5/29/2023 0 Comments Timing belt tensionerConsider using a fixed center drive for only lightly loaded or motion transfer drives. Excessive belt tension caused by the fixed center belt drive design plus the load on the belt due to the drive load could exceed the belt load rating causing very short belt life or belt breakage. Do not use a fixed center belt drive for power transmission drives.These recommendations will maximize the probability of success: Sometimes fixed center belt drives can't be avoided. Two Common Methods of Belt Tension Adjustment: Excessively low belt tension can also decrease belt life as tooth engagement will be non-uniform and belt ratcheting may even occur. Such variations can cause timing belt tensions at installation to vary by 3X or more due to the stiffness of the belts which often have fiberglass reinforcement.Įxcessively high belt tension bends shafts and journals, decreases bearing life, and decreases belt life. Conversely, excessively high belt tension can be created when the reverse occurs. There are also limits to the accuracy that the pulley distances can be maintained on a production basis due to machining tolerances.Įxcessively low belt tension can be created when a relatively longer belt is installed on relatively smaller pulleys with relatively smaller spacing. In any large population there will be a distribution of values. Belt lengths and pulley pitch diameters are not perfect. Belts and pulleys are manufactured to industry accepted production tolerances. The primary pitfall of a fixed center belt drive system is failure to consider the effects of system tolerance stack up on the belt tension. What is the primary pitfall of a fixed center belt drive system? If excessive force is used, then journals and shafts can be bent. Often the belt must be looped over a pulley flange or a loose pulley with the belt wrapped around it must be forced over a journal or shaft. Designers sometimes believe fixed center belt drives simplify assembly, but it can often be more difficult to assemble the pulleys and belt if there is no way to slacken the belt during installation.But this is usually a false economy because product assembly is often more difficult and can take longer, belt life and system dynamic performance can suffer, or higher precision components that cost more may need to be used. Designers sometimes incorporate fixed center belt drives in an effort to save cost by simplifying parts.This fails to consider how the belt life is negatively affected by either too high a tension or too low a tension or how the system’s dynamic performance might suffer. They think the belt teeth will drive the system regardless of the belt tension (within reason). Designers who are inexperienced with toothed timing belts sometimes believe that belt tension is not important.
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