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CHAINS AND GEARS 13

13.1 Introduction

Chain drive consists of an endless chain whose links mesh with toothed wheels known as

sprockets. Shafts centre distances for chain drives are relatively un-restricted. Chains are

easily installed. Chain drives do not slip or creep. As a result, chains maintain a positive speed

ratio and are more efficient because of no slippage. Chain drives are more compact than belt

drives. For a given capacity, a chain will be narrower and sprockets will be smaller in diameter,

thus occupying less overall space. Chains do not deteriorate with age and can operate at higher

temperatures. They are more practical for low speeds.

13.2 Chain Drives

Power transmission chains have two basic components, link plates and pin and bushing joints.

The chain articulates at each joint to operate around a toothed sprocket. The pitch of the chain

is the distance between the centres of the articulating joints.

13.3 Roller Chains

These chains are assembled from roller links and pin links (Fig. 13.1). For joint wear life, these

chains should be lubricated. The dimensional details of a few selected roller chains are given

in Table 13.1, as per the BIS.

Pitch, P

H

Bush

W

Dp

Circlip Link plate

Bearing pin

DrDr

Fig. 13.1 Roller chain