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).
Brake deceleration and efficiency tests on a 'Vermorel' car.
| Identifier | ExFiles\Box 30\6\ Scan196 | |
| 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. On the 'Vermorel' on the other hand, the distances to rest give the following decelerations :- 10 m.p.h. 25.4 ft/sec² 20 m.p.h. 33.6 ft/sec² 30 m.p.h. 33.4 ft/sec² So that on this car the brakes are 25% less efficient at 10 m.p.h. than at 20 and 30 m.p.h. On both cars the brakes are direct pedal operated so that there is no servo to be taken into account. The Vermorel figures are further astonishing because to obtain the pull up given from 20 and 30 m.p.h. the co-efficient of friction between the tyre and the road would have to be greater than unit, actually above 1.05. Though we have heard of results like this being obtained in America, we have never measured anything above .85 ourselves. Still more puzzling are the figures for the Vermorel at 40 and 45 m.p.h. which give the following decelerations :- 40 m.p.h. 23 ft/sec² 45 m.p.h. 17 ft/sec² From these it will be seen that the efficiency of the brakes decreases 48% when pulling from 45 m.p.h. as compared with 30 m.p.h. We therefore get the following curve of efficiencies for these brakes. contd :- | ||