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).
Potential solutions and design comparisons for squeaking brakes on the 20 HP model.
| Identifier | ExFiles\Box 5\3\ 03-page106 | |
| Date | 1st April 1925 | |
| 4257 To Hs.{Lord Ernest Hives - Chair} from DA.{Bernard Day - Chassis Design} DA{Bernard Day - Chassis Design}2/M.4.25. SQUEAKING 20 HP. BRAKES. X.4257 X.4259 X.3531 X.3313 We are going into the question of providing a means of stopping the squeaks on the 20 HP. brakes, and shall send you some sketches in a short while. We are of course taking the matter up with R.{Sir Henry Royce} Our attitude at the moment is that a squeak damper consisting of 4 quadrants of ribbed aluminium held together by spring loaded bolts will appear to be rather a lot, and rather heavy for this particular job. We understand that the one you have experimentally rigged up weighs 10 lbs. a side. We should therefore like to find something lighter, and if possible simpler and we wonder whether you would like to experimentally try a broad strip of steel say .064" thick pulled up around the brake drum with a spring. A spring of about 12 to 14 lbs. load would resist the centrifugal force at 70 m.p.h. but whether this would be enough to give you damping remains to be seen. We are sending this suggestion to R.{Sir Henry Royce} but if any experimental results gave us an indication that it was likely to do any good it would save a fair amount of time. As an alternative to this we are preparing a scheme in which your aluminium shoes are lightened, and the number of pieces reduced. We think we can bring the weight down to about 4½ to 5 lbs. per wheel. Other schemes may occur to us as we go on. It seems to us however that though you want a damper for existing cars, and for the India cars, of which the parts cannot be altered, the actual trouble should lie in some small peculiarity of the design, and if we could find out what this was we should not want squeak dampers. We have looked at the Morris Cowley brake design which are of course notorious squeakers, to see whether there was anything in the scheme resembling the 20 HP. which would give us an inkling as to the cause. The only peculiarity that we can see is the very big overhang of the cam and the fulcrum on the foot brake. As arranged it appears that the operating shaft is run right through forming the cam for the foot brake on the one side of the axle, and the fulcrum for the same on the other. We wonder whether it is this lack of rigidity of anchoring the shoes that may be one of the causes of the squeaks. Applying this supposition to the 20 HP. the only things that could be called flexible in the torsional direction are the cam-shafts, which may be rather small in diameter. They are in fact .675 compared with 1" on the 40/50. You may think this supposition worth investigating or not. Apart from this we cannot see any more reason why the Cowley brakes should squeak than our own. DA.{Bernard Day - Chassis Design} | ||