as to permit the air to escape and thus insure the filling of both cylinders up to the filling holes. The cylinders should be filled to overflowing for all charges with a neutral oil of 0.85 specific gravity, such as the hydroline in service. A denser oil would increase the pressure in the cylinders slightly and also shorten the recoil somewhat. It requires about 10J gallons to completely fill both cylinders. If it is desired to measure the recoil, it can be done on the piston rods by making several turns around them with twine or wire and tying it very tightly just where the piston rod enters the stuffing box. The height of the twine above the stuffing box after firing will indi- cate the counter recoil, which will also be the recoil if the mortar was returned to the firing position. There is a rack on each side of the frame for the purpose of embarring the mortar up to the firing posi- tion provided the springs do not return it. If it is shown that the springs are weak, remove the spring-cylinder caps and screw down the adjusting screws an amount equal to the distance that the trunnion carriages are below the firing position. If, after the next round, the springs do not return the mortar to the firing position, repeat the above operation ; but the total compression by means of the adjusting screws should not be more than 3 inches. ELEVATING SYSTEM. The elevating gear consists of two bronze circular racks, one on each side of the mortar, secured by brackets to the mortar and to a hoop shrunk onto the mortar just in front of -the reinforcing hoops. Each rack is actuated by means of a handwheel and spur gearing attached to the trunnion carriage. One of the gear wheels may be graduated on its face and an index attached to the carriage will en- able the degrees of elevation to be read. The pinion of each handwheel has a conical surface on its inner end which fits against a similar surface on the elevating gear bracket. By screwing up on a nut on the elevating handwheel shaft, these sur- faces may be clamped together and the mortar held in either the load- 9453017 2 10 ing or the firing position. By this means the desired amount of fric- tion can be obtained and undue strains on the teeth of the elevating racks and pinions, due to a tendency of the mortar to change its eleva- tion in recoil and counter recoil, are avoided. In the earlier carriages this clamp nut is provided with two handles by which it may be screwed up. In the later carriages these handles are omitted and the nuts are set up by wrenches hung by chains to the side frames. TRAVERSING SYSTEMS. A circular traversing rack of cast iron No. 2 is bolted to the inner surface of the base ring. A shrouded pinion of bronze gears into this rack and is itself keyed to a vertical shaft which is supported by a bracket bolted to the inner side of the right side frame. The upper end of the shaft carries a worm wheel of bronze geared into a worm of steel on a horizontal shaft which passes through both side frames. This shaft is provided with bearings in brackets bolted to the side frames. Power for traversing is applied to this shaft by means of crank handles at both ends. The traversing shaft is pro- vided with oil tubes and plugs for the convenient oiling of all bear- ings, and an oil tube at the front of the racer is provided for oiling the pintle surface. For the proper oiling of this surface it is neces- sary to traverse the carriage entirely around during the operation of oiling. LOADING APPARATUS. The loading apparatus consists of a shell scoop, carried on the end of a bow lever, the lower end of which is attached to a shaft which passes through the left side frame. This shaft, on the outside, also carries a lever, the upper end of which is fitted with a swivel nut. A screw spindle, called the shell-hoist screw, extending to the front of the carriage, where it is supported in a" suitable bearing, works through this nut and carries a handwheel. The shell, resting in the shell tray, is carried in a truck which delivers it direct to the shell scoop when the latter is depressed. The shell tray 'has trunnions which bear in beds on the trucks, and the barrow forces these trun- nions into beds prepared for them in the shell scoop. There are guides on the racer for the wheels of the truck, so that it is con- strained to move to the proper position. When the handwheel on the end of the screw spindle is turned, the shot in the tray is raised to a proper position for ramming. After the shell is rammed, the shell tray is then lowered in a similar manner into the truck. There are stop nuts on the shell-hoist screw which can be adjusted so as to stop the motion of the shell scoop when the projectile is in the proper place for ramming and, when depressed, to bring the shell tray in M proper position to be run off by the truck. (The truck wheels are provided with rubber tires.) 