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).
Fitting salt-cooled exhaust valves to the Bentley 50 engine, compression ratios, and testing methods.
| Identifier | ExFiles\Box 111\2\ scan0406 | |
| Date | 12th December 1938 | |
| 800? To BY.{R.W. Bailey - Chief Engineer} From RHC{R. H. Coverley - Production Engineer}/G.Mc. C. Rm.{William Robotham - Chief Engineer} RE. BENTLEY 50. Is it considered reasonable to fit salt cooled Exhaust Valves to the above Engine? The cost factor is of great importance as expressed in your memos yet I understand these are to be fitted. The Engine as designed was about 6 to 1 and eventually increased to 6¼ or 6½ to 1, all quite modest compression ratios and our filling is nothing out of the ordinary as the B.M.E.P. is round about 125. At this figure it should be quite possible to run 7 or 7½ C/R with standard Valves and fuel providing the design is right. As you know there are quite a lot of factors bearing on this; but one I pointed out before the engine was made as per my memo' RHC{R. H. Coverley - Production Engineer}/G.Mc.1/FH.17.8.38. received little attention, it was agreed that the trouble existed, but the steps taken were certainly not sound, the action taken was to vent by drilling 5/32 holes, these are sure to close up with very little use and even after a dynamometer run this fact shows up to a degree. The value of Single Cylinder tests in developing an engine is very high and economical providing the results are acted upon and due allowance made for variables that past experience shows necessary, but in this instance little or no benefit seems to have been gained. Generally the lines and layout for an engine of this type are quite good, but I do not think certain troubles should have existed and the cost of numerous tests thereby saved. RHC{R. H. Coverley - Production Engineer}/G.Mc. | ||