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).
Revisions to the Bentley 111 High Compression Split Piston design.
| Identifier | ExFiles\Box 99\4\ scan0123 | |
| Date | 8th December 1938 | |
| BY/NS{Norman Scott} c. Rm.{William Robotham - Chief Engineer} a.{Mr Adams} Rm{William Robotham - Chief Engineer}/OTS. 436 DA.{Bernard Day - Chassis Design}12/G.8.12.38. Swde Lilo BENTLEY 111 - HIGH COMPRESSION SPLIT PISTON. Please receive herewith :- E.CD.1090 Revised High Compression Split Piston - Bentley 111. The normal top of piston has been lowered by .030" in accordance with the suggestion in Rm{William Robotham - Chief Engineer}/OTS.3/JH.2.12.38. to maintain the standard clearance between piston at top of its stroke and the underside of the cylinder head to prevent piston coming into contact with cylinder head in case of failure of a big end bearing when a .030" thick gasket is used. (handwritten note: in original ex 1256 file) As the castings are already made for these pistons we have not corrected the compression ratio, as this would mean adding .033" material on the top projection of piston. The revised ratio is 6.63 to 1 instead of 6.75 to 1. The two top rings are respaced to maintain the agreed depth of top land of .200". All the top lands should, of course, be ground to a parallel diameter of 3.482" to bring them into line with latest production practice. This revised drawing applies to the experimental piston E.CD.851 and E.CD.926. Will you please alter the detail to this design. DA.{Bernard Day - Chassis Design} | ||