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).
Modification to the tappets for the Wraith III model.
| Identifier | ExFiles\Box 10\3\ 03-page067 | |
| Date | 4th September 1937 | |
| E.{Mr Elliott - Chief Engineer} Dept. c. to Rm{William Robotham - Chief Engineer} c. to Hm{Capt. W. Hallam - Head Repairs}/Swdl.{Len H. Swindell} c. to Eb. Leder 654. WRAITH 111 - MODIFICATION TO TAPPETS. Please receive herewith E.CD.50 Modified Crankcase to suit inclined tappets. This design is in accordance with the request in Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}1/R.10.9.37. and includes the following altered features from the original design to LeC.5504.- (1). Face of tappets made slightly conical and tappets inclined to suit, to ensure tappets revolving. (2). The spherical cup for push rod is moved to inside bottom of tappet instead of in cap at top of tappet. (3). The spiral oil groove is deleted from tappet outside diameter, and a larger diameter hole is shown for draining tappet. The following experiments are also included in this design :- (1). Tappets running direct in crankcase material viz. the A/F guide bushes being omitted, the tappets have been lengthened by .125 to maintain the same length of tappet in contact with the bore. The crankcase casting is unaltered, so that the bushes may be reinstated, if found necessary. (2). A small suction release hole has been drilled into the spherical cup in tappet to prevent tappet lifting out of crankcase when removing push rod, this is an alternative suggestion to fitting a retaining plate inside tappet cover as suggested in Rm{William Robotham - Chief Engineer}/TNW.4/JAB.26.7.37. (3). As the maximum width of cam contact on the conical face of tappet is only .212, an experiment should be tried using narrow cams .300 wide, and offset from centre of tappet .275, the tappet face being flat and the axis of tappet vertical as shown in Figure 11 on E.CD.50. It is not suggested that this will be a better job than the conical inclined tappet, but it appears to be worth trying, for if it is as good as the conical tappet it will be much cheaper and simpler to make. | ||