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 Wraith III units concerning the spring drive friction washer and valve grummets.
| Identifier | ExFiles\Box 6\6\ 06-page392 | |
| Date | 8th December 1937 | |
| To By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} c. By/CS. c. Da{Bernard Day - Chassis Design}/Mcs. c. HPS{Horace Percy Smith - Experimental Factory Mgr}/RH.{R. Hollingworth} 600 WRAITH III UNITS. The Wraith III Units have been suffering from dryness of the front "cotton duck" friction washer of the spring drive. Our first attempt was to drill 4 holes in the centre plate similar to the Ph.III (Rm.{William Robotham - Chief Engineer}394) but this proved unsuccessful. Next, the fling holes in the circumference of the rear damper wheel were blanked and upon examination after running with these two modifications, the friction washer was found to be satisfactorily lubricated. We are sending this memo through now in order that the fling holes in the damper wheel be blanked and accordingly deleted from the drawing and instructions issued with regard to the 6 RMC. units. Regarding the holes we have drilled in the centre plate (Rm.{William Robotham - Chief Engineer}394) there is no proof as yet whether they are of any value or not, and therefore we do not wish to include them until we have proved them one way or the other. Further to our memo on Wraith III Valve grummets Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}14/AP.6.11.37 we have now found that 4'-6" of asbestos string is required in order that the spring loading is O.K. after running. The dry weight of this amount of string is 1.6 to 1.8 grams. After producing in the press the thickness is .030 thicker than the drawing EB.1784, but goes down to the latter after running. There is ample clearance when the valve is in the fully lifted position with the thicker grummets. Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} | ||