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).
Comparing Bentley's split aluminium piston design with an alternative design under testing.
| Identifier | ExFiles\Box 77\3\ scan0010 | |
| Date | 11th November 1919 | |
| To CJ. from EH. c. to R.{Sir Henry Royce} c. to Bn.{W.O. Bentley / Mr Barrington} c. to Wor.{Arthur Wormald - General Works Manager} c. to EP.{G. Eric Platford - Chief Quality Engineer} EH6/LG4.11.19. 3Y32 RE SPLIT ALUMINIUM PISTONS. X.3651. With reference to your memo CJ17/E3.11.19, we were aware of Mr. Bentley's split aluminium piston, in fact, we have a model at the works. We do not consider, however, that Mr. Bentley's method of splitting is as good as the method we are using. The differences in the Bentley piston and the ones we are testing are as follows:- 1. The bentley piston is split axially alround the buttom of the piston including the pressure side. This we think is not good because with the heavy loads which come on the pressure side of the piston, one would anticipate the aluminium would deflect a considerable amount at every explosion. It would certainly punish the metal far greater than we do on our scheme. The piston we are testing is not touched at all on the pressure side; the pressure is taken the same as on any standard trunk piston. We only split the piston on the non-pressure side which has a very light duty. 2. The Beltley piston is only split axially. This we do not think is good because the tonges of aluminium which are formed by the splitting will give a varying degree of flexibility at different heights, for instance, it would be much easier to deflect the bottom of the piston than it would be higher up where the splits finish. We do not consider this good because there will be most expansion, due to heat, on the piston where it is least flexible. We split our pistons axially and circumferentially which gives us a uniform amount of flexibility on the whole length of the fitting portion of the piston. We think the chief factor in the piston we are testing is the fact that we start off with a piston which is ground oval and which is quite clear on the gides. This method of grinding was schemed out by Mr. Royce some years ago. It is a very important point and one where we consider we are better than any other split pistons we know of. I believe that the Franklin Car in America have used split aluminium pistons very similar to the Bentley. EH | ||