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Jlinner

Burner Placement

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1 hour ago, Zeb Camper said:

At the risk of sounding like an idiot, why arent burners mounted on the bottom? will it have back pressure problems? It seems to me since heat rises it could be more efficient plus you don't have to worry about the chimney effect. Also you dont have to worry about your hoses dragging the forge body, or hanging above it drying that rubber out. 

On a separate note, would it be a terrible idea to make a very small one burner gas forge just for forge welding damasscus billets? i have never done actual pattern welding, but I feel that I'm ready and my tools are not. I apologize for being off topic.

I built two forges, and the one above is the second. It answered problems I thought the first presented.  I didn't want hot spots on my steel, which would happen if the burners were mounted at the bottom.  There are no back pressure problems.  I can have the back almost completely bricked up and it runs great.  I would imagine that at the temperatures that we are dealing with, and the distance from the bottom of the forge to the top would make the idea of heat rising and efficiency a moot point.  The forge has legs so that the weight of the burners and hoses don't drag it down.  The hoses never get hot.   

Lots of smiths do build forges just for welding.  I know a lot of them build vertical forges, so flux isn't an issue.  I have never used a vertical forge, so I can't speak to those.  I have yet to weld in the above forge, but when I do, I will be casting a tray out of Mizzou to catch the flux.  (or maybe just try dry welding...)

(and you don't sound like an idiot asking questions.  I ask questions all of the time.  So if it does, we both are idiots :) )

Edited by Wes Detrick
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OBSERVATIONS ON QUESTIONS ABOUT BLADESMITHING:

A good portion of the craft is about asking questions, often of oneself, like "How in the heck am I going to do this?" Very often the answer comes from trial and error. When the problem is solved this way it often results in a "Eureka!" post on a forum somewhere. When this method doesn't result in "Eureka" less often it results in a "failure" post. In either case there is a high probability that someone else reads the post, good or bad, and says "I could have told them that if they had asked".

There's a moral in there somewhere.

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Thanks guys. Wes, I wasn't specifically talking about your forge. I watched the video though, it's very cool (I mean hot :P). I was just curious as to why you don't see any burners mounted on the bottoms of forges.

Another question: If I made a tiny coffee can forge with a strong burner hanging out of it, do you think it might have back pressure issues? Or, something I need just try and find out?

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5 hours ago, Zeb Camper said:

At the risk of sounding like an idiot

The only stupid question is the one you haven’t asked.

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I know of one guy who did mount his burner on the bottom.  Flat bottomed forge with an arched top, ribbon burner on the right side with a little wall to keep stuff from falling in the holes.  Air curtain in front to keep the dragon's breath at bay.

The main reason people don't bottom-mount burners is to keep bits of refractory, flux, and scale from falling down in them.

I have used vertical and horizontal forges, swirly and not.  For welding a thick billet I'd take a big horizontal swirly forge with a blown burner any day.  For general smithing a two-brick venturi is enough.  And they don't swirl.  And the fact that I've been doing this for 19 years now and still run coal must say something about me...:lol:  If I went pro or concentrated on damascus gas would be required, and so would a press.  For that matter, if I get annexed by the city I might have to quit coal as well.  The line is about 350 yards away to the north, and 120 to the east.  But, it's a dead end road on the side of a mountain.  Hopefully they don't want it!

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So lets say you have 2 inches of fire wool that's been rigidized and about a 2 inch layer of refractory cement on top of the wool, would that keep the heat from taxing your burners on a vertical setup?

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That will not prevent the chimney effect when you turn the forge off, if you mean burners placed vertical on top of the forge.

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36 minutes ago, Alan Longmire said:

That will not prevent the chimney effect when you turn the forge off, if you mean burners placed vertical on top of the forge.

Thank you Alan, I will move my burners to the 2 o'clock position.

