Flat Belt Pulleys

Flat Belt Pulleys

Introduction

The pulleys are used to transmit power from one shaft to another by means of flat belts, V-belts or ropes. Since
the velocity ratio is the inverse ratio of the diameters of driving and driven pulleys, therefore the pulley diameters
should be carefully selected in order to have a desired velocity ratio. The pulleys must be in perfect alignment in
order to allow the belt to travel in a line normal to the pulley faces.

The pulleys may be made of cast iron, cast steel or pressed steel, wood and paper. The cast materials should
have good friction and wear characteristics. The pulleys made of pressed steel are lighter than cast pulleys, but in
many cases they have lower friction and may produce excessive wear.

Types of Pulleys for Flat Belts

Following are the various types of pulleys for flat belts :

1. Cast iron pulleys : The pulleys are generally made of cast iron, because of their low cost. The rim is held in place by web from the central boss or by arms or spokes. See more…
2. Steel pulleys : Steel pulleys are made from pressed steel sheets and have great strength and durability. These pulleys are lighter in weight (about 40 to 60% less) than cast iron pulleys of the same capacity and are designed to run at high speeds. See more…
3. Wooden pulleys : Wooden pulleys are lighter and possesses higher coefficient of friction than cast iron or steel
   pulleys. These pulleys have 2/3rd of the weight of cast iron pulleys of similar size. They are generally made from selected maple which is laid in segments and glued together under heavy pressure. See more…
4. Paper pulleys : Paper pulleys are made from compressed paper fibre and are formed with a metal in the centre.
   These pulleys are usually used for belt transmission from electric motors, when the centre to centre shaft distance is small. See more…
5. Fast and loose pulleys : A fast and loose pulley used on shafts enables machine to be started or stopped at will. A fast pulley is keyed to the machine shaft while the loose pulley runs freely. See more…

Reference A Textbook of Machine Design by R.S. Khurmi and J.K.Gupta