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).
Technical report discussing findings on piston rings, oil consumption, and connecting rods.
| Identifier | ExFiles\Box 173\2\ img090 | |
| Date | 23th February 1934 | |
| -6- (2) That they had to make their rings give higher unit pressure than ours to avoid blow by.{R.W. Bailey - Chief Engineer} They run .0435 ring depth per 1" of dia. with a free gap opening of .170 per 1". Use a special electric furnace - cast-iron - to stand up to the stresses. They have a very excellent device for checking the uniformity of the radial ring pressure against the bore, particulars of which I have. You can get a ring which laps in perfectly and yet is no good for oil consumption. I think they require a heavier ring pressure than we do because their short piston does not stay square in the box. (3) They find that they cannot use a bedding wider than .5" on the split side of the skirt; otherwise they get a tendency to scuff up. (4) They are inclining towards pinned rings, because they have measured that rings rotate very rapidly at high speeds even in a worn bore. The top ring may have to be free to avoid gumming up. (5) For zero weather they find the hole in the connecting rod supplying oil to be of the greatest value. They have to use a slightly higher unit pressure on their scraper ring when they adopt this, but then their oil consumption is not increased appreciably at top speed. With the hole in the rod the oil gets there instantly they say provided the oil pump will pump. (6) They are strongly in favour of the anodised piston surface (alumalite) which is really an aluminium oxide. I am bringing two sets of this type of piston back for the 20/25. ALLOY. CON. RODS. I had a further talk with the Bohn people. They fit a steel cap to keep the big end round they say. I don't think they know as much as Leylands of the alum. rod in service. AERO. Got hold of Heron to try and get some information re He/Lev.13/AJ.25.1.34. | ||