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).
Analysis of braking curves, critiquing testing methods and comparing deceleration figures.
| Identifier | ExFiles\Box 23\4\ Scan055 | |
| Date | 23th March 1925 | |
| R.R. 493a (50m) (D.B. 175 25-9-24) J.H.D. EXPERIMENTAL REPORT. Expl. No. REF Hs{Lord Ernest Hives - Chair}/Rml/LG23.3.25. ANALYSIS OF BRAKING CURVES. As we have previously pointed out, the results of braking tests are of little value unless they are carried out with great care, and the human element largely eliminated as a measuring device. 'The Motor' tests appear to have been carried out by means of the 'Pass a post and shout' method. In this case the passenger shouts to the driver to stop when opposite a post, whereupon, the driver applies the brakes, the distance from the subsequent position of rest of the car to the post being measured and taken as the distance required for a stop to be made. We find this method to be quite useless at speeds of 10 and 20 m.p.h. as the driver either anticipates the observers command or applies the brakes late, the result being easily affected by 25% either way. This is exactly what appears to occur in 'The Motor' tests. On the 'Bentley' car, the decelerations from the figures given are :- 10 m.p.h. 30.8 ft./sec² 20 m.p.h. 23.2 ft./sec² 30 m.p.h. 23.0 ft./sec² so that for some obscure reason the brakes are 30% more efficient at 10 m.p.h. than at 20 and 30 m.p.h. On the 'Vermorel' on the other hand, the distances to rest give the following decelerations :- contd :- | ||