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).
Tests conducted on a silent tappet rocker system with a hard shaft and nickel eccentrics.
| Identifier | ExFiles\Box 106\5\ scan0081 | |
| Date | 7th March 1933 | |
| V.S.66 E.{Mr Elliott - Chief Engineer} ) from Hs{Lord Ernest Hives - Chair}/Std. RHC.{R. H. Coverley - Production Engineer}) c. to BY.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Std.1/KT.7.3.33. REPORT OF WORK DONE ON SILENT TAPPETS ROCKER SYSTEM (NEW SCHEME - HARD SHAFT & NICKEL ECCENTRICS). UNIT. These tests were carried out on J.II No.1 Large Bore Unit, fitted with new cylinder head (turbulent type) giving compression ratio of 6 : 1. ROCKER SCHEME. This was as previous 'Silent Tappet' scheme except that the rocker shaft was mild steel, case hardened and ground, while the eccentrics were of nickel steel. TESTS & RESULTS. The rockers were fitted to the head and run for a short period, but were definitely not satisfactory, the eccentrics apparently tending to seize on rocker shaft. On dismantling, the eccentrics were found to be so tight on the rocker shaft that some of them were immovable by hand. The shaft and rockers complete were returned to fitters and the eccentric clearances were increased. They were then reassembled and run again - very much improved. The engine was then run for an hour at 3000 R.P.M. (full load) and at the end the tappets were functioning satisfactorily. On running for 10 mins. at 3500 r.p.m. (full load) however, they again shewed signs of the eccentrics tightening up. Also it was noted that the rear four rockers seemed to be starved of oil, and on investigation this proved to be due to considerable variation in push rod and valve length etc. causing the oil hole in the eccentric to be out of register with the oil hole in the rocker shaft, when clearance was correctly adjusted. The shaft and eccentrics were then returned to the shop to have high spots eased off, to free the eccentrics which shewed very definite signs of 'tightening up' when stripped, and to have the eccentric oil holes elongated radially by 1/10" each way, thus making it a radial slot rather than a hole. | ||