What is not so apparent is that a good piece of cord can accomplish the same thing. The use of a straight edge is readily understood. 1).ĭrive alignment can be checked with a yardstick, machinist’s straight edge, or piece of strong cord. V-belt drives are inherently more forgiving of misalignment than synchronous belt drives (Fig. Poor alignment makes accurate tensioning impossible, and causes an imbalance of load across the belt span. Bearing overload also leads to early failure, and can result in the destruction of a motor and reducer.Ī prerequisite to proper tensioning is good alignment. Early belt failure is the norm, because excessive tension over-stresses belt cords. Undue stress is placed not only on the belt, but bearings and shafting as well. Under heavy loads, the drive can jump teeth (ratchet), which leads to rapid belt failure.ĭrive tension that is too high can have other, far-reaching consequences. This movement places severe stress on the teeth, eventually tearing them loose from the body of the belt. Low tension allows the belt teeth to ride up on the sprocket teeth. The effects of low tension on a synchronous belt are equally bad. This action destroys the belts and equipment must be shut down to replace them. If the tension is too low, V-belts slip and glaze or burn. The consequences of improper belt tensioning are costly. All it takes is a few simple tools and techniques to easily and accurately tension a drive to yield the high performance designed into it. In order to achieve this improvement, it is essential that they are correctly aligned and tensioned. They deliver a lot more power in a smaller package. V-belts and synchronous belts have been greatly improved over those of a few years ago. They may have worked satisfactorily 20 or 30 yr ago, but they are inadequate for today’s high-capacity drives. These old rules of thumb for drive tensioning have outlived their usefulness: It is time to abandon them. “Tension the drive until you get a slight bow in the slack side when it is running.” “Press the belt with your thumb until it deflects about 1/2 in.” Metallic and non-metallic reinforcement fibers are available.Whack the belt with a karate chop, and if it feels firm, the drive is properly tensioned.” Reinforcement can significantly enhance the belt’s maximum operating tension. Many metric pitch timing belts are reinforced with fibers or cables in the tension area of the belt.
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