Experiment with a higher toe lift cam form with a reduced diameter base circle for the Wraith III engine.
| Identifier | ExFiles\Box 7\8\ X 607 Camshaft-page05 | |
| Date | 25th June 1937 | |
| URGENT. SECRET. To [redacted] Copy to Rm. {William Robotham - Chief Engineer} [redacted] 107 E {Mr Elliott - Chief Engineer} /PSH/AHP.2/M.25.6.37. CAM FORM WITH REDUCED DIAMETER BASE CIRCLE - WRAITH III. ------------------------------------------------ Following a discussion with Rm {William Robotham - Chief Engineer} /Swdl. {Len H. Swindell} it has been decided to experiment with a higher toe lift on Wraith III. cams as at present silence can only be obtained with .002" clearance. As this is too small for normal running we wish to increase the actual clearance while maintaining the contact point of the tappet with the valve in this position by cutting back the base circle. We are issuing to you herewith a print of RS. {Sir Henry Royce's Secretary} 607 showing the new diameter base circle and the modifications necessary to the cam toes. Please arrange to have two cams on an existing camshaft cut back to these dimensions, and the toes stoned to give the new lifts. Note that the figures given on RS. {Sir Henry Royce's Secretary} 607 are cam lifts and not valve lifts. The new toe lift at the valve is .0198" and the velocity remains constant at .0006 ins/deg. throughout. Att: RS. {Sir Henry Royce's Secretary} 607. R {Sir Henry Royce} /PSH. | ||
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).