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).
Technical memorandum confirming a phone conversation about modifications to the Bensport engine, including stroke reduction and supercharger placement.
| Identifier | ExFiles\Box 3\4\ 04-page062 | |
| Date | 28th June 1932 | |
| E.{Mr Elliott - Chief Engineer} ) FROM R HS.{Lord Ernest Hives - Chair} ) K4553 R1/M28.6.32. C. to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} BY C. to DA.{Bernard Day - Chassis Design} HOY. re. BENSPORT ENGINE. CONFIRMATION OF 'PHONE CONVERSATION OF 27.6.32. It is understood and agree that we wish to run at 5000 r.p.m. and yet be sufficiently below the master period for safety. To enable us to do this with the 7 bearing crankshaft - our usual practice - we have suggested that the best way is to reduce the stroke from 4.1 to 3.875 or thereabouts - say 3.8 or 3.9" This, with the larger journals and pins already under consideration, should give a master period well over 6000. This I understand from E.{Mr Elliott - Chief Engineer} would also put us in a Brooklands class in which we should be better able to compete than with our longer stroke engine of 4.1", viz: We should then be just under 2.2.5 litres. Personally I do not like touching the 4 bearing crank, as at the moment we have no knowledge of how long the bearings will stand up. E.{Mr Elliott - Chief Engineer} also said it would lengthen the engine, which is undesirable. It was pointed out that the great thing that is holding us up is whether the supercharger is to go in front of the engine as originally arranged, or at the side of the engine, and this matter ought to have been settled by experiment some time ago. It is assumed that if the supercharger can be placed at the front end of the engine without trouble with the induction system, this is the best place for it. We have however at WT studied carefully the alternative position of putting the supercharger at the side under the induction pipe, and providing a suitable drive. We shall in a few days be sending a drawing of this alternative, and reserve arrangement. It consists of the usual crankshaft, helical pinion, with a carrier wheel of about 5" dia. very nearly exactly over it, slightly towards the supercharger (which is rather higher than the dynamo.) The supercharger, and also the dynamo are driven by the same size wheel as the crankshaft, and therefore at engine speed. Both gear direct on to the 5" carrier wheel mentioned above. On the carrier wheel shaft we can place a worm gear to drive the camshaft by mitre wheels. We understand that this vertical shaft should preferably be driven at half engine speed, so it would be easy to couple up after replacing the head. (1) | ||