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 a supplier confirming the manufacturing specifications and processes for experimental springs.
| Identifier | ExFiles\Box 52\2\ Scan173 | |
| Date | 7th June 1928 | |
| COPY. FROM:- Thos. Firth & Sons, Ltd., Norfolk Works, SHEFFIELD. REF:- JWF/EQ. TO:- Messrs. Rolls-Royce Ltd., DERBY. 7th June, 1928. Dear Sirs, Experimental Springs. We beg to confirm the decision arrived at this morning when we had the pleasure of fully discussing the results obtained on the six experimental Springs of the American type, the results of which you reported on March 30th, viz. that we put in hand six pairs of 40 H.P. Front Springs in Silico Manganese Steel; all Springs to be of the same type and to be of Firth's modification of the American Spring that is to say, the same as those painted white in your report. Three Springs to be made by each of the following methods - (A) Top Leaf. Eyes to be drop stamped from a billet of thickness slightly greater than the outside diameter of the eye. The centre portion to be forged, leaving 1/8" on each surface and edge for machining. This surface to be milled off. The remaining leaves to be precisely as at present supplied. (B) Top leaf manufactured as per (A), the remaining leaves to be rolled 30/1000ths thicker than the finished size, these to be ground, removing 15/1000ths from each face. The edge also to be ground. (C) Top leaf to be from rolled bar of such a thickness as to allow a minimum of 1/8" machining on each face and edge. The eyes to be jumped up. The remaining leaves to be made as per (A). (D) Top leaf to be as per (C), and the remaining leaves as per (B). All leaves after rolling or forging and before machining to be heated at 900°C. for twenty minutes and cooled in air free from draughts, and to be re-heated to 850°C. and cooled in air. After machining the plates to be hardened in oil at 860°C. and tempered to a temperature to give a Brinell hardness within the present agreed limits. All the material is to be specially prepared from Ingots, and each process to be carefully supervised and records kept as to the actual temperatures. We think the above fully sets out the decisions arrived at, and we shall be pleased to have your confirmation of same, together with the necessary orders. Yours faithfully, THOS. FIRTH & SONS, LIMITED. (Sgd.) N. Burnett. DIRECTOR. | ||