Home Page T-4 Tension Member Curvilinear Trapezoidal Fig. 2    Stress Pattern in Belts • Greater shear strength due to larger tooth cross section. • Lower cost since a narrower belt will handle larger load. • Energy  efficient,  particularly  if  replacing  a  "V"  belt  drive  which  incurs  energy  losses  due  to slippage. • Installation tension is small, therefore, light bearing loads. In  Figure  2,  the  photoelastic  pattern  shows  the  stress  distribution  within  teeth  of  different geometry.  There is a definite stress concentration near the root of the trapezoidal belt tooth, with very  low  strains  elsewhere.    For  the  curvilinear  tooth,  there  is  a  uniform,  nearly  constant,  strain distribution across the belt.  The load is largest in the direction of the tension member to which it is transferred. Because  of  their  superior  load  carrying  capabilities,  the  curvilinear  belts  are  marketed  under the name of Gates' HTD drives.  This is an abbreviation of High Torque Drives. As a result of continuous research, a newer version of the curvilinear technology was developed by Gates, which was designated as Gates' PowerGrip GT belt drives. SECTION 2    GATES POWERGRIP^® GT BELT DRIVES The PowerGrip GT Belt Drive System is an advance in product design over the Gates' older, standard  HTD  system.    The  PowerGrip  GT  System,  featuring  a  modified  curvilinear  belt  tooth profile, provides timing and indexing accuracy superior to the conventional PowerGrip Trapezoidal Belt System.  Plus, PowerGrip GT Belts have a higher capacity and longer belt life than trapezoidal belts. It's difficult to make a true quantitative comparison between the backlash of a trapezoidal tooth drive  and  PowerGrip  GT  drive  due  to  the  difference  in  "pulley  to  belt  tooth"  fit  (see  Figure  3). Trapezoidal  belts  contact  the  pulley  in  the  root  radius-upper  flank  area  only,  while  the  PowerGrip GT system permits full flank contact. PowerGrip^® Trapezoidal Belt Tooth/Groove Contact PowerGrip^® HTD^® Belt Tooth/Groove Contact PowerGrip^® GT^® Belt Tooth/Groove Contact Fig. 3    Comparison of Different Tooth Profiles