Table III: BS Roller Chain Selection Table
Example
Data: 1. Type of application: Centrifugal Blowers 2. Source of power: Electric Motor 3. HP to be transmitted: 40 hp
4. Driving shaft: 600 rpm 5. Driven shaft: 200 rpm
6. Center distance: 19 inches 7. Space limit: Max. 24 inches Step 1 Use Table I and determine the service factor. Service factor (SF): 1.0 Step 2 Obtain design HP Design HP= HP to be transmitted • SF = 40 hp • 1.0 = 40 hp Step 3 Obtain the chain size and the number of teeth of the small sprocket from the selection table for 40 hp and 600 rpm. According to the selection table, the selected chain and sprocket rpms are: (a) RS12B-3 chain and 25-tooth sprocket (b) RS16B-2 chain and 17-tooth sprocket (c) RS16B-1 chain and 25-tooth sprocket * For (a), the necessary number of teeth for both small and large sprockets are 25 teeth and 75 teeth respectively, since the speed ratio is 1/3 (200/600 rpm). But the outside diameter of both sprockets, 6.3 inches for 25 teeth and 18.3 inches for 75 teeth, exceeds the limitation (6.3 inches + 18.3 inches > 24 inches). Therefore, these sprockets cannot be installed. * For (c), the necessary number of teeth for both small and large sprockets are 25 teeth (outside dia. 8.4 inches) and 75 teeth (outside dia. 24.4 inches), respectively. It exceeds the space limitation again (8.4 inches + 24.4 inches > 24 inches). * For (b), the necessary number of teeth for both the small and large sprockets are 17 (outside dia: 5.9 inches) and 51 (outside dia: 16.8 inches). It satisfies the space limitation (5.9 inches + 16.8 inches < 24 inches). A combination of RS16B-2, and 17 teeth and 51 teeth must be used to fulfill all the necessary requirements. Step 4 Use Table IV to determine the lubrication method.
The selection table is based on the following conditions: 1) The chains are operated under ordinary conditions. The ambient temperature range is between 15°F and 140°F. They are not to be used in an atmosphere where abrasive dust or corrosive gas is present or when the humidity is exceptionally high. 2) The two transmission shafts are in a horizontal position and the chains are properly installed. 3) The suggested lubrication system shown on Table IV is used. 4) The load does not change significantly during transmission. The “Service Factors” given in Table I are used when the chains are used under various operating conditions. The load conditions will affect the life of the chain. The increase in the horsepower rating of multiple-strand roller chains cannot be calculated simply by multiplying the horsepower rating of one strand by the total number of strands, since the load on each strand is not exactly the same. In order to estimate the service life of a multiple-strand chain, the “Multiple-Strand Factor” given in Table II must be used.
P • N • n 12
Chain speed (S) =
1 • 600 • 17
=
= 850 ft./min.
12 System B is suggested. Step 5 Obtain the number of pitches of chain (L).
N 2 - N 1 ( ) ( 6.28 C
2
N 1 + N 2
+ 2C +
=
2
)
2 51 - 17
19
6.28
17 + 51
+
=
+ 2 •
2
1
19 1
Note: Refer to page A-77 for details of lubrication system.
= 73.35
74 links
A-52
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