TRANSACTIONS OF SECTION G. 883 



'tegration.' Its effect is, without shock or breakage, to set iu motion a body at 

 Test by the instantaneous action of another moving at a high velocity or to arrest 

 Any mass, whatever be its velocity. The principle is carried out by dividing the 

 mass into flexible elements, which take the form of metallic fibres resembling a 

 brush. On impact each fibre acts independently of the rest, the mass being neglige- 

 able, but the dynamic effect exerted by the sum of the fibres is considerable. 

 The flexibility of the fibres must be in direct ratio to the speed of the moving 

 body or the difference in velocity of two moving bodies. The most obvious appli- 

 ■cations are taking up the recoil of a cannon, arresting a mine cage on the rope 

 breaking, preventing a motor from ' running away ' on the load being suddenly 

 taken off, or the prevention of shock on the load being suddenly increased, and the 

 setting of a signal to danger by a train so as to protect it, or the automatic aiTest 

 of a train by the signal. 



10. The Tancjije Gas Saramer} By Dugald Clerk. 



The paper gives details as to the working, &c., of a gas hammer which is the 

 invention of Mr. Jas. Robson, and was exhibited at the Inventions Exhibition in 

 1885. Since then it has been continually in action at Cornwall Works, Birming- 

 ham ; it has been much simplified and improved in its details, and is as reliable and 

 controllable as any steam hammer. 



It resembles a steam hammer in design, and contains a piston, a piston rod 

 connecting with the top containing the hammer, and an anvil block. 



The cylinder, however, is longer, and a space is left above the hammer piston 

 to contain the necessar}' charge of gas and air. A second piston is arranged to fill 

 and discharge the explosion space. 



The impulse for the blow is given to the hammer piston by the explosion above 

 it, and the return of the hammer to its highest position is effected by means of 

 a volute spring ; when out of action, therefore, the hammer always remains up. 



The charging piston is actuated by a hand lever, and is an easy fit in the 

 cylinder. AVhen the hand lever is moved in one direction, the charging piston 

 moves do^\^lwards towards the hammer piston, and the products of a previous 

 explosion pass through automatic lift valves in it to the upper side. On the 

 return movement the charging piston rises, and the automatic valves, closing, 

 cause the spent gases to be discharged at a port in the trop of the cylinder, while 

 a fresh charge of gas and air is drawn in between the pistons ; at the upper 

 extremity of the stroke the charging piston covers the exhaust port, and then an 

 igniting valve opens to effect the explosion ; the hammer descends, strikes its blow, 

 and when the hand lever is moved to transfer the exhaust gases again, the spring 

 returns it to its upper position. This is the complete cycle of action. 



The hand lever actuating the second or charging piston is arranged to move 

 precisely like the hand lever commonly used in steam hammers for controlling the 

 slide valve ; the similar movement produces precisely similar lesult^, and the 

 effort requu-ed is no greater. The blows can easily be given at the rate of 120 per 

 minute. 



To reduce the force of the blow the hand or foot is moved through a smaller 

 range and a smaller volume of explosive mixture drawn in, arid therefore a more 

 feeble explosion obtained. For very light blows a relief valve is opened to dis- 

 charge a portion of the pressure. 



The energy of the blow may be determined in two ways — first by taking an 

 indicator diagram, and second by measuring the velocity acquired by the hammer 

 before it stiikes the forging. 



Diagrams so taken proved the maximum pressure to be 56 lbs. per square inch 

 above the atmosphere, and an average of 22'5 lbs. during the whole downward 

 movement of the hammer piston. As the cylinder is 7 in. in diameter and the fall of 

 the hammer 6 in , this amounts to 433 foot-pounds, which, after adding on the 

 energy due to the fall of the hammer and deducting that due to the resistance of 

 the springs, becomes 406 foot-pounds, or 3-62 cwt. falling through one foot. 



' Published in eatenso in Indmtries, October 14, 1887, p. 114. 



3 L 2 



