Hi John,
You need to take a pinch of salt with some of what Gerry Tull wrote.
I never saw that pump working though I saw the loco running lots of times, and drove his gold medal winning 5"g IOW O2 based on Don Young's 'Fishbourne' design.
Gerry always said his whistle was 'special' for the O2. I never heard that either! He described in LLAS how he had researched how to make the perfect whistle. (He also described in LLAS how he made the pump).
Anyway jump on 30 or so years and Gerry's IOW O2 is now owned by a guy in the Isle of Man. At my request he very kindly took the whistle off the loco and measured it up and sent me pics. It is just a bog standard whistle – nothing special about it at all!
Bob has very kindly sent me the drawings of his own Westinghouse pump example. I would be very interested to know from Brian how he managed his own examples in 5"g.
Gerry was a wonderful guy and I am sure is sadly missed by many friends. I have quite a considerable correspondence with him, but unlike Brian my letters from Gerry have a printed letterhead with a printed picture of his O2 above!
The Southworth smallest pump is far too big for a standard gauge 5"g loco for scale size of a Westinghouse pump.
Cheers,
Julian