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Greetings,

This will be my first attempt at building a propane forge, so any constructive advice or recommendations would be greatly appreciated.

I'm currently collecting materials for the build and I came across this steel pipe.

It's approximately 14" in diameter, and I'm planning to cut it 16" in length.

My question is, if I plan to put 3" of insulation around the interior, would this still be too big for a 2-burner setup?

 

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Welcome aboard, glad to have you. If you'll put your general location in the header you'll have the chance to hook up with members living close enough to visit. You'll learn more faster in a couple hours with an experienced smith than in days trying to figure it out yourself. 

What are you planning on making? That'll make a mighty large forge, I've been doing this for 40+ years and need a forge that size so rarely, I make a quicky brick pile for the piece.

Frosty The Lucky.

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Thank you for the warm welcome!

I was considering using a propane tank to build my forge but it seemed that this pipe had the same diameter, which is why I grabbed it.I could cut it and then rebend it to a smaller size if I need to. Mostly it's just steel to do with as I need, I'm not committed to that particular diameter.I just figured that 14 in minus 4 in of insulation would give me enough room to work with wider material, such as a double bit axe head. like I said I'm not married to this idea, I'm just trying to get a forge built, lol.

 

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If you include a hard refractory inner liner / flame face you're going to have a forge around 9" ID, you could put a double bit axe in cross ways and have room for a couple knives. Have you figured the volume of the lined forge? The finished volume is what determines how many and what size burners it will require. 

Don't sweat it, everybody builds forges lager than necessary or even desirable. I've been doing this sill long and still do it. Without breaking out my calculator I'm guesstimating your forge as proposed to be about 1,200 cu/in. not counting end walls. That'd require four each well tuned 3/4" propane burners to bring to welding heat. I can tell you from experience that four 3/4" burners will start freezing a 20lb. propane tank in under 2 hours, performance will be falling off earlier than that. 

I would NOT cut and re-roll what you have now, I'd put that pipe in the stock pile and find something else for the forge shell. However, if you have the tools and shop equipment you could cut it into slices and make a pretty nifty oval forge with a reasonable width and height. I'd do something different but it's a possibility. I'd need to do some sketching before actually drawing things up. 

I like simple, the above isn't so simple.

Frosty The Lucky.

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Remember that you don't really need major strength in the shell; just enough to hold things together and protect the shell from whatever bumps it's going to get in the shop. My two gas forges are made from a party balloon helium tank and 16 gauge sheet. Frosty's advice is good.

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2 hours ago, Valeas said:

was considering using a propane tank to build my forge but it seemed that this pipe had the same diameter, which is why I grabbed it.I could cut it and then rebend it to a smaller size if I need to. Mostly it's just steel to do with as I need, I'm not committed to that particular diameter.I just figured that 14 in minus 4 in of insulation would give me enough room to work with wider material, such as a double bit axe head. like I said I'm not married to this idea, I'm just trying to get a forge built, lol.

Most propane cylinders are 13" diameter, so its size isn't terribly over, but it has no ends, which will add to your work. However, what the guys are mainly trying to show you is that a standard propane cylinder forge, is already oversize. Think non-refillable helium balloon or cylinder, or half a car muffler. Saves a lot of gas. You can always build bigger, and will still use the smaller forge to save gas; doesn't work work well the other way around, though.

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I made a few sketches and visualized making a forge shell by cutting that pipe down and reconfiguring it into something reasonably sized. I can buy an over priced piece of 16 ga. steel at one of several local hardware stores, burn up a couple reciprocating saw blades and weld up a shell in less time and effort. Even if I wanted to bend the top into an arch. 

I think for all practical intents and purposes I'd find another use for the pipe. Of course if you want to build a silly too large propane forge, join the club, we all have oversized dust catchers. I do have a LITTLE bragging rights for my first stupid too big forge I built it to reconfigure so I do still use it by closing off 3 of the 4 burners into a single 300 +/- cu/in chamber. On rare occasions I move the center partition and use 2 burners in a long 700 cu/in chamber for long work or to make a second work station on the far side.

My most recent forge is too large too. Maybe the next one won't be 2x too large. :rolleyes:

Frosty The Lucky.

