<s id="A18-2.01.01">1 Since the powers through which one moves a known load by a known force are five, we necessarily have to explain their forms, their application and their names, because these powers go back to one natural principle while they are quite different in form.</s>
<s id="A18-2.01.02">Now their names are the following: the shaft with the wheel, the lever, the block and tackle, the wedge, the screw.</s>
<s id="A18-2.01.03">The shaft with the wheel is made in the following way.</s>
<s id="A18-2.01.04">One takes a hard, square piece of wood in the form of a beam; make its ends round by planing them and fasten to them fitting rings of copper, so the roughness of the axle has no effect, so they rotate easily when they are put in round bronze-clad holes in a firm, immovable support.</s>
<s id="A18-2.01.05">This [piece of] wood, made according to the description just given, is called an axle.</s>
<s id="A18-2.01.06">Then one attaches to the center of the axle a wheel that is fitted with a square hole according to the center of the axle and fitting the measurements of the axle, so the axle and the wheel, when the latter is attached to the former, rotate together.</s>
<s id="A18-2.01.07">This wheel is called Peritrochion, the translation of which is "the surrounding".</s>
<s id="A18-2.01.08">When we have done this, then we make on both sides of the wheel a curl-like groove, so the same may be a winch, on which the ropes wind up.</s>
<s id="A18-2.01.09">Then we make on the front side of the wheel, i.e. on its perimeter, holes, whose number suits necessity, that are made regularly so that when spokes are fastened in them, the wheel and the pulley are set in motion by these spokes.</s>
<s id="A18-2.01.10">We have just explained how one has to construct the axle; how one works with it we are going to explain now.</s>
<s id="A18-2.01.11">If one wants to move a big load with a small force one fastens the ropes tied to the load to the place grooved on both sides of the wheel.</s>
<s id="A18-2.01.12">Then one puts spokes into the holes bored into the wheel and presses the spokes downward so the wheel rotates and the load is moved by the small force and the ropes wind up around the axle or we stack them on one another so they do not wind up on the whole axle.</s>
<s id="A18-2.01.13">The size of this machine has to be set up according to the size of the load that one wants to move with it.</s>
<s id="A18-2.01.14">Its calculation has to take place according to the ratio of the load one wants to move to the force that is meant to move it, as we are going to explain in the following.</s>
