From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Letter to The Society of Motor Manufacturers & Traders Ltd regarding the suitability of brake testing machines for servo-assisted brakes.
| Identifier | ExFiles\Box 155\3\ scan0086 | |
| Date | 11th September 1936 | |
| c. Hs{Lord Ernest Hives - Chair}/Mr. Martindale. X1325 11th. September 1936. BY.3/G.{Mr Griffiths - Chief Accountant / Mr Gnapp} The Secretary, The Society of Motor Manufacturers & Traders Ltd., 83 Pall Mall, London. S.W.1. Dear Sir, BRAKE TESTS IN PALESTINE. With reference to your communication of August 19th. on the above subject, at our Works we have no machine for checking up the individual braking effects, the reason for this being that we have servo braking, the servo being driven by the propeller shaft, and therefore unless all four wheels are being driven the test on the front wheels would show no brakes, and so far as we are aware this is a characteristic of all British made brake testing machines, viz. that they are suitable for testing brakes which use the Lockheed system or a direct foot pedal operated scheme, but they are not suitable for servo operation of our type. We are acquainted with the American Weaver brake tester, and would be quite satisfied with the results shown by this machine, as it is so arranged to give an accurate indication for all four wheels, and is of such a design as to cover servo operated brakes of our type, the servo being driven from the propeller shaft. With reference to the question of the braking efficiency called for, we consider that 70% is a reasonable proposal, and that if brakes would not come up to this standard the car is not suitable for road work, it being remembered, of course, that the 70% is independent of the tyre and road surface as in the Weaver machine a specially rough surface is used to ensure the maximum grip between the tyre and the recording shoe, and therefore it is the actual load absorption in the brake drum which is recorded. Yours faithfully, FOR ROLLS-ROYCE LIMITED. 134 TECHNICAL PRODUCTION ENGINEER. | ||