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 and oil consumption, comparing different piston ring designs and testing methods.
| Identifier | Morton\M3.1\ img008 | |
| Date | 15th April 1925 | |
| TO HS.{Lord Ernest Hives - Chair} FROM R.{Sir Henry Royce} Copy to Mr. BY.{R.W. Bailey - Chief Engineer} E.{Mr Elliott - Chief Engineer} A.{Mr Adams} C. SECRET ORIGINAL PISTON & OIL CONSUMPTION. [Handwritten note]: not at all Lovett It is very undesirable to have any of the faked systems that I and others have suggested, but very desir- able to try everything and then take a review of the most practical. When we tried the L. shaped rings which were intended to be equal to the bevelled rings, we made these latter ourselves, which may have made some difference. Naturally they are better than the bevel because they have more surface, but I cannot think even this L. ring can remain more light- ly loaded in the upper part, since the section revolves round some centre as it is squeezed up or wears, so it should bind in the grooves: even this may have some ef- fect on its action. [Diagrams of two piston ring cross-sections] So far we seem to only know of one recent im- provement - i.e. the L. section. But we have the 40/50 doing about 1000 miles to the gallon with quite simple pistons and rings. We ought to find if stiffer rings have any mark- ed{J. L. Edwards} effect, and if a broad scraper is better than a narrower one; the 20HP said 'yes', and if more rings are better than less, like plenty of narrow rings because of the gas- tightness, or a very gastight piston might, or should, use more oil at full load, and less at light load. Our bed plate test should be road conditions of say ½ minute full throttle, ½ minute throttle closed. I would much rather use the oil quickly at full throttle, than at light running. R.{Sir Henry Royce} [Handwritten note at bottom]: 90% of this was wasted effort; it was Lovett who unearthed the basic reason, viz the changeover from 40/50, hand bedded crankshaft bearings, to the line bored marvel named P1 with its significant increase in diametral clearances & thus much greater 'oil slinging' OC | ||