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).
Letter to supplier Borg & Beck concerning the failure of a clutch pressure plate and subsequent material test results.
| Identifier | ExFiles\Box 129\4\ scan0171 | |
| Date | 15th March 1938 | |
| 110 - Rm{William Robotham - Chief Engineer}/NRC.{N. R. Chandler}10/JH. 15th March, 1938. Messrs. Borg & Beck Co.Ltd., Tachbrook Road, Leamington Spa. Dear Sirs, We are sending you the broken parts of the pressure plate of an 11.A.3. clutch which burst at 4,400 r.p.m. We have cut test pieces from the ring at a point between the driving lugs i.e. where the section is uniform, and our tests show the following ultimate strength. Radial direction 12.5 tons/sq.in. brinell 165. Tangential " 14 " " " You will agree that these test pieces, taken from the best part of the casting, show a rather low tensile, we had anticipated 15-18 tons, but the still more important point is that the metal adjacent to the lugs, where the fractures occurred, is visibly drawn and of very coarse structure, so much so that it might be difficult to cut a homogeneous test piece from that section. We trust you will take this up strongly with your suppliers, both in respect of the properties of the metal as a whole, and particularly the drawing of the metal adjacent to the driving lugs. We feel that it is absolutely essential to improve both of the features referred to as quickly as possible as this is the second case of failure. Yours faithfully, FOR ROLLS-ROYCE LTD. | ||