Chain pull is the result of fraction on the trolleys caused by moving load, vertical dips and rises, and friction in chain flexing around horizontal turns. Also influencing chain pull is lubrication, temperature, and foreign matter collecting on the track.

If parts are to be carried up an incline another figure must be added to the friction chain pull for the lift load. This lift load is calculated by multiplying the total vertical rise in feet by the "live load" per foot of conveyor.

Total chain pull equal the pull due to the friction of the total moving load, plus the lift load.

For extremely long conveyors and conveyors with a complicated chain path, or where more than one drive is required, it is necessary to make an accumulated chain pull computation.

When the maximum speed and total chain pull have be determined, the horsepower required can be calculated by the following formula:

Horsepower= Total Chain Pull in lbs. x max. speed in f.p.m. / 33000 x efficiency

Allowance must be made for losses in V-belt drives, variable speed transmission, chain drives, etc. An efficiency figure of 70% will be correct for most drive units.

A drive should be located at the highest point of conveyor immediately preceding a decline, if possible. Good practice dictates that the drive be located to apply a pulling force ahead of the greatest load.

Drive units can be either sprocket or caterpillar type and constant or variable speed.

Refer to Drive Unit Section and determine the style preferred and size required. Select a specific drive and locate it on the layout drawing.