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).
Letter to E.R. Hall discussing car setup and performance for the Sarthe Circuit (Le Mans).
| Identifier | ExFiles\Box 90a\4\ Scan145 | |
| Date | 4th May 1936 | |
| X262 Exptl. Dept. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}12/KW. 4th May, 1936. E.R. Hall, Esq., 53, Berkeley Court, LONDON, N.W.1. Dear Hall, Congratulations on the very good lap on the Sarthe Circuit. In view of the fact that you only got 4300 revs. down the straight, the gear ratio has been worrying me. First of all, I accept that we want to be over-geared for Le Mans rather than undergeared. I think an ideal speed down the straight if the foot is kept hard down all the way would be 4250 revs. which allows a margin of 250 revs. for a following wind, which should be adequate as it is 6 miles an hour. I do not think the big engine will give you more than 200 r.p.m., down the straight over and above what you obtained last week. The net result is that I estimate that the correct ratio for Le Mans on the figures so far taken would be 120 m.p.h. at 4500 r.p.m., and this would be obtained by 6 x 18 tyres with the 12/41 rear axle. I have not got the figures of how much rubber can be worn off the tyres Indias are going to give you, but even if this is half an inch it is only worth 3%. The thing I want to avoid is throwing away the advantage of the big engine by over-gearing. I also do not want to get over to the other side with the wrong axle and have to change. | ||