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).
Vehicle's on-road performance, including hill climbing, acceleration, and maximum speed.
| Identifier | ExFiles\Box 21\1\ Scan019 | |
| Date | 23th October 1925 | |
| R.R. 493A (50 M) (D.D. St.{Capt. P. R. Strong} 12-6-25) J.H.D. EXPERIMENTAL REPORT. -4- Expl. No. REF. Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}2/LG23.10.25. Below 12 m.p.h. in top gear it is necessary to humour the carburetter. The car is very free from detonation. The engine is not harsh, and remarkably free from periods, possibly due to the fact that the flywheel is used as a friction damper, being only coupled to the crankshaft frictionally. The engine, being very vigorous, is somewhat rougher than the 20 HP. R-R when under full torque; it is very smooth on the overrun. We checked the speedometer (A.T.) of the car over a mile at 30 m.p.h. it was 4% fast at this speed. We tried the car up Brockley hill. The results were :- Start 10 m.p.h. Max. 40 m.p.h. Finish 30 m.p.h. Time 53 secs. This would have been better if the carburation below 12 m.p.h. had not been poor. Similar figures for a Phantom car are :- Start 10 m.p.h. Max. 47 - 50 m.p.h. Finish 34/5 " Time 49 secs. We obtained approximate both way acceleration figures by means of the speedometer and stop watch. These were :- Time secs. Accn. ft/sec2 10 - 20 6.6 2.2 20 - 30 5.7 2.55 30 - 40 6.8 2.14 40 - 50 11.2 1.30 50 - 55 6.8 1.05 We obtained a both way reading for the max. speed of the car, this appeared to be 58 m.p.h. (corrected) contd:- | ||