Author Topic: 3 inch boiler build  (Read 10137 times)

Offline Stuart

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Re: 3 inch boiler build
« Reply #30 on: July 13, 2018, 04:31:11 PM »
Gary
That line was aimed at the post above mine

I know you are making a only one but two are being discussed

I put that line in to prevent any misunderstanding if I was asked

Glad yours is from a published plan it should be ok

Sorry for the confusion
My aim is for a accurate part with a good finish

Offline Gas_mantle

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Re: 3 inch boiler build
« Reply #31 on: July 13, 2018, 04:35:31 PM »
Gary
That line was aimed at the post above mine


In that case can I make it clear that I haven't asked for calculations either  ;)

Offline Florian Eberhard

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Re: 3 inch boiler build
« Reply #32 on: July 13, 2018, 05:40:39 PM »
Hey Gary

I would grind off as much of the solder as possible. Just until you start to see the first spots of copper (a little bit is okay to stay there)
The Idea with the small tipped burr sounds good to me too, as long as you do not go further than approx. the half wall thickness of the end plate. Then apply a lot of flux before resoldering.
For the soldering job, I would use the sievert torch to heat up the whole boiler shell and then the oxy-mapp torch to get the joint up to soldering temperature when the boiler has reached a certain temperature (when it gets dark on the surface)
For that you will need to adjust the torch so you actually have a bit too much mapp. With that flame, the heat is a bit more even and not just on one point (not much though!). Then you will have to move the flame around the whole end plate so you heat it up evenly.
Also important: you should melt the solder with the heat of the copper and not with the flame! To apply solder, remove the flame and then apply solder to the joint.

I don't know if all silver soldering fluxes behave similar but the flux i know starts to get liquid and then when small drops of it start to move away from the flame i am just about to get to soldering temperature.

Oh and about what to solder first:
It looks like you first solderd the back end of the boiler into the boiler shell and then (in a second step?) soldered the tubes.
That is just the way i would NOT do it.
The reason is that you connected the heavy parts first and so the heat will wander off pretty fast.
That means you would have to bring the whole boiler shell and the back end aswell up to soldering temperature - more or less at the same time as you do it with the smoke tube which is pretty difficult without overheating the boiler tubes or the already soldered joints.

The better way would be to first connect the two endplates to the smoketubes and then finally put that element into the shell. This way the heat consumption of both parts is a lot less different and that makes soldering a lot easier.
Of course sometimes you can't choose which parts are joined first. In that case you should apply the heat in about evenly divided to the two parts as the relation of their mass is!

And finally if you have solder applied on a joint and the joint is big enough that it can't be soldered at once, the solder will always run to the hottest spot of the part / joint (as long as it is liquid of course)

So, good luck with your repair and keep trying.

Florian
ps: I always put a lot of flux on the joings - especially with boilers - as it is a lot less expensive as the amount of solder or even copper you need for a boiler. Not to mention the time you loose when you have to do it twice (which ususally for a hobby does not matter though)

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #33 on: July 14, 2018, 09:40:30 AM »
Hi Florian -

Thank you so much for this.

I am knocked out by how much attention and expertise you have brought to bear on my boiler leak issue, and by your advice which I shall follow to the letter as you have clearly understood the situation completely.

Regarding my sequence of assembly, I don't know how you knew it but you are quite right. As a complete beginner, I was terrified above all of having big gaps between the end caps and the barrel, so I erred too much in the other direction, i.e. with caps that were so tight that I had to turn them down to get them in. I thought about making the caps/tubes structure first, but decided it could be a real struggle to get it into the barrel as a complete assembly, hence my decision. And, of course, I was unaware of the heat loss/conductivity issue that you describe. Something for me to do differently next time...

I also realise now that the bronze screws that I put in were unnecessary, especially given the tightness of the caps. They were just an expression of my insecurity  :)

A friend has just pointed out your Cochran boiler thread to me - it looks amazing, and I look forward to reading it.

Thanks again, and have a great  weekend.

gary


Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #34 on: July 14, 2018, 10:00:29 AM »
Gary, just as a matter of interest can you remember what gauge of copper you used ? I realise that isn't anything to do with the problem you are having but I'd like to compare what you used with the materials I have  :)

Peter -

here are the details:

Barrel - C106 copper tube 3" diameter x 7" long (16swg)

End caps - made from C106 copper sheet, thickness 2.0 mm (14 swg)

Central tube - C106 copper tube 1/2" diameter (20 swg)

Outer fire tubes (x4) - C106 hard drawn copper tube 3/8" diameter (16g)

All of the copper came from GLR Kennions apart from the outer fire tubes, which came from Macc Models. These suppliers advised me on grade, thicknesses, etc.

