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).
Analysis of 25 HP engine power output concerning increased valve lift and clearance.
| Identifier | WestWitteringFiles\W\September1931-November1931\ Scan028 | |
| Date | 5th October 1931 | |
| To E.{Mr Elliott - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}2/AD5.10.31. ORIGINAL x5m/u/1. x5090. x5080. 25 HP. POWER OUTPUT. Increasing Valve Lift. We have been analysing the curves on increased valve lift. RM.{William Robotham - Chief Engineer}44. These curves show that - A.{Mr Adams} When the flow round the inlet valve is at all obstructed the increase in lift is of greatest value at 3000 R.P.M. B. Show that the effect of increasing the valve & C. lift becomes somewhat less at speeds of 3500 R.P.M. when the flow round the inlet valve is improved and a better timing used, but that at 3750 R.P.M. which seems to be some sort of critical gas velocity, the gain is almost exactly 5 B.H.P. in each case. RM.{William Robotham - Chief Engineer}45. Appears to confirm RM.{William Robotham - Chief Engineer}44 approximately. RM.{William Robotham - Chief Engineer}40. Shows that the gain is very much the same with a single carburetter. Actually, at 3500 the single carburetter benefits more than the twin from the greater valve lift. Increasing clearance round inlet valve. RM.{William Robotham - Chief Engineer}46 & 47. Are the results of tests taken to see whether increasing the clearance round the inlet valve head had any effect on the power output. With a high valve lift it will be noted that this difference is considerably reduced. Unfortunately, all the tests done on the head before it was machined were with a timing too early for maximum power and therefore the comparisons had to be made with this timing. Naturally the measurement of small differences is not easy and we shall therefore take the first opportunity of confirming these results. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||