The fulcrum of levers used in machinery is usually cylindrical in shape, made of soft metal, and supported in the interior of a cylindrical opening in which the lever works, so as to reduce the friction. The lever is not only oscillating or vibrating, but where the motion is circular the fulcrum becomes the axis of rotation.

Fig. 15.   A Bent Lever.

Fig. 15. - A Bent Lever.

A bent lever (Fig. 15) is often used for peculiar circumstances, but it acts obliquely and, consequently, with less effect.

The rules of leverage apply with equal accuracy whether a lever is straight or bent at an angle. Take, for example, the lever shown in Fig. 16. This lever, it will be noted, has one arm bent up at a right angle to the other and a weight hung on the horizontal arm. Imagine a force applied at the end of the vertical arm as shown. It is plain that the weight W times its distance A from the fulcrum is equal to the force F times its distance B from the fulcrum, just as if the lever were in the same straight line.

It is, of course, understood that in all leverage problems the force must always be at right angles to the arm. Therefore, while the weight acts vertically, the force acts in a horizontal direction. The lever is bent up as the direction of the force on the end that is bent is thus changed.