All of the bushes are bronze, purchased from Polly Models.

I hope that's helpful - feel free to let me know if you need any more info.

All the Best,

gary

Offline Gas_mantle

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Re: 3 inch boiler build
« Reply #35 on: July 14, 2018, 10:02:58 AM »
Thanks, I'll have a look at what I have later. I need to do a bit of homework and plan things a bit before I make a start  :)

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #36 on: July 14, 2018, 10:06:52 AM »
Good luck, and Enjoy!

 :ThumbsUp:

Offline Florian Eberhard

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Re: 3 inch boiler build
« Reply #37 on: July 14, 2018, 01:37:42 PM »
Hi Florian -

Thank you so much for this.

I am knocked out by how much attention and expertise you have brought to bear on my boiler leak issue, and by your advice which I shall follow to the letter as you have clearly understood the situation completely.

Regarding my sequence of assembly, I don't know how you knew it but you are quite right. As a complete beginner, I was terrified above all of having big gaps between the end caps and the barrel, so I erred too much in the other direction, i.e. with caps that were so tight that I had to turn them down to get them in. I thought about making the caps/tubes structure first, but decided it could be a real struggle to get it into the barrel as a complete assembly, hence my decision. And, of course, I was unaware of the heat loss/conductivity issue that you describe. Something for me to do differently next time...

I also realise now that the bronze screws that I put in were unnecessary, especially given the tightness of the caps. They were just an expression of my insecurity  :)

A friend has just pointed out your Cochran boiler thread to me - it looks amazing, and I look forward to reading it.

Thanks again, and have a great  weekend.

gary

Hi Gary

Most of the Information can be read on your picture:
The joint of the smoketube on the outer left has been overheated (the porosity of the solder tells me that). Therefore I take it you have tried soldering for a longer period of time and at some point also reached quite high temperatures. The rest is experience i made myself (not being able to solder a joint when the heat of two parts was not the same)

If you don't feel comfortable to solder the tubes and endplates first out of the shell, you can also do it in the shell. For this you will need to apply plenty of flux and put a piece of solver bent into a ring shape around every tube. (if you have a thick soldering wire you will only need to do 2/3 of the full circle - it only has to stick to the tube and not be able to run away when the water is evaporated from the flux)
Then heat up the whole thing to soldering temperature. As soon as you are there (you should do this with the big torch for an even heat distribution) and the solder penetrated all the joints, you can continue soldering the end plate into the boiler shell, feeding solder with a rod this time.

This whole process can be done pretty quick if you are prepared and then you don't have any issues because of burnt off flux.
Then repeat the whole thing on the other side (which should be covered in flux also - and before you start with heating up!)

The use of bronze screws is a really good idea! I usually do it with copper wire. This is a way to fix all the parts to where they belong and not at all a sign of not knowing what you do (rather the opposite!)

Cheers Florian

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #38 on: July 15, 2018, 09:42:08 AM »


Most of the Information can be read on your picture:


Well, I still wonder if you might be a detective as your day job. Or if boilermaking might be your day job and detectiving a spare-time hobby   :)  .

Your explanation is very helpful indeed. I have been busy with other things the past couple of days but when I get back on to the boiler I'll do as you suggest.

There's only one thing now that I'm not too clear about: other knowledgeable people on this forum have suggested that I flux the whole end cap, which I think is to protect the other joints if the solder should remelt. However, in your very interesting Cochrane boiler thread (which I am currently reading right through), you say that you only flux the spots that are going to be soldered. I realise that there are different ways of doing things, but am interested in whether or not you recommend that I cover the whole end plate in flux, or just flux around the end of the tube.
Also perhaps worth bearing in mind here that I have used three different grades of silver solder overall, that the end plates and tubes were done with high and medium temp solder, and that I am now using low temp for the repair.
Having said this, it may well be that on such a small area any flux will run all over it anyway...

I hope others looking in don't feel I'm ignoring their suggestions or going round in circles with my questions, but I would really appreciate your thoughts on this particular point, Florian.

