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Liquid-cooled Disc Brake Made in U.S.A.
Page 75
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A DISC brake in circuit with the engine 1-1 cooling system has been developed by the Wagner Electric Corporation, St. Louis, U.S.A. The brake is contained within aeast-aluminium housing, inside which is an annular piston. Friction material is bonded to both sides of a circular carrier member, which is splined to the wheel hub.
Copper friction plates are riveted to the inner face of the annular piston, and to the inside of the housing, so that when hydraulic pressure is applied to the piston it moves across and clamps the rotating disc between it and the housing.
Liquid from the cooling system is fed to the backs of both the sections which carry the copper plates, and this coolant passes through the engine water passages and the radiator.
Tests have been carried out with this brake on the 13-mile-long Berthoud Pass, Colorado. This has an average gradient of I in 20, and the vehicle used was a 26i-ton-gross articulated outfit with six-wheeled tractor and tandem-axle semi-trailer. Disc brakes were fitted to one axle Drily, the other axles having the standard drum brakes. A control enabled the driver to actuate the discs independently of the drum brakes An average speed of 35 m.p.h. was maintained during the test descents. For the first test the discs were used in conjunction with the drums. The ambient temperature was 55* F. and the average drum temperature was only 20' F. above this, despite two "crash" stops being made.
For the second descent the drum brakes only were used, but I If minutes after the start, when only 6.7 miles of the hill had been descended, the drum
temperature had risen to 540° P. The two discs were thereupon reconnected, and immediately this bad been done the drum temperature started to fall and had dropped to 230° F. at the bottom of the hill
An off-the-road version of this brake has also been developed. This has two lining carriers, giving four friction faces, and opposed-piston actuation. In both cases an air servo is employed to give the necessary braking boost. The casing is heavily finned all over to assist heat dissipation.