Brazing

I would recommend the Sievert blowlamps too. They are self-blown, so you don't need a compressed air supply. And they're in a totally different league to the kind of blowlamp you might buy from a DIY store.

If you want to try one, you can stop by and see what you think to mine (I'm in Shropshire).

Best wishes,

Chris

How big's your nozzle? I've got one that's nigh on two inches in diameter ( a Sievert branded one ), fueled solely by propane. I've seen bigger ones.

Regards,

What's in your camping gaz? If it's butane or a mainly butane mix then that's your problem.

Butane and propane both give about the same heat output (about 50 kj/g) but butane boils at -5 and propane at -40, so you can get much better gas delivery to the torch using propane (which is what the Sievert torches are designed for). Butane cylinders are usually blue and propane red.

AFAIK gas/air torches are still available though uncommon - they were needed in the days when town gas was carbon monoxide whose heat of combustion is much lower (10 kj/g). Our glassblowers at work use torches with air/natural gas fuel because they need very fine flame control.

MAPP gas will give you higher temperatures and faster energy delivery but won't run on ordinary propane torches.

Otherwise how about better insulation? The ceramic fibre blanket which CuP alloys sell does wonders for keeping heat where you want it.

John,

On the insulation front I use bricks from a storage heater as my hearth, all my Sievert kit runs on propane with no problem and as has been said there are some very large nozzles out there.

I braze and silver solder with no problems.

Martin, I don't have a brazing hearth so I could be wrong, but aren't storage heater bricks precisely the kind you don't want? I was under the impression that they have a high thermal conductivity and were designed to soak up the heat, whereas a fire brick supposely does the opposite?

Anyone who knows better feel free to correct me.

Peter

Hi Peter,

I don't profess to know better but ISTM there are 2 seperate possible uses for a forge : firstly being to quickly heat something up to temperature but secondly to slowly bring something down from temperature. Fire bricks would be ideal for the first purpose but I guess heater bricks are ideal for the second.

Peter,

All I know is that they work for me when brazing or soldering, they keep it warm as I assume their heat loss is slow so I don't waste heat.

Peter -

Storage heater bricks are indeed intended to do what it says on the tin - store heat - so they are designed for high thermal capacity and conductivity, rather than high insulation properties.

If you are trying to build a hearth that will allow you to rapidly bring something up to temp then you would be better off with "insulating firebrick" rather than the conventional solid firebrick - the insulating variety give good insulation and have low thermal mass. This is the type of brick that is used to build modern fast fire kilns for e.g., pottery use. I have a small hearth in my workshop made from some that I had left over from a pottery kiln project - wirks very well.

If you want to go even higher tech, then ceramic fibre is the stuff - better insulation properties & even lower thermal mass.

Regards, Tony

I'm not sure that conductivity is all that relevant for storage heaters

- high conductivity would lead to rapid cooling and cold heaters in the afternoon.

But on the high tech front I remember seeing a demonstration on TV a long time ago of the insulating properties of space shuttle tiles.

The demo involved picking up a piece of tile material that had been heated to red heat with a bare hand. Apparently it's conductivity was so low that it wouldn't conduct heat to the surface fast enough to cause a burn.

Russell

I recently bought two Gas/Air torches of different sizes from "Home and Workshop" at Footscray - =A320.00 each inc new hoses. Could have bought a brazing hearth with a torch for =A335.00, but I don't have any room in mt workshop for one.

Try [utl]

Andy

Snipped

I had one of those "living flame" gas fires ripped out a while back and the whole thing is ceramic insulation in sheet and formed parts. It's awesome insulation properties and it allows a makeshift hearth for free. Next time the gas man comes round to do a service, I'm going to see if I can scrounge some more...

Steve

Whether it is relevant/desirable or not is another question, but the bricks used for heat stortage are in fact higher thermal conductivity than either conventional firebrick or the higher tech insulating refractories. The storage heater construction uses insulating materials around the storage bricks, and controls the airflow through/past the storage bricks, in order to control the rate of heat dissipation.

Regards, Tony

The firebacks from a Baxi Bermuda or similar radiant gas fire are well worth scrounging from a removed unit. Perfect for laying the part on whilst brazing.

Richard

Rather than buy, build.

Mike in BC

When I went to tech school, the machine shop had two air gas torches. It was coal gas then. I have never seen torches like that since the 1950s.

Sigh! As far as I know, Sievert has no presence in Canada. Certainly not on the West Coast where I live.

Steve R.

The forge burners work really well. I've seen Rupert's burners in his furnace, and they really work well.

There are instructions available on various blacksmithing sites for propane burners in sizes from 1/2" pipe, on up to quite huge. They are very cheap to build, too.

Cheers Trev

I'm pretty sure that was a foamed ceramic, maybe silica. Also, it had a little time to cool off before it was picked up, you could see that the edges and corners were no longer glowing, although there was plenty of radiation coming out of the inside.

Yes, 'twas a lightweight fused silica - and very impressive in the early

'Course since then the advent of silica aerogels has changed things a bit - nowadays a 1/8 in layer of silica aerogel, which is too light to feel, can protect a bare hand from an oxy/acetylene torch indefinitely.

Hm, could do with some of that to insulate my garage door. Though no doubt would need a second mortgage.

David

sorry, that's utter nonsense - wheee :(, too much booze - except when it isn't .. don't take it literally ..

.. but silica aerogels are cool.

Gootube knows.

-- Peter