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).
Report comparing the performance and fuel economy of Cable tyres versus Canvas tyres, focusing on climbing gradients.
| Identifier | ExFiles\Box 1\7\ B001_X15 20 46 50 59-page139 | |
| Date | 1st August 1920 guessed | |
| -6- Then another problem has been put forward. On a gradient which a car could hardly climb with ordinary tyres, - yet when fitted with four Cable tyres a great difference in speed has been acknowledged in climbing the gradient. The experiment has been carried out under these conditions. The gradient was 4-5% starting from the level with 218.72 yards running (see figures on the attached table). Jot| In the case of the canvas tyres, the gradient could not be ascended ~~even~~ on the ~~lowest~~ gear, whereas with cable tyres it was easily ascended. Eventually, we have undertaken experiments still more striking. Let us choose a part of a road with a level or descent immediately followed by a gradient stiff enough ~~not~~ to allow the car to climb up in ~~lowest~~ gear. Let us note the speed at which the gradient is taken, and let us climb up with the open throttle without changing the speed. Let us note the point at which the engine stops. The first experiment must be done with canvas tyres, the second with Cable tyres. It will be acknowledged that with Cable tyres the car reaches a far higher point. 4). What economy in fuel is given by the Cable? The above mentioned experiments prove that a car fitted with Cable tyres runs better and gives greater speed, and from that it follows logically that there is an economy in fuel. That economy is difficult to figure out because the difference in the energy absorbed produces at the same time an increase in speed with an economy in combustion, which does not allow of very secure comparisons. The driver can choose either one or the other: practically the Cable gives both advantages at the same time but in that case each one will be smaller. There will be more importance in the gradients because the top gear is kept longer with Cable than with Canvas tyres. Here is an experiment which shews these results. On a mountain road with gradients of 3 to 5% the following figures have been obtained on a total distance of 9.32 miles. Canvas Tyres. Consumption 4.50 gallons for 62 miles. Average speed 19.32. miles per hour. | ||