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 tlie 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 



