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).
Modifications to an aluminium split piston for a 40/50 chassis following engine seizing tests.
| Identifier | ExFiles\Box 77\3\ scan0239 | |
| Date | 2nd February 1920 | |
| To R from DA.{Bernard Day - Chassis Design} Copy to EH. Copy to CK.{Mr Clark} x.3924 DA{Bernard Day - Chassis Design}10/CB20-2-20. RE SPLIT PISTON IN ALUMINIUM - 40/50 CHASSIS. With reference to Mr Elliott's E6/G18-2-20, the cone was altered from .4 to .6 in height in order to bring the top band of the piston out of the combustion chamber, so that there was no part projected into the combustion chamber to require carbon. This was done as a result of the experience on the engine which tried to run for 100 hours with split pistons and seized up. In view of this we should like to know whether we should still be right in reducing the height of the cone. What we did previously to this was to put a flat top on the extreme point of the cone so as to reduce the total height, but we understand that this is not now desired. But possibly you may consider a flattening of the top of the cone to say .850 dia, which would reduce the height to .500. The reduction in diameter on the extreme top band was also done on the recommendation of the Experimental Dept, as a result of the same tests. The result of using it was that the seizing did not occur, though the band got full of carbon. It was thought that the gases were considerably cooled in passing down this annular chamber. It is agreed that there does not seem much justification for putting the rings low down. The Experimental Dept are making tests to shew that lifting the rings gives the same result as cutting the reduced band. DA.{Bernard Day - Chassis Design} | ||