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).
Remarks on interpreting diagram data for vehicle speed and acceleration over measurement periods.
| Identifier | ExFiles\Box 113\2\ scan0173 | |
| Date | 11th November 1930 guessed | |
| -9- SOME REMARKS ON THE DIAGRAM The feed of the diagram paper being operated by the driving shaft of the instrument, is always proportional to the instantaneous speed, and takes place without any lag. The distance traversed during one M.P. is therefore exactly determined. The speed can only be indicated at the end of each M.P., and as an average value of the speeds attained during this M.P. At the time of an acceleration or deceleration, the speed of a M.P. will be indicated at the end of that M.P. The speed will be less at the commencement of an acceleration period and greater at the end. We note on the diagram in Fig. 5, for example, that after the 5th M.P. the average speed has been 36 km/hr. while one second earlier, i.e., in the 4th M.P. the average speed was 31.6 km/hr. and one second later, in the 6th M.P., the average speed was 42.8 km/hr. The speed at the end of the 5th M.P. has therefore been (36 + 42.8)/2 = 39.4 km/hr. or the average between the average speeds of the 5th and the 6th M.P., the speed at the commencement of this M.P. was about the average between the average speeds of the 4th and 5th M.P., or (31.6 + 36)/2 = 33.8 km/hr., this speed corresponds likewise to the speed at the end of the 4th M.P. This approximate calculation naturally pre-supposes a uniform acceleration in the same measurement period (M.P.) This method allows of the determination with sufficient accuracy of the speed after each period of measurement, i.e., over a specific distance. The dotted graph on Fig. 5, determined by this method, gives the real speed, approximately. -------------- | ||