What is "compound lever"

Lever \Le"ver\ (l[=e]"v[~e]r or l[e^]v"[~e]r; 277), n. [OE. levour, OF. leveor, prop., a lifter, fr. F. lever to raise, L. levare; akin to levis light in weight, E. levity, and perh. to E. light not heavy: cf. F. levier. Cf. Alleviate, Elevate, Leaven, Legerdemain, Levee, Levy, n.]

1. (Mech.) A rigid piece which is capable of turning about one point, or axis (the fulcrum), and in which are two or more other points where forces are applied; -- used for transmitting and modifying force and motion. Specif., a bar of metal, wood, or other rigid substance, used to exert a pressure, or sustain a weight, at one point of its length, by receiving a force or power at a second, and turning at a third on a fixed point called a fulcrum. It is usually named as the first of the six mechanical powers, and is of three kinds, according as either the fulcrum F, the weight W, or the power P, respectively, is situated between the other two, as in the figures.

2. (Mach.)

   1. A bar, as a capstan bar, applied to a rotatory piece to turn it.

   2. An arm on a rock shaft, to give motion to the shaft or to obtain motion from it.

      Compound lever, a machine consisting of two or more levers acting upon each other.

      Lever escapement. See Escapement.

      Lever jack. See Jack, n., 5.

      Lever watch, a watch having a vibrating lever to connect the action of the escape wheel with that of the balance.

      Universal lever, a machine formed by a combination of a lever with the wheel and axle, in such a manner as to convert the reciprocating motion of the lever into a continued rectilinear motion of some body to which the power is applied.

n. a pair of levers hinged at the fulcrum

The compound lever is a simple machine operating on the premise that the resistance from one lever in a system of levers will act as power for the next, and thus the applied force will be amplified from one lever to the next (as long as the mechanical advantage for each lever is greater than one). Almost all scales use some sort of compound lever to work. Other examples include nail clippers and piano keys.