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 to Dunlop Rim & Wheel Co. Ltd. detailing the results of stress tests on a Phantom III wheel rim.
| Identifier | ExFiles\Box 159\3\ scan0074 | |
| Date | 22th June 1939 | |
| 13/0. c. Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls} xxx 2424 BY.21/G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 22nd. June 1939. Messrs. Dunlop Rim & Wheel Co. Ltd., Foleshill, COVENTRY. Dear Sirs, With further reference to the question of stresses in wheel rims due to tyre inflation pressure, we have been able to carry out some tests on a Phantom III rim .104" thick (Drawing No.G.83717) fitted with a 7" x 18" Fort tyre. * The tests were made by the "Stresscoat" process, in which the piece under test is painted with a thin coating of a special brittle lacquer. The application or reduction of load when the lacquer is dry causes the latter to crack perpendicularly to the lines of principal tensile strain, the cracks first appearing at the points of greatest stress concentration. By testing, at the same time as the actual specimen, small lacquered tension strips in which the stress is known by simple calculation, the stress corresponding to the formation of cracks is approximately determined. The results, reduced to give the stresses due to an inflation pressure of 35 lbs/sq.in. are as follows. It is considered probable that the actual stress figures are nearer the higher limits of the stresses thus experimentally determined. The stresses were necessarily measured at the 'outside' face, i.e. at the metal surface remote from the tyre. Stress at A = 8 to 12 tons/sq.in. (tension) " " B = 6 to 9 " " (compression) " " C = 8 to 12 " " " " " D = 5 1/2 to 8 " " " (Sketch next page) Note: The cracks at D were radial, denoting circumferential stress. At A, B and C the cracks were circumferential, denoting axial stress. | ||