Yet another boiler making question

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Yet another boiler making question

This topic has 11 replies, 5 voices, and was last updated 20 December 2009 at 15:33 by mgj.

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18 December 2009 at 20:26 #4886
Tony Martyr
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@tonymartyr14488
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18 December 2009 at 20:26 #46388
Tony Martyr
Participant
@tonymartyr14488
What is the best way of getting a small part of a larger copper section up to silver soldering temperature?

I have found no problem in using a 710 deg C solder running on the backplate bushes when the plate is lying on a thermal blanket and I use a large nozzle.

Soldering the tube plate of the firebox with easyflow was OK

But reheating a missed rivet head on the top of the firebox and soldering with Easyflow has been a nightmare.

I have tried stuffing thermal blanket inside the box and all around the critical area but the heat seems to flow out of the mass of copper. Is it better to use a small nozzle concentrated on the spot? I assumed that the hottest part of the flame is just at the end of the blue inner flame – is that correct?

I dread the idea of silver soldering the boiler stays if I can’t get these small areas up to temperature without blasting the whole surface with my biggest nozzle.

I know that the remelt temperature of these solders is higher than the first melt but does that mean that solder wire that has bent because of unsuccessful attempts to apply it to material that is not quite hot enough, is more difficult to melt?

(Must get a refilled propane cylinder before Christmas!)

Tony
18 December 2009 at 21:01 #46389
Les Jones 1
Participant
@lesjones1
Hi Tony,

You could try using your large propane burner on a low setting to heat the bulk of boiler up to something like 500 deg C and then use one of the small torches that use a cylinder about 3 ” dia. and about 9″ long to heat the local area. These cylinders are available with either propane or MAPP gas. The MAPP gas is hotter than propane so this might work. Screwfix seem to sell the cheapest torch at £17.54 but they no longer sell single cylinders of MAPP gas (Sometimes called MAP Plus) Toolstation sell the MAPP gas but their cheapest torch is £38.20. Maybe a good plumbing suppliers will have both items. The other option would be to find someone with oxy/acetylene.

Les.
18 December 2009 at 21:36 #46393
mgj
Participant
@mgj
Tony, I have no experience of copper boilers as such, beyond reading Alec farmers book.

Inside the firebox was a heat problem, and he mentions it specifically.

With respect Les, oxy acetylene is not generally recommended for silver soldering, especially with the cadmium bearing alloys. However, Tony may be a dab hand with the high temp localised heat toches? Farmer’s answer was a second propane torch. A big Sievert nozzle clamped in place to provide general heating, and then a second torch, with either a cyclone burner or a more normal sized burner as appropriate which is the one you hold and manipulate.

Anyone live near you with a torch you could use.

If all else fails, pm me and I can lend you a torch and 2 bar regulator. May not be ideal, but its better than spending another £50 with Machine Mart, plus the big burner.
18 December 2009 at 21:49 #46395
Les Jones 1
Participant
@lesjones1
Hi Meyrick,

This it what I like about forums like this. Even when not asking a question you learn things. I think I have read somewhere that MAPP gas has some similar characteristics to acetylene so that may rule out my first suggestion as well. (I am assuming some reaction between cadmium and acetylene.)

Les.
18 December 2009 at 21:49 #46396
John Baguley
Participant
@johnbaguley78655
Tony,

is it just a rivet you’ve used to hold the firebox wrapper to the tubeplate and end plate whilst soldering these joints? I presume you haven’t installed the firebox into the boiler shell yet?

If so, I wouldn’t worry about it at this point in time. Wait until you’ve got the whole boiler assembled and you come to do the stays which you obviously intend to silver solder. You are going to have to get the whole firebox and outer wrapper damned hot to do the stays anyway so try and put a dob of Easyflo on the offending rivet then (inside the firebox). There’s a good chance it probably sealed anyway with the solder that has been drawn into the initial joint.

Incidentally, you’ll probably need to get a Cyclone burner to do the stays inside the firebox. If you have already soldered on the firebox backplate it’s very difficult to keep an ordinary burner alight in such a small space.

John

Edited By John Baguley on 18/12/2009 21:53:43
18 December 2009 at 23:24 #46400
mgj
Participant
@mgj
No Les, its just that an oxy acetylene flame is very hot, but without all that much energy, so 3 things are possible.

1. The localised heat can overheat the flux quite easily.

2. You can cause the cadmium to boil off – if using Cd bearing alloys.

3. You are more likely to cause heat distortion.

Whether those comments also refer to oxy acetylene with a proper multiflame brazing nozzle I am not sure.

Its just the old heat versus temperature thing.

——–

No Tony – you don’t alter the liquidus by heating, and bending the wire. (Unless you have done something terrible to the alloy!) The problem very often is getting enough heat into the wire to melt it, without it being melted by the torch flame first. If you can, heat from the far side – that way you are sure that its the heat of the joint that melts the wire. Loadsa flux provides a hot lake. Or try a thinner wire. I have changed to 1mm sticks for that reason.

Edited By meyrick griffith-jones on 18/12/2009 23:25:51
19 December 2009 at 09:12 #46406
Tony Martyr
Participant
@tonymartyr14488
I noticed in one of the books a photograph of a boiler being soldered with two or more people and two torches involved. Perhaps I will have to recruit my son two wield the big torch while I deal with a smaller one plus the solder.

