THE use of a power medium in brake control points at once to the possibility of simplifying the brake system so that its characteristics, once established, can be expected to remain uniformly effective throughout extended periods without adjusting, with correspondingly long life of brake-linings. The author says also that, if the greater retarding effect possible with mechanically operated four-wheel brakes is to be fully realized, it is necessary to do one of three things: increase the pedal pressure, increase the brake leverage and consequently the pedal movement, or increase the “self-energizing” effect.
The vacuum-type brake described is stated to be an amplifier which provides power to supplement muscular strength and assists the driver to apply the service brake, thereby reducing the required pedal stroke and pedal pressure without interfering with the regular service-brake hook-up. The description is illustrated with a drawing on which the parts are lettered for reference so that their operation and the way in which the forces are amplified can be understood readily. The capacity of the various vacuum brake-units manufactured by the company represented by the author is stated, and a chart is presented which shows graphically, for each size of unit, the pull it can develop on the brake-rod either with or without the assistance of the amplifying device.
Discussion of the paper includes a comparison of the brake-pedal force required for two-wheel and for four-wheel brakes, assuming that the lever ratios and the general foundation of the brake design remain undisturbed; statements of the amount of vacuum that can be depended upon to operate the brake unit; and an explanation of the effect on carburetion resulting from the air that is admitted to the intake manifold at the time of brake application.