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