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).
Methodology for conducting road acceleration and tractive resistance tests.
| Identifier | ExFiles\Box 113\2\ scan0034 | |
| Date | 26th February 1923 | |
| 26.2.23. ROAD ACCELERATION AND TRACTIVE RESISTANCE TESTS. These tests were carried out under moderately favourable climatic conditions - there was, however, a gusty wind - all results are the average of readings both ways. The timing was done with a good stop watch - the drop in speed noted on the speedometer. Both speedometers were checked for accuracy at various speeds, that of the 40/50 also for lag. The print consists of the Graph of 4-G-11 super-imposed upon the Graph of 6-EX. Fig.A. The tractive resistance curve of the car is obtained by declutching and taking the time for the speed to fall 5 m.p.h. The tractive resistance of the car and engine is obtained by switching off the ignition, fully depressing the accelerator, and taking the time for the speed to fall 5 m.p.h. Errors are most noticeable at high speeds because :- (1) It is difficult to get clear runs at high speeds as when passing vehicles it necessitates getting on the side of the road where the tractive resistance increases owing to the unmetalled surface. (2) The decelerations with the clutch in, are very rapid at high speeds - an error of one-fifth of a second in timing therefore makes a difference of as much as 15 lbs.per ton. Fig.B. The acceleration curve is obtained by accelerating and taking the time for the speed to increase by 5 m.p.h. The low speed spe readings suffer from the fact that the greater the acceleration, the smaller the increment of time, and the greater the error occasioned by one-fifth of a second inaccuracy. Fig.C. The curve is obtained directly from Fig.A. For the purpose of obtaining the true H.P. to turn the engine over, and so obtain the mechanical efficiency, this Graph is corrected for rotating parts by compounding with Graph 3. contd:- | ||