11 SHOT TRUCKS. Forty-one of these carriages have been altered for direct loading by means of shot trucks, type 12ME, Plate VI. The truck is equipped with a hydraulic stop and a brake. For loading, the mortar is brought to its position of minimum elevation and locked by means of the elevating clamp nuts. The shot truck, aided by guide rails on the racer, is moved up to its proper position at the breech of the mortar, the hydraulic stop on the truck absorbing any jar of impact between the two. The brake is applied holding the truck at rest while the projectile is being rammed into place. FIRING APPARATUS. The mortar may be fired either electrically or by lanyard. The current for firing the mortar electrically is obtained from a firing magneto. FIRING MAGNETO. The magneto is inclosed in a bronze case and is provided with high ratio gearing and a lever for operating. It is not necessary to raise the lever violently, as a slow motion is sufficient to fire the primer. One pull of the lever should suffice when the magneto is working properly. A clutch is provided on the intermediate shaft, making it possible to move the lever back into its normal position without re- versing the armature shaft. The lever is held in its off position by a catch, when not in use. For further information, see Ordnance De- partment Pamphlet, Form No. 1814. LANYARD PULL. In case the electric firing system does not work properly the service lanyard may be used. In connection with this lanyard, an auxiliary lanyard is applied in order to provide a pull on the friction primer as nearly direct as possible when the mortar is in the firing position. It has a hook at the mortar end and passes under a pulley attached by a bracket to the pit ladder and through a hole drilled through the removable floor plate. A lanyard stop attached to the rear end of the auxiliary lanyard fits into a lanyard washer secured to the floor plate and prevents the lanyard from falling into the pit. The lanyard stop is provided with a loop for the attachment of the service lanyard. Carriages for the steel mortar differ in the following respects : 1. Distance pieces are placed under the guides (that are secured to the side frames) that guide the breech end of the mortar, and cause the mortar to travel in a true vertical plane. 2. Distance pieces are used to secure the elevating rack to the mortar. 12 3. Packing rings are put on the trunnions in order to take up the lateral play due to the difference in width between the rim bases of the cast iron and steel mortar's. 4. The brackets that are bolted to the mortar and are used to brace the elevating arcs differ from those on the cast-iron mortar. 5. The clamping nut for the elevating gear is without the clamping handles and is set up by means of a wrench attached to the carriage. 6. The buffer located in the front transom and holding the mortar in a horizontal position is longer. 7. The hickory stake that is secured in the front transom and limits the extreme elevation of the mortar is longer. 8. There are supporting brackets for the spring cylinder extension. NOTE. Care should be taken by officers and employees at the forts in ordering parts of carriages to state by whom the carriage (for which the parts are ordered) was manufactured and whether the car- riage is for a steel or a cast-iron mortar. In ordering conical traverse rollers, state whether one or two flanges. ASSEMBLING THE CARRIAGE. IMPLEMENTS. The assembling requires machines and implements for mechanical maneuvers usually found at forts, such as falls, blocking, jacks, slings, garrison gin, etc. GENERAL REMARKS. The size of the carriage is such that it must be partially dismounted for shipment, so that when it arrives at its destination it has to be assembled. In assembling the carriage, as in all machinery ', no parts should ~be directly struck with a steel hammer or sledge. Soft metal drifts, copper or lead hammers should be used. In unloading or han- dling the parts care should be exercised that the edges or finished sur- faces do not become upset or burred. When two bearing surfaces are brought together* it is especially necessary that both parts should be absolutely clean, smooth, and well lubricated. The following description gives a statement of the order in which the parts should be put together : Base ring. Move the base ring to its position over the pit by means of skids and rollers. Lower the ring, by means of jacks or a derrick, into its position over the foundation bolts, care being taken to have the bolts central in the holes in the ring. Level the ring by means of wedges driven under the flanges near the foundation bolts. For leveling use a machinist's level and straightedge. The greatest care should be taken in using the level and straightedge