DESIGN CONSIDERATIONS OF DRIVE BELTS

Cycle Life
Cycle life, defined as the useful life of Dymetrol® Mechanical Drive belts in various applications, varies with the flexural stresses (bending radius),  tensile stresses (load), and rate of cycling. 
To simulate extreme cases, DETP 4205 belts have  been tested at 43 cycles per minute under various loadings employing a 180°wrap around rotating idler pulleys. Figure M shows how reduced load and increased diameter dramatically increase the cycle life (defined as an incipient delamination 10 between the holes of a punched specimen even though the belt is still fully functional).
Unpunched or solid belts  generally 5-10 times higher cycle life than punched belt since essentially no stress-risers are present. Under lighter loads, such as experienced with, for example, 
windshield wiper systems, 1 to 10 million cycles have been demonstrated with punched belts. 

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Cycle Life vs Thickness
A second series of tests shown in Figure N
illustrates how cycle life is increased as belt thickness decreases. This is a natural result of the lower flexural stress in thinner sections.

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Drag Force 
 Drag force for belt in an un-lubricated channel under load at 6 in./second testing speed has been measured. This data is shown in Figure 0. As an example, if the belt were to carry a load of five lbs through a 90°twist taken in a 6-inch length, the drag force would be about two lbs. As a second example, the belt loaded to five lbs would have an additional 12 lbs drag load if it took a 90°flat bend with a 2-inch radius. The existing data are adequate for either compressive (push) or tensile (pull) loading. At speeds under 6 in second, the drag forces are lower. It is expected that the tension-compression curves to diverge under high loading, and the drive system to be more efficient in a pull than a push mode. However under higher load, one might choose a thicker belt or the stiffer DET 4000 series in a compressive (push) dominated design. This data is preliminary and prototype testing is highly recommended in all cases.

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FLEXIBILITY
ELASTICITY

TENSIL
STRENGTH

CREEP
RESISTANCE

THERMAL
AGING

CHEMICAL & 
WEATHERABILITY