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 25HP and 45HP balanced crankshaft.
| Identifier | ExFiles\Box 14\2\ Scan092 | |
| Date | 23th December 1930 | |
| E.{Mr Elliott - Chief Engineer} RG.{Mr Rowledge}) FROM R.{Sir Henry Royce} BY.{R.W. Bailey - Chief Engineer} HS.{Lord Ernest Hives - Chair}) (At Le CanadelHenry Royce's French residence.) Copy to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} K 010 R2/M23.12.30. X.5010. 25HP. & 45HP. BALANCED CRANKSHAFT.X.7010. X.634. We thank RG{Mr Rowledge}/TSN. for his work, and blueprint of 18/12/30, and I THINK we can perhaps finesse this a little more before making a trial in the present crankchamber. (1) I fear it would be much work to go all the way until we get the new crankchamber. Might we therefore try half-way, perhaps an increase if any in the dia. of the shaft of .125, and perhaps the pins also .125, and fit 4 balance weights instead of 8. This might also be more comparable to the longer stroke which will certainly bring down the master period still more. (2) I am assuming that our practice of balancing will be governed by the master period. In any case we do not expect to be able to fully balance, so that we can at once go as far as our master period will allow us. (3) I have not proposed that we should alter the length of the journal or big ends, but I leave this to E.{Mr Elliott - Chief Engineer} and RG.{Mr Rowledge} to settle. I am not in favour of webs thinner in proportion unless we are forced. I do think that we should watch carefully to increase the radius of the corners - i.e. stress change points likely to be neglected when working for stiffness. (4) If we fit 4 only, or even when we use 8 counter-weights, could we arrange the outside ones, which are at 30° from the crankpin to reduce the load on the bearing to a minimum. Being at 30° from opposite the crank we cannot reduce it to zero but we might make it of such a weight that each bearing would probably require two different sizes but the total weight would be less and the bearings could be more relieved. [Diagram Annotations] Probably balance weights cast iron. Unavoidable resultant. Clearance. End balance weights probably larger. As there are two cranks at 120° it may not need so large a C.W. for minimum bearing pressure. 2nd. from the end probably smaller. Trust to friction for exact tightness but studs can position by short fit. | ||