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).
Modifications to the raised crown piston for the Wraith model, referencing specific drawings.
| Identifier | ExFiles\Box 9\1\ 01-page20 | |
| Date | 18th January 1939 | |
| 636 To By/CS. c. to Da{Bernard Day - Chassis Design}/Mc. c. to Mx.{John H Maddocks - Chief Proving Officer} Rm{William Robotham - Chief Engineer}/CTC.16/JH.18.1.39. PISTONS. With reference to the raised crown piston for the Wraith. The latest detail drawing EB.4499 incorporates all the modifications to the piston crown as follows. (a) Crown lowered by .030, making the piston .060 from top of cyl. block to enable the use of .030 Klingerite gasket. (b) .200 depth of top land. (c) Parallel grinding of the lands to a diameter of 3.482. This is in line with latest production practice, and the same as the Aerolite piston on Bentley. Another detail drawing is now desireable as follows - (d) The shape of the bump on the piston should be modified to be in line with our latest Bentley, piston EB.4587. This drawing is urgently required, so that we may produce pistons for the next 15,000 miles Wraith. Rm{William Robotham - Chief Engineer}/CTC. | ||