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Page:Popular Science Monthly Volume 89.djvu/310

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296

��Popular Science Monthly

��mounted close together to receive a cross- shaft which carries a tubular body four inches or more in diameter. This tube is preferably square in cross-section, and the shaft passes through it midway be- tween its ends.

At one side of the tube is a small gear- wheel which meshes with a gear twice the diameter. The latter gear is mounted on the end of a shaft thirty inches long, which has a journal-bearing near the large gear; its other end is journaled to the side of a post. Between the two bearings the shaft is bent to provide a crank so that two men can operate it.

The important features are to load the thrower and release the missiles, both of which functions are provided for by simple mechanical expedients. The loader comprises a lateral opening in the side of the tube, and covering this open- ing is a stationary disk which has a con- centric opening therein which extends half way round. A chute covers this opening, the lower end of the chute being gradually drawn in to the tube, so that when a hand grenade is dropped into the mouth of the chute and the opening reaches the upper end of the concentric opening, the inclined side of the chute will cause the grenade to move toward the throat of the tube and finally drop to the discharge end.

This motion of the grenade takes place while the discharge end of the tube is moving downwardly, and as the tube is in constant motion on its axis the mis- sile swings around one-half of the ark formed by the end of the tube, a dis- tance of nine feet before it reaches the ejecting point.

The ejecting end of the tube has a lid hinged at its side, and a bell-crank lever arm projects out at one side. This arm is connected by means of toggle-jointed levers, one of these being hinged to the tube near its axis. The two levers are connected together by means of a rule-joint hinge, and are of such length that when the lid is closed they are out of line with each other, and thus auto- matically prevent the lid from opening and discharging the missile in the tube. When the tube reaches a predetermineil Ijoint the toggle-jointed levers strike a s|)ring finger which causes them to swing back and instantly oi)en the lid,

��drawing down the bell-crank lever arm. The result is that the grenade is free to shoot out.

Immediately thereafter the projecting lid reaches a cross-bar on the frame, whicii swings it back to a closed position, ready for the next missile. To provide a means for regulating the point of dis- charge the frame is provided with a pair of bars hinged together so as to assume an A-shaped form, the lower end of one bar being hinged to the top stringer, while the lower end of the other bar is hinged to a horizontal arm which rests on the stringer. This bar is provided with a pin so that by moving it back and forth the upper jointed ends of the two bars, where the spring finger is located, will determine the tripping point for releasing the missile.

Two men can easily swing the tube at the rate of ninety revolutions a minute, and assuming that the bomb weighs eight pounds, the unit of force transferred to the grenade is 230, com- pared with 45, the maximum available when throwing by hand. The advantage of the device is the great accuracy with which the bomb can be thrown. When the speed of the swinging tube is the same the bombs will reach the same area unfailingly. From fifty to a hundred missiles can be thrown a minute.

��To Compress a

��■ Ml W

��Coil -Spring COMETIMES

��to compress a coil- spring. The spring always seems to fly off at the wrong time. To eliminate this, place the spring in a vise and com- press it as far as it will go. Then run a piece of strong twine through the inside and tie it. The spring is hekl in a clamp, or if not too strong is held in the fingers, and the part that was tied is placed in the vise and another piece of string tied through the coil. This gives two strong holdings and the spring is then slipped over tile shaft. — NoKMAN S. McEwen.

��A good way to com- press a recalcitrant coil -spring

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