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).
Testing die-pressed Ferodo brake material on rear foot brakes, comparing its heat expansion properties to cast iron and bronze shoes.
| Identifier | ExFiles\Box 26\4\ Scan013 | |
| Date | 10th July 1914 | |
| From Exp. Dept. Copies to :- J.{Mr Johnson W.M.} R.{Sir Henry Royce} By.{R.W. Bailey - Chief Engineer} Hs.{Lord Ernest Hives - Chair} Wor{Arthur Wormald - General Works Manager}/Hy{Tom Haldenby - Plant Engineer}5/B10714. July 10th. 1914 Report on Rear Foot Brakes. We have received the die pressed Ferodo and have tried it on a car. It is very quiet in working and is fairly powerful. It does not squeak, in fact it has not made a sound so far. On these large diameter brakes expansion due to heat plays an important part. When using, say cast iron shoes under severe and prolonged application much heat is generated by the friction and this causes the drum to expand. Also the brake shoes and straps expand. As the drum is external it is cooled somewhat by the air and the shoes being enclosed get hotter than the drum. Therefore they expand more than the drum and this reduces the clearance between the two so that they rub after hard use. Bronze shoes have a similar effect but are worse, the bronze expanding more rapidly than the cast iron. Quite a different effect is obtained with Ferodo. The Ferodo being a bad conductor of heat does not expand or transmit much heat to the brake straps. Therefore little or no expansion occurs to the brake straps, but the brake drum gets hot and expands perceptibly. This causes the clearance between the shoes and drum to increase which is just the reverse to what happens with metal brake shoes. The expansion of the drum is so much that with continual application of the brake the pedal gradually goes down to the floor. xy/9 R E.R. 25M (100) (B) (100) 12-3-14 C.C.&S. | ||