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).
Gear ratios and their effect on car economy and road speed.
| Identifier | ExFiles\Box 178\1\ img054 | |
| Date | 21th November 1925 | |
| - 7 - EXPERIMENTAL REPORT. EXPL. No. REF. Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}/LG21.11.25. GEAR RATIO. It is for this reason that a high gear ratio reduces the petrol consumption; though the actual work required to drive the car is the same. With a high gear less work is wasted rotating the engine. GRAPH II Typical curves taken from American Journals. AXIS LABELS: PETROL CONSUMPTION M.P.G ROAD SPEED M.P.H. CURVE LABELS: GEAR RATIO 3.5 TO 1 GEAR RATIO 4.42 TO 1 GEAR RATIO 6 TO 1 TEXT BOX: EFFECT OF GEAR RATIO ON CAR ECONOMY GRAPH III AXIS LABELS: I.H.P. MINS OF WORK DONE PER MILE OPTIMUM SPEED ROAD SPEED M.P.H. ROAD SPEED. We have actually plotted the indicated horse power expended driving a Phantom at various road speeds. It will be seen from this that its most economical speed is likely to be (contd). | ||