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).
Analysing vehicle stopping distances and times, including a graph.
| Identifier | ExFiles\Box 178\1\ img075 | |
| Date | 12th October 1925 | |
| - 13 - REF. Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}2/LG121025. in which a car can be brought to rest varies directly as the square of the speed at which the car is travelling. If therefore a car's best stop from 20 m.p.h. is 20 ft., it may be safely predicted that under the same conditions its best stop from 40 m.p.h. will be (20 x 4) or 80 ft. approx. Time to rest. Though as above, the distance varies as the square of the speed, the time to rest is directly proportional to the speed. That is, if a car under the conditions above could be brought to rest in 1 1/2 secs. from 20 m.p.h. it could undoubtedly be stopped in about 3 secs. from 40 m.p.h. Graph: ROAD SPEED M.P.H. vs{J. Vickers} MINIMUM TIME TO REST (SECS) Co-efficient of friction) between tyre and road ) = .7 'A' - Values for car in which all four wheels can be locked. 'B' - Rear wheels only locked - front to rear = 40 to 60. REAR BRAKES ONLY 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. (contd). | ||