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).
Investigation into valve gear trouble on the Wraith III model due to a collapsing grummet.
| Identifier | ExFiles\Box 10\3\ 03-page093 | |
| Date | 8th November 1937 | |
| To By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} c. By/CS. 654 Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}14/AP.8.11.37. WRAITH III. VALVE GEAR. Trouble is being experienced on Wraith III. valve gear due to collapse of the bottom grummet EB.1784 and showing up in the form of surge and valve bounce at a lower speed than desired. The detail drawings show that the valve spring length in the closed position should be 1.525 and which is so when the unit is first assembled, but after running, increased to 1.600" due to the grummets collapsing. This means that the valve seating load is approx. 37 lbs. whereas at correct dimension of 1.525 should be 45 lbs. We have investigated the production of the grummet EB.1784 and find that it is possible to get another 50% of asbestos material into it and still squash down in the press to the drawing dimension. The grummet is at present made of approx. 2' of asbestos string with a dry weight before waxing of .8 grams. Will you please give the grummet for the Wraith a new number specifying for approx. 3' of asbestos string with a dry weight of 1.2 - 1.3 grams. Other than the quantity of material used the dimensions after being pressed, to be as EB.1784. This should only apply to Wraith III, included in the specification for the 6 which RMC. is to build. Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} | ||