Author Topic: Compressed Air Propane Torches (Read 28952 times)

catceefer · « **on:** January 19, 2015, 03:24:36 AM »

I am building a large copper dragon and up until now, I have managed with propane gas powering a MAPP torch. However, as the bulk is increasing, I need a more powerful torch to get the heat into the metal. Due to the size and shape of the work, it is not practical to surround it with fire bricks or the like.

I have read odd bits, here and there, about compresed air assisted toches and was wondering whether anyone has any experience of either using them, building one or converting a standard one to work in this way. Due to cost and space, I would rather avoid going down the bottled oxygen route and the cost of MAPP gas itself makes it prohibitive for the size of job. In addition to the MAPP torch, I have a Clarke torch: the cheap sort that are sold under various brands and come with three nozzles and an air compressor.

Any advice would be appreciated.

Thank you.

James.

chipenter · « **Reply #1 on:** January 19, 2015, 03:39:03 AM »

Have a look for foundry sites for burners and ideas http://www.backyardmetalcasting.com/ .

hermetic · « **Reply #2 on:** January 19, 2015, 07:59:25 AM »

There is a type of torch used on brazing hearths which use compressed air/propane. Mine has a small rotary compressor under the brazing hearth. I also have another torch from a brazing hearth which I use portable with a gas bottle and an airline from my main compressor (nicknamed the blowlamp of doom!) you can braze quite easily with this, but your main problem will be as the dragon grows, the copper will conduct the heat away faster. Use a glassfibre or ceramic blanket to keep the heat in, and you shouldnt have a problem. if you do a google image search on "brazing hearth" you will see all types of air/propane set up. If you are soldering beware, as the blanket may keep enough heat in the job to melt completed joints.............not desirable!

Phil.

vtsteam · « **Reply #3 on:** January 19, 2015, 09:01:14 AM »

catceefer I'd be very interested in what you find as well for a compressed air/propane brazing torch.

I did a thread here on an atmospheric torch but it required a hearth of sorts to contain enough heat for brazing. I'm sure you're already aware of Backyard metalcasting, as I am, but I haven't seen any specific information on constructing a torch that operates without a hearth, in free air, that concentrates heat to the degree required to braze locally on a large object.

There was a thread here on using an old oxy-acet torch, I believe, with compressed air and propane, but I don't recall seeing if it was attempted with brazing rod.

The big question is can the heat be focused adequately, not whether there is enough temperature in an air/propane flame, as some have claimed.

I think it probably can be done -- but that would be the design effort -- compacting the flame.

catceefer · « **Reply #4 on:** January 20, 2015, 02:31:40 AM »

Thank you for the replies. I shall have a look at the variouslinks and, if I succeed in making anything useful, I shall update this topic.

Regards,

James.

DMIOM · « **Reply #5 on:** January 20, 2015, 03:23:15 AM »

James,

If you're able, I think we'd be grateful if you could advise any results, both what works and what didn't, as it helps our collective learning, especially if you can say why it didn't work.

Dave

catceefer · « **Reply #6 on:** January 21, 2015, 02:47:18 AM »

Dave,

Certanly: once I get to experiment, I shall update this with my efforts, good ro therwise.

Regards,

James.

vtsteam · « **Reply #7 on:** January 21, 2015, 09:12:18 AM »

The Bullfinch Autotorch seems to be able to bronze braze even as an atmospheric burner

http://bullfinch-gas.co.uk/blowtorches/autotorch-brazing-sys

Unfortunately, I don't see that one available in the US. I'd love to get one of the burners to try out.

For compressed air/propane brazing there is also the Flamefast T4 torch -- also a UK product (you guys are brazing torch rich!)

http://flamefast.co.uk/heat-treatment-equipment/t2-t4-gas-torches/

vtsteam · « **Reply #8 on:** January 21, 2015, 09:29:00 AM »

Remarkable find,,,,,,Bullfinch actually has a video of their torch burner made of glass. There's an internal bullet shaped mixer. Acts as a convergent divergent nozzle I think:

Jasonb · « **Reply #9 on:** January 21, 2015, 10:14:19 AM »

The "Flamefast" brazing hearths come up for sale quite regularly and have a torch with them. They may need rejetting for bottled propane if they were being used on mains gas. Use to have a couple in the workshop at school and they certainly put out plenty of heat.

mcostello · « **Reply #10 on:** January 21, 2015, 11:52:47 AM »

Majorly cool picture.

catceefer · « **Reply #11 on:** January 21, 2015, 03:07:41 PM »

"For compressed air/propane brazing there is also the Flamefast T4 torch -- also a UK product (you guys are brazing torch rich!)"

I have just contacted the makers of this torch. They recommended a different model, but at £324.00 +VAT, I regret that it is out of my price range. I shall keep an eye out for a second furnace or similar, as suggested, or try making something.