that the middle of the level is equidistant from the points of contact of the straightedge with the surface being leveled, and that these points of 13 contact on the straightedge are equidistant from either end. In using the level it should always be reversed and the mean of tht< readings in the two positions be considered the true reading. Level at first three points and then the intermediate points on top of the roller path. Then with the roller path leveling gage level the path radially. When it shows level at every point the nuts should be tightened evenly on the foundation bolts. Caliper the pintle surface. The diameter should not differ by more than 0.01". Again check the leveling of the ring, and should the pintle surface still be eccen- tric, it must be scraped round ; then pour grouting under .the base ring, care being taken to have it run under every part of the ring. Distance ring and traversing rollers. Thoroughly clean the lower roller path and rollers and assemble the distance rings on the rollers ; then run the rollers around several times by hand to see that they work properly. Racer. Move the racer over its position on the base ring, making sure that the roller path and pintle surfaces are thoroughly clean. Lower it into place by means of two jacks, each one engaging on the inside upon a projecting portion jusfc below the seats for the side frames; a short piece of timber should be placed on top of each jack. After the racer is lowered to its proper position, run it around by hand several times to see that it runs freely and that the pintle sur- faces do not bind. Bolt on the dust guards to prevent dust from getting on the roller paths and rollers. Side frames. If. the spring cylinder extensions, recoil cylinders, pistons, and trunnion carriages are not assembled to the side frames when received, they should be so assembled before the side frames are put in place. This will be most conveniently done with the side frames in a horizontal position on blocking. After the springs are compressed, a garrison gin will be found convenient for raising the side frames to a vertical position on the racer. All bolts and bolt holes are numbered so that there will be no difficulty in locating the bolts ; but in case this has been neglected, the accompanying list of parts will indicate their size and location. Spring cylinder extension. This should be first bolted to the side frame, screwing in the two studs first. Attach the balata buffer to the bottom of the slides. On carriages having the bracket for sup- porting the spring cylinder extension, this bracket should be bolted to the racer before the side frame or the spring cylinder extension is erected in place. Recoil cylinder. The recoil cylinder must be assembled next, but before doing this, clean the piston rod carefully as well as the slides for the trunnion carriage, and move the trunnion carriage on the slide to see that it works easily. In assembling this cylinder the bolts going through the side frame should be inserted first, and then those 14 joining the recoil cylinder to the spring cylinder extension. Do not, at this time, key the trunnion carriage to the piston rod, but see that the bronze cylinder head, not the follower, is screwed down hard, and that the piston rod is moved as far to the top as possible. Recoil springs. Remove the cap of the spring cylinder and move the trunnion carriage on the slides until there is a space of about 18 inches between the top of the spring cylinder and the underside of the projecting bracket; this space is required for the insertion of the coiled springs; if more convenient, the trunnion carriage can be en- tirely removed from the slides. Assemble the springs together, a small coil inside a large one, and place the separator plates on the ends. Insert the ends of the compressor rod : which is threaded for a distance of about 6 feet 9 inches, into the hole in the bottom of the spring-cylinder extension, and push the rod through until the end comes to the top of the spring cylinder. String on this rod the end plate and the 11 coiled springs with their separator plates, then string the top plate and the small washer of hardened steel, which has an annular projection fitting the hole in the top plate. Push the compressor rod through the hole in the bracket on the trunnion car- riage, placing the small cast-iron washer and nut on top of the bracket; on the bottom of the rod put on the centering washer and nut. With the ratchet wrench furnished with the carriage, screw down the nut on the top end of the rod and compress the springs until the trunnion carriage can be keyed to the piston rod. Remove the com- pressor rod and cast-iron washer. Screw into the threaded hole in the bracket the steel adjusting screw and bring it to bear hard enough on the hardened washer to make