Product Manual
Using Idlers
Idlers are used to take up slack, change direction of transmission, or for clutching action.
Idler failure usually occurs when the bearing fails due to lack of lubrication or foreign particles.
Idlers with precision ground double sealed bearings usually will last longer than other types.
Use bushings to reduce idler bores. If bushing is too tight to insert by hand, gently tap with
hammer USING SUPPORT UNDER INNER RACE OF BEARING. Bushings are available with
or without shoulders. If bushing is loose in bore, use Loctite or make a scratch mark on bushing
with le.
Selecting Pulley Types
Cast iron and machined steel bar stock are recommended for heavy duty applications.
Stamped steel is commonly used with outdoor power equipment and lawn & garden equipment.
Use die cast in light duty applications.
Use A type pulley with A or 4L (1/2” wide) belts Use B type pulley with B or 5L (5/8” wide) belts.
Combination groove pulleys can be used in many applications, but not all. The A/B type can be
used with B or 5L and A or 4L belts.
Smaller size belts will run deeper in groove.
Determining Pulley Sizes
When retrotting or designing a new pulley drive it is important that the equipment operate
at the recommended speed. The pulley size ratio determines the speed ratio.
First determine the speed at which the equipment should be operated. Look at the name plate
or contact the equipment dealer or manufacturer.
Next determine the engine or motor recommended operating speed, often marked on the name
plate or in the instruction manual.
Using this formula, or the chart below, nd the pulley sizes needed to obtain the desired
equipment speed:
Engine Pulley Dia. X Eng. Speed =
Equip. Pulley Dia. X Equip. Speed
When both pulley sizes need to be determined, start with any practical pulley size
and then calculate what the other size should be.
When a pulley size is changed, a different length belt will be needed. The belt length
is determined by adding the diameter of the two pulleys and multiplying this sum by 1.6.
Add double the distance between shaft centers to this sum to get the approximate belt length.