gas forge burner question

Gday all, is there any advantage or disadvantage to using a blown burner over a venturi or atmospheric type?
I trying to decide which type to build, I know I know, build both and
test.... :-)
Rusty_iron
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Hi Rusty,
Both have their up side.
The venturi or naturally aspirated are portable, and can be taken anywhere you can carry a gas bottle.
Blown requires an extra air source, whether delivered by hand or by an electric motor.
Some say that you can't get the temperature to forge weld with a naturally aspirated burner... bollocks to that, it can be done.
The forced air burner in theory can get hotter than a venturi style, but I find that propane without air is enough for me. I smelt bronze also with a naturally aspirated burner. I don't think I could smelt wootz, but I have an experiment in the pipeline (thanks to an earlier post :-) )
It really depends on the size of your firebox and if the flames from the burner are forming a vortex.
Give me the details of the forge it's going into (if it's going into a forge at all that is). Is it for a forge application?
Regards Charles
Rusty_iron wrote:

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The one I've heard is the force air type is easier to get up and running the first day. ;)

I wonder if that's really true if the naturally asprirated type is designed and ran at optimum? It's still just air and propane... unless they are talking some sort of pressurized setup?
Rust, got a little blower? Brand new ones ain't exactly cheap and the small ones I've found at the scrap yard lately were all 240v.

I missed that post somehow. :/
There's some sort of limit to propane's heat, especially diluted with air. It'll be interesting what you can do with it. :)

Hmmm... if you're down-under my voltage problem may not effect you?
The scrap yard's always got lots of little blowers in old central heat type furnaces, a good scrapyard will let you remove them and sell them to you for scrap metal prices. :)
Alvin in AZ
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snipped-for-privacy@XX.com wrote:

Alvin, central heaters are in short supply here in subtropical Queensland - Brisbane. But we have plenty of airconditioners, so perhaps I can get one from there.
Please post all your 240v units to Chilla and I, we use 240v here, like the British :-)
I have a nice new blower I got off the shelf while I was OS about 2 years ago, cost $20 pacific peso's. Wish I'd got a couple of them :-)
I have power to my smithy, and a handcranked blower if I need it. Portability would be nice and thats a good selling point. Thanks for the idea, its important, I'd not considered it. DOH!!!!! :-)
Rusty_iron
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Rusty_iron wrote:

Mitre 10 has a Fathers day special a 1 hp dust extractor for $99 AUD, just use it to blow instead of suck (I don't know about you guys, but I've got a dirty mind and this somehow sounds filthy :-) ).
Regards Charles
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Way too much air and noise if you sak me. (but you didn't ask me ;)
http://www.panix.com/~alvinj/burner.htm (used RR signal-case blower)
http://www.panix.com/~alvinj/burnerhead.htm
The holey screen was picked up off the ground at the scrapyard it's some sort of automotive exhaust system guard for them newfangled Cadillac;) converters.
Cut round, edges-ground all around to form an "edge" like a cold chisel, bent in one spot then screwed right into the pipe threads.
http://www.panix.com/~alvinj/furnace.jpg
Nothing but a stack of insulated firebricks. The darker yellow bricks are the "common, cheap and heavy" fireplace liners the others "feel like" styrofoam. Inside where you can't see it are 2 more insulated fire bricks for the "floor".
None of that stuff is prob'ly what you're needing, but shows you what's posible.
The first time I fired it up with the new insulated firebricks... tried heat treating a small O1 knife blade I didn't see the steel go through its "arrest point" so kept heating the knife blade. The O1 blade got so soft, it got all jiggly-n-wiggly. :)
I suppose that's hot enough for forge welding?
Search for- ron reil burner ...it's prob'ly the best way to go anyway?
Alvin in AZ
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snipped-for-privacy@XX.com wrote:
This link is busted :-( Charles

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Ooops. :/
http://www.panix.com/~alvinj/burnerhead.jpg
Fixed. :)

Alvin in AZ
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"bollocks to that" is exactly correct. I've done a lot of pattern welding with a venturi burner, no problem. I don't know if forced air would have been faster, I've never forged with a forced air burner. Preheating the air would definitely be faster, but I've never tried that either.
<snip>
Regards,
Adam Smith Midland, Ontario, Canada
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Chilla wrote:

Charles, I've aquired some lengths of pipe, 10 & 12 inches in diameter, I'm going to put 2 1 inch layers of Kaowool, and coat it with ITC 100HT. pipe is currently 18 inches long but I may cut that down. I plan to build a smaller unit from the left over kaowool - its 7.2m*0.61m so there should be plenty left over from building 2 forges - to use for small stuff. I plan to put a fire brick in the bottom. As I have not constructed them yet, I'm still sorting details - like burner type - I don't know the exact volume.
Yes I know thats a fairly large forge, but i wanted a large unit to accomodate some larger work. I was thinking if i put 2 burners in, I could just use a firebrick or 2 to cut the internal size, and only run the front burner. Ok so perhaps I'm kidding myself or my thinking is faulty, I don't know yet. Thats why I'm asking.
Is there some rule or guide as to the number of burners per area within the forge?
Rusty_iron
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Rusty_iron wrote:

Hi Rusty,
Hmmm that's a big firebox, potentially 8 - 10 inch diameter x 14 - 16 inches long, that's going to require a lot of propane to heat up.
Let's see 352 - 503 sq inches, if you want to make that into a forge as is that will definitely require 2 burners to effectively heat it up.
I'm just thinking the only reason you'd want to heat up that amount of metal at one time is for heat treating, or the item is bulky.
What do you want to make? We might be able to design something a little more purpose built for your desired application, that wont cost a fortune to run.
There may be some rule about burners per area, but I prefer common sense.
I made the mistake of telling the blacksmith class how easy it is to set up a forge and now I have to make 5 portable modified propane tank forges. These will be able to make swords, anneal sheet for raising operations and be used as a melting furnace for non-ferrous metals.
I was tempted to buy a 7 metre roll of Kaowool, but thought I'd use up what I've got first. I did buy 10 litres of "Kaowool Rigidizer", and have found this to be an excellent product.
Anyway tell me what large item you want to make and we can design something appropriate.
Regards Charles
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Chilla wrote:

Gday Chilla, ok I was basing my building on these plans for a start:
http://www.iforgeiron.com/Blueprints01/BP0192gasforge/BP0192gasforge.shtml
I've seen pics of forges made from old gas tanks, but i don't have one to use, except one of the large size that are about 5 foot high. So based on this guys ideas I asked a mate for pipe offcuts in the 10 to 12 inch diameter.

I mentioned I intended to build a smaller unit while I was at it :-) but you are right it is a lot to heat. I've never used nor witnessed the use of a gas forge, so I only have what I've read on the net to go on. I have a coke forge that I've been using for years, and have found that extra space in the forge never goes astray, but its true I don't have to heat all of the space in the coke forge at once, which does not apply to the gas forge.

Hmmm you could make 6...... ;-) If I were you I'd make one as a demo and let them go for it, unless you are charging for each unit and making a profit out of it..... Your time is worth something.

Ok the guy at Thermal Ceramics told me it was a 7m role. He was only new there, so I ahve as yet to speak to one of their experts. What is this "Rigidizer" product? The Itc100 was recommended by a blacksmith i did a course with. Heres a pic of his setup.
http://www.traditionaliron.com/Tools/Tools.htm
Thanks to everyone who has given me feedback, I appreciate all your comments and ideas, keep them comming.
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Wow that -whole thing- (website writing forge etc) is really cool. :)
The two bricks look like they were one brick sliced in two?

The roller is really cool.
What's "SG iron"? :)
Somehow I know it's going to be "duh, I shoulda knowed that". :/
Alvin in AZ
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Rusty_iron wrote:

My time is worth something... well so people tell me. I'm going to ask them to just pay for materials, as I'm using the forges to work out the kinks in a commercial design I'm working on.

I bought the "Kaowool Rigidizer" from Thermal Ceramics, and Thermal Ceramics "only" sell the Kaowool by the roll, however you can get Kaowool at any kiln or potter supply place, this is where I bought my first metre :-)
I did this test, get an oxy acetylene torch and point it at your Kaowool... it disintegrates very quickly, apply "Kaowool Rigidizer" to another piece of Kaowool, wait the 12 hours drying time (if you force dry, the Kaowool shrinks a lot). Apply the torch and nothing happens to the Kaowool, except it gets hot to touch. Apply some thixotic zirconium paint and heat is reflected back :-)
I couldn't get ITC100, so I got the rigidizer instead. Is ITC100 a reflector as well as a hardener or is it just a hardener. Kaowool Rigidizer costs $23 for 5 litres from Thermal Ceramics.
Regards Charles
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Chilla wrote:

I'm not sure if it's the same or not, but a common rigidizer is colloidal silica. You can find it on the net. I got some in liquid form, from what I hear there is a colloidal silica powder sold as an additive for fiberglass resin.
I've been using the colloidal silica with good results. About the only problem with it is that it's very brittle. A little pressure and it cracks up.
I ended up buying a bag of fine-milled silica powder from a ceramics supply place and made my own colloidal silica by mixing it with water. Whatever didn't drop out of suspension in a week or so was decanted off to another jug. It's cheap and seems to work just as well as the expensive stuff.
Jeff Polaski
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snipped-for-privacy@rgs.uci.edu wrote:

The Kaowool Rigidizer contains a lot of colloidal silica, but the additives make the difference... I guess. At $23 AUD for 5 litres and no screwing around... I can afford that :-) Charles
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Rusty_iron wrote:

I have a single burner forge that is 8" inside diameter and 14" long. One burner is marginal, but it works. I haven't done any welding with this particular forge.
I used to have a forge with 10" ID and 24" long. It had 3 burners. This worked very nicely, worked well for pattern welded billets.
Both forges were atmospheric (Reil burners) and insulated with 2" Durablanket. I used some Satanite as a rigidizer, no ITC.
Steve
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Chilla wrote: ...

...
Getting complete combustion -- involving all available fuel with sufficient oxygen -- will get the highest theoretical temperature for that fuel. That is, the peak temperature of the flame.
A naturally aspirated burner will have a small range of operation where the fuel burns fully -- or is more 'finicky' to operate. This works well. Any time you vary the amount of fuel -- the pressure -- you have to adjust the draw of air. Pretty straight forward. You adjust the air to get complete combustion, adjust the amount of fuel for total amount of heat you want.
Similar with the blown air forge. The temp is pretty constant - just keep the blower providing enough air for complete combustion. Too much air will cool the resulting burn, but the adjustment is less critical than getting the naturally aspirated burner to peak temp.
A blown forge is capable of more heat. Both have the same peak temp with the same fuel. But the naturally aspirated burner has a limit to the amount of air it can draw, which limits the amount of fuel that can be burned effectively. A blown burner is also limited by the rate at which air and fuel that can be burned, but the blower can typically supply much more air than the naturally aspirated burner can draw, thus allowing more fuel to be burned effectively. With the typical air choke plate, a blown burner can easily be adjusted for very low pressure/heat operation, too.
A naturally aspirated burner could theoretically be built to burn any large amount of air -- at the cost of giving up operation at lower pressures of fuel. The Reil style burner often uses a choke to limit air draw, but stable operation at lower, choked-down air flow may be more difficult to set on the larger burners.
Blown burners may also have an advantage in forges with an open side, or open ends. They can create a larger peak heat region in the firebox, even with one or more sides open as with a farrier's forge. The naturally aspirated burner will be more susceptible, at lower fuel pressure operation, to movement of air around the firebox.
Designing the volume and shape of the forge, capacity of the burner, fuel selection, all work best when they are in the right range to suit the other components. For many larger firebox uses, two or more burners of either type can be much more flexible than a single, larger burner. Sometimes. It depends.
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<snip> That was cool, Brad, you ain't messing around. :)

All I really do is heat treat so my setup with the blower and rather "open box" has worked out great. :)
But there has been a few times where I used the burner for "out of the box" stuff like pre and post heating welds and bending heavy steel parts... stuff like that. I have a bunch of different sized "double-heads" and a "single head" too.
Like Brad said, mine sure as heck ain't finiky about full blast or with the baffle all the way shut (for smaller heads than shown).
http://www.panix.com/~alvinj/burner.jpg
http://www.panix.com/~alvinj/blower.jpg
http://www.panix.com/~alvinj/furnace.jpg
http://www.panix.com/~alvinj/burnerhead.jpg
The side-outlet-elbow there is a 1" with 3/4" elbows holding the screens. Since then I've screwed in a couple 1/2" reducer bushings with their own screens, right on top of the screens shown. I've had better luck heat treating my little pocket knife blades and springs with the smaller flames. Easy as pie to run it too, I just "close" the baffle and it leaks enough air to give me the flame I want. :)
To heat treat a butcher knife, all I have to do is take out the 1/2" reducer bushing and run it with the baffle sitting a little more closed than what's shown.
Not that what I'm doing is a direct use to anyone else... the whole thing is done by the seat of your pants... that's just where I'm "sitting" is all. ;)
Alvin in AZ
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Gday Folks, so the nice people at iforgeiron have put together a page "getting started in blacksmithing" with links to their forge plans etc. It may be of use for someone here.... ok thats me ;-)
http://www.iforgeiron.com/Blueprints_200-300/p2_articleid/223
Oh my head is now spinning after all the posts :-)
Rusty_iron
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