Brazing

Help please
About fifty years ago I remember using a brazing torch that was fuelled by town gas and compressed air.
Recently I was doing a job where my largest brazing torch, fuelled by
my Camping Gaz bottle, was struggling to maintain the heat needed to make the braze run nicely.
I don't remember any trouble with maintaining heat with the gas and air torch and wondered whether they were still available?
I haven't been able to find any big torches on Google, although there are plenty of small torches for jewellers etc.
Also any ideas of what the domestic gas companies think about using their product for this sort of thing?
Thanks.
John
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On Fri, 28 Nov 2008 15:19:40 -0800 (PST), John

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,
--
Stephen Howard
Woodwind repairs & period restorations
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Stephen Howard wrote:

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
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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.
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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 P "Norman Billingham" <norman.at.tumulus.org.uk> wrote in message

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On Sat, 29 Nov 2008 11:30:03 -0000, "campingstoveman"

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
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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.
--
Boo

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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.
Martin P

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On Sat, 29 Nov 2008 11:51:33 +0000, Peter Neill

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
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Tony Jeffree wrote:

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
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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
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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.
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newshound wrote:

Yes, 'twas a lightweight fused silica - and very impressive in the early 80's.
'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.
--
Peter Fairbrother

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

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On Thu, 4 Dec 2008 23:21:41 +0000, David Littlewood

Yep - I guess you'd need a larger back garden to store the shuttle while you stripped its tiles off <G>
Regards, Tony
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That would look cool stood in the front garden, A shuttle stood on bricks ....
John S.
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John S wrote:

Could you cut a little slot in it for the mail? And the Canada boom would be great for the really heavy parcels . . . JW
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On Fri, 5 Dec 2008 03:31:42 -0800 (PST), John S

Yep...leave it in your front garden too long, someone would put it up on bricks for you...
Regards, Tony
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wrote:

shuttle
up
No, the pikies would have it away!
AWEM
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wrote:

As long as they are not metric bricks one side and Imperial on the other.
Cliff Coggin.
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