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 discussing a formula for calculating tire resistance and applying it to a 40/50 touring car.
| Identifier | ExFiles\Box 160\2\ scan0011 | |
| Date | 28th March 1923 | |
| X4578 ROLLS-ROYCE OF AMERICA, INC. SPRINGFIELD, MASS. Oy2-W-32823 PERSONAL March 28, 1923. Mr. E.{Mr Elliott - Chief Engineer} W. Hives, Mickleover, near Derby, England. Dear Hives: Re Tire Losses Many thanks for your letter of March 5 with attached blueprint of road performance of 20 H.P. and 40/50. This is immensely interesting and will stand a lot of study. Have you seen Professor Lockwood's paper in the S.A.E. Journal for November, 1922, on chassis friction losses? It appears to me that the findings of this article would be very interesting to you, especially the formula for frictional resistance of cord tires, page 422. I attended the meeting and got this formula down right. It should be R = (L-200 / 100) x {1.06 + ((90-P)^2 / 7000)} but is wrongly written in the paper. This allows for load and inflationpressure which he finds are the only two factors appreciably affecting tire resistance. On this formula I have worked out our tire losses for a 5 passenger 40/50 touring car fully loaded, as follows: Front wheels - 1260 lbs. each on tire Rear " - 1500 " " " 1 - Standard inflation pressure: 50 lbs. in front 60 " " rear Total tire resistance - 57 lbs. (all four wheels) | ||