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).
Letter from Dunlop Rubber Co. providing recommendations on tyre inflation pressures for driving on different types of sand.
| Identifier | ExFiles\Box 114\4\ scan0016 | |
| Date | 29th January 1937 | |
| DUNLOP RUBBER CO.,LTD. TELEGRAPHIC ADDRESS: "INFLATOR, PHONE, NORWEST, LONDON." TELEPHONE: MUSEUM 5400 (struck through) 16 LINES. EUSTON 3434. EXTENSION No. YOUR REF: OUR REF: NWHF/MC.3. DUNLOP HOUSE, 1, ALBANY ST.{Capt. P. R. Strong}, LONDON N.W.1. 29th January 1937. Humfrey Symons, Esq., The Cutting. Givons Grove. LEATHERHEAD. Dear Humfrey, With further reference to your letter of January 11th, I now have pleasure in passing on to you the information received from our Technical Department, for your talk before the Royal Geographical Society. - In general our recommendations for tyres when used on sand are based on the following considerations: 1. For fairly hard sand inflation pressures of 20-lbs./ sq.inch. seem satisfactory. 2. For soft sand inflation pressures of 15-lbs./sq.inch. seem necessary. 3. For very soft sand inflation pressures as low as 10-lbs./sq.inch. are necessary. In each case a tyre size is chosen which will carry the maximum load at a reasonable deflection (22% deflection above the flange seems satisfactory for sand work. 18% is used for main road work.) On this basis the average contact pressure works out at about - 33-lbs./sq.inch - for class 1 above - fairly hard sand. 25-lbs./sq.inch - " " 2 " - soft sand. 20-lbs./sq.inch - " " 3 " - very soft sand. It should be noted that this contact pressure is based on the ellipse area, since any pattern is quickly filled with sand. The ellipse areas quoted have been obtained on a hard surface and in practice on sand there will be some variation from these areas, depending on the type of sand and the way in which it packs. The large increase in tyre size required when a vehicle operates in sand results in considerably increased power consumption, and to minimise this difficulty the following procedure can be adopted. When running on Contd... | ||