A finite element analysis based design of a non-pneumatic wheel chair castor

Abstract

The non pneumatic castors (NPCs) exhibit various advantages over pneumatic castors such as, higher load bearing capacity, lower rolling resistance and less occurrence of the blowouts in harsh environments. We have conducted an FEA based design optimization study of wheel chair non-pneumatic castors (NPC); and compared its mechanical properties with a Pneumatic castor of same characteristics. NPCs with different number of holes and hole diameter, were subjected under vertical load and rolling along a discrete rigid road. Based on results; the NPC with 25 no. of holes and 8.75 mm hole diameter is considered as the optimal design, because the stiffness and rolling resistance of the castor with 8.75 mm diameter hole size overlapped the characteristics of Pneumatic castor. In order to avoid failures due to stress concentration, the stress distribution at various locations was also investigated for the NPCs as well as pneumatic castors. The stress concentration in NPC was observed “along the circumference that passes through the hole centers”. The minimum stress is induced in any individual hole when it’s not in contact with the ground, while as the castor rolls from 0 to 360°, stress changes in a sinusoidal form for every individual hole.