Experimental life prediction of electric hub motor bearings using telemetry

Balun Y., Orhan B., Gören A.

Energy 360, vol.6, 2026 (Peer-Reviewed Journal)

Abstract

The applications of electric motors are crucial for reducing greenhouse gas emissions and preventing global warming. Electric hub motors provide an efficient alternative to internal combustion engines by delivering torque directly to the road surface, which maximizes overall vehicle efficiency. However, the reliability of these in-wheel motors depends heavily on mechanical friction; thus, bearing selection and precise structural life analysis near operational limits become critical. This study evaluates the ball bearing service life of an electric hub motor used in a lightweight three-wheeled solar electric vehicle under circuit race conditions. The theoretical framework integrates International Organization for Standardization (ISO) 281 standards and the Ioannides-Harris fatigue theory to determine the modified rating life, utilizing dynamic vehicle loads derived from steady-state track simulations. A key novelty is the validation of this simulation model using physical real-time strain gauge telemetry collected during the Albi Eco Race 2025. The statistical comparison yields a Root Mean Square Error of 132.28 N, a Mean Relative Error of 39.65%, and a Coefficient of Determination (R2) of 0.8128. While the rigid-body simulation framework captures the overall trend and provides a conservative upper-bound for structural safety margins, the transient track data highlights localized discrepancies due to vehicle compliance and dynamic load fluctuations. Under limit cornering conditions at 67 km/h, the simulation indicates that the dynamic equivalent load completely exceeds the dynamic capacity of the inner bearing, signaling an immediate risk of localized plastic deformation. Based on the experimental constraints of steel bearing friction models, hybrid ceramic configurations are evaluated as a prospective solution; their reduced rolling element density offers a theoretical basis for minimizing internal centrifugal forces, suggesting a potential pathway to optimize net motor efficiency under extreme load cycles.

The applications of electric motors are crucial for reducing greenhouse gas emissions and preventing global warming. Electric hub motors provide an efficient alternative to internal combustion engines by delivering torque directly to the road surface, which maximizes overall vehicle efficiency. However, the reliability of these in-wheel motors depends heavily on mechanical friction; thus, bearing selection and precise structural life analysis near operational limits become critical. This study evaluates the ball bearing service life of an electric hub motor used in a lightweight three-wheeled solar electric vehicle under circuit race conditions. The theoretical framework integrates International Organization for Standardization (ISO) 281 standards and the Ioannides-Harris fatigue theory to determine the modified rating life, utilizing dynamic vehicle loads derived from steady-state track simulations. A key novelty is the validation of this simulation model using physical real-time strain gauge telemetry collected during the Albi Eco Race 2025. The statistical comparison yields a Root Mean Square Error of 132.28 N, a Mean Relative Error of 39.65%, and a Coefficient of Determination (R2) of 0.8128. While the rigid-body simulation framework captures the overall trend and provides a conservative upper-bound for structural safety margins, the transient track data highlights localized discrepancies due to vehicle compliance and dynamic load fluctuations. Under limit cornering conditions at 67 km/h, the simulation indicates that the dynamic equivalent load completely exceeds the dynamic capacity of the inner bearing, signaling an immediate risk of localized plastic deformation. Based on the experimental constraints of steel bearing friction models, hybrid ceramic configurations are evaluated as a prospective solution; their reduced rolling element density offers a theoretical basis for minimizing internal centrifugal forces, suggesting a potential pathway to optimize net motor efficiency under extreme load cycles.