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).
Brief specification for building a 3 1/4' Bore Engine Unit.
| Identifier | ExFiles\Box 82\4\ scan0110 | |
| Date | 30th March 1935 | |
| To RHC.{R. H. Coverley - Production Engineer} x200 Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}3/KW.30.3.35. 3 1/4" Bore Engine Unit. With regard to this engine unit, we think it would be best to build a complete unit up. The following is a brief specification :- (1) 20/25 HP. crankcase, machined to take the larger cylinder barrels. (2) Bentley bottom half and clutch pit so that a geared starter motor can be fitted. (3) A Bentley cylinder block opened out to 3 1/4", the chamfer at the top of the bore to be reduced to the absolute minimum, say .010" a side. (4) Standard Bentley cylinder head with machined combustion chamber and larger valves to the attached specification. (5) Aerolite pistons to be supplied by Rm.{William Robotham - Chief Engineer} (6) Please prepare 3 special gaskets, (a) in the same alloy as used for the Aero head joints (b) mild steel (c) copper. The thickness of the gasket does not matter very much. Actually we have run gaskets from .012" thick to .050". We think that the aluminium gaskets will have to be more than .030" thick, the others can be any gauge that you happen to have to hand, preferably not less than .020". You will appreciate that this specification is for the unit in which we are endeavouring to make the minimum modifications, i.e., we are not spreading the cylinder studs. We should like you to go forward with a second unit in which the cylinder studs are moved out .125", and in this case the stud which comes between the cylinder bores will have to be moved towards the inlet side until the requisite gasket width is obtained. | ||