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).
Comparison of laboratory and road test figures for cord tyres, highlighting discrepancies in rolling resistance due to deflation.
| Identifier | ExFiles\Box 160\2\ scan0025 | |
| Date | 25th May 1923 | |
| X4578 DISCREPANCY BETWEEN PROF. LOCKWOOD'S LABORATORY FIGURES ON T.R. OF CORD TYRES AND ROAD FIGURES. (a) Dunlop Co's Figs. May 25th./23 "Autocar". H.P. consumed at 60 lbs. per sq.in. - 2.05 H.P. " 40 " " " - 2.95 No other details are given but this is sufficient to show that they find the % increase due to deflation between 40 and 60 lbs.per.sq.in. to be - 44%. Prof. Lockwood in his chart shows a cord tyre to have a rolling resistance - 12 lbs. at 60 lbs. per.sq.in. 14 3/4 " " 40 " " " Or increase of T.R. of tyres due to deflation only 23%. (b) We found on Canadian Dunlop Cords :- T.R. at 90 lbs.per sq.in. - 13.5 lbs. per ton. T.R. at 30 " " " - 27.5 " " " Increase in T.R. due to deflation - 104% Prof. Lockwood gives - T.R. at 90 lbs. per sq.in. - 10.9 lbs. T.R. at 30 " " " - 18.1 lbs. Increase in T.R. due to deflation - 66% It will be observed that in (a) prof. Lockwood's percentage is just over half that of the Dunlop Co's. In (b) his percentage is again just over half what we obtained on the road. It would therefore appear from the tests so far made by two absolutely independent parties, that Lockwood's figures do not correspond too well with those obtained with British tyres. The Dunlop Co. do not state whether their tests were made on Drums or on the road; if the latter, we should say that the main cause of discrepancy is the difference between the T.R. of tarmac and Prof. Lockwood's drums. In any case it looks as if it would be worth while to investigate a little further so that we can say definitely whether Lockwood's figures can be used for reference or not. Perhaps we might get the Dunlop Co. to do it for us if we sent them a copy of these figures. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||