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I recently found an unused propane forge shell at the scrapyard---with a poorly designed burner in the pile near it.  It was way too long.  One of my Minions took it to cut it in half and make 2 propane forges from it of reasonable size to be equipped with Frosty T burners.  I suggest start small and it will still be there if you need it later!

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19 hours ago, Mikey98118 said:

Most propane cylinders are 13" diameter, so its size isn't terribly over, but it has no ends, which will add to your work. However, what the guys are mainly trying to show you is that a standard propane cylinder forge, is already oversize. Think non-refillable helium balloon or cylinder, or half a car muffler. Saves a lot of gas. You can always build bigger, and will still use the smaller forge to save gas; doesn't work work well the other way around, though.

So I also have a helium cylinder that's 12.5 inches in diameter and about ten inches in workable length.

 

Still too big?

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20 hours ago, Frosty said:

I made a few sketches and visualized making a forge shell by cutting that pipe down and

Frosty,

I'm trying to find your plans for the burner, but I'm not having any luck.

 

Any suggestions or help?

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On 11/23/2020 at 12:59 AM, Frosty said:

I made a few sketches and visualized making a forge shell by cutting that pipe down and reconfiguring it into something reasonably sized. 

Frosty The Lucky.

So I decided to scrap the idea of using the pipe, a propane tank, it any other thing.

Now I'm building my forge from scratch using sheet steel I salvaged and a cut out section of that pipe for the roof of the forge, to get the curve.

I feel like if I use the curve in the roof and offset the burner 10°, I should get good swirl inside the forge.

My question now is, with final exterior dimensions of 8.5 in wide, 15 in deep, and 9 in high with 2 inches of insulation all around...

Do I only need one burner, or should I go ahead and put two? I plan to use your T burner design.

I calculate the interior volume after insulation to be about 338 cubic inches.

Thank you for helping this newbie out. I really appreciate it.

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Ease up on the quotes, the mods are getting restless. You can highlight a line and drop down tag sking if you wish to quote it will appear. That way you can indicate specific things you want to ask or talk about. Quoting the whole post, especially if it was only a little way back in the thread tends to take up bandwidth to no good purpose. 

15" deep is a little long for a single burner if you want the interior temperature even. Two 1/2" NA burners have the same output as One 3/4" NA burner. The only thing that makes multiple burners a LITTLE trickier is supplying propane twice. I favor using 1/4" copper tubing with flare fittings connected to an iron pipe plenum then the hose. This gets the hose well away from high heat and with the inclusion of 1/4 turn valves to each copper line you can run one or all the burners. 

Your 10* angle sounds good to me. I think you have a good plan and we'll be proud to help you tweak it.

Frosty The Lucky.

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Good Morning "V",

You need to have a positive Game Plan. The Forge you are looking at is still bigger that what has been suggested. The Burner configuration can come from the bottom, the top, or the side. You have to decide which way you are going to build it and be prepared to change it. There is no 'Best Way' except when the 'Best Way' is a proven way.  You have to make decisions and stick with them until proven otherwise. Some people learn from their mistakes, some people continue making mistakes.

No, Life is not simple. It is simply, Life!!

Neil

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When you're talking about forge size the ONLY dimensions that matter are the inside dimensions, after lining. Telling folks what the outside dimensions are only throws a monkey wrench in the discussion. Expecting us to do the subtraction and check your arithmetic for you isn't a good idea. Too many folk who are eager to help folks can't calculate volume. I've had guys come by for instruction who couldn't calculate the volume of a cube in sq/in. They still want to be helpful and will give you answers though there's no telling to what. 

You also need to be consistent with the order in which you present them. I THINK up till now you've been ordering them width, depth and height. This latest post I THINK you're listing them Width, Height, Depth.

If so then 4.5"w x15"d x 5"h are the proposed dimension of this plan. Yes? For a volume of 338 cu". That sounds close but I'm not getting out a calculator and checking your work. 

Let's assume it is, that falls mid range for a 3/4" NA burner. Range being 300-350 cu". The Illustrated T burner direction lists the ratios that bear on NA burners. They apply to ALL sizes. mixing tube length is = to 8x it's ID at the throat. a 3/4" tube is 6" long. A 1/2" tube is 4" long.

It's all laid out in plain English or as plain as I could write it with help.

