Silver solder

Hi I am just starting to build a boiler for 11/2 scale engine which solder do I need please I will be using Map gas canistors for heat

Hi Alan,

You'll want a solder that will flow easily as most hard solders need high temperatures to work, which is a problem on larger pieces because it's hard to deliver enough heat with regular gases like propane.

So therefore i propose the 55% silver content will be the best. It's expensive but behaves much better.

If you live in England, you can get calor propane 3ish kilo bottles, which have alot in them but don't cost much, you can get a decent brazing torch from machine mart and that might save you money on canisters. 

Michael W

Edited By Michael Walters on 09/11/2016 16:23:40

55% silver solder will do for all or you could also use a higher melting point one for some of the initial assemblies. Something like 455 from Cup would be your mainstay.

I think you will struggle with Mapp gas, yes it is a hot flame but the burners are not really large enough to get the amount of heat into the whole boiler, you need to be looking at teh Kw rating of the burner something along teh lines of 26KW

J

Is it possible to measure the output of your own burner? is this solely governed by pressure and the dia. of the nossle?

Michael W

Edited By Michael Walters on 09/11/2016 16:28:40

Probably easier to look up the makers data and see what they quote as the output, with teh MAPP cannisters the actual mix of gass will also play a part.

I'm sure someone will come up with the formula based on a measured temp of the flame

Interesting, Thats probably true, too difficult to measure without that.

What do you make of the Oxy/turbo torch set CuP make?

**OxyTorch**

Doesn't give me the specific Url, so you'll need to scroll down a bit to view it. 

Michael W 

Edited By Michael Walters on 09/11/2016 16:45:28

Not really suitable for boiler work as the flame is very concentrated and in teh wrong hands could just burn through teh copper. I'm sure Keith will be along later and may be able to fill us in on its Kw rating but may only be 2 or 3 Kw. Fine for very small work or a bit of lead burning maybe even to chase round a boiler once it has been brought upto temp with a big burner to give that last bit of heat to flow the solder. But just won't put enough heat into a big lump of copper.

If you want mixed gas/air then a propane burner with forced air will be ideal, the Flamefast burners can be run off mains or bottled propane with teh right jets and the hearths or chip forges with burners come up for sale quite often as schools sell them off.

Edited By JasonB on 09/11/2016 17:00:46

I allways used my sievert torch with the appropriate burner & still do but for larger jobs my flamefast beats it hands down, when I got it it had natural gas jets in, I phoned flamefast & they quoted me £30 per gun [I worked in the d&t dept then but they did me no favours] so I tried it on propane & it works a treat, the only thing you have to watch is it's sensitive to adjust but it only uses 2-3 psi & I saved myself £90 for my 3 guns.

Mapp Gas and Propane burning in air have very similar flame temperatures - 2010 and 1925 deg C respectively.

Mapp gas has a 40% higher flame speed which allows you to push more gas through a burner and develop more heat.

However the size of burner on a hand held canister is unlikely to be big enough to consume the amount of gas to develop Jasons' 26kw. Your hand is also going to be too close to the boiler for comfort.

I would suggest that you opt for a propane torch starter kit. It is reasonably priced and has a burner to develop that 26kw. But, equally important, it will give you all the flexibility of heating that you currently , and may in the future, require. Simply changing burners (£20ish) and altering the pressure via the regulator, will give you a heating capacity of between 0.25 and 86KW.

Fitting a longer neck tube to the handle gets your hand away from the heat.

If time allows, see this at Ally Pally.

I would not recommend the use of any oxy-gas flame, in isolation, to build a boiler. That includes the oxy-propane torch to which Malcolm refers! They are best used after first pre-heating the joint with propane. Their more precise focused flame will enable you to develop the heat pattern required to control the metal flow and ensure complete penetration of the silver solder into the joint.

Depending on the size and joint design, you may well be able to achieve what you want, from a single propane burner, by simply moving the point of attack of the burner. Your decision!

It is very difficult to achieve good overall heating of a joint with oxy-gas flames. The professionals don't do it......!

Poor heating technique is the most common cause of silver soldering difficulties and problems.

