Gas burner for pot boiler

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GTB
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Re: Gas burner for pot boiler

Post by GTB » Tue Aug 09, 2022 3:12 am

jefran wrote: Mon Aug 08, 2022 6:06 pm The original union was silver soldered directly into the tank, so I will have to plug it: is there a better way than soldering a piece of 1/8" rod (rather than copper pipe) into a nipple and tightening it in with a union nut?
I make my own pipe fittings and just turn up a blank cone when I want to block off an unused line. Soldering an offcut of brass or copper rod into the cone, or olive, might be a bit quicker I suppose.

Grant is likely thinking of wear in the chassis bearings and after 20 yrs in storage, oil could also dry out and turn gummy. It would probably be easier to support the loco upside down on the bench and run it on air, than fiddling around with an airline outside on the track.

As you did, it is always good practice to do a hydraulic test on a pressure vessel after any repairs, or modifications. It wouldn't be the first time a silver soldered joint opened up a pinhole when reheated.

My comment about compressors when testing on air was just putting numbers on why a chassis can sometimes run better on air than on steam. A workshop compressor is an unlimited supply of air for a small loco chassis, while model boilers can usually only supply just enough steam to successfully run the loco. when everything is working properly. I'm not sure if measuring air usage would tell you much, but it would be easier to do on the bench than on the track.

Graeme

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Re: Gas burner for pot boiler

Post by jefran » Tue Aug 09, 2022 6:02 pm

Progress has been affected by a family bereavement, so please don't think that I am ignoring you if I don't give much in the way of response for a few days.

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Re: Gas burner for pot boiler

Post by jefran » Thu Aug 18, 2022 5:34 pm

I have had some opportunity to do a little more; I blanked the union with a 5/32" ball with some PTFE tape spread across the union body. It held tight on air-under-water at about 30 psi. I have had the whole loco together, the radio control connected and tried it yesterday afternoon with mixed results. The burner is certainly much less prone to go out, but it is very, very quiet and when turned up at all I was seeing orange flames above the boiler and that suggests to me that I need to enlarge the air holes by the jet, to draw in more primary air. The loco, once again, barely moved itself, let alone the train I had assembled. I brought the airbrush compressor down and set it to provide air at around 30 psi and the loco ran up and down, with train connected and the compressor was running between a third and a quarter of the time. I was relieved to see it run, but it wasn't as smooth as when on blocks.

This morning I put the loco back on blocks and tested the glands with soapy water: they all blew. They were all made with O rings, 3/32" ID on the steam chest and 1/8" on the piston, but to replace these was going to be very difficult, so I have tried twisting a length of PTFE tape and wrapping 3 turns round the valve spindles and 4 on the piston rods, but with the O rings still in place to press the tape into the body of the gland. The loco now runs more smoothly (on blocks) and very slowly, so I will try the loco out on compressed air on the railway when I get the opportunity.

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Re: Gas burner for pot boiler

Post by LNR » Fri Aug 19, 2022 1:01 am

What's the phrase, "slowly slowly, catchee monkey" glad to see you are making progress slowly.
Grant.

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