clearance between the washer and the bracket. There is a curved surface under the projecting arm of the trunnion carriage which sometimes bears hard on the top plate and forces it sideways so that it is difficult to make it enter the spring cylinder. This can be overcome by putting pieces of iron between the projecting arm and the top plate and removing these pieces when the adjusting screw is brought to bear on the spring columns. When assembled, the small washer prevents the top plate from striking the curved sur- face of the arm. Bolt on the spring cylinder cap. Lift the side frame to a vertical position and bolt to the racer. The turned tap bolts go through the holes which are 1J inches in diameter, i. e., the two front and two rear holes, and should be put in first. The rough bolts go into the holes which are !$ inches in diameter. The springs can be compressed after the side frame is bolted to the racer. This requires that the compressor rod be inserted from the top through the hole in the bracket on the trunnion carriage after all the 15 springs have been put into the spring cylinder. But there is some- times difficulty in inserting the lower end of the rod through the holes in the separator plates and especially through the hole in the bottom plate. It will be most convenient to pack the stuffing boxes when the side frames are in the horizontal position, using Garlock's five-eighths hydraulic packing for this purpose. MOUNTING THE MORTAR. If the mortar is to be mounted by means of blocking, it will be found more convenient to do it before the transom is assembled. If the mortar is to be mounted by means of a derrick, the transom can be assembled first. To mount the mortar with blocking, build a run of blocking in front of the carriage at such a height that the trun- nions of the mortar will just clear the front-top edges of the trunnion slide. Pull the mortar in until the trunnions can enter the channels of the trunnion carriages, then, by means of jacks, lower and move it into position, care being taken that the bearings are not bruised or jammed. Pieces of hard wood may be used on each side to guide the trunnions at the point where they reach the bronze bushings. With the steel mortar the packing rings must be placed over the trunnions before the mortar is lowered into the trunnion carriages. After the mortar is down, assemble the trunnion caps, insert the balata and iron buffers and bolt on the cap squares. Place the transom in position and bolt to side frames. TRAVERSING GEAR. Bolt the. worm-wheel box to the right side frame and push up through its bearing the vertical traversing shaft until there is room to bolt the lower bracket to the racer, being careful to assemble the sleeve between the two brackets. Hold the shrouded pinion in place and lower the shaft through the lower bracket and pinion and put on the worm wheel. Push the worm shaft with worm attached through the worm-wheel box from the right and screw the worm in place, placing the middle bearing on the shaft before it passes through the left side frame. Assemble the three bearings for the shaft. Assemble the equalizing pipes and fill cylinders with oil. AZIMUTH CIRCLE. Bolt the index ring brackets to the base ring. Bolt the sections of the index ring to these brackets and to the angle iron supports. Level the angle iron supports and set the outer ends in the concrete platform. Put on floor plates, pit ladder, etc., and secure them in place. 16 ELEVATING GEARING. Bolt the elevating gearing to the trunnion carriages, and after the brackets have been secured to the mortar, the elevating rack can be bolted to them and to the elevating band. LOADING TRAY. Put the shaft for the loading arm through the left side frame and key to it, on the outside, the arm with the swivel nut. If necessary remove the nuts from the end of the shell hoist screw and screw this end through the swivel nut. Put the swivel bearing with the large end to the front and its accompanying bushing and collar onto this shaft and bolt the bracket for this bearing to the left side frame. Attach handwheel and nut. Lay the loading arm on the floor plate, lifting up the end for the shaft and holding it against the shaft, at the same time turning the handwheel until the key and keyway come together. Then push the arm on the shaft and put in the pin. Assemble the shell scoop and adjust it by means of the screw and nut. The guides for the shell barrow can now be attached and also the azimuth pointer. CARE OF THE CARRIAGE. Carriages should be traversed from time to time throughout their entire movement. The mortar will be habitually elevated so that it will be parallel to the piston rod and the breech cover left off. The translating roller will be left in place. At posts, where the sand blows onto the breech mechanism and at all posts