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 interference fits, materials, and a comparison of various drum designs.
| Identifier | ExFiles\Box 85\1\ scan0033 | |
| Date | 4th March 1936 | |
| -4- Hs{Lord Ernest Hives - Chair}/AFM.{Anthony F. Martindale}22/KW.4.3.36. The interference fits we have used are as follows:- "Brimol Austenitic Iron; .012" Millenite Iron: .026" High Carbon Steel: .026" We are going to increase the interference of the latter to .030" in one drum. We are proposing to use aluminium shoes with a 90° arc of contact in conjunction with these drums. In view of the increased drum stiffness we are going to try weakening the shoe in its middle (not its ends) and we are not going to use a tipping shoe. The Ferodo will be S.5805, a type of zinc F.B.A. During the next few days we shall complete the tests to obtain the outstanding information required to permit of a final design being prepared for these drums. Hs{Lord Ernest Hives - Chair}/A.F.Martindale. P.S. We find we have omitted to compare the 14" drums with the drums mentioned on page 2, or describe the 3 ways of keeping drums cool mentioned on page 1. We can draw up the following table to clarify the position. Table Data: Column Headers: Drum, MAX. temp. attainable on 4¼ litre Bentley., WEIGHT Increase of car. Row 1: Standard 12" Bentley, 350°C., 0 Row 2: Aluminium, 200°C., - 8 lbs. Row 3: 14" Bentley, 305°C., + 26 lbs. Row 4: 12" Bentley with helical ribs., 200°C., Increase on 2 rear drums. + 7 lbs. | ||