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).
Tests conducted on split-skirt pistons.
| Identifier | ExFiles\Box 48\1\ Scan169 | |
| Date | 10th October 1925 | |
| R.R. 498a (So H) (D.D. 31. 12-6-25) J.H.D EXPERIMENTAL REPORT. -2- Expl. No. REF: Hs{Lord Ernest Hives - Chair}/ACL/1G101025. gave us quite good results. They are as follows :- Standard pistons with the skirt split on both pressure and non-pressure sides in exactly the same way as the non-pressure side is split on the standard piston, and made to just fit the bore (fore and aft) when cold. In operation these were quite silent over the whole range from starting up cold up to normal running temperature. The only disadvantage experienced was that of rattle occurring when running at high speeds but this was less noticeable as the other mechanical noises also increased with the speed. In another test however we turned the pistons round so that the stiffer side - i.e. the one with the bosses at the end of the horizontal split and the side which is normally the non-pressure side - became the pressure side, and this proved to be a great improvement. However it is possible that if this piston were designed to embody this arrangement of split it would be very satisfactory because it must be remembered that this was only a standard piston converted to test the idea. We also noticed during tests with this type of piston that the engine was always very free to turn after running at high speeds - a condition we do not often get with the standard piston. It is also thought that there was a slight gain in power but this we are not able to say definitely because we have not comparative power readings for this particular engine taken with standard pistons. We intend to determine this. The other type was also a standard one in which an contd :- | ||