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).
The failure and testing of Wraith type flat bottom tappets on a Phantom III engine.
| Identifier | ExFiles\Box 10\3\ 03-page205 | |
| Date | 1st May 1939 | |
| 654 + 354 To By. {R.W. Bailey - Chief Engineer} from Rm {William Robotham - Chief Engineer} /Swdl. {Len H. Swindell} c. Da. {Bernard Day - Chassis Design} c. HPS. {Horace Percy Smith - Experimental Factory Mgr} c. Da {Bernard Day - Chassis Design} /Jnr. {Charles L. Jenner} c. Da {Bernard Day - Chassis Design} /MeS. Rm {William Robotham - Chief Engineer} /Swdl. {Len H. Swindell} 9/MH. {M. Huckerby} 1.5.39. WRAITH TYPE OF FLAT BOTTOM TAPPETS ON PHANTOM III. Barrel type of rotating tappets with vertical bores and flat faces as against the inclined bores and conical faces used on Wraith III, have been tried on the Phantom III in accordance with the scheme ECD.635. After 3 hours endurance running at 4000 R.P.M. one tappet failed completely at the base. An inspection of the remainder reveals cracks running from the oil drain hole to the base and cracks from the windows down to the base in several tappets. This is a similar failure to that experienced on the early type of B.60 tappets and up to the present has been made satisfactory by deleting the drain hole, strengthening the base and RHC {R. H. Coverley - Production Engineer} /Vs. {J. Vickers} ensuring the correct iron, grey not white or mottled. Additional to the above, we consider the wall thickness should be increased. The rotation of the tappets is not very positive and evidence of this was shown during the early stages of running by several light radial score marks on the faces. By increasing the cam width towards the outer edge of the tappet the moment of rotation would be increased sufficiently we consider, to overcome this trouble. Other than the failure, the condition of the tappets both on the face and the bores, is very satisfactory, likewise the cam profiles. Regarding the quietness of the valve gear, this was good and equal to, if not better than, the present Wraith production standard, this applying up to tappet clearances of .014. Other than the fact that we require a satisfactory bottom tappet to replace the present guided type which is giving considerable trouble on Ph.III., we should like the above mentioned modifications put through and tested for information for our other models. The chief interest in this respect lies in the | ||