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 stopping distances and times, including the effect of gradients.
| Identifier | ExFiles\Box 39\2\ Scan217 | |
| Date | 12th October 1925 | |
| R.R. 498a (50 M) (U.D. 31. 12-6-25) J.H.L. EXPERIMENTAL REPORT. -12- Expl. No. REF Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}2/LG121025 rate at which it could pull up on the level on w the same surface minus the acceleration due to the gradient. Conversely, up hill, the car can be pulled up more quickly than on the level, the retardation due to the gradient being added to that due to the surface. Example = .7 Level - distance to rest from 40 m.p.h. = 75 ft. Up hill ) - " " " " " = 58 ft. 1 in 5 ) Down-hill) - " " " " " = 102 ft. 1 in 5 ) Distance to rest. On any surface with a fixed co- efficient of friction and a given amount of braking, the distance in which a car can be brought to rest varies directly as the square of the speed at which the car is travelling. If there- fore a cars 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 pro- portional to the speed. That is, if a car under the conditions above could be brought to rest in 1½ secs. from 20 m.p.h., it could undoubtedly be stopped in about 3 secs from 40 m.p.h. contd :- | ||