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59 minutes ago, Jlinner said:

So lets say you have 2 inches of fire wool that's been rigidized and about a 2 inch layer of refractory cement on top of the wool, would that keep the heat from taxing your burners on a vertical setup?

Mine came with quick disconnect fittings.  I forgot to un do them once last weekend for 15 or so minutes. They got hot enough I almost needed gloves.

 

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1 hour ago, Jlinner said:

Thank you Alan, I will move my burners to the 2 o'clock position.

As long as they're pointing up they will chimney.  That's another advantage of the swirl type, you put the burner at a horizontal tangent to, or even slightly downhill from, the top of the lining.  Makes it harder to find the hot spot that way, but your fittings and hoses will never get hot.

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50 minutes ago, Alan Longmire said:

As long as they're pointing up they will chimney.  That's another advantage of the swirl type, you put the burner at a horizontal tangent to, or even slightly downhill from, the top of the lining.  Makes it harder to find the hot spot that way, but your fittings and hoses will never get hot.

Can you show me what that looks like on the inside or the forge?

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Look a few posts up at Matt Walker's forge video.  It's the best (propane) welding forge I've used.

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Just something I've noticed is why do "most- not all" forges for sale seem to be square with the burners facing straight down?

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image.png

 

So we are talking the same issues with this Majestic brand forge as well, just for example purposes and not baggin on them.

Edited by Jlinner

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4 minutes ago, Jlinner said:

image.png

 

So we are talking the same issues with this Majestic brand forge as well, just for example purposes and not baggin on them.

Thats one way to eliminate the hot spot....make the whole forge a hot spot. lol  I cant answer your question but I am guessing that fuel line has a quick disconnect set up also.

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Square shapes like that are quicker and easier to manufacture with off-the-shelf components.  Fire brick is a lot easier to get in square/rectangle shapes than round.  Then all the alignment after that choice gets easier with squares, too.  

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36 minutes ago, Jlinner said:

Just something I've noticed is why do "most- not all" forges for sale seem to be square with the burners facing straight down?

Ease of manufacture is my best guess. Way back, when you had to use dinosaur flatulence to power a forge, knifemakers were limited if they wanted a store-bought-turn-key gas forge. There were just a couple of farrier's forges out there and one was decidedly "less than optimal" (to be generous) for knifemaking. It seems to me that many today are copying its design.

Edited by Vern Wimmer

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Yep.  Cheaper to make, especially by people who don't understand forge design. 

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Ok great guys. I really appreciate all the help/advise.

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I'm building a round forge with horizontal burners coming in near the top to make a swirl downwards.

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Good choice.  To elaborate on the square ones with top vertical burners, they were designed for horse shoeing.  Farriers don't care about oxidizing atmospheres, decarburization, or scale.  They just want something that will quickly produce a good orange heat.  For that reason, coupled with that type of forge, for years it was a tenet of faith among blacksmiths that gas forges produced heavier scale (they did), and that it was impossible to forge weld in gas (it was).  It took lots of tinkering with forge and burner design to produce a gas forge that had an adjustible atmosphere that could reach welding heat.  With today's bladesmithing community that is very much concerned with oxidizing atmospheres, scale, and decarb, we have many designs that will run a slightly reducing atmosphere and will let you weld without flux.  A far cry from the old days of 30 years ago!

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To agree with Alan and to attempt to beat the horse to death I would add that square forges, being inefficient by today's standards, require more burners to meet expectations. In the American way "more must be better" and as a result of that and an amount if OCD over common sense, some overlook the cumulative effect of multiple burners in a closed, efficient space as they extrapolate the predicted heating ability vs cubic inches in a straight line fashion. As a result of this we see folks worrying about whether or not they have enough room, on the exterior, to mount the number of burners they have calculated the interior will need.

Hmmmm.

Edited by Vern Wimmer

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Here is what I have so far, suggestions on a round swirl forge.

20171121_185149.jpg

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Here is what I have so far, suggestions on a round swirl forge.

20171121_185154.jpg

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