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).
Confirming a telegram and detailing modifications for increasing the bore of the 20 HP chassis engine.
| Identifier | ExFiles\Box 103\2\ scan0203 | |
| Date | 21th April 1929 | |
| R.{Sir Henry Royce} from E.{Mr Elliott - Chief Engineer} +5000 E1/M21.4.29. c. to SG.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. to Hs.{Lord Ernest Hives - Chair} BY.{R.W. Bailey - Chief Engineer} Da.{Bernard Day - Chassis Design} 20 HP. CHASSIS - 3.25" BORE. X.5050 X.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 ~~EXIDE~~ turbulent head, the cyl. 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 S.S. 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 20 HP. retaining the present form of head. The modifications have been kept down to the min. compatible with making a sound job. The present carb., and exhaust and inlet manifolds remain unaltered. The gas passage-way through the cyl. block necess- arily 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 passage, even if only the inlet valve. contd :- | ||