Volume Eleven - Pre-Victorian to the Present Day - some more aspects - Large Testing Machines in South Wales, 1829-1906 . . .

The bed-plate and foundations are inert and entirely unstrained, but when the piece breaks and the statical stresses are released the sliding-bed is free to shoot out and relieve the elastic pressures referred to, but the cylinder which carries the fulcrum plates is restrained from any perceptible recoil, first of all by its own mass, secondly because it is bolted to the bed-plate which under-lies the whole length of the machine from end to end, as is clearly shown in the general view, and thirdly because this bed-plate is bolted and keyed to solid foundations. With this construction there is no sensible kick upon the knife-edged fulcra, and their accuracy is unaffected even by such violent reactions as take place on the sudden release of a 350-ton load.

The sliding-bed in this form of construction enables a movable straining crosshead to be locked at any part of the bed, so that the straining head can be brought close up to the weigh-bridge to test as short a sample as a rivet, or rolled away to any suitable distance for holding longer specimens without the use of making up lengths.

The weight for measuring the load is divided between stationary weights at the long end of the steelyard and a rolling weight which, by the introduction of a double-armed steelyard originated by the author, counter-balances it by passing on to the negative end of the lever, Fig. 6 . Thus the rolling weight of half a ton on this machine is balancing another half a ton concealed in the long end of the steelyard.

Fig. 6 - 350-ton Horizontal Testing Machine, 1906 - Elevation of the Steelyard. [198] [716]