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).
Timing procedures for F.11 and F.12 engines.
| Identifier | ExFiles\Box 43\3\ Scan168 | |
| Date | 6th October 1927 | |
| To EP.{G. Eric Platford - Chief Quality Engineer} from Hs{Lord Ernest Hives - Chair}/VH. c. to Hs{Lord Ernest Hives - Chair}/TMW. c. to Hs{Lord Ernest Hives - Chair}/TAG. (4003) Hs{Lord Ernest Hives - Chair}/VH2/LG6.10.27. RR. F.11. and F.12. TIMING. X1770 X3822 With regard to the timing of these engines, it is necessary that we should :- (a) Declare a timing all round the cycle for cyls. A1. and B1. so that the A.I.D. shall have a standard for comparison purposes (see 2 and 3 below). (b) Establish a suitable method of timing, when the engine has left the Works (4 and 5 below). The only piston position we can find with ease and accuracy is top-dead-centre, and the corresponding points in the valve position cycle which nearly approximate to this, are I.O. and E.C. At this position we propose to establish a base circle tappet clearance on either the exhaust or inlet cam which will arrange for the corresponding valves to be just closing or opening, respectively, with a .010" feeler in position between the valve stem and rocker. (The .010" feeler is specified as being a convenient thickness, allowing the point of contact to be instantly felt). When timing an engine, previous to the 1/2 hr. final, the following procedure is to be adopted :- (1) Set the camshafts to I.C. 38° A.B.D.C. with .030" clearance. (2) Take a record of the timing IO, IC, EO, EC, with .010" " ". (3) Time the magnetos to fire 35° BTDC. in the position corresponding to full throttle, when the controls are interconnected. (4) With the piston exactly at T.D.C. (end of exhaust stroke) set the exhaust and inlet tappets so that there is just .010" clearance. (5) Take a careful record of all clearances, when the engine is turned so that the rockers rest on the 'back' (base circle) of the cams, before re-setting the tappets to the std. .020" clearance. Enter records in Log book, or Night Shift book. (4) and (5) should be repeated as often as possible (on A6. and B6. as well as on A1. and B1.) to obtain a good average of the 'base circle clearance' required to give an I.O. and E.C. at TDC. using a .010" feeler. This will be the only accurate timing method available on supercharged engines having a reduction gear fitted. Hs{Lord Ernest Hives - Chair}/V.Halliwell. | ||