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).
Design memorandum for a crankshaft with increased diameter journals and revised balancing for the B.60 and C.I. Conventional 6 models.
| Identifier | ExFiles\Box 123\5\ scan0349 | |
| Date | 28th February 1939 | |
| BY/BY c. Rm.{William Robotham - Chief Engineer} c. Rm{William Robotham - Chief Engineer}/ 10HH DA.{Bernard Day - Chassis Design}5/G.28.2.39. B.60 and C.I. CONVENTIONAL 6 - CRANKSHAFT WITH INCREASED DIAMETER JOURNALS AND REVISED BALANCING. Please receive herewith :- E.CD.1227 Crankshaft with increased journal area, Revised balance weight system and simplified oil drillings. B.60. and C.I.Conv. 6. The journal diameters are increased from 2.500" to 2.750" to give an increase in bearing area to allow of the use of Vandervell bearings; the bearings and the required modifications to the crankcase are the same as for the B.80 and C.I. Conventional 8 design shown on E.CD.1186. file 617. Wraith 111 balance weights EW.1544 are used and arranged in the positions on crankshaft proposed by BY/B. in memo BY/B.8/G.29.12.38. The balance weights are moved outwards radially by .125" to enable the facings on the crank webs for the weights to clear the thrust washers at the centre bearing, this increases the balancing by 5% and will further reduce the bearing loads. At the same time the crankshaft inertia is increased slightly, but, as the shaft is stiffened by the larger diameter journals the critical speed of the shaft should not be altered much. The oil retaining thread at the rear end of shaft is as shown on E.CD.977, and the rear flange of shaft is to suit G.CD.1065 clutch. Owing to the new position of the balance weights, we have been able to simplify the radial oil holes for crankpin supply, there now being only one hole supplying each crankpin and the ends of holes are plugged by the balance weight dowels. The rear end journal bore is plugged by a disc type plug at its rear end only, as shown on E.CD.1186. All the other journal bores are fitted with Wraith 111 plugs. In accordance with BY's instructions, the radial oil holes in the intermediate journals are increased in number from two to three-holes per journal. This does not apply to the front, central or rear journals, the front and central journals will still have two holes and the rear journal none, as there is no feed from the rear journal to a crankpin. | ||