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

[lordedmond]

looking good

I told you would need a lot of heat as things progressed

what about the wet header bush and the stays in the smoke box?

good luck with the 2x wp test the joints look fine but until the pressure is up you never know


Stuart

just spent all day fitting out the smoke box plenty of dummy bolts and rivets to put in now I have to make up the working vacuum ejector for the side of the smoke box not looking forward to the ejector steam and vac cones

 

[doubletop]

Stew

Looking good; and an excellent reference thread for those of us who've never done this before. Not for the feint hearted I'd say. I've found I have all the parts for one of these in my stock as it appears my dad bought the whole Rob Roy kit and then had the boiler built professionally. So I may give it a go sometime.

The only thing I don't have in my toolkit is a John Bogs. Must do wonders for your confidence with one close at hand.

Pete

 

[Blogwitch]

Pete,

You are quite right, it is not for the feint hearted.

We were really a little under torched, but it is a very close thing between having too little heat and too much. It is very easy to undo previously soldered areas, and planning the stages and boiler position were the main issues, plus working as a team to get the heat and solder in the right place.

You are completely wrong when you say I am a necessary item in Stews toolkit, it was a combined effort, and Stew had just as much input as myself.

It was such a shame that we didn't get a couple of the tubes on the first firing, it is very difficult to see when the temp is on there and so much flux about. The first firing looked perfect, then we had to do the local repairs, which didn't come out too neat as we were afraid of remelting previous joints. But it is only cosmetic and should easily clean off with a little elbow grease.

John

 

[Paolo]

Hi stew
this is an excellent reference thread all of us. I'm following your post with particular attention, you know why, fingers crossed for your pressure test!!
Best regards
Paolo

 

[SBWHART]

Thanks for your good wishes Guys.

I spent the day making the blanking plugs for the pressure test, when it came to the steam dome I found that I was short of a couple of 8BA screws so they ar on order, I did notice that one of the backhead stays inside the firebox doesn't seem to have have any solder around it, so that causing me some concern, it's at the front so it can be got at. Don't know how it was missed because everything was carefully checked, but its not always easy to see what's going on, and I think repeated heating and pickling show things up.

We will see

Stew

 

[doubletop]

You are completely wrong when you say I am a necessary item in Stews toolkit, it was a combined effort, and Stew had just as much input as myself.

John

I wasn't saying a necessary part of the toolkit. Just that knowing you have the tools helps, but you may never need to use them.

EDIT

Actually that's all you guys. The online toolbox of knowledge

Pete

 

[SBWHART]

As it will be a couple of weeks before I can pressure test for real I was bitting at the bit just to do a low pressure test.

Before I go on just a warning so that no one gets the wrong message:- DO NOT CONNECT A BOILER TO A COMPRESSOR IT IS VERY DANGEROUS.

Ok what I did was make a connector for a bicycle pump, immersed the boiler in water and with a few strokes of the pump just enough to raise the pressure by a few PSI to see if there were any leeks, the only leeks I had were from the screw plugs for the regulator and the longitudinal stays which are easily fixed, there was nothing from any of the soldered joints:- so far so good.

Stew

 

[lordedmond]

get your self a bottle of Glenfarclas 105 to celebrate

http://www.whiskyshop.com/Shop/Detail.aspx?whisky=Glenfarclas-105-Cask-Strength-Whisky&pid=2569

beware though its about 140 degrees proof drink with care ;D


Stuart

 

[Blogwitch]

Stew,

I hope you made sure Dot wasn't anywhere nearby when you took it into the house to test it in the kitchen sink.

But thinking about it, you must have, you are still alive to post about it. :big:

Nice one.

John

 

[SBWHART]

Thanks Stuart/John

Dot was still in bed when I tested it, by the time she got up everything was cleared away ;D

Stew

 

[arnoldb]

Stew, that's good news from your test

Best wishes for the tests with the boiler inspector!

Regards, Arnold

 

[SBWHART]

Thanks for the good wishes Arnold.

