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).
Investigation into the Merlin engine's main pressure lubrication system and bearing metallurgy.
| Identifier | ExFiles\Box 141\2\ scan0223 | |
| Date | 22th July 1940 | |
| Rm.{William Robotham - Chief Engineer} from Rm{William Robotham - Chief Engineer}/TAS.{T. Allan Swinden} Rm{William Robotham - Chief Engineer}/TAS.{T. Allan Swinden}I/ML.22.7.40 MERLIN MAIN PRESSURE LUBRICATION. The following investigation is divided into four parts :- 1. A comparison between Merlin and Bentley lubrication systems. 2. An examination of the Merlin system for possible losses of oil pressure due to flow restrictions, etc., 3. A review of development work in progress. 4. An examination of the method of lubricating the centre main bearing. ----- I. Before commencing any debate on the mechanical, or lubrication, aspect of the Merlin system it is first essential to obtain a sketch view of the metallurgical developments which have taken place. Originally, all Merlin main bearings were in a ½% silver BZ/L alloy, and all big end bearings in a 2% tin alloy. The ½% silver alloy was abandoned owing to cracks at the flanges, particularly on the centre main, and cracks which developed on the faces of the intermediates after some 300 hours running. 1% tin alloy was substituted, being superior to ½% silver in anti-friction and fatigue properties, but inferior in oil shortage tests. After 2,300 development hours a number of seized bearings caused a reversion to ½% silver for all save the centre main bearing. This state of affairs will continue until the stock of tin bearings is used, when a complete return to ½% silver on all bearings will be made. The tin bearing would undoubtedly be superior if better lubrication could be devised. At present, therefore, the centre bearing, being in 1% tin, is the one with the greatest claim to improved lubrication. Superficially, the centre bearing lubrication resembled the unsatisfactory system used on the intermediates of the early 3½ litre Bentley. - Continued - | ||