Design and Manufacturng of Self Actuating Traction Drives with Solid and Hollow Rollers

The friction drive speed reducer proposed by Flugrad and Qamhiyah in 2005 was mainly investigated in this paper. That self actuating traction drive uses six intermediate cylindrical rollers to transmit motion. Those rollers fail by fatigue. So, this research built a numerical simulation model to find the optimum size of those rollers which give the least contact stresses and so the longest fatigue life. Then those rollers were replaced by hollow ones. The numerical simulation results showed that the contact stresses values decreased in case of having the rollers hollow, which means longer fatigue lives of those rollers. The hollow rollers were found to live more than 30 times the solid ones under same loading conditions. To validate the simulation results and practical application of the proposed model by Flugrad and Qamhiyah, two traction drives were manufactured from aluminum with the optimum dimensions found numerically. The hollow rollers were manufactured with 60% percentage of hollowness, that the ratio of the internal diameter to the external diameter was 60%. The hollowness was filled with rubber which has very low modulus of elasticity, which is very close to represent the hollow space. The two friction drive models were experimentally tested and could successfully transmit motion and reduce speed.