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).
Summary of tests conducted on various types of bottom tappets.
| Identifier | ExFiles\Box 96\2\ scan0268 | |
| Date | 8th November 1937 guessed | |
| Summary of tests with various bottom tappets. (1) Cast Iron Bottom Tappets, with chilled face. Rockwell C.50-55. Surface of Tappet stays in good condition with slight cross grooving. The camshaft gets badly worn with I/C tappets. (2) S/ZN tappets with hardened face. Rockwell C.57-65. get badly cross grooved and score up on the surface. (3) S/ZN tappets with chromium face (Standard). Undoubtedly far superior to 1 and 2, have had very little trouble other than plating flaking at the edges. (4) Tests proceeding with tappets 1, 2, and 3 show that running in with Hi-press oil is beneficial. This can only be used on a rig as oil attacks the steel parts. (5) Choc-a-bloc of valve gear when cam is fully lifted is fatal to bottom tappets. (6) Removal of bottom tappet springs makes little or no difference. (7) Small base circle cam to reduce rubbing velocity gave no appreciable improvement. (8) Solid rocker gear does not wear tappets anywhere near as bad as auto tappets. | ||