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).
Modifications to the 'Goshawk II' carburettor and addressing a cracked induction pipe.
| Identifier | ExFiles\Box 180\M1\1\ img055 | |
| Date | 12th September 1921 | |
| To HS.{Lord Ernest Hives - Chair} from R.{Sir Henry Royce} Copy to C.J. " W.O. " P.T. ORIGINAL SEP 12 1921 R10/G14/9/21. RE "GOSHAWK II". X4219 I was pleased to hear that the poor slow running could be accounted for by the cracked induction pipe. The difficulty of overcoming this may not be very urgent, but Mr. Elliott is making you sufficient designs to test. Regarding the carburettor proper, you will remember that we decided to make the floatchamber a little larger so that it would not be quite so delicate. Mr. Elliott is sending you particulars of this in the correct thickness of material for the float, which appears to have been the cause of the trouble. Regarding the throats, we agree that these shall be in brass or gun metal instead of aluminium, but the sizes originally suggested, namely, .500 and .750" appear to be quite correct when we consider that the 20 H.P. engine should do nearly 60 H.P. against the present 40 H.P. car engine doing 80 H.P. Regarding the springing of the extra air valve, this will be worked out to be exactly the same in proportion to the 40/50 H.P. so as to get to the top of its stroke with the same vacuum in the mixing chamber at the full H.P. which we understand occurs at 3,000 revolutions. I am suggesting a very definite modification to the extra air valve by lengthening the stroke so that it need not be quite so tight to fit. We think by making the stroke relatively longer than the 40/50 H.P. we shall have a better chance of getting the carburettor to work accurately. I have also suggested that the upper fitting part of the piston be lengthened and the use of an air tight groove in such a way that the mowement of this extra air valve will be slower than at present, so that it has a longer stroke and a more air tight piston to reduce its (Contd.) | ||