3.6-INCH B L FIELD-MORTAR, MODEL 1890. (REVISED NOV. 11, 1892.)
Fig. 50.
| Metal | steel |
| Total length | 2.05 feet |
| Calibre | 3.6 inches |
| Weight | 245 pounds |
| Grooves | 20 |
| Twist of rifling | 1 in 40 to |
| 1 in 25 cal. | |
| Powder-chamber | cylindrical |
| Vent | axial |
| Muzzle velocity | 650 ft.-sec. |
| Maximum range | 3450 yards |
It consists of a single piece of steel, the trunnions being forged solid with the piece.
Fig. 51.
The breech mechanism, [Fig. 51], is generally similar to that of the field-guns, except that the Freyre obturator is used, and in the locking arrangement the lever-handle is replaced by a bolt (a) which is turned by hand. This bolt operates the locking-stud on the left side of the block, and its handle bears also a vent-shield (f,) which keeps the vent closed until the breech is locked.
THE CARRIAGE FOR 3.6-INCH B. L. MORTAR.
Fig. 52.
This carriage, [Fig. 52], is of cast steel and in one piece, and consists of a frame complete with transoms and soles.
It is 39½ inches long and weighs 275 pounds. The axis of the trunnions is 14 inches above ground, and the piece can be fired at any angle between 0 and 60 degrees. At the centre of the front transom is bolted the elevating-clamp, which embraces an arc bolted to the under side of the mortar. The lever on the left side of the carriage turns a shaft, which causes the clamp to take hold of the arc when the elevation has been given.
A pintle-fork is attached at the front end of the carriage, and a ring on the side of either cheek to which the ends of the restraining rope are fastened.
Nomenclature of 3.6-inch Mortar-carriage.—Carriage-frame; elevating-arc; elevating-arc bolt; elevating-arc guide-pin; double hook; double-hook pin; double-hook bracket; double-hook bracket-pin; cap-square; cap-square keys; cap-square chain eye-pin; pintle-fork; pintle-fork bolt; elevating-arc jaws; shaft for jaws; lever for shaft; bushing for shaft; nut for shaft; screw for bushing; separator; separator-bolt and nut; screws for pointing.
PLATFORM FOR 3.6 MORTAR.
Yellow pine or oak. Weight complete, 200 lbs.
Fig. 53.
This equipment consists of one wooden platform, one cast-iron pintle-block, eight stakes, one anchor-stake, two handspikes, and one pointing-scale. The platform consists of two side-rails, 3-inch, into which are framed and bolted eleven deck-planks, the latter secured to each other by dowels. A 4 × 3-inch piece is bolted to the rear deck-plank by three bolts. Wrought-iron straps, bolted into cross-pieces, embrace the side-rails. The pintle-block is fastened to the front of the platform by four wrought-iron bolts. The pintle-fork on the carriage embraces the pintle, forming the centre of motion of the traversing carriage. The platform is held in position by stakes, two on either side; those in front passing through square wrought-iron rings attached to eye-pieces bolted to the front end of the platform. A brass socket, in which works the brass pivot at the end of the pointing-scale, is placed at a suitable point in the axis of the platform. The anchor-stake, 4 ft. long, is driven in front of the platform. Around the anchor-stake, and held in position by the two pins passing through the stake, is wound the middle portion of the restraining rope, the ends of which fasten to the rings in the cheeks of the carriage.
The rope is given five feet slack for recoil.
Fig. 54.
The Pointing-scale.—This is made of hard wood, graduated on one side, the unit of the scale being one thousandth of the range, and each division one five hundredth of the range. A brass index-slide moves with friction along the scale and is clamped by a screw when regulated. For reference-marks a brass screw is placed at the end of each cheek of the carriage, and the scale is so arranged that it can be applied to either cheek. The carriage admits of a motion around its pintle of about 15° on either side of the axis of the platform.
THE GUNNER'S QUADRANT.
Fig. 55.
Used in giving elevation. The arc is 45°, but by applying different sides an elevation of 90° can be given. The least reading is one minute, which is given by the setting of a sliding level on a slightly curved arm.
The setting to any given degree is made by moving the arm by hand, which is done by pressing back the head of the arm to release it from engagement with the notches on the interior of the arc, then moving the arm to the required position and allowing the spring to react.
AMMUNITION.
The full charge of powder is 16 ounces, sphero-hex. (U. F.). The projectiles are those used with the 3.6 gun and have already been described.
The charges, required to cover all ranges from 400 to 3350 yards with angles of elevation between 15 and 45 degrees, are four in number. These charges are made up of three cartridges containing 4, 6, 10, and 16 ounces respectively.
The Fuze for Shrapnel is the Frankford Arsenal point-combination fuze, model 1894, burning 28 seconds and weighing 19.75 ounces. The time-train of this fuze is arranged to be cut at intervals of 1/5 second.
The Fuze for Shell is fuze M, model 1894. It is identical in construction with fuze C (see page 102), except that a portion of the plunger-spindle is reduced in diameter to lessen the friction of the spring-ring in arming on account of reduced charges. It is distinguished from the C fuze by two grooves across the flat of the base. This fuze is designated for separate transportation, to be assembled with the projectile at or near the firing-ground, and is not to be transported fixed in the projectile.