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. =