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).
Energy absorption and resistance tests conducted on 'Canvas Cover' and 'Cable Cover' type tyres.
| Identifier | ExFiles\Box 1\7\ B001_X15 20 46 50 59-page138 | |
| Date | 1st August 1920 guessed | |
| -5- 2. What energy they absorb: The tests on this point have been of two kinds. In the first trial, it has been ascertained what energy is necessary to run under a load of 1320 lbs with one R.U. and one Cable, 880 x 120, the tyres in-flated at 70 lbs pressure. The tyres were simply drawn along by a great fly-wheel worked by an electric motor, and the consumption of current has been measured in both cases. After having deducted the energy absorbed by the resistance of the apparatus the following figures have been obtained. For the Canvas Cover - 1,320 watts - say 1.8 H.P. For the Cable Cover - 1.040 " " 1.4 H.P. The difference nearly amounts to one-half h.p. which would make nearly two h.p. for the four wheels. In the second test an electric car has been equipped with 895 x 135 Covers successively in canvas and Cable. In both cases the load per wheel was - rear 1540 lbs, front 1320 lbs - speed 38 miles per hour. The energy absorbed has been measured :- Canvas Cover 15.6. h p. Cable 12.8. h.p. Difference 2.8. h.p. in favour of the Cable. 3. Their resistance in running. It has been necessary to find on a good road a regular gradient at the end of a level. The car was placed at a point of the gradient 109.36 yards above the lowest point of the level, the engine stopped and gears disengaged. The car would run down the gradient, and the point on the level where it stopped had to be carefully noted. This test has been effected with 935 x 135 tyres with a car weighing 5510 lbs. a). With the canvas tyres the car ran 318 yards on the level. Maximum speed reached in the descent 18.64 miles per hour. b). With cable tyres the car starting exactly from the same point ran on the level 440 yards, that is to say, nearly 1½ times as far as with the ordinary tyres. The maximum speed reached in the descent was 20.50. miles per hour. | ||