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).
With graphs analyzing the effect of gear ratios and road speed on fuel economy and engine efficiency.
| Identifier | WestWitteringFiles\N\2October1925-December1925\ Scan162 | |
| Date | 12th June 1925 | |
| R.R. 493A (50 H) (D.D. 31, 12-6-25) J.H.D. EXPERIMENTAL REPORT. -7- Expl. No. REF. Hs{Lord Ernest Hives - Chair}/Rn{Mr Robinson}/LG21125 GEAR RATIO. It is for this reason that a high gear GRAPH II PETROL CONSUMPTION M.P.G. EFFECT OF GEAR RATIO ON CAR ECONOMY. GEAR RATIO 3½ TO 1 GEAR RATIO 4½ TO 1 GEAR RATIO 6 TO 1 Typical curves taken from American Journals. ROAD SPEED M.P.H. 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 III 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 17½ m.p.h. If the speed is pushed up to contd :- | ||