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).
Quieting the timing gears on experimental Wraith III units, addressing 'whine' and 'rattle' issues.
| Identifier | ExFiles\Box 136\1\ scan0275 | |
| Date | 19th January 1938 | |
| To By.{R.W. Bailey - Chief Engineer} C. to Hs.{Lord Ernest Hives - Chair} C. to RHC.{R. H. Coverley - Production Engineer} c. to Da.{Bernard Day - Chassis Design} c. to Mx.{John H Maddocks - Chief Proving Officer} c. to La.{L. A. Archer} WRAITH III TIMING GEARS. We give herewith our experience with regard to quietening the timing gears on the Experimental Wraith III units up to date. Regarding "whine", we have had very little trouble in getting rid of this feature in any of the units. In each case of "whine", the gears when checked were found to have desorepencies with regard to their relative tooth helix angle. Such cases have been quietened at the first attempt at stoning the gears and we are of the opinion that when produced on a production basis with correct helix angle, there will be little or no trouble due to "whine". Gear rattle has been much more persistent, however some progress has been made and we anticipate that eventually all objectionable rattles will be eliminated. On the first Wraith III unit which went to France originally in 26.G.IV there was a very bad low speed rattle which at that time we could not touch, either by alteration to the cam balancer or reduced back lash in the gears. Since that time however we have found that this was due to fore and aft movement of the camshaft and set up by the thrust exerted by the cone faced tappets on the cams. By means of a simple spring loaded plunger arranged between the wheelcase and the nose of the camshaft this rattle is entirely cured. Based on these results, the plunger has been adopted for Wraith in accordance with the scheme EOD.402. When we reduced the valve lift from .400 to .350 to improve valve gear noises, this rattle was reduced appreciably in intensity but is still sufficient to warrant the thrust plunger. Up to the moment we cannot find any merit for the | ||