Finally, on the bronze screws - ok, I'll take the credit for that while it's going - thanks!   ;)

 :ThumbsUp:

gary

Offline Stuart

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Re: 3 inch boiler build
« Reply #39 on: July 15, 2018, 12:23:40 PM »
Clean work , plenty of flux ( esp. on tube plates and foundation rings)

You can limit the flux a little for bushings

Flux is cheaper than silver solder and gas

And do not do it in bright sunlight ,you will not see the colour of th job subdued light is best
My aim is for a accurate part with a good finish

Offline Florian Eberhard

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Re: 3 inch boiler build
« Reply #40 on: July 15, 2018, 04:21:02 PM »
Hi Gary

Nope, but i am an engineer and so i guess it comes with being an engineer to observe every detail  ;)

I would have just put the flux where I need it. But plenty of it then. The flux would by the way not protect the other joints pretty much (only from oxidation) since the solder is already in its place and made contact to the boiler components.
I also have to mention that this (flux thing when reheating it)  is not any knowledge that I was taught, its just what seems logic to mee. So probably there is a reason for putting on some flux again that i don't know.

Oh and Stuarts point about the sunlight is a very good one too! Because in bright sunlight, the copper will look only dark whereas in the shadow you would see it glow dark red!

Florian

Online Jasonb

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Re: 3 inch boiler build
« Reply #41 on: July 15, 2018, 04:33:34 PM »
One reason for fluxing the whole end is that if the heat spreads and causes a hole to open up around another tube and you see it you can quickly feed in some more solder. If it were not fluxed you would then have to let things cool, then have the cleaning problems again followed by resoldering another joint. I'd rather spend 10 seconds putting on a bit of extra flux than risk having to go through the whole process again.

Offline Florian Eberhard

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Re: 3 inch boiler build
« Reply #42 on: July 15, 2018, 04:45:01 PM »
Hi Jason

Though without flux, the hole wouldn't open up as easily as with flux.
But if there is the danger of a hole opening up, I agree it is easier to just put some flux on it and you're good then.

Florian

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #43 on: July 15, 2018, 04:53:11 PM »

Nope, but i am an engineer and so i guess it comes with being an engineer to observe every detail  ;)



And me? I'm a family and systemic psychotherapist for my job, so it's fairly similar in that respect :)  .


Thanks to you all, gentlemen.

I'll think about what you have said and make a decision about the flux.

Hope to get it done before I go off to France next weekend.

Will let you know how it goes.

Florian - your Cochrane boiler is a thing of rare beauty.

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #44 on: July 17, 2018, 10:58:59 PM »
The saga continues.

Following good advice from quite a few of you guys, I 'dremelized' most of the silver solder off the offending tube end, swabbed it with acetone and put a large dollop of flux around the end of the tube. When heat was applied the flux ran all over the cap anyway so not a dilemma after all.

Then began my first problem: no sooner had I got the whole boiler up to the temperature at which it turned black than the Sievert torch went out and was very tricky to relight again in the 'heat' of the moment   :) . I struggled with this for a while, particularly with the fiddly and counterintuitive bottle regulator that came with the torch. At this point I was acutely aware that all the time the boiler was losing heat, so I swapped over to the oxy-mapp and concentrated on the end plate. I found it difficult to hold the oxy/mapp mixture steady to a 'soft' flame, and this torch also went out on me and I watched in dismay as the top of the boiler turned into a sooty mess as I fumbled about trying to relight. I despondently let the boiler cool and threw it back into the pickle, resolving to find out what I was doing wrong with the torches (though I didn't remember having this much trouble with either of them before apart from the time the nozzle of the Sievert was loose) and thinking I was back to square one again.

Half an hour later I fished the boiler out of the pickle to look at it. Imagine my surprise when I saw that the joint in question had formed into a smooth, round pristine collar of silver solder round the neck of the tube. It's now the best-looking joint on the boiler, and unless anything else opened up with the heat (and I have no reason to think that happened) it may be that the boiler is now intact.

I say 'may be'. It went straight back on to my hydraulic testing rig. When I upped the pressure I noticed a leak from where the neck of the adaptor I had made for the test pressure gauge was screwed into the boiler bushing so I took a spanner to tighten the adaptor ... and sheared off the threaded section at the end!
Wonderful things, screw extractors...

Maybe I should have made the adaptor out of bronze instead of brass... but in any case I'll have to make another one before I can re-test the boiler, and realistically I may or may not have time to do this before I go off to France on Saturday. I might have to spend the best part of the next three weeks in trepidation about the moment of truth that I have to face shortly after I come back on 6th August.

Am I completely useless or is this normal for beginners?

 :paranoia:

gary