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).
Design considerations for a 2nd compression ignition test unit, including crankshaft, bore, stroke, and bearings.
| Identifier | ExFiles\Box 178\3\ img180 | |
| Date | 28th May 1932 | |
| EG. FROM R.{Sir Henry Royce} C. to SG.{Arthur F. Sidgreaves - MD} MOR. HS.{Lord Ernest Hives - Chair} C. to E.{Mr Elliott - Chief Engineer} GD. Mr. HHH. RL/M24.5.32. Sent off 28.5.32. x4453. re. 2nd. COMPRESSION IGNITION TEST UNIT. As this is being specially prepared for 2 stroke work I have thought it would be better if it could be fitted up with a double throw crankshaft, (as we could get steady turning without an excessively heavy flywheel.) The size suggested is the Kestrel bore of 5", and the Buzzard stroke of 6.6", because there is no doubt that a C. I. engine should at least have a somewhat longer proportion of stroke. At the same time the stroke must not be excessive, or the piston length becomes so great unless limited to the sleeve type. We have studied very carefully the pitch of the centres so as to admit of a variety of constructions being fitted to the unit, and think that 6.5" for a 5" bore is the best. There is a slight question as to whether the unit should have 5 bearings or 4, as we prefer that at least on the flywheel side there shall be 2 bearings between it and the first crank. We can in this way however take off any drives we wish, and so to represent more accurately an actual engine. Perhaps we ought to manage with a single bearing only at the non-flywheel end, but there seems to be a great temptation to make it symmetrical about the centreline, and make a 5 bearing crankshaft, which we are doing at the moment. We propose for convenience to keep the crank in the lower half, which is of a substantial thickness of cast iron, and as there is very little diagonal pressure on the main bearings we are arranging them to fit in the base plate only without cross bolts - i.e. like the existing unit. Increase in the The/pitch of the centres is good for the big end, crank webs, and main bearings, because as we have before mentioned, we think it is very difficult to get satisfactory con. rods for this type of engine, when we come to more than one cylinder per crank. (1) | ||