Issues with chromium-plated tappets on the Phantom III and a new proposed reclamation process.
| Identifier | ExFiles\Box 96\2\ scan0307 | |
| Date | 14th July 1939 | |
| 35H SWDL {Len H. Swindell} File Hd {Mr Hayward / Mr Huddy} from Mx {John H Maddocks - Chief Proving Officer} /SB {Mr Bull/Mr Bannister} c. Dr c. RHC {R. H. Coverley - Production Engineer} c. Rm {William Robotham - Chief Engineer} c. JPH/GT Mx {John H Maddocks - Chief Proving Officer} /SBS/MG.14.7.39 PHANTOM III - TAPPETS We have now gained sufficient experience to know that Chromium plated tappets are a menace, in that the Chromium has a pronounced tendency to flake off on the edges, and the bits of chromium then get taken round in the tappet chamber to act as an abrasive, the final result then being worse than the evil which the chromium was intended to cope with. Progress is still being made to clear the final issue, but in the meantime we are quite certain that we can run unplated tappets with at least as much success as plated tappets, provided the surface hardness is sufficient, and at the same time eliminate at any rate one potential source of trouble and also facilitate the reclamation of existing tappets, of which there are some 17,000 in service. We are prepared, therefore, to go straight ahead and delete Chromium plating, and substitute the following operations to reclaim existing tappets: 1. Grind off chromium plating. This will be better than acid stripping, since it avoids etching the surface and gets rid of any surface defects at one operation. 2. Crack test. 3. Cyanide harden to a Brinell of approximately 700. 4. Cloudburst harden, which should give a Brinell of about 800. Mx {John H Maddocks - Chief Proving Officer} /SBS | ||
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).