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).
Page discussing proposals for improving eccentric bearings and oil supply.
| Identifier | ExFiles\Box 17\6\ Scan196 | |
| Date | 20th February 1934 guessed | |
| -4- for its effective working on the maintenance of an oil film between the eccentric white metal and steel of the shaft, is entirely unsuited to the work which it has to do; the high local pressures and the very small movement of the eccentric will effectively prevent such a film being formed. If attempts are made to move the eccentric while under valve spring load, a very large force is necessary - it is obvious that the static friction of the eccentric under load is high. One effect of this, which has been shown experimentally on J-III, is that if an engine is shut down during its warming up period, or when it is very hot, owing to this static irreversibility of the eccentrics, the valves will be held open when the engine is cold by an amount equal to the difference between the cold and hot clearances. My suggestions in regard to eccentric bearings are as follows :- (1) We should try a form of needle or roller bearing. This would in all probability cure our troubles, but would be expensive. (2) We should try a form of knife edge bearing, since this type of bearing is ideally suited to the eccentric's work; also it would be largely independent of slight shaft distortion. (3) If either of above schemes are considered impracticable, we should make the eccentric of duralumin. In this way, since the white metal and phospher bronze floating bush could be dispensed with, we could use a shaft .100" larger in dia. For same size rocker, the clearancewould increase with rise of temperature of engine, and if desired, oil holes could be drilled in eccentrics, as in Cadillac type. Further, we should clamp the shaft down by means of caps as is done in the case of a bearing, and not by studs passing through a hole in the shaft - these weaken the latter to a great extent. This modification has already been asked for, I believe. OIL SUPPLY. (1) The present inclined drilling of casing is not satisfactory and the previous drilling is preferable, but by no means ideal. We are at present about to try another oil metering scheme. | ||