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).
Development and design decisions for Bentley pistons, specifically regarding skirt and land dimensions.
| Identifier | ExFiles\Box 86\2\ scan0051 | |
| Date | 28th August 1933 | |
| Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} E.{Mr Elliott - Chief Engineer} C. Mx.{John H Maddocks - Chief Proving Officer} x 286 BY.3/G.28.8.33. BENTLEY PISTONS. Further to my memo BY.9/W.25.8.33. on the above subject, which was intended merely to indicate that no bulk of pistons were in hand as no decision had been arrived at in regard to modified dimensions, it occurred to me after leaving the Works that my memo might be misunderstood, and I am therefore stating the position broadly so that the matter can be generally understood. In considering the Bentley pistons, particularly in view of the longer skirt and increased diameters, with a furthere fact that E.{Mr Elliott - Chief Engineer} was desirous of having a wider bearing at the top of the skirt, Mx.{John H Maddocks - Chief Proving Officer} did a considerable amount of development work within about a month of receiving instructions to go ahead with chassis, which resulted in his arriving at a stage, as a result of a number of tests making small changes to the top and bottom diameters of the skirt which enabled us to use E's larger area at the top of the skirt and eliminate hard markings on the edges, but we could not get complete diametral bedding on the lower edge without producing hard markings. The pistons for the 15 chassis were instructed on these lines, and were .007 smaller on diamter at the upper end of the skirt, but there was no difference made between this diameter and the lands, both being reduced the same amount. I have spent the weekend trying to recollect clearly the position, and the above gives an accurate summary of what was aimed at and achieved. We could have maintained a somewhat larger diameter at the upper end of the skirt if we had given up trying to work to the wider bearing surface E.{Mr Elliott - Chief Engineer} asked for on his LeC. drawing, but at the time I personally thought it was desirable in view of the higher inertia loads to have a wider bearing surface, this being a point particularly that Mx.{John H Maddocks - Chief Proving Officer} consulted me upon. BM BY.{R.W. Bailey - Chief Engineer} | ||