Worm and Worm Wheel

Worm and Worm Wheel

It consists of a square threaded screw, S (known as worm) and a toothed wheel (known an worm wheel) geared with each other, as shown if Figure. A wheel A is attached to the worm, over which passes a rope as shown in the figure. Sometimes a handle is also fixed to the worm (instead of the wheel). A head drum is securely mounted on the worm wheel.

Let                  l           =          Radius of the effort wheel

(or a length of the handle)

r           =          Radius of the Load Drum,

W        =          Load lifted,

P          =          Effort applied to lift the load, and

T          =          No.of teeth on the worm wheel.

In one revolution of the wheel (or handle) the distance moved by the effort.

= 2 π l

If the worm is single – threaded (i.e., for one revolution of the wheel A and Screw S pushes the worm wheel through one teeth), then the load drum will move through


And distance, through which the load will move

Now                M.A.   =

And efficiency,