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).
Goshawk engine timing, comparing the Goshawk I and Goshawk II models and recommending new camshafts.
| Identifier | WestWitteringFiles\K\July1923\ Scan28 | |
| Date | 19th July 1923 | |
| TO HS.{Lord Ernest Hives - Chair} FROM R.{Sir Henry Royce} c.c. to SJ. ORIGINAL GOSHAWK TIMING. V3942 In reply to your HS{Lord Ernest Hives - Chair}1/LG16723., the Goshawk 1. timing if made to the original instructions should be the same as Goshawk 11. since the timing and valve lift drawings - LeC.1044. & 1050 - are common to both engines. There is no reason that we can see for any longer cams because we can get it out of the overlap if you want any different timing. The result of the experiments shews the increased efficiency of overhead valves as regards the freedom of extry and exit of the gas and shewing itself by enabling you to close the inlet earlier and to open the exhaust later. We may however be deceived by the experiments on Goshawk 1. not being applicable to Goshawk 11. because Goshawk 1. has larger valves and larger and differently shaped passages. If this latter assumption is correct and there is not the enormous advantage in efficiency of the overhead valve, then the proposed new timing of Goshawk 11. will want modifying, in which case 108° between the cams will be found too much, so that we recommend, two camshafts being made for Goshawk 11. one with 108° as suggested, and one with 112°. The latter camshaft would have less overlap and either or both exhaust and inlet opening earlier and closing later respectively. The timing diagrams for these two shafts based on the average Goshawk 11. timing with Goshawk 11. cams given on your HS{Lord Ernest Hives - Chair}1/LG16723., would be as follows:- (1) | ||