PROPER brake testing is stated to involve the measuring and recording of vehicle deceleration and rate of speed for every foot of individual wheel travel during the period from the initial application of the brakes up to the moment the car comes to a standstill.
The brake synchrometer, designed to duplicate the conditions under which a vehicle is tested on the road, embodies the principle of traction between each tire of the vehicle, on one hand, and a rotor on the other hand. The kinetic enegery of the four testing rotors must be equal to the energy of a vehicle of a certain weight at a given testing speed.
The author describes a brake synchrometer designed for testing vehicles of 3500-lb. weight, which machine, however, is adjustable to compensate for greater or lesser car weight, so as to include heavier or lighter vehicles in its test range. He explains the method of testing all the brakes of a vehicle individually at the same time, or of measuring and recording the combined capacity of the four brakes.
By an electrical method, accurate records are obtainable of the average speed in miles per hour of each wheel for each foot of travel during the braking period. These records serve as a basis for distance-speed curves, giving percentage readings of deceleration-rate variation.
The plotting of curves showing differences in synchrometer operating speed required to compensate for differences in vehicle weight is described, and experiences are given to illustrate the operation of the brake synchrometer in practice.