A Vintage Braking System
The Publicity Manager of Westinghouse has sent for our inspection three extremely interesting books issued in vintage times by The Westinghouse Brake & Saxby Signal Co. Ltd., whose works were in London and Chippenham.
These books deal with the Westinghouse vacuum power brake, which in those days had wide applications and was as well known as the brake-boosters and vacuum assistance for applying disc brakes that are in use today.
The first book is dated May 1924 and contains splendid illustrations of many nostalgic vehicles, such as Edwards Motor Transport’s 6-wheel Leyland Carrimore that operated daily services between London and the West Country, an Allchin 6-wheel steam lorry owned by Talbot-Serpell Transport Ltd., an enormously long Thornycroft 6-wheeler, J. E. Hall’s Hanford ten-tonner, a model-7 A.E.C. 65-h.p. 6-wheeler, etc., all of which were users of the Westinghouse brake. It was claimed that a 4-ton lorry could be brought to rest from 19 m.p.h. in 70 feet on the pressure brake, whereas the normal handbrake took the same stopping distance from 12 m.p.h.
The system on which the Westinghouse brake worked was that gas from the engine cylinders, or air from a separately-driven compressor on steam and electric vehicles, was delivered to a reservoir and released, as required, to operate diaphragms in extra brake cylinders coupled by rod to the normal brake levers. Control of this pressure servo was by either a hand lever or foot pedal. Claims included reduced insurance rates and higher average speed, “without exceeding the legal limit.” because the driver knew he had “this powerful stopping or retarding force at his command.” A 30-h.p. Daimler limousine is shown so equipped, the control lever extending from below the steering wheel like a modern stalk gear-lever, although its purpose is revealed by clumsy pipes leading from it. The system was quite complex, as gauges for cylinder and reservoir pressures (reading up to 60 and 200 lb./sq. in., respectively) and various supply, cheek and relief valves were required and a strainer and drain-cock on the reservoir called for. An emergency valve ensured that if a trailer broke away from lorry or tractor the brake was applied automatically. A further book dated November 1927, shows many fascinating commercial vehicles, including 55-h.p. Leyland, Karrier W06, Minerva tractor used by Browne & Eagle Ltd., Thornycroft and Mack, all using this additional brake, together with a Power Petrol tanker the make of which isn’t given but which is I think, a Saurer, which I have always associated with air brakes. For those not wishing to obtain pressure from the engine cylinders, which could cause sooting up of the system’s valves, Westinghouse made various compressors of which their Type C.35A absorbed approximately 1/2 b.h.p. and displaced 2 1/4 cu. ft. of free air per min. at 750 r.p.m. Reservoirs were tested to 400 lb./sq. in.
The third book serves as a reminder that a refined version-of the Westinghouse Air Brake was used in recent times, notably on London ‘buses ihat undertook a 12,000-mile tour of the U.S.A. and Canada and on the A.E.C. Type RT and Leyland Type RTL London Transport ‘buses that completed a 6,300-mile Continental tour in 1953. By now an engine-driven air compressor was universal.
It is interesting to be reminded of this servo brake, with its own control dating back to mid-vintage years. Incidentally, Count Zborowski had Westinghouse braking on his aero-engined Mercedes ” Chitty III,” and insisted on a proper railway-type regulator valve.—W. B.