Installation

When designing chain drives, it is important to adhere to certain layout guidelines to assure optimum drive efficiency and life.

Chain Wrap and Center Distance

Under most circumstances, the small sprocket is the drive sprocket. Roller chain wrap (amount of chain containing the sprocket) (A) must be a minimum of 120 degrees of the small sprocket.

Sprockets can be placed at any center distances and must be aligned with each other. Optimum center distance is 30 to 50 times the pitch of the chain. In the case of a pulsating drive, center distance should be lowered to 20 times the pitch of the chain.

Layout

When designing a roller chain drive, it is best that the centerline of both sprockets be as close to horizontal as possible. The angle of installation however, can be up to 60 degrees (B). Applications with sprocket centerlines over 60 degrees require special tensioners and/or chain adjustments to prevent the chain from slipping off the lower sprocket.

Tension & Slack

It is important to maintain the proper amount of chain tension. If the chain is excessively tight, rapid chain wear and loss of lubricant will occur. If chain is too loose, excessive vibration and pulsation may occur causing chain damage.

For normal drives, adequate slack should be adjusted to 4% of the chain span. [Example, if the chain span is 46.5", slack should be 46.5" x 0.04 = 1.86"] (C).

For drives with:

1. Vertical or near vertical center lines (over 60º)
2. Heavy loads with frequent starts and stops
3. Center distances of over 3 feet
4. Sudden backwards rotation or dynamic braking

Chain slack should be adjusted to 2% of the chain span. It is essential to inspect such drives regularly for correct chain tension. Idlers are recommended.