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).
Brake drum liner interference fit and thermal expansion analysis.
| Identifier | ExFiles\Box 121\1\ scan0347 | |
| Date | 31th October 1940 guessed | |
| a) Interference necessary a 12" drum to take brake torque should not be less than .012". b) Experience has shown that interference fit must disappear at about 200°C or else drum will expand plastically, resulting in reduction of interference when cool. c) At working temp. of 100°C is used & should not be exceeded. A little calculation will show that with expansion figures of 18 x 22.4 these conditions are impossible to satisfy. For iron & RR53C, reduction of shrink fit per 100°C for a 12" drum = (22.4 - 12) x 10^-6 x 12" x 100° = .0125 app. For Grindal & RR53C, (22.4 - 18) x 10^-6 x 12" x 100° = .00524 approx Therefore for a working temp of 100°C, max possible interference with "Grindal" is only .005" & this is not sufficient, & the liner always slips. 5) We tried iron with .040" interference cold but this always automatically reduced itself to .026" when once it had been heated to 200°C. We adopted .026" - .030" as the best interference. 6) We tried steel liners. These have virtually the same exp. coeff. as iron. But they always burst the aluminium. The only possible reason is the difference in Youngs modulus. This is why I have always been opposed to thick liners - I was terrified of a serious drum failure. An iron liner .200 thick should be just as detrimental as | ||