5" Gauge Boilermaking - Heat Required For Silver Soldering

Hi, I'm a newbie here making a first post so please be gentle with me!

I am currently building a 5" gauge GWR 78XX to Martin Evans' s "Torquay Manor" design, it was purchased a few years ago as a second-hand set of castings with some machining done, since then I have made steady progress and now have a rolling chassis complete with tender and can put off making a start on the boiler no longer.

Many years ago I built a small 3.5 gauge boiler without any difficulties and am confident about most aspects of copper boilermaking but the concern I have is about the amount of heat required to silver solder a boiler of this size, particularly with modern cadmium free alloys. In the past I have used a small torch with integral disposable butane/propane mix cartridge which with the largest available burner (7kw) and plenty of firebricks always provided enough heat, however it is quite obvious that this won't be nearly enough for the Manor boiler so the question is can anyone who has built a similar size boiler using modern silver solders recommend a suitable propane torch and burner? The Sievert pro models seem popular and a 2942( 32mm dia / 26kw ) burner on a suitable neck tube and handle sounds as though it might be up to the job but has anyone any experience of using this torch for boilermaking in this scale?

Oxy-acetylene would obviously do the job but I don't wish to get involved in the costs and contracts associated with cylinder hire or the H&S issues of storage for a one-off job, particularly as I already use propane as a caravaner .

All advice and comments appreciated.

Ian.

I struggled like mad with propane last time - and it wasnt easy with oxy the time before that! It will get hot enough but you will need to brick everything up and be patient for the heat to build.

I've never built a boiler that size, but it might be worth considering an old fashioned parafin blowlamp, as a general heater, and use the propane torch to heat locally as required.

I found the low-temp silver-flo doen't need much more heat than easy-flo.

Why not get two propane torches, the 32mm for background heat, and a 12 or so for targetted heat?

Neil

You'll get away with a lot less heating if you can keep the heat contained. Fire bricks are commonly quoted, I did mine with a pumice chimney liner and a couple of offcuts of vermiculite board, just arrange the bits to suit, see my photo album.

Cheers

You'll get away with a lot less heating if you can keep the heat contained. Fire bricks are commonly quoted, I did mine with a pumice chimney liner and a couple of offcuts of vermiculite board, just arrange the bits to suit, see my photo album.

Cheers

Edited By Durhambuilder on 04/05/2012 20:56:16

Thanks for the friendly and helpful replies, lots of useful food for thought. I have to say I've haven't yet used any of the Silverflow alloys so I'm perhaps pre-judging them on what I've heard. I have used Argo-braze 56 simply because I was able to get some very cheaply and have fount it rather difficult to use compared to Easyflow, of which I still have a few preciously guarded sticks. To be fair though Argo-braze is a specialist application material not intended for the general purposes I use it for. The suggestion by Durhambuilder of using vermiculite board for heat containment triggered a thought so I tested the heat resistance of some of the missus's gardening vermiculite and found it has potential for piling up around the job like the old books advise with coke, I also like his method of encasing the barrel in a chimney liner.

I would still be interested in knowing what equipment others have used to successfully silver-solder similar boilers before I invest in a torch.

Ian.

Hi Ian,

It might be worth having a look a the thread "Boiler making hearth" from 2009. It is on the same subject.

Les.

I used a Sievert 3526 cyclone burner which was more than adequate for by 4.75" dia x 18" long AJAX boiler. I did keep a second full gas cylinder nearby, the last thing you want is to run out of gas half way through a heat up

Cheers

Julian

Try and get Alex Farmers Book:- Model Locomtive Boiler Making he makes two torquay manor boilers in it. Uses OXY/ACET

Thanks again for the replies.

Les, The "Boiler Making Hearth" thread is interesting, one post mentions using a barbecue which is exactly what I am using at present, mine is lined with radiants from old gas fires, I will need a larger one for the planned boiler though. I'll also get some thermalite blocks from B&Q as they are said to work well at very low cost.

Julian, it is encouraging to know that your Sievert equipment did the job, I think the cyclone burners may achieve a higher flame temperature than the standard power burners as they are the only ones recommended by Sievert for brazing, although they quote much smaller maximum pipe sizes than a boiler barrel! Unfortunately the 3526 burner is now discontinued, the largest now being the 3525 with a 10kw output. I will be watching ebay for a used one though. I noticed two gas bottles in your photos and did wonder if you were using 2 torches. I don't know what Calor's exchange policy is at the moment but hopefully I can temporarily swap one of both of my 6kg caravan propane bottles for larger ones.

