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).
Notes on valve assembly details, covering hardening, dimensions, and seating issues.
| Identifier | ExFiles\Box 99\3\ scan0050 | |
| Date | 19th January 1938 | |
| -6- The depth of the .4687" dia. bore(2.975") requires increasing by at least .025" to permit a more generous allowance for valve adjustment without the valve sleeve fouling the .4375" dia. section. Valve Assembly details. The Valve adaptor FB.3462 being cyanide hardened after final machining tends to "grow", consequently either allowance must be made on the sealing diameter prior to hardening for this increase or(as in the case of the first set of dampers) it must be reground to size after hardening. It is essential that the sealing section be a good fit in the bore, therefore the latter method seems to be preferable. The same remarks apply to the valve sleeve bore. A feature which is not acceptable from an inspection point of view, is that the root diameter of the thread is less than the sealing diameter, consequently the thread cannot be cut with a die, nor can it be inspected with a screw gauge. This can of course be overcome by reducing the "sealing" diameters in the cartridge and the valve adaptor to just under .420", the disadvantage being that these diameters become non-standard dimensions. It is particularly important that the burrs be removed before hardening. The depth of the valve seat must be given as a definite dimension from the top face of the adaptor, and the valve and sleeve assembled to close limits, or the valve must be given a definite clearance(.025") to allow for an adjusting washer - the latter is shown on the scheme but not provided for on the details. The seating bore of the valve adaptor possesses a +.005" limit, equivalent to a 6% variation in area, also permitting variation in the depth of the valve seat relative to the face of the sleeve - this is a point requiring the allowance for the adjusting washer previously mentioned - and should be reduced. It is also essential that the seating bore be true with the sleeve bore, at least until such times as the test section determine the rate of valve leakage permissable, and even so depends upon whether such leakage is best obtained by prelifted valve or by drilling the valve. continued | ||