This is the crosshead pump on the right side of the 3003. I will build a similar pump for my model, and just obtained the stainless steel balls needed for all the pumps and valves. (surprisingly cheap, 100 stainless balls each of 4, 5 and 6mm diameter cost only US$ 9, i.e. 3 cents per ball!)

The original locomotive has cup-formed valves inside the pump, but they're impractical in 1:8 scale. In addition to this crosshead pump, it has an injector on the left side - this I will make as a mock-up only, I believe the crosshead pump will be effective enough, and I will also have an emergency hand pump in the tender. Naturally, there will be check valves on all the boiler feed lines.

This is the silver soldered but yet unpolished pump body. The stroke is the same as the piston stroke, and the plunger is of stainless steel Ø 6 mm (1/4"). There will be a gland with an O-ring to seal the crosshead end of the pump cylinder. The air chambers are purely cosmetical, but do contain the ball valves.

Tender Pump

I already made the tender pump (it doesn't exist in real size), with two ball valves and a 10mm plunger of brass - the pump is powerful enough to bring the pressure up to over 10 bars (150 lb/ with just a squeeze of the thumb! (In fact, I could have got the needle exceeding the scale, but didn't do it, in fear of busting the manometer...)

Here is a drawing of the teder pump - thanks to the ball valves, the pressure held pretty well after I stopped pressing the plunger (which did leak a little since the O-ring was still missing when I did the test). I got a shower of water when I unscrewed the manometer from the pump! So, I expect no problems feeding water into the boiler, where the working pressure will be less than 8 bar (115 lb/

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