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 Attwater & Sons Ltd. providing specifications for moulded fabric gears.
| Identifier | ExFiles\Box 136\1\ scan0313 | |
| Date | 2nd March 1940 | |
| Established 1868. Telegrams: "ATTWATERS, PRESTON." Codes: 5th & 6th Edition and 5 Letter, "A,B,C,", Western Union, Bentleys and Marconi. Telephone No. 4045 (two lines). No. ______ ATTWATER & SONS LTD., HOPWOOD STREET MILL, PRESTON, All orders are accepted subject to supplies of the necessary raw materials being obtainable and at the price at which they were contracted for, also to there being sufficient amount of labour. FA/S.888 Rm{William Robotham - Chief Engineer}/FJH{Fred J. Hardy - Chief Dev. Engineer}/IMH. Dear Sirs, Moulded Fabric Gears. Specification for: (1) LOAD. We cannot give this for Mouldings. All we can say is that when made in sheet form the sheet complies with Admiralty specification K/788A - i.e. Proof tests: Compression Strength - 18 tons per square inch, Tensile strength - 5 tons per square inch. Impact - Sample 2 x 0.4 x 0.4, un-notched. Blow applied 21 mm above grip normal to the plane of fabric, 1.85 foot lbs. We are well aware that the results on a moulding will be very much lower and very variable. As a matter of fact Messrs. Ford Motor Co. had a special testing machine made for cut gears but they never gave us any idea of their results beyond saying they were "very good". (2) HEAT TREATMENT. Complete shrinkage has taken place after 72 hours in an oil bath at 250º Fehr. (3) The Laminae in the rim are as far as possible normal to the pressure line of the teeth. (4) Approximately 200 layers per inch. (5) Cloth is 2½ ozs per square yard. Weft 56 threads per inch. Warp 72 threads per inch. At one time American car manufacturers used to call for a crushing load on the blanks, but this was found eventually to have no relation to tooth strength. Ford Motor Co. This firm specifies that the Rockwell Hardness of the rim after machining shall be 85 "B" scale minimum 60 kilos load, ⅛" ball. Yours truly, ATTWATER & SONS LTD. The Development Engineer - Chassis. Messrs Rolls Royce Ltd., DERBY. | ||