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).
Braking tests conducted in North Devon.
| Identifier | ExFiles\Box 30\6\ Scan176 | |
| Date | 12th July 1923 | |
| R.R. 403A (40 H) (SL 42 12-7-23). J.H., D.{John DeLooze - Company Secretary} EXPERIMENTAL REPORT. Expl. No. REF: Ha/3a/LGS.2 24. BRAKING TESTS - NORTH DEVON. Porlock hill - Length 2 1/4 miles. average grade 1 in 9 1/4. steepest 1 in 4 1/4. Countisbury hill. - Length 2 miles. average grade 1 in 9. steepest 1 in 4 1/4. Surfaces heavy. We have carried out further tests on the servo lined with cast iron, on Porlock and Countisbury hills. The servo shoes were equipped with carriers containing a number of sentinels. The temperature of the drum when each of the sentinels melted was previously ascertained (on the test rig) by calibration with a thermo-couple, with the carrier in position on the shoe. The drum attained a temperature of 400 - 450°C when descending Porlock at from 10/15 m.p.h. - about 500°C when descending the hill from 20/25 m.p.h. A certain amount of smoke and smell emanated from the servo on the lower portions of the hill - the movement of the drum against the shoes was also audible. The servo jaggered somewhat when warm and applied severely. In these tests the car was held by the foot brake only with the clutch out. On completing the descent, the rear end of the gearbox was unpleasantly hot and could only be touched momentarily. The Hispano servo, after similar tests, was just warm. The brakes on the 40/50 did not appear to lose their efficiency at all through being overheated. We consider that had the servo been lined with Ferodo the material would have been roasted, as it was, no appreciable increase in wear or co-efficient of friction took place. The brakes required rather too much pedal pressure for comfortable continued use down these hills, backwards they were sufficiently powerful to make their application for brief periods on a 1 in 4 1/4 gradient a reasonable proposition, and very much better than the Hispano in this respect. It was not necessary to make any adjustments to the brakes during these tests, their behaviour being remarkably consistent throughout. We ascertained that under normal running conditions, using the engine as a brake and excluding very severe gradients, the servo drum temperature does not exceed 200°C. | ||