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 modifications for a Phantom III crankshaft featuring wider intermediate journal bearings.
Identifier | ExFiles\Box 93\5\ scan0147 | |
Date | 11th December 1937 | |
317 BY/NS{Norman Scott} c. Rm.{William Robotham - Chief Engineer} DA.{Bernard Day - Chassis Design}1/G.11.12.37. PHANTOM 111 - CRANKSHAFT. We send herewith E.CD.284 Crankshaft with Wider Intermediate Journal Bearings - Phan. 111. This design has been made in accordance with request in memo Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls}1/AP.19.11.37. The thickness of webs 2, 3, 4, 5, 8, 9, 10 and 11 has been reduced from .775 to .600 and the radii at ends of all journals and crankpins have been reduced from .125 to .075 giving corresponding increases in lengths of journals and crankpin bearings, all the metal removed from the above mentioned webs has been removed from the journal side of webs. The intermediate journal bearings are increased in area by 47%. The length of effective bearing area for the front, centre and rear journal bearings and also for crankpins is increased by .100 owing to the reduced end radii. In order to bring the crankshaft into balance after thinning down the webs, we have had to alter the front and rear weights by increasing their moment and offsetting the angular position of their centre of gravity, and as we are unable to alter the facing on crank web for the balance weight, the result is an unsymmetrical shape of balance weight which means the front and rear weights require handing. To avoid wrong assembly of weights we have added a small locating peg offset both sideways and radially. The increased width intermediate bearing caps should be produced from the rear cap forging. The crankcase requires an alteration to suit the wider intermediate bearings, and to avoid extensive pattern alteration, we have left the webs joining the intermediate bearings to crankcase walls unaltered. The existing oil caps in bores of pins and journals nearly block the oil supply holes in the thinner crank webs, so we have shown suitable oil caps of similar design to those used for the Wraith 111 engine which will incidentally save about 6/- per engine. Will you please detail and instruct the parts for this experiment, the crankshaft to be produced in .4 carbon steel, heat treated to 400 brinell. The balance weights on the central webs are same as for Lec.5230 and the crankshaft forging should be produced from the standard dies. DA.{Bernard Day - Chassis Design} | ||