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).
Advantages and difficulties of the cylinder block design for 25/30 and Bentley models.
| Identifier | ExFiles\Box 86\1\ scan0234 | |
| Date | 5th April 1937 | |
| Sg.{Arthur F. Sidgreaves - MD} Hs.{Lord Ernest Hives - Chair} c. Fm/Gry.{Shadwell Grylls}/E/JRR. 20 1 36 219 26 6 32 Da.{Bernard Day - Chassis Design}2/HP.5.4.37. Cylinder Blocks - 25/30 and Bentley. The question seems to condense down to whether we want to use the present engine construction or not. Its advantages are:- It is reasonably light because of the aluminium top half crankcase. There would never be any need to use hydraulic tappets. We are relieved from anxiety as to the rubber rings on the liners in an aluminium engine. The oil is kept reasonably cool. It is reasonably economical. (A) There appear to be three main difficulties which are being experienced:- (1) Difficulty in getting good castings, up to 50% scrap. (2) Distortion of the bores due to long bolts to crankcase. (3) Distortion of the lower bore due to the thin projections into the crankcase. (1) We understand that the casting difficulties of the present block are being investigated elsewhere, and the results may modify the conclusions we have come to, which are - Due to the increase of bore to 3.500, the water spaces have become very thin, and especially between the cylinder bores, also the cylinder itself has become very thin. The justification for this has been that the American engines are equally thin in the jacket, or more so, but we think this is only partially true, the American engines we have examined having a narrow water space between the cylinders, but | ||