The influence of roadsurface on powerloss
The design of an experimental apparatus that mimics roadsurface and measures powerloss
Q.F. Bongers (TU Delft - Mechanical Engineering)
J.K. Moore – Mentor (TU Delft - Mechanical Engineering)
G. Papaioannou – Mentor (TU Delft - Mechanical Engineering)
R. Happee – Graduation committee member (TU Delft - Mechanical Engineering)
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Abstract
Road-induced vibrations dissipate energy through the bicycle structure and rider’s body beyond what classical rolling resistance predicts. To measure this effect a laboratory apparatus is used that reproduces realistic road surface characteristics. This thesis presents the design, construction, and validation of such an apparatus and characterises the powerloss on a 3D-printed klinker road surface across six speeds (5–30 km/h) and five tire pressures (3.5–5.5 bar).
The setup measures the total resistive force acting on an athlete and racing bicycle using two loadcells: a main loadcell and an interface loadcell that captures the longitudinal force exerted by a two-bar linkage stabilization mechanism, isolated from the vertical load by a parallelogram flexure. Multiplying this force by the belt speed gives the powerloss. The force is measured with an expanded uncertainty of ±0.41 N at the 95% confidence level, corresponding to a powerloss uncertainty of at most 3.4 W at 30 km/h.
Powerloss increases approximately linearly with speed for all pressures, ranging from about 30 W at 5 km/h to 234 W at 30 km/h. Much of this loss is not classical rolling resistance: at 30 km/h the classical term accounts for only about 82 W, so roughly 64% of the total powerloss is attributed to vibrational losses. Tire pressure has a smaller effect: depending on the speed setpoint, an optimal tire pressure can be identified, although at lower speeds the error bars overlap and no clear optimum can be determined. The near-linear speed dependence shows that although the vibrational losses are large, their speed-growing quadratic component remains weak on the relatively smooth klinker surface (BRI ≈ 40). A stiffer underlayer and a rougher surface are recommended before the apparatus can be used to quantify vibration transmission from the road surface through the bicycle to the rider’s body.