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).
Analysis of engine shaft period, power curve, and a comparative acceleration test between cars.
| Identifier | ExFiles\Box 22\4\ Scan066 | |
| Date | 6th November 1926 guessed | |
| contd :- -2- Our belief that the main shaft period is at 3800-3900 r.p.m. is strengthened by the fact that we can detect a definite, but very slight period at 1250-1300 r.p.m. or one third of the main period speed. We shall therefore be interested to see the dimensions of the shaft which we imagine must be very stiff. Judging from the marked revolution counter and the maximum speed claimed, the peak of the power curve is about 3100 r.p.m. The normal running temperature of the car under the prevailing climatic conditions is fairly low and detonations are not very pronounced. If the running temperature is raised by means of a large blanking plate, however, detonations at once become more emphatic, being comparable to those on the high compression 20 HP. We carried out a careful top gear acceleration test between a standard 20 HP. car, the high compression 20 HP. car and the Lorraine. The acceleration of the high compression 20 HP. was absolutely identical with that of the Lorraine from 20 to 25 m.p.h. Above that speed the Lorraine had the advan-tage, while below 20 MPH. the better carburation and lower gear ratio of the R-R enabled it to put up a better performance. The standard 20 HP. was very markedly inferior to the other two, being some two lengths in arrears at 40 m.p.h. The details of the high compression 20 HP. and the Lorraine are as follows (allowing for tyre size) contd :- | ||