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).
Performance and design of different types of piston rings.
| Identifier | ExFiles\Box 144\3\ scan0122 | |
| Date | 13th October 1936 | |
| -3- Ring Finish. We notice that most American rings have a fine turned finish on the periphery, do you think this is an advantage in getting the rings to give a normal consumption without a long 'running-in' period ? From our experience so far, a turned finish does not appear to help much in this respect. From the condition of some of our rings it appears that with having a turned finish the periphery is by no means as true as when using a ground finish, and consequently the ring rubs down quickly at the high spots but there appears to be a condition when there is one bad portion of the ring not bedded, while the rest of the ring is quite alright; consequently we come to the stage where 90% of the ring is run in and requires just about as much time to run in the other 10% as if we started off with a true ground finish ring in the first place. Scraper Rings. Do you consider the slotted and grooved scraper rings to be the most efficient ? Have you any definite ideas on the action of scraper rings ? That is, does the ring actually scrape oil from the cylinder wall, or does it rely upon a certain amount of blow-by from the compression rings to force the oil through the slot ? Our own experience shows that we can control oil consumption better with compression rings than by altering the scraper rings. We have varied the scraper ring pressure from 18 to 47 lbs/sq.in. without the slightest difference to oil consumption, and yet by merely substituting a perfectly new top compression for one that had been run in, we altered the oil consumption from 1 pint/hour to nearly 4 pints/hour, and we had to wait until this top compression ring had run itself in before we got back to our normal consumption. Bevel Rings. Do you consider bevelled rings a necessity in order to get quickly to the nominal oil consumption ? Do you use with this type of ring about 1° taper on the diameter ? | ||