Tube runs for injectors

[Michael CallaghanParticipant @michaelcallaghan68621]

Well I am almost at the stage of thinking about injectors. The twin clack valve is at the top of the boiler around 3 inches back from the smokebox. The tubes need to run down the sides of the boiler to the running boards. And here things get tricky. The model by the way is a 5inch gauge royal Scot. My only option I think is to fit a 90 degree bend which will be fit nicely behind the name plate and then run the tubes along the running boards to another 90 degree bend which will take the tube down to a 3rd bend and into the injector. My fear is that 90 degree bends are not a great idea within injector tubing. But I can’t imagine any other path. It’s very busy between the frames and then I would still need 90 degree bends to clear the firebox grate. As anyone got 90 degree bends in their injector pipe work and are you ok with it. Thanks

[BazParticipant @baz89810]

Shouldn’t have problems with 90 degree bends, keep the bends as big a radius as possible. The problem comes when using elbows.

[Michael CallaghanParticipant @michaelcallaghan68621]

Thanks, looks like I need to make a bending tool now

[noel shelleyParticipant @noelshelley55608]

You do not mention what size of pipe and though I expect 8mm to be way to large, 8mm end fed swept elbows are available at about £4 for 10. Noel.

[Nigel Graham 2Participant @nigelgraham2]

Without compromising the locomotive’s appearance, can you alter the first two from the injector to 45º bends with a sloping leg between them? This would reduce the bends loss slightly, and might not even need joints. I don’t know the Royal Scot design nor what space you have available on the model, but the injector pipework on some full-size locomotives did use slopes in that area.

8mm pipe and solder fittings are used for micro-bore central-heating systems so are easily obtainable; but are too hefty for a 5″ g. locomotive’s plumbing. It might be possible to find smaller from suppliers to refrigeration engineers and gas-fitters: the model-engineering suppliers tend to sell only union-fitting elbows.

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You can buy small plier-type tube-benders for 8mm and lower diameters from our usual tool-suppliers, and I have put mine (3 to 6mm I think) to plenty of use.

Yes, I could make a tube bender, and indeed had to make a new press-tool for my Rothenberger pipe-bending set; but really here we might ask if it’s worth taking precious model-building time to make a small tool likely to cost about the same in material and electricity to manufacture, as to buy! It’s worth buying a proper tube-cutter, too.

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A common practice is to experiment first with thick, preferably copper, wire to obtain the general shape and length of a wriggly pipe.

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