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).
Engine power output variations caused by piston skirt dimensions, with plans for further piston friction reduction tests.
| Identifier | ExFiles\Box 144\3\ scan0030 | |
| Date | 13th February 1934 | |
| -5- Hs{Lord Ernest Hives - Chair}/ths.1/KW.13.2.34. We have from time to time had variations in the Power output of engines when using standard Pistons, and this we put down to the fact that the skirt diameter varies considerably. We have known cases where Pistons after running have been as much as .002 over the bore size when measured at the base of the skirt, while in other cases the Pistons have been .001 under the bore size. We intend to carry out further tests to see if we can still increase the Power output by reducing the Piston friction still more. In this respect we are fitting Pistons E.57122, in which there is no sawcut in the skirt, and the skirt has been reduced in diameter so that it is .020 under the bore size. The skirt of this Piston we have also shortened by .500, so that although these Pistons will be of no practical use, they will give us a figure for the maximum Power we may expect by reducing the Piston Friction. We also intend repeating these Piston tests with semi-split Pistons E.B.1404 as soon as possible. On the attached chart (B.V.18) of the Heat Balance there is also a large scale diagram of the Heat picked up by the oil from various sources. Attached are also curves B.V.19 and 20. It will be noticed that on the latter the I.M.P. continues to be practically a straight line with no falling off at the high speeds. ME/R.Matthews. | ||