Sample Roller Chain Drive Selection

The power source is an electric motor. The driven equipment is a two-cylinder pump. Input power is 40 hp. The driver shaft turns at 900 rpm and is 2.375 in. in diameter. We want to turn the driven shaft at 300 rpm and it is 3 in. in diameter. The desired center distance is 40 in. and the shafts and centers are both horizontal. The center distance adjustment can be 2 in. or more if needed. Lubrication will be what is recommended by the ratings. There are no space restrictions or unusual drive conditions. 

Input power is 40 hp and the service factor is 1.5. Thus the design power is 40 hp x 1.5 = 60 hp. Step 4 Select a Preliminary Chain Size 

Entraing Table 5-13, the rating table for no. 80 chain, at 900 rpm shows that no. 80 chain on a 21-tooth sprocket has adequate capacity. The no. 80, 21-tooth sprocket will accept the 2.375-in. diameter shaft (Table 4-7) and is very close to the suggested minimum of 22 teeth for no. 80 chain at 900 rpm. Examining Table 5-15 and Table 5-11, the rating tables for no. 100 and no. 60 chain, shows that a no. 100 chain on a 19-tooth sprocket or a no. 60-2 chain on a 28-tooth sprocket would also be adequate. Both of these sprockets will accept a 2.375-in. diameter shaft. 

The suggested minimum number of teeth for no. 100 chain at 900 rpm is 23. The no. 100 chain on a 19-tooth sprocket might run too rough. A no. 60-2 chain on a 28-tooth sprocket would be 

The speed ratio is 900/300 = 3.0. Thus the large sprocket should have 3.0 °° 21 teeth = 63 teeth. This is a nonstock sprocket for most manufacturers. The nearest size stock sprocket is a 65-tooth sprocket. The 65-tooth sprocket gives an output speed of 291 rpm, or 3% less than the desired speed. If maintaining the output shaft speed is critical, the added expense of a made-to-order 63-tooth sproeket might be justihed. In this example we will assume that a 3% speed difference is aeeeptable and select the stock 65-tooth sprocket. 

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