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).
Crankshaft forging, machining costs, and design considerations for the Phantom III engine.
| Identifier | ExFiles\Box 148\5\ scan0215 | |
| Date | 12th November 1937 | |
| -2- RHC{R. H. Coverley - Production Engineer}/SB.{Mr Bull/Mr Bannister}1/MJ.12.11.37.Contd. A definite reduction in forging and machining Cost could be obtained with a four bearing crankshaft, with integral balance weights but this could not be introduced without completely re-designing the engine, and definite figures for the resultant saving could not be obtained unless an actual design were available. The foregoing remarks apply also to present Phantom lll Crankshaft, but in addition this has integral balance weights making it exceptionally difficult to forge. It is impossible to rough shape the billet before entering the first die, hence it is necessary to allow a large surplus of material to ensure that the die is completely filled. The dies used for this crankshaft are expensive to manufacture and maintain due to their intricate shape all of which increases forging Cost. A scheme providing oval webs and loose balance weights of the Packard type to LeC.5230 is already in existence and results in a substantial economy of both forging and machining, full figures being given on the appended sheet. It is considered that this crankshaft represents the most economical proposition which could be put forward for Phantom lll engine. FORGING. There are many points in connection with the actual forging operation which have an influence on Price. When at the English Steel Corporation we were informed that Labour employed on R.R. Chassis Crankshaft Forgings is the best available, being paid up to 20% above the Rate of men engaged on Mass Production Crankshafts. Greater care is taken with Rolls-Royce forgings throughout manufacture and inspection is more critical, all of which naturally increases the Cost. The Price of Forgings and Dies is again appreciably increased by the Test Piece which is demanded on every Rolls-Royce Crankshaft as a check on material quality, but which other manufacturers do not require. The wastage of material when forging R.R. seven bearing crankshafts approaches 50% of the finished forging weight due to the abrupt changes of shape, particularly in the case of Phantom lll with integral balance weights. With both 25/30 HP. and Phantom lll Crankshafts there are three distinct die forging operations with re-heats from the cold state, it being necessary to de-scale the surface before each operation and handle the V.C.M. material carefully to avoid oxidisation. | ||