I've had this on hold for a few weeks, as I've been waiting to have some pressure gages checked out I'd acquired them over the years and was not sure if they were working OK and I didn't want to test the boiler with them not being sure if they worked. The guy who was going to check them let me down somewhat so last weekend I retrieved them.

After giving it some thought I thought the best thing to do was to make a manifold so that I could compare the gauges one with the others (I've four to choose from) that way a faulty gage would be eliminated by the other three.

I connected them to the boiler feed pump I made, like this looks a bit heath but it worked.

I couldn't get the gauges to tighten so that you could see both faces.

But this is what I got.

They were all different scales but I was able to detect that one gauge was reading 20 PSI light so that was dumped the other three were Ok and gave similar readings with each other.

Tomorrow will know be the big day:-I'll fix a couple of leeks i've got with the screw coupling on the regulator and one of the screwed longitudinal stays, then it will be fingers crossed.


This will be own test if all goes well I'll cut the end off the stays off and submit the boiler for official inspection.

Stew

 

[Blogwitch]

Good luck Stew.

If you need a hand, just shout out.

John

 

[SBWHART]

Thanks John


Well I sort of tested the boiler yesterday, I took it up to 40psi there was a leek from the inside of the hollow blower stay, so I gave the nut a tweak, when ping the bloody thing broke.

:'( :'( :'( :'( :'( :'(

So did a bit of investigating the drawing calls for 5/32*22g copper pipe I was supplied 3/16*22g pipe as part of the boiler kit which I turned the end down and threaded 5/32 * 40 which had the effect of thinning the wall of the tube down that and being one turn short to tighten the nuts down resulted in overloading and the break. So I've got to order some 5/32 pipe next week before I can conduct the test again. On the positive side as 40 psi there was no signs of any other leeks.

Stew

 

[lordedmond]

looking good so far, don't forget take it to say 40 hold for ten mins let off pressure ,then take it to say 80 for ten mins then let it off



this is to work the copper a bit as its in a fully softened state at this time this will put some strength back into the copper


Stuart

 

[zeeprogrammer]

Sorry to hear about the pipe.

Neat idea with the pressure gauges.

 

[Blogwitch]

Stew,

If that is standard 5/32" (4mm) copper tubing, I have a load in the back of my shop.

I thought I had given you some, but if you want to call round, you can have a goodly length.


John

 

[SBWHART]

I thought that was 1/8 John ??? :- I'll check it out before I order any.

Thanks

Stew

 

[Blogwitch]

No Stew, it was 1/8" I gave you last week, I thought I had given you some 5/32" many moons ago, or it might have been someone else, the brain cells aren't too retentive nowadays.

But if you don't have any, there is plenty here for you to be going at. I will never use all I have.

John

 

[SBWHART]

An update:-

I've now tried two more blower tubes using tube from different suppliers, John and maccmodels, Johns tube was 5/32" I don't know what the wall thickness was, the macc tube was 5/32 * 22g (0.028 wall thickness) they both went ping when I tried tightening them down, now you're probably thinking I over tightened, but this is far from the truth, as a rule I'm what you would call a gentle engineer, some times I would admit I'm too gentle, and having one tube break I was extremely careful. The drawing calls for 5/32" tube it doesn't say what gauge. To put some numbers around the problem in the UK the standard gauge for 5/32 pipe seems to be 22g (0.028" or 0.71mm) this has to be threaded 5/32*40 ME that will leave a wall thickness less than 0.015" or 0.38mm no wonder it's breaking.

I'm left with a number of options:-

Find some 3/32 tube with a thicker gauge, I've located a supplier who has some 20g (0.036" or 0.92mm) tube but I think he will only be interested in supplying a couple of tons which is out of the question I'm going to call him on Monday and see if he will supply me a small sample (don't ask don't get)

I can get 3/16 * 18g (0.048" or 1.2mm) tube, I would have to increase the thread in the fitting to 3/16 * 40 ME this would leave me a wall thickness of 0.032" or 0.81mm or more than twice what I've got know.

Fit a solid stay and rout the blower around the outside of the boiler.

I think I'm going to go for the 3/16 tube unless any of you Guys can suggest anything else.

Stew