Regards,

James.

vtsteam · « **Reply #12 on:** January 21, 2015, 03:28:36 PM »

I'll take a shot at doing the convergent-divergent nozzle in my atmospheric torch when I finish this pipe and bolt engine. It's got me curious.

vtsteam · « **Reply #13 on:** January 21, 2015, 05:15:33 PM »

Also catceefer, it looks like the Bullfinch torches are much less expensive, though they are atmospheric, instead of compressed air.

vtsteam · « **Reply #14 on:** January 21, 2015, 10:16:56 PM »

Let's not forget Ironman's compressed air-propane torch conversion, also:

catceefer · « **Reply #15 on:** January 22, 2015, 03:27:30 AM »

Vtsteam,

Thank you for the video. That is the thing that first set me off thinking about the conversion in the first place. I seemed to recall seeing something, somewhere, a while back when looking into different types of torches, but could not find it again. It looks just what I want and I can even get hold of an old oxy-acetylene torch with which to experiment.

I shall look at it in detail this evening.

Regards,

James.

Will_D · « **Reply #16 on:** January 22, 2015, 05:55:10 AM »

Just make sure to fit flash-back arresters/non return valves to both lines! You dont want air in your propane or propane in your compressor!

vtsteam · « **Reply #17 on:** January 22, 2015, 02:13:19 PM »

That's true, Will. And true of oxy-acet, oxy-prop, too. Unless flashback arrestors are built into the torch itself.

I have them at the regulators and the torch.

I found Ironman's full thread on his propane torch:

http://madmodder.net/index.php/topic,9208

vtsteam · « **Reply #18 on:** January 22, 2015, 02:26:11 PM »

In the video, Ironman shows an early trial with just a conventional oxy-acet welding tip, and the flame blows out. This actually also happens with oxy-propane, not just propane and compressed air.

Oxy-propane tips have a recessed orifice. they need what I would call a flame holder beyond the orifice. I was successful in modifying a #2 Victor oxy-acet weldng tip to burn oxy-propane by adding a counterssunk end in the tip. That's what I use for small parts brazing now -- I used it extensively on the Pipe and Bolt engine.

So I'm wondering if Ironman might have had better luck if he had countersunk the welding tip. By adding the larger shroud he got the same effect, I think. But it's a large flame. I might be interested in a smaller flame than that, and I do wonder if my modified oxy-propane tip might stay lit with compressed air, instead of blowing out, as ironman's did in the video.

Manxmodder · « **Reply #19 on:** January 22, 2015, 03:16:52 PM »

Well this is developing into a very interesting and potentially fruitful thread indeed.

I say this because amongst the recent haul of machinery and equipment acquired by a mate and myself there are several oxy-acetylene torches of various sizes,and an oxy-propane cutting torch.

The likelihood of either of us investing large sums in oxy or acetylene cylinders is next to nil . We both use propane torches and have large cylinders of that gas,so if this thread enables us to modify the oxy-acetylene kit to propane-compressed air for brazing,then it's going to be smiles all round......OZ.

catceefer · « **Reply #20 on:** January 22, 2015, 03:55:43 PM »

I did have a go at doing this last year, but without any success, but I can see why now. I borrowed an old oxy-acetylene torch and tried it with propane and compressed air, but unsuccessfully. Either the flame went out with the air turned on or was it large, flaring and cold orange with just the gas. I did try enlarging the jet, but to no avail. I did not try shrouds of any sort or countersinking the jet.

I shall be getting the torch back again shortly, so shall have another go, this time with a bit more structure to my efforts. I need a large, hot flame, not just a hot one. The atmospheric torch that I normally use brazes perfectly well, as long as the piece is small enough. The dragon in the attached picture is at the limit of current rig.

Regards,

James.

Manxmodder · « **Reply #21 on:** January 22, 2015, 04:56:56 PM »

WOW! I like your Dragon very much,James.

.....OZ.

vtsteam · « **Reply #22 on:** January 22, 2015, 06:01:51 PM »

Hey, Cool catceefer!!

dsquire · « **Reply #23 on:** January 22, 2015, 06:41:28 PM »

James

Now you are geting our attention. I can see a lot of back yard treasures turning into front yard art pieces. Well done.

Cheers

Don

catceefer · « **Reply #24 on:** May 04, 2015, 12:55:33 PM »

Just a quick update: I have obtained an oxy-acetylene torch, bought a length of fat tube, found and drilled some scrap steel and cobbled together a large burner. On just propane, it puts out a large amount of heat, but with a scarily diffuse, large and unusable flame. I now need to try and hook up the oxygen pipe to the compressor and try again.

UPDATE TO UPDATE. Just hooked the torch up to the compressor and tried again: success! It has a nice, bright blue flame, totally controllable and, if the roar is anything to go by, very powerful. I need to tidy the burner up a bit, mainly because the jet is in at a slight angle and the flame is not central to the shroud, but otherwise, it is ready.

Once it is finalised, I shall post some pictures and, if possible a video of it in use.

Regards,

James.

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Author Topic: Compressed Air Propane Torches (Read 28952 times)