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 push rod vibration on the Wraith III valve gear and the proposed solution.
| Identifier | ExFiles\Box 10\3\ 03-page107 | |
| Date | 13th January 1938 | |
| To By.{R.W. Bailey - Chief Engineer} c. to Hs.{Lord Ernest Hives - Chair} c. to Ds. c. to HPS.{Horace Percy Smith - Experimental Factory Mgr} 654. Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}6/JH.13.1.38. WRAITH III VALVE GEAR. It has been observed on several units that we pass through a sharp period of push rod vibration at approximately 2,000 r.p.m. This has been an in and out period and one which has been so indefinite as to render any results difficult to produce. The engine we now have on test however has shown up this period more pronounced and it has been possible to leave it running on the period and carry out comparisons. The noise on this period is outstanding and the vibrations can be felt on the push rods. By substituting 5/16" dia. push rods in place of the existing 1/4" dia. rods (E.1412) the period is completely cured and the rods by feel are free of any vibration. The increased weight of larger rods is such that the valve bounce speed is reduced from 4350 r.p.m. to 4300 r.p.m. and can be regarded as negligible. Further confirmation in favour of the larger dia. rods has been provided by By/Mr. Bowers who has calculated that the actual load exerted by the valve gear upon the push rods is in excess of the collapsing load of the 1/4" dia. push rod, whereas the 5/16" dia. rod has an appreciable safety margin. From the figures and results it is quite feasible to assume that the period at 2,000 r.p.m. is where the non collaps-ible strength of the rod coincides with the load to which it is subjected. Will you please hold up in the austractions for the push rods in regard to the release of the 100 sets of parts and in the meantime issue a detail drawing for the 5/16 dia. rods and for HPS.{Horace Percy Smith - Experimental Factory Mgr} to make 6 sets of rods accordingly. It is most important that we should get a set on the 15,000 miles unit in 26.G.VI. Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} | ||