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).
Piston pin lubrication methods and suggesting experimental modifications.
| Identifier | ExFiles\Box 15\3\ Scan007 | |
| Date | 9th December 1927 | |
| To BY.{R.W. Bailey - Chief Engineer} from E.{Mr Elliott - Chief Engineer} c. to BJ. Hs.{Lord Ernest Hives - Chair} +7040 E1/M9.12.27. LeC.2494 - PISTON. X.3040 X.7040 In reply to your memo. BY8/G7.12.27. the method of lubrication of the piston pin is that oil is supplied by the drilling shewn from the back of the scraper ring to the piston pin bearings in the piston. Oil is also supplied to these same bearings at the ends by the grooves in the skirt. These grooves collect and distribute the oil around the skirt, but at the same time we expect they will discharge a certain quantity of oil into the cavities at the ends of the piston pin. Having now supplied the piston pin bearings in the piston generously with oil we think the lubricant will undoubtedly work its way into the little end bush. The piston pin is supposed to be a floating fit throughout when the piston is hot, which means that it will be somewhat tight in the piston when the latter is cold. To avoid trouble due to distorting the piston dia. caused by force being used on the pin, the longitudinal web of the piston has been made as deep as possible. Returning to the question of lubrication of the little end, what suggests itself to us is that some holes should be added through the piston pin itself into the bore of the little end bush so that oil fed in by the skirt grooves can have the chance of passing directly into the little end. The alternative to this would be to make the little end bush a press fit in the conn. rod, and pin it in some suitable manner, and then utilise the web formed by the boring of the rod on top of the little end to supply oil through drillings in the bush. The latter scheme is more in accordance with the usual practice, but we are inclined to doubt whether any oil would get splashed into the top of the rod. We should be glad therefore if for the first experimental sets of these pistons you would add some small holes, say .093" dia., in the piston pin itself. We should think three holes in the middle of each half of the little end bearing, making six holes in altogether, zig-zagged so that there is always one hole at the bottom and one at the top. E.{Mr Elliott - Chief Engineer} | ||