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).
New design for flat barrel type tappets for the Phantom III engine.
| Identifier | ExFiles\Box 96\2\ scan0286 | |
| Date | 2nd May 1938 | |
| BY/NS{Norman Scott} c. Rm{William Robotham - Chief Engineer} c. Rm{William Robotham - Chief Engineer}/Swdls c. BY/B Files DA{Bernard Day - Chassis Design}/2/G.2.5.38. 354 PHANTOM 111 - FLAT BARREL TYPE TAPPETS. Herewith please receive E.CD.635 Camshaft and Barrel Type Tappets - Phantom 111. The objects of this design are to eliminate the necessity for chromium plated tappets, to reduce tappet wear, and to reduce cost. The new tappets are in cast iron with chilled flat contact face, the cup for push rod being at the upper end of the tappets to avoid lengthening push rods, the cams are narrow and offset .175" from axis of tappet for the purpose of revolving the tappets. In view of Wraith 111 experience, the valve lift is reduced from .400" to .350", and as we have been able to just squeeze in 1.000" diameter for tappets, we have retained the standard rocker arm ratio of 1.333 to 1, giving a cam lift of .2625". Will Mr. Bower please look into the figures for the revised cam form to suit the requirements of this design. It will be noticed that in accordance with the request of Rm{William Robotham - Chief Engineer}/Swdls. we have made the push rod and tappet spherical cups of sufficient depths, to prevent the push rods jumping out of their cups if a valve should stick in its open position. In order to get in the 1.000" diameter tappets, we have had to cut away a portion of each top half of camshaft bearings, the cams and tappets are also slightly re-spaced, and this slopes the push rods a little in the side elevation. The crankcase, cylinder head, valves and rocker gear are unaltered by this design, except for the longer tappet adjusting screws to suit the deepened spherical cups at top of push rods. Will you please detail and instruct the necessary parts for the experiment. Particulars of the cam forms will follow. DA{Bernard Day - Chassis Design} | ||