As it is I find handling thin solder and a powerful flame while wearing heatproof(ish) gloves is quite tricky and the garage window ledge already bears witness to how tricky!

I have posted a photo of the firebox in its rough, post soldering, state and there are 2 rivets that do not show solder rings around the heads, one on the side plate which is probably OK and one holding the crown stay which may not be OK because the surface contact is lost on the radius of the stay.

I am going to give the box a proper dressing over and consider what to do after the Christmas clean-up of the workshop.

Thanks for the help

Tony
20 December 2009 at 09:01 #46439
Ian S C
Participant
@iansc
Speaking of 1mm silver solder,I see its being sold in coils on Trade me the NZ trading site at quite a reasonable price,so if any fellow Kiwis are interested……..
20 December 2009 at 09:54 #46443
mgj
Participant
@mgj
Ian – perhaps my boy can bring some back for me. He takes up a job catching mice in the New year – we tease him. Ground nesting birds is the serious part of it.

Tony – I don’t think you have a problem. That is a nekkid firefox, so you can still get at everything – the difficulty is getting the heat inside, and you still have to drill etc for all the stays.

What you need to get the heat inside, and you’ll need one anyway to do the stays, is a cyclone burner to fit the torch. If I’m not telling my granny – its an ordinary burner on its own swan neck. At the outboard end of the swan neck is an air admission port. This means it will take its own air in to the flame, and it will stay alight in a confined space.

You will then be able to touch up your soldering and get the stays done as well.

Also, at that point, how big a burner do you have? The BIG Sievert one should fry that firebox quite easily. So you may simply not have enough heat.

That is what it looks like with all that SS all over the place. Get the whole joint properly hot and fluxed and the SS will flash along the whole joint, and because the biggest heat reserve is in the joint, and because of capilliary action, it stays IN the joint, so you get a very neat line of braze.

Forgive me, but it looks as if you are trying to solder with marginal heat. Also from what you say, you are putting the rod in the flame?

As a suggestion- get the joint hot (dull red) before a rod goes anywhere near it. The flux has gone all clear and sort of mobile. Move the torch a touch forwards of where you want to solder by a little bit to keep the heat up. Touch a fluxed rod to the area and it should melt and flash down the joint, without 1/2 melting the rod and giving it the droops and the blobbed ends. If you have a long linear joint you can keep pulling the solder along the joint with heat and keeping the rod well fluxed.

Again at the risk of grannnys.

1 You must have a gap INTO which the solder will flow, so centre pop all joints to keep them marginally apart by a couple of thou.

2. The heat to melt the rod comes from the base metal and not the flame.

More economical too. You are trying to silver solder the joint, not the boiler.

Edited By meyrick griffith-jones on 20/12/2009 09:56:08
20 December 2009 at 13:49 #46456
Tony Martyr
Participant
@tonymartyr14488
Thank you Meyrick

No risk of teaching granny to me on this subject; I truly belong in the ‘marginal heat’ of the beginner’s forum – if we ever get onto dynamometers I will claim some expertise but not yet!

Now I know the special purpose of a cyclone burner I will get one – a late post-Christmas present and I was concerned that the flame would be quenched in a confined space. Can I assume, for my small firebox that a 3524 would be OK?

The large radius of the end plate means that the solder goes quite deep into the ‘trench’ but it can be seen as a thin line inside the box – I intend to sort out the doubtful rivets when I am ready to fix the tubes.

Tony
20 December 2009 at 15:33 #46461
mgj
Participant
@mgj
Tony – I would suggest that you get Tubal Cains Soldering and Brazing. WP series. Very good on a number of aspects.

cyclone burners. Now you got me, because while I did a fair bit of silver soldering on the various racers suspensions and more recently on the TE, I know relatively little about boilers. Only enough to know which questions to ask.

My gut reaction is to go for 2 burners. A 2493 for the outside. And the bigger of the 2 cyclone burners- on the basis that you can always turn a biggun down, but its difficult to turn a tiddler up. And you can never have too much heat, if you take my reasoning. Not only can you be sure of hitting temperature, but there is much less danger of exhausting flux.

However, there may be problems of space and access which would lead one to a different decision.

It would be good if someone who knew more about the specifics of copper boilermaking could advise.

One thing is certain – chuck the damn heatproof gloves, because you don’t need them till after the soldering is done and the thing is ready to pickle. Flux job with paste, heat it up, get it hot – play flame onto the thickest metal -, remove spare hand from pocket,(or coffee cup) pick up stick, warm stick in flame and add flux to stick, touch stick to job (its only in contact for a few moments – literally. If it don’t melt sharpish the job isn’t hot enough). Put gloves and face thingy on, drop job in pickle, carry on with coffee.

In fact about the only time you need gloves when you have the torch running is to join all the end stubs of vastly expensive rod together.

I wish you all the best – personally I love welding and silver soldering – in fact nowadays I very rarely soft solder because for me SS is so quick and controllable, and it sticks so tightly to the hot spots that you get such a neat finish – IF YOU GET IT HOT ENOUGH!!!!!!!!! (and that is bloody vital if you have chosen an alloy with a long melting zone because you want a fillet.)

Edited By meyrick griffith-jones on 20/12/2009 15:35:28
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