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).
Report page detailing crankshaft design modifications and performance considerations for a 20 HP engine.
| Identifier | ExFiles\Box 25\3\ Scan381 | |
| Date | 26th November 1928 guessed | |
| contd :- -5- Alfa, which is still smooth at 6000 r.p.m. I myself am convinced that 90% of the difference will be found inside the crankcase. On the attached prints I shew an attempt I made to see what could be got into the space available in the 20 HP. The crankshaft is developed from the one I shewed attached to a previous report, but has been modified to reduce the weight slightly and also facilitate construction. Four complete balance weights are saved by combining those at the kind Journals where cranks are at 120°. The other weights have been made detachable. Balance weight includes the big ends. The estimated stiffness and inertia are 62,100 lbs.ft/radian and .079 slugs ft2, the torsional period would be near 4500 r.p.m., which is rather too high, but shews that we need not be afraid of making crankshafts too heavy. I think it would be alright with 1.875 pins and 2.750 journals instead of 2.000 and 3.000 as shewn. The other sketch shews a way in which I thought we might give some more support to the bearings, the idea being to get closer to the 1-G-1 type of crankcase; I believe it could be made satisfactorily for experimental purposes by temporary alterations to existing patterns. I doubt whether the 20 HP. will ever be very enjoyable at 3500 r.p.m. as it is at present, and I think new ground will have to be broken sooner or later on this subject and new ideas tested on a pretty large scale. I am afraid I have taken a lot of your valuable time with my ideas, but they appear to me as promising lines of development and are the result of a great deal of thought. Hs{Lord Ernest Hives - Chair}/S.S.Tresilian. | ||