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).
Valve clearance issues, oil consumption complaints, and piston performance testing.
| Identifier | ExFiles\Box 87\2\ scan0133 | |
| Date | 10th February 1936 | |
| -3- Hs{Lord Ernest Hives - Chair}/Mths.{Reg Matthews}1/KW.10.2.36. In any case this is a case of valve clearance and we are trying to reduce this as much as possible and we intend trying chromium plated inlet valve stems as we think we may be able to run with .001 clearance or thereabouts. Inlet valves have been run successfully on Ph.III with chromium plated inlet valves having .001 clearance. Unfortunately we cannot chromium plate KE-965 exhaust valves, but the trouble of overoiling should of course be caused through excessive clearance in the inlet valve guide. We are however trying other materials in place of KE-965 which have not such a high coefficient of expansion, and will take chromium plating, as this should at any rate reduce the rate of wear of valves in guides. During the last two quarters 21 complaints of high oil consumption have been dealt with at Derby, and of these 18 were EB.1299 pistons and 3 Aerolite. In the case of Aerolite pistons the complaint was overcome when the rocker shaft had been fitted the correct way. Complaints of piston knocks have been negligible, and there are no reports of piston seizure from the Repair Dept. during the last 9 or 10 months. It is also interesting to note that the Repair Dept. have not yet used the more efficient scraper ring to EB.2686 for Aerolite pistons, although they have quite a large stock of them. This ring has a wider groove and consequently narrower lands, which give a higher unit pressure on the cylinder wall. Tests on the bed at 4,000 r.p.m. however have so far proved that this ring is only about 10% more efficient than the standard scraper ring fitted to Aerolite pistons. Our standardisation test on the test bed for pistons consists of 20 hours, each hour being run as follows :- 30 mins. at 4,000 r.p.m. full throttle 25 " " 4,250 " " 5 " " 4,500 " " Pistons passing this test have been proved to be equal to the requirements of the 10,000 miles test. EB.1299 pistons have passed this test, but not so easily as Aerolite pistons. | ||