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).
Page detailing the physics of vehicle retardation and braking distances under various conditions.
| Identifier | WestWitteringFiles\N\2October1925-December1925\ Scan45 | |
| Date | 12th October 1925 | |
| R.R. 493A (50 H) (D.D. 31, 12-6-25) J.H.D. EXPERIMENTAL REPORT -8- Expl. No. REF Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}2/LG121025 maximum retardation which will be the rate at which it could pull up on the level on 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 mph. = 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 therefore 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. approximately! 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. contd :- | ||