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).
Page from a test report analyzing and comparing performance graphs for engine power, efficiency, and resistance.
| Identifier | ExFiles\Box 113\2\ scan0035 | |
| Date | 26th February 1923 guessed | |
| contd:- -2- Fig.D. Shows the results of this correction and also a correction for the fact that in using the momentum of the car to turn the engine over, we transmitted the power via. the crown wheel, pinion and gearbox. We assume that this caused us to get readings 5% higher than if the engine has been turned over directly. Fig.E. Consists of Clutch B.H.P. and Dynamometer H.P. curves which are an average of the type of engine and chassis in question on production, and I.H.P. curves which are obtained by adding Graph 'D' results to the B.H.P. curve. Fig.F. Shews the road H.P. as calculated from Graphs 'A' and 'B' and corrected for rotating parts. These are compared with average dynamometer parts. H.P. curves for the types in question. The correct Road H.P. curves should come slightly above the Dynamometer H.P. curves for the following reason. On the road we take the tractive resistance of everything in the rear of the clutch i.e., we include the power required to turn over the clutch thrust race, gear box shafts, universal joint and crown wheel and pinion with their respective oil churning losses. On the dynamometer drums the power is measured at the tyres. We consider that this Graph is very useful in that it demonstrates the percentage accuracy of our 'A' and 'B' readings. It would appear that those of 4-G-11 are very nearly correct, those of 6.EX too low. Fig.G. The mechanical efficiency is calculated from Graph 'E'. We intend to investigate further the discrepancy between the two cars which manifests itself at engine speeds of 500 r.p.m. Figs. 1, 2, and 3 are inserted to give an indication of the way rotating parts affect a test of this kind. Only the 4 wheels, brake drums and flywheel are considered. 1 and 2 for 4-G-11 are omitted to avoid confusion. Summarising the information obtained from the Tests. We consider from Graph 'A' that the wind resistance of the Goshawk is, in proportion to its weight, greater than that of the 40/50 H.P. From graph 'B', that the Goshawk shews greatest inferiority in acceleration at low speeds. contd:- | ||