Silver solderinga boiler

This topic has 13 replies, 7 voices, and was last updated 18 January 2020 at 11:00 by Keith Hale.

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27 December 2019 at 14:56 #1893
Ken Ratcliffe
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@kenratcliffe25229
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27 December 2019 at 14:56 #443493
Ken Ratcliffe
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@kenratcliffe25229
Hi, I have started on a traction engine using the How to.by George Hughes. I cannot get the silver solder to run on the boiler. I am using a mapp gas torch with a second butane torch, I have the boiler mounted in fire bricks and I have cleaned the surfaces (sandpaper, wire wool and a pickle bath). I am using Medium Silver Solder Strip, with Easy Flo Flux Powder 250g UN3288

Any help, suggestions or direction to existing threads much welcomed
27 December 2019 at 16:29 #443506
JasonB
Moderator
@jasonb
"Medium" is a term mostly used for jewellery solder not the type used for boiler work so not ideal. you want a 55% solder this also melts at approx 100deg C less than the medium.

Your heat sources also sound too weak for all but teh very smallest of traction engine boilers you want something with at least 7kw mimumum.

These weak burners will also take a long time to get any heat into the work by which time your Easyflow solder will be exhausted, better to use Tenacity No5 or HT5.

Have a read of the guide "best brazing practice" on CuP's site

Edited By JasonB on 27/12/2019 16:30:34

Edited By JasonB on 27/12/2019 16:34:25
27 December 2019 at 17:18 #443509
Ken Ratcliffe
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@kenratcliffe25229
HI Jason,

Thanks for the input……as you can guess, this is my first foray into steam engines ! I will get hold of those products and have another go !

Ken
27 December 2019 at 17:52 #443513
Dave Halford
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@davehalford22513
Hi Ken,

Where did the firebricks come from? The ones from a fireplace soak up all the heat and are useless.

You need the CUP style hearth bricks or thermalite blocks or even mineral wool from loft insulation ( just not glass fibre)
27 December 2019 at 18:28 #443516
Former Member
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@formermember19781
[This posting has been removed]
27 December 2019 at 19:28 #443521
Ken Ratcliffe
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@kenratcliffe25229
I had some Vermiculite firebricks……so definitely from a fireplace. I will get some Celcon blocks as well as 55% silver solder and HT5 (already ordered !)

Thanks
30 December 2019 at 13:40 #443874
Bill Dawes
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@billdawes
Hi Ken,if you don't mind taking some advice from a beginner in silver soldering terms, I too struggled with my 5" loco boiler (my first and not yet finished) I found things much improved after changing to a bigger burner, a Sievert 2943 I think, about 43kw.

I also found you have to be patient, it takes quite a while to heat a boiler up to 600+ degrees for the solder to melt. I use 455 solder in the main, 438 on bits that are likely to be reheated a few times.

I usually get my solder and flux from the excellent CUP Alloys.

My hearth is an old BBQ stand and using builders aerated blocks, they seem to work well, cuts easily if you want to make any special shapes, I also bought some wool blanket from CUP.

I can well understand the frustration, it seems that everybody but you finds it easy.

Good luck.

Bill D.
30 December 2019 at 14:07 #443883
old Al
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@oldal
My first boiler attempt was a 2" traction engine boiler and i followed a similar path to you. Complete failure. As described above, the flux gave out long before the solder started to run. I also used only one grade of silver solder and had to heat almost all of the boiler material. so as i was heating one part, another part let go on me. Oh it was fun. I did learn a lot.

If your finances allow, treat yourself to an Oxy propane outfit. Loads of heat and localised.Even on a 2 1/2" loco boiler, the results are significantly different.

Silver soldering is not difficult with the right equipment , a bit of knowledge and help, good luck
18 January 2020 at 09:04 #447288
Ken Ratcliffe
Participant
@kenratcliffe25229
Hi – took a while, gradually doing various things, but in the end, I think it was heat ! Or at least not enough heat ! I got a Seivert burner, backed up with a Mapp gas torch and low and behold the solder ran !

Here's another one then……..It looks like in my beginners mode, I may not have got solder everywhere, i.e. my boiler may leak. How best to remedy that. No way I can restart now, bond way too good, so how can I patch any leaks ?

Thanks to everyone who helped me get this far, all good fun when it works in the end !
18 January 2020 at 09:30 #447294
Former Member
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@formermember19781
[This posting has been removed]
18 January 2020 at 09:32 #447295
Keith Hale
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@keithhale68713
Hi Ken

Take the time, make the effort, understand the process. Learn what you have to do and why.

There are no shortcuts. These inevitably lead to poor and expensive joints.

There is no better source of information than CuP Alloys. Their livelihood depends on their customers being successful. We have guys who have, between them, over 100 years experience of promoting efficient brazing on a daily basis.

Ring 01623 707955.

Or see them at ally pally.

They are more accessible than a forum

Success is at the end of a very short tunnel!

Keith
18 January 2020 at 09:37 #447298
old Al
Participant
@oldal
There must be someone in your local club that has oxy propane. Its a pinpoint flame that can be directed straight at the leak area without affecting anywhere else
18 January 2020 at 11:00 #447307
Keith Hale
Participant
@keithhale68713
Hi Ken.

The root cause of all silver soldering difficulties lies in one place – behind the torch. Poor joint design.fluxing, heating technique, alloy selection to name but four!

Make the joints correctly first time and there is no need for any rectification.

Ask yourself – where did I go wrong. A poor joint is the product of a deviation from the basic principles of the process. Appreciate that and you are well on the way to successful brazing.

An oxy-propane torch may enable you to recover the situation but it inevitably produces local thermal stresses that can cause other problems. Be aware of that and react accordingly.

Instead of trying to put over the situation in a few lines on a forum, why not discuss it with people who know? Old fashioned it may be, but talk-talk is better than chalk-chalk.

And the next statement is aimed at all model engineers. Can you spare 10 minutes to get help quickly. Why not use Skype or a video call to show us the problem?

Keith
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