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).
Secret memo discussing design modifications to the 'Japan 3' engine, focusing on connecting rod length, flywheel, and clutch assembly.
| Identifier | WestWitteringFiles\V\October1930-February1931\ Scan294 | |
| Date | 2nd May 1931 | |
| FROM E.{Mr Elliott - Chief Engineer} G.{Mr Griffiths - Chief Accountant / Mr Gnapp} to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} C. to HS.{Lord Ernest Hives - Chair} PH. SECRET. JAPAN 3. ENGINE. LeC. 2853. ORIGINAL May we refer again to the above print sent with our memo. of yesterday in connection with the following points: (1) LENGTH OF CONNECTING RODS. Now that camshaft gear is at rear of engine we can reduce crankcase height .250 since no provision is required for a wheelcase flange joint. This naturally reduces the con. rod length and the height of the engine by a similar quantity. We do not want to sacrifice any of the water cooling by shortening the cyl. block but should like to drop the piston pin .250 lower in the piston to improve the distribution of side pressure on the bearing area of the piston skirt, this bearing area being very narrow at the top end where the skirt joins the piston head. The aggregate effect would be to shorten the rods 10" to 9.5" and they would then be 1.9 strokes long. LeC. 2853. still shews the 10" rods but we propose to instruct the modification to 9.5 forthwith. (2) FLYWHEEL AND CLUTCH. Concerned in the question of crankcase height is flywheel casing. This latter has a maximum radius of 8.25 on the present 25HP. engine and this would come within the 8.5 to which we propose to shorten Japan 3. crankcase. We have not yet investigated what alterations will be necessary to clutch and flywheel for the larger engine but the Bijur pinion of the starter motor prevents maximum use being made of the space available within the present flywheel case. We should like to have the sequence starter but this | ||