Ian, I do have a copy of Alex Farmers excellent book, acquired at great expense as it's apparently something of a collectors item now. Unfortunately, as you say he uses oxy-acetylene which in these days of H&S and fire safety legislation is very difficult in a domestic environment. For me it's a definite no as quite apart from the cost I simply do not have the space to comply with BOC's risk assessment requirements for storage of acetylene cylinders. I also hate to think what my home insurers would say about it!

Ian

Ian

can't tell you about Calor's policy but I got a "spare" empty cylinder from a car boot and just exchanged for a full one no issues. Don't think the size matters that much ( or hasn't for me so far)

Regards ian

Cheers Ian, I know they introduced some restrictions a few tears ago meaning cylinders could only be exchanged within "groups" however the following year my local supplier told me that policy had been abandoned.. I hope that is still the case.

hi ian

i have built a few boilers. i dont think you will have any problems using propane for your MANOR boiler.

plenty of thermolite blocks or vermiculite. main problem isnt how you get enough heat but how you produce your tapered barrel. check with your club boiler inspector what type of joint is acceptable on the barrel. the dovetailed castlelated joint requires a high degree of precision even if this type of joint is acceptable these days. a plain castlelated joint may not be acceptable either. how you plan to silver solder the stays is also a concern.... if silver soldering the stays (which i would recommend) you will need to leave the inner firebox door plate off IMHO.

a 4942 burner will be adequate. things get pretty hot and take about 10-15mins to get to temp. then a few seconds of silver solder disappearing very quickly! i havent had any problems with silverflo 55 either, in fact i prefer it for boiler work. main problem with lots of proper firebricks as a furnace is the very intense heat throwback when trying to do the silver soldering. the extra services of another club member with their own propane torch and bottle for the final bits of the foundation ring and the backhead can be recommended.

i do all my siver soldering in doors where i can judge and see the temperature better, and the gas bottle keeps warm! (yes, i leave the door open!)

cheers, and good luck!

julian

Thanks Julian for your informative reply.

At the weekend I managed to acquire another calor gas bottle and traded an empty propane for a full large one, also purchased a decent used Sievert torch and a quantity of Silverflo 55 so I'm getting organised. I already have the copper sheet for the plates and so made a start on flanging the backhead at the weekend. It was surprisingly easy getting it up to annealing temperature packed in refractory blocks but as you have said the heat throwback is considerable and I did feel something like a fireman on a full size loco.

I am planning to produce the tapered barrel by rolling it round a wooden former of the correct shape, my plan was to use a plain castelated joint but your much appreciated comment on the acceptability of this type of joint means I will need to seek advice before committing myself. I have no objection to using a jointing strip either internally, externally or even both. The biggest problem with the barrel at the moment is buying, or at least paying for the large sheet of copper from which to make it! I do plan to use plain silver soldered stays fitted before the doorplate and backhead go on.

I totally agree that the temperature can be better judged indoors but my confined space means I will have to work outside, at least in the later stages of the job which will mean avoiding sunny days. I can't see that having having much effect on available hours though and it will at least save having to use a patio heater to keep others warm!

Thanks again,

Ian.

Hi

If you find someone who is throwing out one of these old electric storage heaters grab it it is full of firebricks.

Bob

Hi Bob,

thanks for your comment. unfortunately I doubt that storage heater bricks are ideal as they are designed to absorb and hold as much heat as possible meaning that quite a lot of heat would be wasted heating the blocks as well as the boiler up. I think a lightweight refractory material such as vermiculite which has both heat resisting and insulating properties would be more suitable. I've read elsewhere that some model engineers have found ordinary lightweight concrete building blocks to be perfectly satisfactory and given that they're the size of six bricks and about a quid each I'll be trying some.

Ian.

My back still aches after shifting about 7 storage heater's worth of bricks two years ago!

I understand that the 'fuelsaver' bricks used to reduce the area of a coal hearth are agood choice.

Neil

As Ian said, don't use storage heater or refractory bricks which absorb too much heat.

Just use cheap aerated concrete building blocks which reflect heat, are light and can be sawn to shape.

I suspect Ian has finished his boiler as this is an 18month old thread!!

J

Edited By JasonB on 17/02/2014 10:57:02