Tech Tip: Belt Drives

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Under which two construction categories are V-Belts generally found?

Envelope and Raw Edge are the two broad construction categories.  The envelope variety is fully enclosed with a rubber-impregnated fabric and resists exposure to oils, greases, dirt, water, and most chemicals.  The raw edge variety is essentially the same as the envelope construction without the envelope, although there is a fabric on the back of the belt to resist abrasion when running on a back-side idler sheave.  

Which type of v-belt is capable of covering a load range from fractional to 500 HP?  

Classical v-belts are capable of covering a load range from fractional (less than 1 HP) to 500 HP.  They are less efficient than narrow v-belt systems and generally contribute to higher overhung bearing loads.  However, classical v-belts have a high tolerance for poor operating conditions and unusual drive conditions such as reverse bending and twisted drives.    

Estimating a Belt

An easy-to-use and remember formula for calculating belt drive center distance is twice the drive’s center distance plus one half the sum of the pulley or sprocket diameters.  This will provide you with a belt length selection close enough to allow your drive take-up mechanism to absorb the difference.

Installing a Belt

When installing belts on multiple groove pulleys or sheaves, replace all belts at the same time--not just one at a time.  Using belts from the same manufacturer will assist your installation efforts and allow you to properly tension the drive for maximum efficiency. As you install the belts, do not pry or force the belt onto the sheave; do not roll the belt onto the sheave; but do make sure that there is sufficient clearance to allow you to comfortably slip the belt over the sheave or sprocket outer edge.

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