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).
Vehicle braking performance, including a graph and analysis of wheel locking and retardation.
| Identifier | ExFiles\Box 39\2\ Scan218 | |
| Date | 12th October 1925 | |
| R.R. 493a (50 H) (D.D. 31, 12-6-25) J.H.B. EXPERIMENTAL REPORT. -13- Exptl. No. REF Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}2/LG121025 ROAD SPEED (M.P.H.) MINIMUM TIME TO REST (SECS) A B Rear Brakes Only Coefficient of friction) = .7 between tyre and road ) 'A' - Values for car in which all four wheels can be locked. 'B' - Rear wheels only locked - front to rear = 40 to 60. Windage. As will be seen from the attached graph, windage is of no importance at the speeds from which ultra-rapid stops are usually made. Pedal pressure. The increase in pedal pressure required to lock the wheels at high speeds is largely due to the energy of the rotating parts. Even if the wheels are not locked suddenly, the rotating parts increase the work to be done in stopping the car rapidly. The magnitude of these forces is illustrated in the attached graph. Maximum probable retardation. On a car on which we could lock all wheels we have never measured a greater retardation than 20 ft/sec2 on the road. A retardation of 12 ft/sec2 is about the limit for the personal comfort of the passengers seated in the rear of the car. Hs{Lord Ernest Hives - Chair}/W. A.{Mr Adams} Robotham. | ||