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).
Investigation into squeaking and bending issues with 25/30 HP brake pilot shoes.
| Identifier | ExFiles\Box 102\3\ scan0183 | |
| Date | 25th May 1936 | |
| x506 To A.F.C. c. to By.{R.W. Bailey - Chief Engineer} c. to Ba. c. to G.W.H. HS{Lord Ernest Hives - Chair}/AFM.{Anthony F. Martindale}17/JH. 25.5.36. 25/30 HP. Brake Pilot Shoes. With reference to your E.4/HP.18.3.36. We have examined several shoes off customer's cars which had been squeaking, and we also found that the clearance of .010" between pilot shoe and main shoe had disappeared. This does not necessarily mean that the pilot shoe had bent. We handed to our inspectors a pair of tipping shoes and they find that instead of bending as G.W.H. thinks they bend if anything in the opposite direction. This is what we were expecting owing to loading considerations. There is a definite bending movement on the weak main shoe and which might easily bend it so as to take up the very small clearance, especially when the aluminium is softened due to temperature rise. Unfortunately machining limits are not so close that we can guarantee that this has happened, and in any case we are not in favour of stiffening parts up while the design of the tipping shoe remains unsound. We understand that if the pilot shoe is to work satisfactorily the tip of this shoe must touch the drum before the main shoe does. We know that the geometry of the shoes is such that maximum wear of lining should occur at a point approximately opposite the end of the main shoe, and we have seen linings that have worn in this manner; but we also know that a Bentley front drum expands under heavy brake load .030" opposite the shoe middle and contracts .035" between the shoes. This means that when cars are not used as town carriages the pilot shoe toes will wear heavily | ||