SEED Guides Component Selection - Chain Drives < >

Figure 8 Sprocket Notation

Chain and Shaft Forces

Chain drives enable power to be transmitted between shafts and the torque contribution is achieved by means of the chain tension acting tangentially at the sprocket pitch diameter. As the line of action of the chain tension is offset relative to the shaft centre, the force will have a linear as well as a rotary effect on the drive system components. The chain tension, for example, will cause the transmission shaft to bend and will also impose significant loads on the supporting bearings. To analyse the shaft and bearings it is necessary to consider the chain tension acting at the pitch diameter in terms of equivalent components - a torque and a direct load acting at the shaft centre as shown in Figure 9.

Figure 9 Chain Load Components

Speed Ratios

Chain drives deliver constant speed ratios and the reduction possible by a pair of sprockets is dictated by the range of sprocket tooth numbers available. The following chart shows the various reduction ratios possible using generally available chain sprockets.

Chain Reduction Ratios Using Standard Sprockets