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).
Windage and power losses in rotating wheels, with data on different tyre sizes.
| Identifier | ExFiles\Box 158\2\ scan0040 | |
| Date | 9th June 1939 | |
| -2- (2) Windage losses in a rotating wheel. In order to measure these losses the rear wheels were jacked up clear of the ground and the rear axle torque was obtained. To separate wheel windage from axle friction, the wheels were then removed and the tests repeated. The small poundage recorded at the end of the two foot torque arm was now measured by a 0 - 12 lb. spring balance instead of the previous hydraulic gauge. Tests were made with 6.50 x 16 India tyres on wire wheels. M.P.H. H.P. Loss. ---------------------- 45 0.45 62 0.8 93 1.3 On removing the wheels there was no measurable poundage at 90 M.P.H. hence rear axle friction is negligible under no load, and the above figures represent only the losses in a pair of rotating wheels. These are themselves very small, and negligible compared with the tyre losses. (3) The effect of tyre size on power loss. (Curve sheets 8,9). The following tyres were included in this test. India 6.50 x 16. Rolling circum. 88 at 34 lb.in.2. " 6.50 x 17. " 91 " " 5.50 x 18. " 90½ " Dunlop Track Racing. 6.50 x 16. Rolling circum. 87¾ at 44 lb.in.2. 6.50 x 19. " 99¼ " | ||