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).
High power camshaft tests, comparing timing and performance of Phantom II and China 25HP engines.
| Identifier | ExFiles\Box 92\2\ scan0132 | |
| Date | 1st May 1931 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. SE. Nor. c. DS. H.{Arthur M. Hanbury - Head Complaints} c. Ev.{Ivan Evernden - coachwork} OR/Y7771 Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}2/AED. 5. 31. Y7090 HIGH POWER CAMSHAFT P.II. We have now run a number of tests on the new 120° camshaft to LeC.2918. The best power we have so far obtained is 158 B.H.P. with a 4.9 - 1 C/R.{Sir Henry Royce} and a single Claudel Eagle IX carb. giving a depression of less than 2" Hg. at 3000 R.P.M. Considering the timing diagram obtained with this camshaft, we are not getting so high a specific power output relatively as on the 25 HP at the same compression ratio. As it is generally accepted that the larger cyl. should have a higher thermal efficiency than the smaller cyl. this result was contrary to our expectations and we have been trying to find some explanation for it. Curve I. shews a H.P. curve taken on China with a carb. on the exhaust side and indicates that at 5 - 1 C/R.{Sir Henry Royce} a specific output of 23.6 BHP/litre can be obtained with a depression of 2.6" of Hg. With a more abnormal timing, a lower carb. depression and the same C/R.{Sir Henry Royce} the 40/50 only gives 20.75 BHP/litre or 13% less. TIMINGS .013 Tappet Clearance. CHINA 25HP 116° SHAFT (Diagram showing timing values: EX opens at 54, closes at 7. IN opens at 48, closes at 0.) Inlet Duration 227° Exh. " 235° BHP/Litre 23.6 Valve area/litre 2.22 Ratio Lift 2.55 Valve dia. P.II 40/50 120° SHAFT LeC.2918 (Diagram showing timing values: EX opens at 62, closes at 37. IN opens at 65, closes at 0.) Inlet duration 242° Exh. " 249° BHP/Litre 20.75 Valve area/litre 2.106 Ratio Lift 2.46 Valve Dia. | ||