Building a Boiler for a 3 1/2" Gauge Locomotive

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sbwhart:
Thanks Nick that would be useful

Stuart

Thats a good point about the seal I've bin thinking that screwing the joints up tight mite not be the right way to go to get a seal, the hollow stay has to take the loading from the boiler pressure on the tube plate, so any additional load from tightening is not a good idea, I was thinking of using bosswhite or somesuch sealant, how does the copper slip work does it need to harden off with the heat from the boiler ?.

Thanks very much all for your input.

Stew

NickG:
Stew,

I was thinking the same last night when I took mine out. (sorry no pics yet) It's designed to seal on the screw thread itself rather than up to a shoulder I think so it doesn't need to be tight and as you say, it could make it worse when it's compounded by the boiler expanding longitudinally.

I measured mine as best I could and it's 5/32" OD and I measured 0.098" ID so probably 22g the same as you had. it seemed fairly robust when I was screwing it in hand tight into the front tube plate bush - I think it should only be hand tight, you just need some sort of sealent.

Is your tube soldered into the valve at the backhead end? Mine is.

Been thinking about it again and hopefully when the new boiler inspector sees it, he'll agree to leave it unsoldered as it would be handy to be able to get it out if it ever gets blocked. Otherwise I think I may to a solid stay and route outside. I had problems once with an old 5" engine I had with the hollow blower stay being bunged up.

Cheers,

Nick

Thanks,

Nick

sbwhart:
Thanks for that Nick

I've just had delivered a 5/32 solid stay but I'm thinking of having one more go with a hollow stay with some sort of sealant.

I wasn't thinking of soldering the valve our boiler inspector doesn't seem to concerned if its soldered or not.

Cheers

Stew

lordedmond:
Stew

boss white will do but copper slip will enable you get the threads in they will be 99.9999999% of the time out of phase that in its self will ensure a seal

but as I said use a solid one with a a pipe out side , a hollow stay will not add that much strength anyway

BTW my chassis and boiler are going to Myfords open day and to the Warwick show on the NSMEE stand

sbwhart:
Thanks Stuart:- I'm going to try copper slip, I was thinking of going over to the Myford show I under stand they have lots of kit for sale recovered from workshop clearances, If I go I'll look out for your loco, will you be their ?.

Well today i took delivery of a solid stay, it didn't break but a I still had difficulty getting the threads to seal I tried ptfe tape but the joints just kept weeping, next try I'll use copper slip.

But I did get it up to 160 psi a couple of times and it held pressure long enough for me to check out all the soldered joints and they were all good, I'm now going to cut off the spikes and book the boiler in for a test with the inspector.

:D :D :D :D :D :D :D :D

Happy Stew

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