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).
Performance of raised crown pistons versus high power heads in Bentley engines.
| Identifier | ExFiles\Box 148\1\ scan0159 | |
| Date | 9th June 1939 | |
| 1256 By.{R.W. Bailey - Chief Engineer} from Hm.{Capt. W. Hallam - Head Repairs} c. Da.{Bernard Day - Chassis Design} c. Da{Bernard Day - Chassis Design}/Jnr.{Charles L. Jenner} c. Da{Bernard Day - Chassis Design}/McS. c. Hm{Capt. W. Hallam - Head Repairs}/FD.{Frank Dodd - Bodies} c. Hm{Capt. W. Hallam - Head Repairs}/Wym.{G. Harold Whyman - Experimental Manager} c. Hm{Capt. W. Hallam - Head Repairs}/LMW. Hm{Capt. W. Hallam - Head Repairs}2/R.9.6.39. At one time we thought that the raised crown piston was so good that it would make the conventional engine a serious competitor with the high power engine where output alone is concerned. Further experience has shown that the raised crown piston is somewhat carbon conscious, and in practice we are finding that it barely enables us to raise the c.r. of the standard Bentley from 6.5 - 7:1 for a given degree of detonation after carbon has formed. The Brooklands figures show how remarkably well the high power does at 6.4-1 i.e., a lap at 89.5 on a B.50. Clearly we have a lot more development work to do before we can say that we have got the best out of raised crown pistons. At the moment, the move to the High Power head seems to be more than justified. Hm.{Capt. W. Hallam - Head Repairs} | ||