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).
Methodology for calculating acceleration and tractive resistance graphs for the 49-GB vehicle.
| Identifier | ExFiles\Box 113\2\ scan0027 | |
| Date | 24th January 1923 | |
| Hs.{Lord Ernest Hives - Chair} X1725 24.1.23. GRAPHS OF 49-GB. CUT-OUT CLOSED. The acceleration graph is calculated from a number of both-way readings with a speedometer that has been checked for lag. Tests were carried out by proceeding at a fixed speed, and then, at a given signal, accelerating until the speedometer showed a rise of 5 m.p.h., the time being taken by two stop watches. This method, of course, introduces carburation troubles, and does not give so even a result as accelerating right up from 10 to 60 m.p.h. observing the time taken to reach various speeds. We used it for convenience in timing, but shall revert to the latter method for future readings. Accelerations of 3 f.p.s. and over suffer considerably from inaccuracies in timing, 1/5 of a second making a very appreciable difference. We hope to reduce this error by using more reliable stop watches. The tractive resistance graphs are obtained by observing the deceleration caused at various speeds. (a) When the clutch is put out and the car allowed to coast. (b) When the engine is switched off, throttle closed, clutch left in and the car allowed to coast. The difference of these two gives the tractive resistance occasioned by turning the engine over, from which is calculated. The horse power required to turn the engine over at any speed. As this includes the gear losses in driving through contd:- | ||