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 correcting a calculation slip concerning tyre resistance, horsepower loss, and inflation pressures.
| Identifier | ExFiles\Box 160\2\ scan0015 | |
| Date | 1st May 1923 | |
| X4578 Expl: Dept: Messrs. Rolls-Royce Ltd., Derby. England. 1st. May 1923. Rolls-Royce (America) Inc., Springfield, Mass - America. OY. from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} Thank you very much for your letter ref. OY2/W32823 re. "Tyre Losses" which Mr. Hives has handed on to me. I think there is a slip in the calculation re. tyres inflated to 80 lbs. per sq.in. - I make the total tyre resistance 50.8 instead of 40.8 lbs. which makes the H.P. loss at 60 m.p.h. 8.13 instead of 6.54. This considerably reduces what appeared at first sight to be a large advantage to be gained from hard tyres. We calculate that the normal inflation pressure only makes the car 1/4 m.p.h. slower at 60 m.p.h., than it would with tyres at 80 lbs. per sq.in. pressure. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||