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).
Calculation of acceleration and braking curves for a 40/50 car with four-wheel brakes.
| Identifier | ExFiles\Box 113\2\ scan0070 | |
| Date | 19th March 1925 | |
| To PN.{Mr Northey} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}1/LG19.3.25. ACCELERATION - FOUR WHEEL BRAKES. In reply to PN{Mr Northey}10/DN17.3.25. We are sending you some curves shewing the acceleration and braking which may be expected from an open touring 40/50 car. The acceleration curve is evolved directly from some figures which we believe you already have. The braking curves we give you have been calculated. The reasons we have cal{Mr Calvert}- culated these curves are as follows :- The variables which can enter into any tests of braking on the road are so great that any curves which are the result of one test are likely to be misleading. These variables can be divided into two sections :- (A) Those which can be accurately estimated. These comprise :- (1) The height of the centre of gravity and the length of the wheel base of the car being tested. These have to be taken into account, unless during the test all four wheels of the car are to be locked. (2) The wind resistance of the car. This is important at high speeds and can be accurately estimated if the tractive resistance of the car at all speeds is known. (3) The method of conducting the test. This is most important. Unless the personal error is eliminated by some mechanical device, the obtaining of any average results to be used for the basis of comparison with tests taken by other people, is a most tedious business, as scores of tests have to be taken to eliminate this personal factor. (B) Those which cannot be accurately estimated. (1) The co-efficient of friction of the road surface. contd :- | ||