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).
Technical memo detailing a method for testing inefficient brakes by measuring servo output with spring balances.
| Identifier | ExFiles\Box 30\6\ Scan220 | |
| Date | 12th October 1933 | |
| 261 To W.Or. from Ha/Gry.{Shadwell Grylls} C. E.{Mr Elliott - Chief Engineer} C. D.{John DeLooze - Company Secretary} C. Da.{Bernard Day - Chassis Design} BY.{R.W. Bailey - Chief Engineer} C. Hdy.{William Hardy} Ha. C. Br.{T. E. Bellringer - Repair Manager} EP.{G. Eric Platford - Chief Quality Engineer} C. Mx.{John H Maddocks - Chief Proving Officer} Ha/Gry.{Shadwell Grylls}11/KT.12.10.33. INEFFICIENT BRAKES. In most cases of complaints of inefficient brakes the servo is at fault, and not the brakes themselves. We have been experimenting to determine the output from an efficient servo for a given input. Set-up spring balances are used to measure the loads; being inserted between the pedal and countershaft lever (off-side) for the input, and between the bottom of the balance lever and front brake differential for the output. The rear brakes are wired off at the axle, the back wheels jacked up, and the transmission run at 20 m.p.h. The balances are so arranged that they do not read below 200 lbs. On both 20/25 and Bentley the output is less than this for 300 lbs. input on a bad servo, and is therefore not measurable. In such cases we find, and demonstrated on a car at 'H', that continued pressure on the brake pedal giving a 300 lbs. input for several minutes causes the servo to smoke and the output suddenly to rise to about 300 lbs. On allowing to cool down an efficient servo results giving about 300 lbs. output cold and 350 at normal temperature. We recommend this practice on complaints. It is immediately seen if the servo is at fault, and if at fault when the linings have been again made efficient. The running of the test should be ceased immediately the output rises or the linings will be ruined. Will Ed.{J. L. Edwards} please issue a Depot Sheet. We attach a sketch of the spring balances, Ex. 9690. Replace by balances. FRONT. REAR. | ||