QB
Q.F. Bongers
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The influence of roadsurface on powerloss
The design of an experimental apparatus that mimics roadsurface and measures powerloss
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. ...
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. ...
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.
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.