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).
Rules for calculating the winner of a 24-hour race using a performance index figure.
| Identifier | ExFiles\Box 160\3\ scan0317 | |
| Date | 31th December 1939 guessed | |
| (I5) The stipulated mileage was completed at a time H (the race having started at zero hour), the additional mileage terminated at hour 24. If D is the total distance covered in 24 hours, M the minimum distance to be covered according to cylinder capacity, we get : Mean hourly speed ( D - M for this additional ) = ----- mileage ( 24 - H D will be obtained by adding : 1. - The distance representing the total whole number of laps covered before the end of the 24 hours with, if necessary, a correction on account of the position of the car at the start. 2. - The distance representing the fraction of the lap during which hour 24, which is the finish of the race, was reached. Said distance is calculated according to the average speed maintained on this last lap which the competitor is under the obligation of completing in accordance with the provisions of article 14. The H hour will be computed according to the average speed realised for the lap during which the competitor terminated the minimum mileage he had to cover by reason of his basic cylinder capacity. 3. - Performance index figure If M stands for the minimum distance a car should cover according to its basic cylinder capacity. D the distance which counts for the classification; this distance is equal to the total distance covered in 24 hours subject to the exception provided for in paragraph a hereinabove; Then the only cars entitled to a place are those for which D is equal to or greater than M.{Mr Moon / Mr Moore} The value of the quotient D/M determines the performance index figure of the car. The calculation of the index figure will not be carried further than three places of decimals, the last figure being increased by one when the figure immediately following it is 5 or more. The winning car will be the one with the largest index figure; the other cars being placed according to the decreasing value of their index numbers. In the event of there being two or more equal index numbers rounded off to three places of decimals, the classification will be reckoned according to the lesser difference between the average speed realised on the minimum distance M and the average speed realised on the distance D - M.{Mr Moon / Mr Moore} Example A car A which should cover 1,700 kil. covers 1,950 A car B which should cover 1,800 kil. covers 1,910 A car C which should cover 2,200 kil. covers 2,540 ... | ||