Measurement of rolling resistance and scrub torque of manual wheelchair drive wheels and casters.

The effort needed to maneuver a manual wheelchair is a function of the occupied wheelchair's inertia and energy loss. The primary source of energy loss is due to the resistance of the drive wheels and casters on the ground. Specifically, manual wheelchairs have two major sources of frictional energy loss: rolling resistance and scrub torque. The objective of this study was to develop and validate component-level test methods to evaluate the energy loss properties of drive wheels and casters on different surfaces and with different applied loads. Rolling resistance is measured using a weighted coast-down cart and scrub torque is calculated by measuring the force required to rotate a plate that is loaded onto the tire's surface. Each test method was iterated and then applied to a cohort of drive wheels and casters. Both test methods demonstrated acceptable repeatability and the ability to distinguish energy loss parameters between common wheelchair components. The results show that caster and drive wheel energy losses can vary significantly across surfaces and with increased load on the casters. However, the findings also illuminate complex relationships between rolling resistance and scrub torque performance that embody a tradeoff in performance as applied to mobility during everyday life.