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).
Instructions for modifications to the Wraith III engine, concerning valve guides, oiling arrangements, and tappets.
Identifier | ExFiles\Box 108\2\ scan0011 | |
Date | 3rd February 1938 | |
By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} c. to Da.{Bernard Day - Chassis Design} 600 also 654 Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}1/AP.3.2.38 WRAITH III. Will you please instruct for the following on the 100 sets of parts which are being ordered:- (1) Valve guides EB.3238 raised from .405 to .450 which in conjunction with latest valve grummets give a correct settled down length of valve spring in the closed position of 1.525. We have reproduced the above on the 15,000 miles car by making grummets which are thicker by .050. (2) Although the existing valve oiling arrangement is satisfactory over general running it is a slow process to get oil to the bottom tappets when first starting. By bringing the oil feed holes in the rocker shaft more in line with the rocker holes feeding the push rods this condition is improved and in addition to our own test has been confirmed on the first production built engine by LA.{L. A. Archer} Will you accordingly include this mod. on the LOP. for 100 sets, which is - 6 - .075 dia. holes raised from the present horizontal position to a 10º upward inclination. (3) Although we have had little or no tappet wear on the outside diameter one of the tappets on the first production engines was badly worn and showed signs of digging in on the sharp bottom crankcase guide edge. We should like this to be radiused sufficient to take away the razor edge. The limit allowed on the bottom tappet in its guide appears excessive .001 nominal to .003 maximum and would recommend this to be reduced .001 nominal to .002 maximum. (4) By experience gained on Phantom III. regarding oil getting down the inlet valve guides, will you please arrange that the diametrical clearance between the inlet valve and its guide be made between the limits of .0015 and .002 as per Phantom III. Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} | ||