Experimental investigation of rolling losses and optimal camber angle

University essay from KTH/Maskinkonstruktion (Inst.)

Author: Bethuel Karanja; Elin Skoog; [2015]

Keywords: ;

Abstract: This Bachelor thesis project is an experimental investigation of the effect of camber and toe angles on rolling resistance. The experiments are done on Sleipner, a Prototype car made by KTH students, which takes part in the Shell Eco Marathon competition in Rotterdam. In order to succeed in the competition it is crucial to reduce energy losses in order to get an as energy efficient vehicle as possible. The experiment involves tests where Sleipner is manually dragged across a flat floor and its position and the dragging force are logged with a pulse encoder and a load cell respectively. This is done ten times for each chosen wheel alignment (specific camber and toe angle), in order to be able to find the optimal setting with respect to minimization of rolling losses. The tests are performed in the Integrated Transport Research Lab at KTH. The obtained data is then used to calculate the magnitude of the rolling friction.It is found that the more negative the camber angle, the larger the rolling resistance. The smallest camber angle investigated is -3º which gives a coefficient of rolling friction (Cr) of 0.0052. The second camber angle is -5º giving a Cr value of 0.016 and the largest camber angle is -7º giving a Cr value 0.019. It was also found that, with the minimum camber angle, toe out gives a larger coefficient of rolling resistance than toe in; 0.0081 compared to 0.0052.The report also delves into additional effects of camber and toe angles on the vehicle’s behaviour while driving and it is found that negative camber angle gives better stability in the car when cornering and that toe in gives better stability in straight line driving.With these results it is concluded that Sleipner should have a slight camber angle of -3º and toe in of 0.5º so as to have the best results in the Shell Eco Marathon.

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