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 confirming a telegram and detailing modifications for increasing a 20HP chassis bore to 3.25 inches.
| Identifier | WestWitteringFiles\T\March1929-December1929\ Scan090 | |
| Date | 21th April 1929 | |
| R.{Sir Henry Royce} FROM E.{Mr Elliott - Chief Engineer} [R.{Sir Henry Royce} is struck through] C. to SG.{Arthur F. Sidgreaves - MD} WGR. HS.{Lord Ernest Hives - Chair} BY.{R.W. Bailey - Chief Engineer} DA.{Bernard Day - Chassis Design} [WGR. HS.{Lord Ernest Hives - Chair} BY.{R.W. Bailey - Chief Engineer} DA.{Bernard Day - Chassis Design} are struck through] SECRET. re. 20HP. CHASSIS - 3.25" BORE. [Top Right] SUNDAY. E1/M21. 4. 29. [Handwritten:] +5050 / +5000 We beg to confirm the following telegram received from you on Friday evening with reference to the above: "YOUR VALUABLE DISCOVERY OF THE POSSIBLE QUARTER INCH INCREASE SHOULD GO TO DERBY AS QUICKLY AS POSSIBLE. IT PROVIDES JUST THE NECESSARY MOVE "WITHOUT LOWERING THE GEAR" On Thursday last we posted to Le CanadelHenry Royce's French residence, and to Derby prints of LeC. 2695. We now attach a further print of LeC. 2695 more complete, and also one of LeC. 2696. LeC. 2695. deals with the alterations to G.4. for increasing the bore to 3.25, and shews the modifications required to the turbulent head, the cylinder block, and the crankcase. Complete particulars of G.4. crankcase however are not yet available. We are dealing with the alterations for the 4 point mounting, and the application of the SS.{S. Smith} moves on separate schemes. These will be completed at an early date. LeC. 2696. shews the alterations that would be required to adapt the 3.25 bore to the present 20HP., retaining the present form of head. The modifications have been kept down to the minimum compatible with making a sound job. The present carburetter, and exhaust and inlet manifolds remain unaltered. The gas passage-way through the cylinder block necessarily restricted by the larger bore is made in the form of a machined venturi, the minimum diameter of which speeds up the gas about 70%. We do not anticipate that this will offer any appreciable resistance to the gas flow, and certainly not where we chiefly want the increased torque. We suggest it might be beneficial to increase the valve diameter without altering the gas passages, even if only the inlet valve. It is understood from BY.{R.W. Bailey - Chief Engineer} that the comparatively simple pattern alterations called for on LeC. 2696. could be got in on 'O' series of 150 'twenty's' if desired and authorised. A print of LeC. 2696. is also attached to BY's copy of this memo., a print of LeC. 2695. having been sent yesterday to him. E.{Mr Elliott - Chief Engineer} [Handwritten note at bottom:] We are a bit behind with our promise but we had an unexpected visit from FL Sat morning which delayed us. | ||