Changes in inertia and effect on turning effort across different wheelchair configurations

1. Changes in inertia and effect on turning effort across different wheelchair configurations Jayme J. Caspall, MS; Erin Seligsohn; Phuc V. Dao, MS; Stephen Sprigle, PhD, PT

2. Aim • Measure changes in inertial reactance or wheelchair inertia due to configuration changes in adjustable manual wheelchairs. • Relate inertial changes to differences in torque required to overcome caster scrub and accelerate wheelchairs during turning. • Relevance • When executing turning maneuvers, manual wheelchair users must overcome rotational inertia of wheelchair system.

3. Method • Measured inertias of various configurations of ultralightweight wheelchair. • Compared: • Adjustments in axle position. • Changes in wheel and tire type. • Addition of several accessories.

4. Results • Configuration with highest rotational inertia (solid tires, mag wheels with rearward axle) exceeded configuration with lowest (pneumatic tires, spoke wheels with forward axle) by 28%. • Greater inertia requires increased torque to accelerate wheelchair during turning. • At representative maximum acceleration, reactive torque was 11.7 to 15.0 N-m across wheelchair configurations. • At higher accelerations, torques exceeded that required to overcome caster scrub during turning.

5. Conclusion • Results indicate that: • Wheelchair’s rotational inertia can significantly influence torque required during turning. • This influence will affect active users who turn at high speeds. • Categorizing wheelchairs using both mass and rotational inertia would better represent differences in effort during wheelchair maneuvers.