Abstract
Hydraulic power development may be divided into two groups, first, one in which mechanical and civil engineering developments combine to use natural forces for power production, and second, the phase of hydraulic power development which it is proposed to consider, namely that appertaining to mechanical production and automotive traction. Until recent times, no phase of engineering development has remained comparatively stationary for so long a period as that of power operation by hydraulic means. It is true that there has always been a field where the characteristics of hydraulic power were essential, but in the more recent drawing and stamping industries, hydraulic operation was unable to compete until developments in collateral fields removed all disadvantages.
Prominent amongst the developments to this end, has been the introduction of the variable-delivery pump to each machine, as against the central pumping station. These self-contained units are available with a normal maximum pressure of 1,000 lb. per sq. in., but in certain cases no less than 5,000 lb. per sq. in. can be obtained.
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