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).
Comparing the petrol consumption of the Phantom model against the Silver Ghost, discussing the effects of front-wheel brakes and testing conditions.
| Identifier | ExFiles\Box 47\1\ Scan371 | |
| Date | 1st November 1926 | |
| W/S. H.{Arthur M. Hanbury - Head Complaints} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. Br.{T. E. Bellringer - Repair Manager} [Handwritten: X417] [Underlined: Hs{Lord Ernest Hives - Chair}/Rml/TS.11.26.] Re: The Hon. H.D. Maclaren - Chassis No.15-TC. [Handwritten: X459] With reference to H8/GM/4.11.26, we consider that the fixed road speed petrol consumption of Phantom is slightly better than that of the Silver Ghost, everything else being equal. The main difference we ourselves have found between present cars and pre-front-wheel-brake cars is that with the former a higher average speed is maintained owing to front wheel brakes being fitted, with consequent detriment to consumption. (See Fundamentals of Car Performance). This is equally true of 'India' and G.2 cars and we have made a number of tests which confirm the point. We anticipate that it should be possible to obtain 14 to 14 1/4 m.p.g. from a well run in Phantom car if driven at a steady speed of 30 m.p.h. We should like to point out that when taking consumptions in this way, the car should be fully warmed up on the road, because the tractive resistance of the tyres decreases as their temperature rises; also tyre inflation pressure should be kept well up to the recommended figure. Actually in the Test Dept., when the cars are new, and therefore piston friction, etc. may be expected to be a maximum, an average consumption of 13 1/2 to 14 m.p.g. is obtained. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||