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).
Technical document discussing tyre design, including section increases, inflation pressures, and construction materials.
| Identifier | ExFiles\Box 53\2\ Scan039 | |
| Date | 21th August 1923 guessed | |
| 2. -Ease of manufacture - Chassis clearance - Tyre handling - Cost. I have found that in place of normal sections it is feasible to increase the section by 50% retaining normal outside diameters, loads and tyre weights. To go beyond this increase of 50% would introduce such differences in clearances as would make the adoption of such tyres a matter of difficulty to the chassis makers. INFLATION. Inflation pressures used in normal tyres are needlessly high for large section tyres - I find that with 50% section increase the pressure is best reduced by 50% of the normal when fitted to the same cars and carrying same loads. 4. I realised that modern Cord construction enables much larger sections to be used with tyres of a given outside diameter than is the case with woven Canvas material. The reason being that the plies of Cord can be laid at any suitable angle, whereas the Canvas tyre must use a square woven fabric which cannot be readily built up with large section small diameter tyres. 8. REDUCTION OF SCANTLINGS. As with a known inflation pressure the load carrying capacity of a tyre varies as the square of the cross section it is obvious that pressures can be greatly reduced. 9. MAINTAINING SAFETY FACTOR. In effect the large Low pressure section can be made much thinner than in the case of normal tyres while still maintaining the normal factor of safety as a pressure containing vessel. 10. CONTACT LENGTH INCREASE. It is obvious that a tyre of given outside diameter when distorted more vertically must have a larger contact area on the road. | ||