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).
The development and testing of various main bearing alloys, focusing on anti-seizing and fatigue properties.
| Identifier | ExFiles\Box 115\2\ scan0578 | |
| Date | 19th June 1940 | |
| To E.{Mr Elliott - Chief Engineer} c. Lr.{Mr Ellor} c. Bn.{W.O. Bentley / Mr Barrington} c. Lf/Lov.{Mr Lovesey} c. Hl/EJW. c. Lr{Mr Ellor}/LBH.{Mr Hall - Aero Design Engineer} COPY. Lf/AT.2/EAH.19.6.40. MECHANICAL TESTING. MAIN BEARING DEVELOPMENT. The present position with regard to development is as follows :- Whilst the 1% tin alloy has been rejected for the centre main bearing on account of it's unreliable anti-seizing properties, we have as yet no bearing alloy which it is anticipated can be produced with so small a production percentage of scrap. Of the alternative alloys, L.20 is expected to be the easiest to cast, but no engine or rig tests have yet been carried out to determine it's other properties. Inaddition to high production percentage scrap the ½% silver alloy suffers from the disadvantage of fatigue or breaking up. L.A.4. and L.25.S. have given good results on certain main engine tests and the one rig test carried out on the former showed very good anti-seizing properties, but there is no evidence that either alloy will show any improvement in castability and their resistance to fatigue over the ½% silver alloy in regard to castability and fatigue properties. Improved lubrication, i.e. By's scheme results in the seizing point of the 1% tin alloy being raised above that of the ½% silver alloy with normal lubrication but there is no evidence that it would have any influence on the failures of the ½% silver alloy. The alternative type of improved lubrication (Allison type of grooving with 8 oil holes) has shown up well on T.V. engine tests but has not yet been assessed for seizing value on the rig. Tests show that the anti-seizing properties of a bearing can be increased by (a) increasing the depth of the flanges to increase the resistance to nip in, or (b) decreasing the thickness of the shell to give a more flexible bearing. The following is a brief summary of tests already carried out on the Merlin and Kestrel bearing rigs. (A) Seizure Tests. Figures of merit expressed in comparison with the anti-seizing properties of 1% tin ungrooved bearing with Merlin lubrication - 100. | ||