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 tyre sizes, axle ratios, and gearing for a car.
| Identifier | ExFiles\Box 90a\3\ Scan071 | |
| Date | 12th June 1935 | |
| 6A X262 Exptl. Dept. HS{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}3/KW. 12th June, 1935. E.R. Hall, Esq., 53, Berkeley Court, London, N.W.1. Dear Hall, Thank you for your letter. Here is a speed chart with the size of tyre you mention. The 6 x 19" tyre which you are proposing for the rear puts up the axle ratio 5%. If therefore we use last year's axle ratio we shall be doing 111 miles at 4,500 revs, which I think even with the additional horse power may definitely over-gear the car. This really definitely depends upon the improvement gained by the streamlined wings. The next axle ratio which we have available is 11/43, which brings us back to almost exactly the same ratio as we ran at last year, i.e., 105 m.p.h. at 4,500 revs. Since we are proposing to give you about 20 additional B.H.P., it is possible that with this the car may be under-geared. I am therefore proposing to get them to fit the same axle to the car as last year, and you will have to have a run round the track and decide whether it is over-geared or not. The Directors insist, quite rightly, that we are too busy to do your car in here, so that I shall not be able to give the time to it which I could have wished. However, I hope that everything will work out alright, though as you know there is nothing I dislike more than half doing a job. | ||