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).
Analysis of crankshaft deflection and bearing support, specifically 'unwinding' and 'bell-mouthing' phenomena.
| Identifier | ExFiles\Box 6\1\ 01-page098 | |
| Date | 9th December 1927 guessed | |
| contd :- -3- Std. Phantom 5.5% Sports Phantom 2.0% Std. 20 HP. 6.0% ----------- It appears that a shaft with thin crankpins as its weakest part is more prone to 'unwind' its throws, thus relying very much on its bearings for support, and increasing the liability to 'bell-mouthing'. Tests with a dial indicator shewed a maximum movement in one journal without a bearing (20 HP.) of about .002". A calculated value for the Stutz crankshaft is shown in graph.2, which will shortly be verified by test. We are hoping with the aid of models to modify Carter's formula so as to cover the case of two cranks between each pair of bearings, as in a 4-bearing 6-cyl. engine. We are also doing tests to show if there is any effect on the stiffness when the outside extremities of the webs are cut off at an angle as on the recent India lll. and KAS.10 and 14 shafts and also on the Stutz. Deflection of Journals. We twisted a 20 HP. shaft in the crankcase with the centre bearing out and a dial indicator on the journal to measure the up and down movement. The position of the shaft was with cranks 1 and 6 pointing vertically downwards and the shaft was twisted through nearly 2°. The resultant motion of the central journal in a vertical plane is given by graph 2. We are carrying out some further experiments on the sports Phantom crankshaft to measure the movement of all the intermediate journals, and also to measure the amount of support given by artificially 'bell-mouthed' bearings. Hs{Lord Ernest Hives - Chair}/S.S.Tresilian. | ||