Some Measurements of Brake Usage in a High-Speed Saloon Car

Abstract

The paper describes equipment which has been developed to record the duties imposed upon automobile brakes in service under various normal conditions. The principal measurement required was the rate of energy dissipation at the brakes, and this was recorded, together with the drum speed and deceleration, on a roll-chart recorder. The principles involved in these measurements are discussed in some detail, together with an outline of the practical precautions necessary to preserve the accuracy of the readings. From the results it will be possible to develop improved testing cycles for the test machines used in the development of brake lining materials but, in addition, some points of fundamental interest have emerged from the investigation. The results quoted in the paper show that the energy dissipated at the brakes is directly related to the mean journey speed for a given journey when other factors are kept constant and that: Energy dissipated at the brakes = (mean journey speed) n where n has a value of about 3.4 for the conditions encountered in this investigation. The effect of mean journey speed is shown to be much greater than that of the other variables considered although it must, of course, be taken in conjunction with the characteristics of the road. Braking in hilly country is shown to be appreciably more severe than on corresponding roads through flat country.