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 thickness and material considerations.
| Identifier | ExFiles\Box 120\2\ scan0108 | |
| Date | 9th November 1936 | |
| -2- Rm{William Robotham - Chief Engineer}/AHW.1/AP.9.11.36. 1. Weight considerations. We do not save much weight when we use aluminium drums on Bentley (4 lbs. per car) but we get better braking. If we thicken up the liner we shall save less weight still. 2. The minimum stopping distances of our cars, even Bentley, are not good. One day we shall have to improve them by using a higher proportion of front braking. Also, with the present tendency to put more weight on the front axle, to maintain our present brake performance we shall require a greater proportion of front braking. This will mean that the bulk and weight of the front drums will have to be increased, but Rm{William Robotham - Chief Engineer}/Les.{Ivan A. Leslie} and Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer} want it kept as low as possible so that the ride and steering are not adversly affected. We think that thicker liners, since they are not absolutely necessary, should not be used. 3. Conductivity. The heat generated on the rubbing surface should be transferred to the aluminium as quickly as possible, and to achieve this we use a thin liner, as it's conductivity is poor. 4. Stress. The compression stress in the liner is 12 tons/sq in. This has to be resisted by the aluminium. The thicker the liner, the greater the stress in the aluminium. Although no drum has ever burst that was made to Ex. details, two N.schm. drums have failed, therefore we are against increasing the stress by thickening the liner. 5. We know that Hispano Suiza use a liner .180" thick, and Aston-Martin liners are .150" thick but Sr. tells us, and we have verified this, that all Hispano liners crack, and we have burst both Aston-Martin drums that we have tested. Therefore it can hardly be argued that other people's designs are superior to ours. A point we overlooked when the G.{Mr Griffiths - Chief Accountant / Mr Gnapp} Department drums were detailed was that, owing to the shrink fit, a liner detailed .100" thick when finished turns out to be only .090" thick. We have asked By/TWD.{T. W. D???Aeith} to rectify this matter by altering his details to show the liners .110" thick. The above will shew you that liner thickness has received our careful consideration, and we can only repeat that for the present we prefer them to remain .100" thick. Rm{William Robotham - Chief Engineer}/A.F.Martindale. | ||