during the cold season when snow and ice may collect and form around the breech mecha- nism, the mortar will be kept horizontal, with the breech cover on. The mortar should, however, from time to time, when not in use, be elevated and depressed throughout its range of movement. It is especially required that all parts of carriages be kept free from rust at all times. If this be allowed to accumulate its removal from all bearing parts, and especially piston rods, requires particular attention in order that the clearances shall not be unduly increased. The use of sandpaper for this purpose is forbidden and emery cloth No. 1, being coarse enough for any ordinary rusting, should be used, the rust being softened, if necessary, by kerosene. CARE OF EECOIL CYLINDERS. The recoil cylinders should be kept filled with hydroline oil of specific gravity of about 0.85 at all times as full as the location of the filling holes will permit. If leakage occurs from the recoil sys- tem it should be immediately remedied, calling, if necessary, upon the district armament officer for the services of skilled labor. 17 The repacking of stuffing boxes may be done, if necessary, by trained enlisted men under the supervision of an officer, but will preferably be done by skilled labor, as follows : To PACK A STUFFING Box. Draw the oil from the cylinder ; unscrew the follower and take out the gland. For this purpose special extractors, consisting of iron rods threaded at one end, are furnished with each carriage. All of the old packing should now be removed, using for the purpose the packing extractors provided for this purpose. This extractor consists of a bronze cage fitting around the piston rod and provided on one end with several hooks which engage in the packing when forced against it and rotated counterclockwise. The cage is provided with notches on opposite sides into, which pinch bars may be engaged if necessary and the packing withdrawn until it reaches the threads of the stuffing box. From this point the packing is withdrawn by turning the extractor in a counterclockwise direction until packing is entirely removed. This, method avoids injuring the packing by drawing it across the threads. The extractor is provided with han- dles by which to rotate it and is made in halves hinged together so. that it may be readily applied to or removed from a piston rod. The old packing should be examined and all unfit for use discarded. If any of it is again used, it should be put in after the new. To repack, put on the piston rod one ring of 0.625-inch Garlock's " waterproof hydraulic " packing and force it well to the bottom of the stuffing box by a wooden stick and mallet. Treat each layer of packing until five rings of new packing have been inserted, or an equal amount of new and old when any of the latter is used. Care should be taken to break joints of the packing; that is, the joint of each ring as inserted should be on the opposite side of the piston rod from the one preceding it. Clean out from the screw threads all the particles of the packing that have caught in them, push in the gland and screw up the fol- lower. No more force should ~be used on the spanner wrench than that of two men, and generally that of one man is sufficient. The addition of a pipe to the end of the spanner wrench should not be permitted. When the box is properly filled and the follower tightened there should not be more than three-fourths of an inch of space between the flange of the follower and the piece into which the follower is screwed. The follower should be tightened from time to time. If the follower is screwed into the stuffing box too tightly an unneces- sary amount of friction will be produced on the piston rod. When the follower is screwed in until the flange strikes the box, another ring of packing should be inserted. It is to be expected that a slight amount of oil will soak through and drip from the boxes of carriages when not in use. Also when 18 tightening the followers a slight amount of oil will squeeze out of the saturated packing. This oil should be caught and not allowed to render the carriage unsightly. Recoil cylinders should be emptied at least once in every three months and thoroughly cleaned once every six months or oftener if their condition requires it. For cleaning these cylinders a plumber's hand force pump will be supplied each coast artillery post. The pump should have a suction hose about 10 feet and a rubber dis- charge tube about 15 feet in length. The following method will be followed in cleaning the recoil cylinder. To CLEAN RECOIL CYLINDERS. (a) Remove the oil from the cylinders through the drain hole in the emptying coupling. (&) Remove all throttling and filling plugs from each recoil cyl- inder and the plugs in both ends of the by-pass cylinders and the equalizing pipe. (