io6

SHOP TOOLS.

weight. Water, however, being 500 times as heavy as steam,involves the consideration that its weight acts with, andincreases that of, the piston. Tor instance, in the case of arivetter worked from a differential aecumülator through a 1-inch pipe, the velocity with which the water is forced by theaccumulator through the pipe to the rivetter is increased ordiminished according to the speed of the rivetter ram, by whichthe mass of water in the accumulator cylinder and pipe actsboth to increase or diminish the effect produced by the ram.Assuming, as is the case in practice, that the motion of theloaded ram of the accumulator is six times as fast as the rivetter

Fic. SO.

ram, the inertia of the accumulator load is 36 times as great asit would be if it moved at the same speed as the rivetter ram.Further, the force 'due to the inertia of the water passing intothe rivetting cylinder is more than 6000 times as great aswould be the case if the water and rivetting ram travelled atthe same speed, owing to the fact that the velocity of the wateris 81 times as great as that of the ram. This results in theweight of the ram, which closes the rivet at each stroke, exertinga force of 300 tons.

Professor Unwin has shown by indicator diagrams the actionthat takes place in a rivetter cylinder. Fig. 30 is a diagram