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).
Comparison of brake tests conducted in North Devon between the R.A.C. High Speed Servo and Hispano systems.
| Identifier | ExFiles\Box 30\6\ Scan179 | |
| Date | 1st February 1924 guessed | |
| BRAKE TESTS - NORTH DEVON. R.A.C. HIGH SPEED SERVE AND HISPANO SYSTEM COMPARED. Gradients up to 1 in 4 measured with gradieometer. Steeper - local intelligence obtained. OBSERVATION. Forward braking. Backward braking. Max. temperature attained by servo drum. Ordinary touring temp: attained by servo. No severe gradients. Adjustments required throughout tests. Change in functioning of brakes due to tests. Objectionable features observed during tests. R.A.C. (Cast iron servo linings.) Will hold on 1 in 4 - considerable pedal pressure. Will hold on 1 in 4¼ with about the same pressure as is required to hold the Hispano on 1 in 7¼. 500º - 550ºC. Below 200ºC None. Not appreciable. Rather too much pedal pressure required for comfortable continued application down long hills. Servo jaggers slightly when warm and applied severely. Smoke and smell from servo when very hot. Bogging when applied suddenly and occasional front axle jaggers. HISPANO SUIZA. Will hold on 1 in 4 - reasonable pedal pressure Hold on 1 in 4½. Max. personal effort required. 50º - 60ºC Barely warm. None. Not appreciabl,e Far too much pedal pressure required for backward braking on severe gradients | ||