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).
Oerlikon Mounting 3.SLa for the 40 m/m Naval Gun Mark V, detailing mounting discrepancies and sight modifications.
| Identifier | ExFiles\Box 175\3\ img030 | |
| Date | 19th July 1940 | |
| SECRET. Gun 3 To Rm.{William Robotham - Chief Engineer} from Ev.{Ivan Evernden - coachwork} C. to Ve. C. to Rm{William Robotham - Chief Engineer}/HH. C. to Rm{William Robotham - Chief Engineer}/RM.{William Robotham - Chief Engineer} Ev.{Ivan Evernden - coachwork}1/JH.19.7.40. re Oerlikon Mounting 3.SLa for 40 m/m Naval Gun Mark V.{VIENNA} Attached to Rm{William Robotham - Chief Engineer}/HH's. copy of this memo. are PL.292 (sheet 1 and 2) which are tracing made from arrgt. drawings of the Oerlikon Gun Mounting. Type 3SLa, drg. Nos. GA.002 sheet 1 and GA.003 sheet 2. The mounting appears to be identical with that supplied to us for the exptl. gun, except that the distance between the trunnions of piece No.122 on the drawings is 9.000" and on the actual mounting 9.250". This is a mystery which will have to be cleared up. We shall also endeavour to obtain details of the trunnion spring and casing, for if we decide to move back the trunnion and use such a balancing spring, the identical parts could perhaps be used. We also attach the original of PL.293 shewing the exptl. gun in position on the mounting, using the adaptor plate-brackets of PL.281. With this present position of the trunnion a max. depression of 10° is obtained and an elevation of 30°. The sights have a centre line in the horizontal plane (approx.) of the gun. This is controlled by the shape and position of the shoulder rest, which in turn fixes the position of the gunners eye. This position for the sights may not be too good as all vision to the right when firing is masked by the gun. As pointed out by Mr. Parry when the cradle is shortened, the arm rest might be raised and the sights raised accordingly 5" or 6". The centre line of the sights will then be above the top of the gun and the gunner will see the whole horizon. If we can move back the trunnion 9" and use a balancing spring as on the Oerlikon gun, the max. angle of elevation will be increased. Whilst the raised sights will obviate placing the mounting on a base block. This latter seems necessary with the present sights, as with max. depression angle, the gun is too low, in the lowest position of the mounting. P.T.O. | ||