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).
Methods for measuring tyre rolling losses and resistance, concluding on design benefits.
| Identifier | ExFiles\Box 158\2\ scan0037 | |
| Date | 5th June 1939 | |
| - 7 - BY/B.4/G.5.6.39. (a). to each of the oppositely rotating tyres, on which the torque and force is measured. (b). A much simpler variant of the above method would be to run two opposed wheels together but without the band between. This should give the dynamic and bending losses correctly, but not those due to rubber extension and scrubbing, (which would in any case be different for a steel surface from an actual road surface). It should give more accurate results than the drum method, and is worth trying on account of its simplicity. It would not be suitable if there was any possibility of the tread patterns interlocking. (c). A spring loaded wheel is towed behind a car on a level track and is mounted inside a casing which shields it from air resistance. The towing pull between the wheel and the casing is measured by a remote reading method. (d). Measuring rolling losses when transmitting torque is a more difficult matter, but it would be possible to mount two wheels in a casing, as in (c), and connect them by a slipping device which tends to revolve them in opposite directions, the whole constituting a pre-loaded arrangement as in the Lanchester gear testing machine. One wheel would then be driving and the other braking, and the longitudinal force and torque on each or either wheel would be measured. From these measurements the rolling resistance torque would be deduced. From the above will be seen the value of light treads, light loads, high inflation pressures, and large diameter wheels, in reducing rolling resistance at high speeds. BY/B. G.L. Bower. | ||