Performance implications of increasing the 25 HP engine's displacement to 4.7 litres, with weight comparisons to a Chrysler chassis.
| Identifier | ExFiles\Box 5a\1\ 01-page010 | |
| Date | 6th January 1931 | |
| To Wor. {Arthur Wormald - General Works Manager} From Hs {Lord Ernest Hives - Chair} /Ra. Y 5770 Hs {Lord Ernest Hives - Chair} /Rm. {William Robotham - Chief Engineer} 4/&J.6.1.31. 25 HP. FUTURE PERFORMANCE. Our present engine and gearbox weigh 678 lbs. for 3.67 litres displacement. Assuming the engine weight increases as the displacement, the projected 4.7 litre engine will weight 865 lbs. i.e. an increase of 187 lbs. 18-34. car empty weighs 3900 lbs. Therefore the increase in power (which may be taken as approx. proportional to increased displacement) is 28 % for no more than 4.6% increase in total car weight. We therefore should get something over 20% increase in acceleration from the proposed alteration. We consider that our chassis design is as good as anyone else's i.e. we have no superfluous weight that is not used to advantage. The weight of the Chrysler chassis we analysed in Derby less engine and gearbox is 1621 lbs. and the engine displacement 4397 c.c. or 370 lbs. of chassis wt. per litre displacement. The weight of the 25 HP. R.A. chassis at present less engine and gearbox, is 1918 lbs. If to this chassis we fit the proposed 4700 c.c. engine we find we shall have 410 lbs. of chassis wt. per litre displacement. In other words we believe that we can do what Chryslers do, and that since we already have 10% extra chassis wt. in hand with the 4.7 litre engine there is no justification for prematurely demanding alterations, without test, to the transmission etc. Hs {Lord Ernest Hives - Chair} /Ra. | ||
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).