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).
Secret memo discussing the installation drawing and fitment challenges for a 13.2mm machine gun into an aircraft wing.
| Identifier | ExFiles\Box 176\1\ img056 | |
| Date | 30th August 1940 | |
| SECRET. To Rm.{William Robotham - Chief Engineer} from Ev.{Ivan Evernden - coachwork} re Installation Drawing type A7A. Gun. 13.2 m.m. M.G. We have now received several prints of QA.1100, the installation drawing of the 13.2 m.m. M.G. type A.A. As we think that still more information should be added to the drawing before it can be considered to shew all that is necessary to enable a plane maker to design the gun into a wing, or Messrs. Nash & Thompson to install it in a Turret, we have marked up a print which we enclose herewith. The one item all would like to read is the bearing load. As the gun contains no recoil mechanism of known characteristics this load must depend on the rigidity of the mounting. We thought it would be better if you were to take up with Ve. the question of adding the proposed information to the drawing in question. Progress is being made with a scheme for fitting this gun into the Spitfire Wing, but certain difficulties have been encountered which are not met with in the case of the ½ ins. Browning M.G. On QFL.131 herewith we shew the two guns superimposed. The barrel centre lines coincide and so do the axes (vertical) of the breech blocks. In any given wing section this would be the relative positions of the two guns. It will be seen that rear ward extension of our gun is the lesser, which is a good feature, although it aids us not at all. The forward lengths are almost identical. The height above the barrel centre line of our gun is 1.575 ins. greater than that of the Browning or 57.5%. This is a great drawback in a narrow wing such as the Spitfire. P.T.O. | ||