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).
Letter from The Light Production Co. Ltd. regarding piston design, clearances, and performance characteristics.
| Identifier | ExFiles\Box 86\2\ scan0220 | |
| Date | 21th June 1934 | |
| X236 TELEPHONE: VICTORIA 0671 (5 LINES). CODES: A.{Mr Adams} B. C. 5TH EDITION. ALL COMMUNICATIONS TO BE ADDRESSED TO THE COMPANY. ON ADMIRALTY, WAR OFFICE AND AIR MINISTRY LISTS. THE LIGHT PRODUCTION CO. LTD. PROPRIETORS OF THE LONDON PISTON RING CO. LIMITED. CHAIRMAN & MANAGING DIRECTOR: M.V. ROBERTS. DIRECTORS: C.W. GEORGE. WM. THIRTLE. ENGINEERS TELEGRAMS: INLAND, NAPOLEONIC, SOWEST, LONDON. FOREIGN, NAPOLEONIC, LONDON. 60/66, ROCHESTER ROW, WESTMINSTER, S.W.1 WORKS AND GOODS ADDRESS: 61/67, GREENCOAT PLACE, WESTMINSTER, S.W.1. OUR REF. CHB/IR YOUR REF. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}7/KW. 21st June 1934. Messrs. Rolls Royce Ltd., Experimental Dept., DERBY. Dear Sirs, For the attention of W.A.Robotham Esq. We have studied the data you give with your communication of the 16th in connection with your remarks, and the figures would appear to indicate, as you suggest, that the pressure face diameter at the top of the skirt should not exceed 3.247" for a cylinder bore of 3.250". We should quite expect an increase in horse power with progressive increase of clearance up to the point where further increase is limited by the introduction of audible cold slap. It has been our experience with many designs of pistons that a reasonably silent life cannot be obtained without the absorption of a certain amount of horse power in piston friction. You will no doubt recall that the results of the first set of pistons in 122 alloy indicated that the point of audible cold slap is reached when the clearance at the "I" dimension on your chart equals .0055", with our No. 14 form and a parallel piston. We are inclined to feel that possibly the taper has introduced a greater frictional loss than | ||