Back this latest forge proposal. As I said in the burner plans the burner output size to volume is ideally for a mono dimensional chamber, cube or sphere or reasonably close. This proposal is better than 5x as long as wide or high. A single burner will make a HOT zone under the burner and temperature will fall off the farther it gets from the hot zone.

If you like a hot zone in a forge you're good with that one. However if you want reasonably even temperatures you need more smaller burners. Two 1/2" NA burners evenly dividing the length is a good start.

The jet hardware is the same for any size burner, a 0.025 mig tip is a good jet size.

Frosty The Lucky.

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Thank you for explaining all this to me. I really do appreciate it.

This will be my first propane forge build ever. That's why I'm asking so many questions, because I don't want to waste a whole lot of time and money and not end up with the best I could do.

I've literally never run a propane forge. All my experience has been with coal forges with hand crank blowers, so this is all new to me.

Yes, the planned internal dimensions would be 4.5"w, 15"d, 5"h.

I honestly have no idea whether I would want a hotspot or not. I plan to use the forge to heat treat steel and eventually be able to do some blacksmithing.

I've read in several places on the internet that having an even temperature in the forge would be best for what I want to do, but that doesn't mean that it really is the best, right?

If I were to run the two half inch burners like you suggested previously, the nipple length would be 4", that's pretty easy, but what size would the T be? On your plans you listed the air intake as 2D, So would I get a 1" to 1/2" T? I just want to make sure before I go buy the parts.

Thank you,

Val

 

 

 

 

 

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You're welcome, it's my pleasure. Even if I'm in a grouchy mood I don't really mind explaining things.

The intake size is confusing and doesn't really have anything to do with the burner type. 2d is for any NA burner whether it's a Reil type linear or a jet ejector. A T intake is automatically 2d, each side of the T is an intake port. Make sense?

However I discovered early on that making each port 2x the tube diameter increased air induction so I could run a larger jet and induce the correct amount of air.

I need to come up with a better label for intake port size though because doubling the diameter is quadrupling the intake capacity. The area of the intake ports is the important number pi r square just like burner output. So, a 1/2" T burner runs well and is easy to tune with a 1/2" x 3/4" T. Increasing the diameter of a circle by half, doubles the area. The area of the tube, intake port, etc. determines the carrying capacity of pipe. 

If you buy your plumbing from a real plumbing supply rather than a big box store you'll find specific components more easily. Also real plumbing supplies get pipe in lengths on pallets they cut and thread in house. When shipping pipe it's already threaded and to keep the threads from being damaged they have thread protectors on them. 

A thread protector only looks a little like a coupler but are no good as a coupler. They can't be sold so a real plumbing supply almost always has a bucket full in back waiting to be shipped back to the factory or waiting for the next dump run. Ask the guy at the counter when you buy your T, nipple, etc. for a couple. Be sure you don't intend to use them as couplers or they'll say no, there is too much liability if someone used them as a coupler and a B A D thing happened.

Anyway, last time I asked for a few they made me take the whole bucket. I said okay because they threw in the bucket. 

Thread protectors are not only free, they have a smaller OD so your burner ports in the forge can be smaller and they're steel not cast iron so welding things to them is easy peasy. I weld thread protectors to my ribbon burner plenums and interchange T burners with other forges. They just unscrew from one and screw into another thread protector, easy peasy.

They act like a step nozzle of Mike's description and so enhance induction some. Thread protectors aren't as effective an a step nozzle ALA Mikey. I first started using them to mount the burners and as sacrificial nozzles. Using hole saws I cut large washers from some 14 ga sheet steel, measured the depth I likes and welded the thread protector to the "washer". Those burners just stand on my too large, 4 burner shop forge the "washers" are the only mount. The copper tubing fuel supply are just rigid enough to act like guy wires. 

And no, I don't like vertical down burner orientation in a rectangular or square forge but I built that one more maybe 20 years ago. Of course a guy with hole saws can install a longer pilot bit and drill angled holes in a larger or differently shaped piece of sheet steel so the T burner stands at an angle. Hmmm?

Make sense?

Frosty The Lucky.

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Good; I hope you will document your burner build; people need to see more information about 1/2" size "T" burners. Of course, we all know that Mikey loves to complecate things, and getting people to build two burners is about the only way to do it with this design :D

Complicate; that's definitely spelled with an "I" (dad burn old brain)!

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