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 and issues with engine valves, pistons, and main casings.
| Identifier | ExFiles\Box 119\1\ scan0128 | |
| Date | 23th August 1938 | |
| -4- The very fine needle running from spring to valve was a makeshift and had not a proper head. The sharp end dug into the valve; but the proper end should prevent this. This valve was designed for use with bellows control. We do not need controlable front shock dampers on B.III, therefore the needle is unnecessary and the valve should be re-designed at once (preferably by 'F' Dept) to give the simplification thus permitted. Pistons. We started running with "chromidium" (as cast) pistons in one damper and high carbon steel pistons in the other; but after 18 hours a valve failure caused the 'chromidium' pistons to bottom and break. The external metal stops are required to prevent this. The chromidium pistons were replaced by C.1 pistons heat treated to 450 brinell and these completed the running. Cast iron pistons break during assembly when the interference of the pin is .0035; therefore they are unsuitable. Steel pistons are satisfactory but we are going to try malleable iron. For the time being the L.O.F. should show S/HC pistons. The chamfer on the piston skirt should be cast in and not machined. The run of the piston crown should be thickened by .025 and the valve pieces modified accordingly. The limits on the depth of the refill valve face diam. and width of retaining ring groove could be increased to at least .005", the only stipulation being that a note be added to the drawing that the valve face be a good finish. Main Casing. The present flanged bushes will have to be retained at present but we are going to run a damper without flanges on the bushes, next time. Increased clearance is necessary in the upper part of the damper casing to obviate machining above bores. Rm{William Robotham - Chief Engineer}/AFM.{Anthony F. Martindale} | ||