‹‹‹ Vitr. 10.2.2 | Table of Contents | Vitr. 10.2.4 ›››
3A block containing three pulleys is denominated Trispastos; when the lower system has two pulleys, and the upper one three, Pentaspastos. A machine for raising heavier weights requires longer and stouter beams, and the pins for joining them at top, as well as the axle below, must be increased in proportion. Having premised this, the raising ropes lying loose, are first distributed; then to the shoulders of the machine are made fast the guys, which, if there be no place to which they can be otherwise firmly fixed, must be attached to sloping piles driven into the ground, and steadied by ramming the ground about them.
3This kind of machinery, revolving with three sheaves, is called a trispast. When there are two sheaves turning in the block beneath and three in the upper, the machine is termed a pentaspast. But if we have to furnish machines for heavier loads, we must use timbers of greater length and thickness, providing them with correspondingly large bolts at the top, and windlasses turning at the bottom. When these are ready, let forestays be attached and left lying slack in front; let the backstays be carried over the shoulders of the machine to some distance, and, if there is nothing to which they can be fastened, sloping piles should be driven, the ground rammed down all round to fix them firmly, and the ropes made fast to them.