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).
Continued document detailing engine timing specifications, clearances, and variations.
| Identifier | ExFiles\Box 43\3\ Scan170 | |
| Date | 6th October 1927 guessed | |
| contd :- -2- in the fully advanced positions. The 35º will be obtained by two marks on the thrust housing E.30557 :- *1.19" or 35 X .632 = 22.1º apart for a .632 geared engine, and 1.04" or 35 X .550 = 19.3º " " .550 " " - allowance being made for any slack in the gear when turning the propeller. (*Spacing of marks on periphery of housing). The second requirement (2) will be based on an average taken over as many engines as possible - the limits of variation being given. For the records taken up to date, a .010" clearance has been used i.e., using a .010" feeler in the .020" clearance, which is a standard working setting on these engines. With smaller set clearances the limits of variation would be much wider - as the opening or closing position approaches the toe of the cam - and this is the reason for the preference for larger set clear- ances in the Expl: Dept: when timing engines. The average timing to date, using a .020" tappet setting with a .010" feeler (.010" actual clearance) is :- Variation. I.O. 4º B.T.D.C. 1/7º B.T.D.C. I.C. 52º A.B.D.C. 48/60º A.B.D.C. E.O. 46º B.B.D.C. 39/48º B.B.D.C. E.C. 18º A.T.D.C. 12/25º A.T.D.C. Any difference between the above and the timing prescribed by the D.O. may be accounted in the following ways :- contd :- | ||