BRAKE DESIGN

Dominion, Volume 22, Issue 75, 21 December 1928, Page 19

BRAKE DESIGN

URGED ON BY HIGHER SPEEDS.

Each year the average speed of traffic increases, as does the average speed of the car, and also the volume of cars on the congested road. Brakes, therefore, must improve equally as rapidly as the speed of the car; more rapidly, in fact, for brakes have been a long wav behind speed for years past, and it is only since the relatively recent arrival of four-wheel brakes that 're ieral safety has been at all assured. Progress has been made with brake systems, and, indeed, is being made quite rapidly by those manufacturers of.cars who are keen enough to study the performance of efficient contemporaries. A year or two ago cars wirh four-wheel brakes took 90 to 110 feet to pull up in emergency from 40 m.p.h. To-day many brake systems need attention if the vehicle cannot make an emergency str from that speed in bO to 70 feet, and stop smoothly at that. Attention to efficiency in the mechanism has obtained these results. Men and women are capable of exerting a certain average pressure with a single foot, and there is a limit of only a few inches of travel over which this pressure can comfortably be maintained. These two factors pro vide all the leverage for brake applica tion that is available. If the system of leverages and tie-rods leading to the brake shoes is efficiently designed and made, then this • available force is quite sufficient to give adequate control for a car up to 20 h.p., and capable of 60 m.p.h. Larger cars of greater .weight and speed need to have some form or mechanical assistance, or servo system, in order to relieve the driver of hard work. Servo motor brakes of the vacuum operating type are ceasing to find place on the small and medium sized car because detail improvement in actuating gear is making them less necessary, and partly because of price, but on larger cars in which expense is more or less a secondary consideration, such systems are falling into regular use, to say nothing of the mechanical type of servo brake and the hydraulic-ally-assisted brake..