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).
Analysis of brake drum performance with recommendations for future developments and design improvements.
| Identifier | ExFiles\Box 85\1\ scan0272 | |
| Date | 2nd December 1936 | |
| -5- Bearing these facts in mind, it should be easy to re-design Bentley, 25/30 and P.III drums to run cooler, but any increase of weight of the front drums will lead to increased tramping tendency and steering goggles, unless more damping is used. We have not gone forward with our helically ribbed drums, although for a given weight of metal they are more efficient, as we think there would be too much Sales resistance to them. Another way to keep drums from getting too hot is to make the pedal pressure heavy. We consider that increasing the servo torque multiplication is doing the customer an ill-service, and gives us much more trouble. Bentley rear wheels lock at about 140 lbs pedal pressure, while we agree we ought to build brakes that will stand up to their job if the wheels lock at 120, or even 110 lbs, we consider this is quite sufficient and Phantom III pedal pressure we consider too light, as the wheels lock at about 82 lbs. If we have drums that do not exceed 200°C we can concentrate on finding a lining which does not squeak, neglecting its other qualities, but at present we have to consider its fading and wear resisting properties. (4) There is room for improvement in the bedding of our brakes. Now that we have anti-judder parts we can increase the drum rigidity, as we do with aluminium drums. When an aluminium back plate is used, the pivot pins should be located in a patch of steel fixed to it. With steel drums a steel back plate should be used, with aluminium drums an aluminium back plate should be used. In conclusion, we would say that future developments should take the following lines:- (a) A modified brake operation system, preferably wedge operated, with a high mechanical advantage inside the drums, and a high overall ratio, enabling us to use low u linings, rigidity throughout the system being carefully studied. (b) Brake drums so designed that they never exceed 200°C on the rubbing surface under any conditions that the customer is likely to be able to reproduce. | ||