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).
Skid pan tests, slip angles, and self-centering properties of various tyres for the Bentley III.
| Identifier | ExFiles\Box 158\1\ scan0215 | |
| Date | 27th September 1936 | |
| 1339 To By.{R.W. Bailey - Chief Engineer} c. to Ds. c. to Da{Bernard Day - Chassis Design}/Rv. c. to Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls} c. to Hm{Capt. W. Hallam - Head Repairs}/IHW. Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer}1/JH.27.9.36. BENTLEY III TYRES. We have been carrying out a number of skid pan tests on various makes of tyre to determine which are suitable for use on B.III. The Avon India Rubber Co. are trying to develop a tyre suitable for our use and have so far submitted three types. The results of our tests on B.III size tyres 6.50 x 16, are shown on the attached graph No.1. The Dunlop Fort, Dunlop 90 and India Super all have a satisfactory slip angle but the Avon tyres are not yet suitable from this point of view. The Avon Co. are using the 4 ply construction as the majority of American tyres are of this type and we prefer it on the score of weight and cost. We have further tests to do as the Avon Co. are producing some modified tyres and the India Co. are also producing a new tyre. We have recently improved our method of measuring tyre slip angles by making the car steer itself round the skid pan. The arrangement of this is shown on the attached sketch No.1. This considerably increases the accuracy of the measurements and reduces the time required for the tests. The method is suitable only for rear slip angle measurements as the tension in the cable affects the front slip angle and so upsets autosyn measurements of under or over steer. We have also recently investigated the self centring of tyres. We have known for some time that the steering is heavier and that there is more tendency to low speed wobble when the front tyres are worn. We therefore decided to measure the self centring of various types and conditions of tyres. The measurements were made on the bumper drums as shown on sketch No.2 attached. The self centring torque was measured by spring balance B and the sideways load by balance A - B. The slip angle was also measured. | ||