Norman and Bob, I also used an LBSC design as the basis for my pump. This was from the DIANA 4-6-0 G1 locomotive which assumed a casting for the pump body was available. I made my body from brass stock, silver soldering the various bits together.
As the Graham engine runs at much higher rpm than the average G1 steamer I first geared it down 2:1 and I also reduced the ram diameter to 1/8". I have a bypass valve going back the the water tank. When I start up the Graham the bypass is open so the pump is not working against pressure. Once the Graham twin is warmed up the bypass is closed. There is a small reduction in rpm as it works against the boiler pressure, but it's not significant and it drives the loco just fine at nice prototypical speed in low gear. Bob, if it won't pump through the check valve then I'd suspect the valve seats for the ball valves. They may be seating OK with little back pressure, but failing under pressure. I used the usual "whack the ball with a hammer" technique to create the valve seats and they work fine. The other thing is to make sure you have cut slots in the openings above the ball valves so the valves don't close off the outflow ports if they lift too far. I forgot this on the inlet ball valve and sure enough it locked up. I detected it when the boiler cooled. I'd closed the bypass so that the vacuum would suck water through the pump and fill the boiler. Well it started and you could hear the ball valve clicking until it finally locked up against the opening above it. Cutting the slots cured this and I ended up with a nice working pump. It also refills the boiler under vacuum silently. Cheers Keith -- ======================================================================= Keith Manison Phone (876)702-0337 7 Mulberry Close Fax (876)702-0661 Jacks Hill P.A. Email [EMAIL PROTECTED] Kingston 6, Jamaica W.I.
