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).
Race performance, pit stop issues, and tyre strategy for a race car.
| Identifier | ExFiles\Box 90a\2\ Scan182 | |
| Date | 6th September 1934 | |
| -2- Hs.{Lord Ernest Hives - Chair}3/WJ.6.9.34. Cont'd.{John DeLooze - Company Secretary} We attach herewith a power curve which shows the difference in power of the engine as fitted to the car in the race and the average production. We arranged with Mr. Hall to let him have one mechanic he supplied the other one and controlled entirely the pit arrangements. We carried out tests on the engine test bed with a Bentley unit similar to the one which ran in the race and ran it under over-load conditions to be sure that the engine would be reliable. During the race the only people allowed to work on the car at all were the two mechanics and the driver. They carried out a lot of practice in changing wheels and filling up petrol and during this practice they reduced the time to 1 min. 50 secs. Actually, during the race, they did nothing like as good as this but this was due to the fact that the wheel nuts became very tight. The serrations on the hub were also our Standard fit which are too tight for quick change of wheels. Actually I should estimate that we lost nearly one minute from this cause. The reason can only be put down to lack of experience of wheel changing under racing conditions. Rm.{William Robotham - Chief Engineer} was out there during the practice. The Bentley car ran more practice laps than any other in order to get information as regards petrol and oil consumption and tyre wear. The Dunlop experts were there advising on tyres. After practice the tyres were changed from 5" section to 6" section in order to improve the life of the tyres. These larger tyres altered the gear ratio so that the car was actually slightly slower, but it was realised that an extra change of tyres was equivalent to over 2 M.P.H. on the average speed. The Dunlop people estimated from the result of practice that one change of tyres would be all that was necessary, in fact, they thought there would be a generous margin on this. E.R.Hall's pit arrangements and timing was all set out to include one change of tyres and one fill up with petrol. After the 3rd. or 4th. lap Hall was picking up so much on handicap each lap that he was signalled from the pit to go slower. It came as a complete surprise when the car had to go in at the end of the 12th.lap for a complete change of tyres. This meant that the whole schedule of running had to be modified in order to make up this time. It was realised that most of the other big cars would have to come in for a second change of tyres but the little cars like the M.G's. would get through on the one change. It was very unfortunate after the second change of tyres | ||