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   a.  16 to 24 Hour Service
   b.  Across the Line Starting
   c.  Heavy Shock Load
   d.  Heavy Starting Load
   e.  Reversing Drives

The above factors which apply to a specific drive should be added together to get the total Overload Service Factor. The horsepower of the driver is then multiplied by this total Overload Service Factor to get the Normal Rating of the Drive.

"Design Horsepower" Required
Design horsepower is the normal horsepower to be transmitted, multiplied by the composite Service Factor selected from Table 14 and corrected with the above correction factor.

3.2 Drive Selection
The most economical chain drive selection usually consists of a combination of:

a.    b.

The shortest pitch single strand chain which has the required "design horsepower" rating when used with the desired size sprocket at the selected sprocket speed. The selection of a center-distance that insures a chain wrap of at least 120º (meshing with at least 1/2 of the teeth) on the smaller sprocket.

Table 15 indicates the horsepower transmitting capacity of No. 25 single strand chain. These roller chain power transmission ratings are established for chain operation under the following conditions:
    1.  Service factor of 1.
    2.  Chain length of 100 pitches.
    3.  Use of recommended method of lubrication.
    4.  Two-sprocket drive arrangement.
    5.  Sprockets aligned and mounted on parallel horizontal shafts.
A service life of approximately 15,000 hours may be expected when operated at full rated capacity under conditions as outlined above.

TABLE 15 HORSEPOWER RATINGS--SINGLE STRAND ROLLER CHAIN No. 25

480