STRENGTH OF MECHANICAL FLAT DRIVE BELTS
The strength of Dymetrol mechanical flat drive belts and regulator tape varies with cross section, perforation configuration and composition. The separate listing of currently available belt sizes contains actual break strength for a wide range of currently available configurations. Depending on size and type, break strengths approaching 1500 lbs. for unpunched and in excess of 550 lbs for punched belts are achievable. Four-tooth engagement is a minimum condition. Higher values are achieved with higher numbers of engaged teeth.
Figure A shows the PSI (kg/cm2) vs elongation for solid 2000 type standard modulus flat drive belts. It can be used for predicting elongation at various operating temperatures.
Tensile Strength / Elongation
Strength kg
Strength psi 3500, 3000, 25000
-40F -40C Add Conversions.
Tensile Strength / Elongation
Strength kg
Strength psi 3500, 3000, 25000
-40F -40C Add Conversions.
As shown in Figure B, high modulus belts exhibit higher tensile strength than their standard modulus counterparts at equivalent elongations. This advantage is at the expense of low temperature flexibility where the standard modulus belts excel. Comparison of standard modulus (DETP 2005) and high modulus (DETP4205) punched belts shows a roughly 25% higher stress at 7% elongation for the high modulus formulation. At break, the high modulus belt is 20% stronger. Both formulations exhibit essentially the same elongation at break.
Most applications utilize punched belts. Perforating a belt reduces its load bearing capability. The reduction in load bearing capability compared with solid belts varies with the relative size of belt-to-hole cross section, spacing of the holes as well as the number of drive sprocket teeth engaged with the belt . A test apparatus (Figure C) is routinely used to evaluate load bearing capability of punched belts . The fixture is mounted in an Instron Testing Machine ( where four teeth are engaged at each end of the belt ) and the belt stretched to failure. The 1 data from this test are shown in Figure D.
Figure D.
In general, the break load has been found to be approximately linear (i.e. one tooth = 100 lbs, two = 200 Ibs) until the break load of the solid cross section is approached. From comparisons made on solid vs punched belts, samples using a conservative simulation of 4 tooth engagement, a load bearing capability of roughly 40-50% of solid belt values is observed
with punched belts of the same size and composition.
Figure D specifically illustrates typical load vs elongation curves for the same belt (DETP 4205) un punched vs punched with “standard” hole (8.1 mm pitch, 3.6 mm length x 2.3 mm width) configuration at the engagement (worst case, i.e., small sprocket and/or less than 180° engagement).
Designers should strive to achieve maximum tooth engagement possible within the system configuration limits by employing the largest sprocket diameter and maximum possible wrap.
In general, the break load has been found to be approximately linear (i.e. one tooth = 100 lbs, two = 200 Ibs) until the break load of the solid cross section is approached. From comparisons made on solid vs punched belts, samples using a conservative simulation of 4 tooth engagement, a load bearing capability of roughly 40-50% of solid belt values is observed
with punched belts of the same size and composition.
Figure D specifically illustrates typical load vs elongation curves for the same belt (DETP 4205) un punched vs punched with “standard” hole (8.1 mm pitch, 3.6 mm length x 2.3 mm width) configuration at the engagement (worst case, i.e., small sprocket and/or less than 180° engagement).
Designers should strive to achieve maximum tooth engagement possible within the system configuration limits by employing the largest sprocket diameter and maximum possible wrap.
