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).
Modifications to the petrol vacuum pump and camshaft for the 'SS' engine.
| Identifier | WestWitteringFiles\S\September1928-October1928\ Scan057 | |
| Date | 8th September 1928 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/ACL. c.c. to BJ. Wo r.{Sir Henry Royce} c.c. to E.{Mr Elliott - Chief Engineer} DA.{Bernard Day - Chassis Design} e.{Mr Elliott - Chief Engineer} to BY.{R.W. Bailey - Chief Engineer} ORIGINAL Hs{Lord Ernest Hives - Chair}/ACL1/LG8.9.28. RR. 'SS{S. Smith}' ENGINE. PETROL VACUUM PUMP AND TAPPET ROCKER SHAFT LUBRICATION. X7510 We have modified the vacuum pump as suggested by spacing the ports .800 apart and adding .200 to the top of the piston in order to avoid exposing the top port. The compression space has been preserved the same by adding a washer under the head cap (see print). Upon re-testing this modification it was found to have effected a considerable improvement and at some speeds more than doubled the previous delivery. Under the suction of the pump the fuel delivery through a standard autovac lifting the fuel 32" is now well in excess of the maximum full throttle demand of the engine as will be seen from our appended curves. Therefore having a pump of this delivery capacity should permit us to reduce the reserve tank capacity of our present autovac. With regard to the valve timing, we think the 116° camshaft referred to in a previous memo. (E2/M 30/8/28) should give a distinct improvement in allowing better filling at the higher speeds. From the shape of the power curve it appears that at present we are not using the best camshaft to take full advantage of our larger inlet valves. We shall have this camshaft put through as quickly as possible for test. In the meantime we already have available the cam forms for the contd :- | ||