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).
Specifications for carburetor components including the suction piston, taper needle valve, and diffuser.
| Identifier | ExFiles\Box 13\4\ 04-page037 | |
| Date | 21th September 1932 | |
| -4- Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell}12/KT.21.9.32. (8) Suction piston & chamber. The diametrical clearance between the suction piston and chamber is .003 to .004, or circumferential clearance of .0015 to .002, throughout the whole lift, these limits must be adhered to, otherwise variations in the speed and travel of the piston will occur. It must be seen that the piston definitely seats on its bronze seat (E.33409) in the closed position. At full throttle the piston commences to lift at 550 r.p.m. and is fully lifted at 2700-2750 r.p.m., the maximum lift being .600 - .650 The movement of the piston must follow directly the throttle position whether opening or closing, without any signs of sticking. On assembly, the piston central steel guide and bearing should be lubricated with sperm oil. (9) Taper needle valve. The needle valve has a straight sided taper, the larger diameter being .145 and the smaller diameter being .095, the length of taper 1.075". The needle is pivoted on a pin (E.17652) which takes its bearing in the piston guide and should possess a universal action to allow for variations in alignment. Occasionally we have had trouble with the piston sticking due to the needle binding in its guide, but if this is lightly tapped in during assembly, no further trouble will occur. (10) Diffuser. The diffuser has a ful bore of .213 and higher emulsion bore into which the air bleeds of .250 diameter. There are two rows of bleed holes, the top row consisting of 4 - .039 diameter, and bottom row of 4 - .055 diameter holes. The delivery from the diffuser into the choke is through 4 holes - .125 diameter. In the outer guard tube (E.33067) the 4 main air intake holes are .125 dia. All the burrs after drilling the above holes should be removed before assembly. Between the top of the inner guard tube and the diffuser body a clearance of not less than .100 should be maintained | ||