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).
The design and performance of reduced toe camshafts for the J.III & China engines, including ideal timing diagrams.
| Identifier | ExFiles\Box 102\5\ scan0142 | |
| Date | 10th October 1932 | |
| X5090 E.{Mr Elliott - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to By.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}5/KT.10.10.32. REDUCED TOE CAMSHAFTS J.III & CHINA. We have now established the fact that, even with a turbulent head, we cannot use much more than 105 M.E.P. open exhaust owing to audible detonation. Also that 14° overlap is about our limit for slow running with a reduced toe camshaft, 10° may be the limit with the toe you have produced. The fact that we don't want more than 105 M.E.P. at 1000 r.p.m. and also that we have no long toe now to spoil our torque at low speeds, both indicate that we can conveniently use a slightly longer duration cam for our reduced toe camshafts on J.III. Curves Rm.{William Robotham - Chief Engineer}J7 and Rm.{William Robotham - Chief Engineer}J8 show our two most successful camshafts. It is clear that with a reduced toe the one using two exhaust forms to E.57386 gives the best results. If we could alter the exhaust cam slightly we should give as an ideal timing - [Diagram with angles: T.D.C, 10°, 62°, 43°] Valve Lift Curve Sch. 1543. Rm.{William Robotham - Chief Engineer}J7 shews that with 5.5 c/r we get just about 105 M.E.P. at 1000 r.p.m. which is what we want. Considering China, this with its restricted carburetter is probably not worth while altering, the existing timing being - [Diagram with labels EX, IN and angles 14°, 44°, 43°] Valve Lift Curves Sch.1542/3 Cam forms E.57174 E.57175 Camshaft E.57177 | ||