455 silver solder is ideal and will be the mainstay of the build. If you feel that you want to build the boiler using a two stage approach, use a higher temperature alloy eg 438 first and follow it up with the 455.

For more information go to **LINK**

See also **LINK**

Keith

I'm guessing your boiler will be similar to my 1" minnie boiler that is still under construction .. and a lot of early advice from experienced folk in that thread that's worth reading.

I thought I'd done enough reading and watching videos but actually having a go is necessary to get the experience: It takes some practice and I found not as easy as you'ld think. Silly things like getting the flame too close to the work and losing all surrounding oxygen and having the flame go out... so I keep a hand can torch running nearby for fast re-start. As I'm doing more that's hardly needed now. I also find it better to do my novice soldering outside when dark (under a floodlight) so I can guage the colour as the copper heats up better. It really needs to get almost yellow hot for easy flow of 38% (in my hands). Higher temp solder - the 24% and I just didn't get on. In comparison the 55% is way way nicer. Getting those extra degrees of heat staying in the metal can be a bitch - and has been pointed out to me it's all about insulating the work from heat loss and inevitably that reduces access and handling.

There's lots of experienced advice on here but every person varies in opinion, skill and practice so some it it you just have to fgure out by doing... which is why i started out expecting to make two boilers before i got one right and possibly three. It would be that or make simpler soldered constructions first.

Its a hobby (for me) so the learning curves, frustrations and triumphs are all part of it so long as it's fun - enjoy.

Well thanks all, I now have more problems than I started with, I have been silver soldering with my bottle and torch but with solder found at work this is flux coated, I just though I ought to find out what I should be using thanks for the answers to that. Now I need a new torch lots of money!!!. Alan

Its not just the torch. You also need to ensure that heat cannot escape - by surrounding the work with insulating material (or charcoal) and protecting the area from drafts, etc. Charcoal for barbeques is good, as it is not likely to give off fumes which will affect the soldering process, and it has the advantage that it glows in the flame, surrounding the job with a hot layer - just what you need.

Do remember to douse the charcoal with water when the soldering is complete. Otherwise it can glow quietly, covered with grey ash, until you pack up for the night, and could then set stuff on fire.

Regards, Tim

Yes Tim, this is quite important as a block of steel, although flame retardant, will leech any useful heat away and make hard work of it. I don't use ash myself but have blocks of vermiculite that i have screwed together to make a small hearth then mounted on a couple of bricks.

The vermiculite, like the charcoal becomes exothermic and radiates heat back onto the sitting work piece and continues to radiate for a long time after, so it does pose a bit of a fire risk that needs to be recognised, i'm sure you'd feel the heat though.

This isn't a very big hearth though so for the bigger pieces i'd probably need an "open topped" setup like yours because i wouldn't have the money or the room for a big vermiculite hearth.

With regards to the Oxytorch, I actually quite like the look of this and i could see a need it would fulfill,

i do have a very competent medium (22mm head) burner that will heat up a nice big area of copper, but it's the localized joint penetration that it seems to have trouble with, especially on harder solders.

and unless i have a big stick of solder it gets too hot to put my hand anywhere near it. so i'd like the idea of having a concentrated jet that i could use as a secondary operation to chase the solder around the joint and reach fine areas.

Just to say i agree this a specialized burner and it couldn't replace the versatility of a propane burner for a beginner, but this is good for one problem i have. 

Michael W

Edited By Michael Walters on 10/11/2016 20:36:14

I invested in a bunch of thermalite blocks and vermiculite and assemble different shaped hearths as needed on a simple trestle outside the shed. even with welding gloves on hands can get toasty.

Thanks all for your Replies have now ordered a torch and solder and flux from CUP hope I can make it work Ps I allready have the soldering hearth bought from CUP at Spalding should have spoken to them then but we live and learn hopfully thanks again Alan

Edited By Alan Wilkinson 1 on 22/11/2016 17:29:20

Hi Alan.

You are not alone! Call us any time. Help is at hand and it is only a phone call away.

Stick to the basics, understand what you are trying to do and why.

YOU WILL BE SUCCESSFUL

Regards

Keith