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I Forge Iron

Before you build your first forge.


IanOhio

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I just wanted to share my experience to hopefully help steer anyone away from the bigger is better newbie mentality.  I obviously fell into it and most I see post here do the same.  So I'll just post a few pictures of my first and second. The first, built from an old airtank, uses 3 burners, interior dimensions 9"wide, 6.5"tall, and 22" long. I spent probably 40 hours on it, and way too much money. It works well for large pieces, I never tried to reach welding temp with it, so I couldn't say for sure. I only have a 20psi regulator on my tank and I doubt it honestly.  It does have a brick floor as well which wouldn't help. 

The second forge is a 8" ID pipe. Mine happens to be 1/4 wall but something that heavy is unnecessary in my opinion. 2" of kaowool. And a firebrick floor. Which is failing fast. Go for the kiln shelf that everyone recommends. I have some ordered myself, to replace the green glass that my brick has turned into. Interior dimensions are 4.5" wide, 5" tall and 8.5" long. Hard fire brick for the doors, I'm sure there's a more efficient solution, they are failing too. This thing will reach welding temp easily. Only uses 1 burner, and I've used it for a month at least 3-4 nights a week on less propane than I could run the 3 burner forge for a couple days. I built it out of scraps I have laying around and left over kaowool and itc100 from the big one. If you bought everything I'd guess you'd have maybe $100 in it. It took less than an hour to build, minus the burner and waiting for the itc to dry. 

Feel free to critique either anyway you wish. I would put the burner in tangent as is often suggested if I did it again and come up with a horizontal door somehow like my big one has. But works great as is. Maybe even 2x 1/2" burners instead of the one 3/4"

Build the small one first! Easy, cheap, and will get you going far quicker. I found this forum about 2 weeks too late to save myself....don't be like me :)

 

PS don't mind the wild copper line, I was adding that side shelf and hadn't finished plumbing it in yet. 

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Forgive the sideways pictures. 

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5 hours ago, Frosty said:

Nice forge. Are those Porter burners?

Frosty The Lucky.

Thanks Frosty, the are some version of them yes. I did not have the actual plans, but I had seen pictures of Mikes and the Trex, and looked at the basic design of a handheld propane torch. Since then I have read alot here and learned about several things such as how to figure tube length and the size of the air openings. Before i just played until they worked. I'll give it a better go one of these days but for now they're working ok. 

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5 hours ago, basher said:

I run a 1" burner forge capable of getting 15kg billets of damascus to welding heat, I am always bemused as to why so many people seem to go overkill with multiple burners etc.

 simple is often best.

I can only speak for my own motivations. There is so much information out there, and before you actually begin, you have no idea about what you need past the name of an object. Other than the images of blacksmiths with seemingly huge brick coal forges I had little experience with the craft.  A few Google searches later and I find more big ones than little ones. I have an air tank, and go.   I built my coal forge first. And I had trouble getting anything good out of it. Nevermind the fact that I had no idea what I was doing, how to control the fire or what kind of coal to use. Must be it's too small. 

Fast forward 6 months or so, I start to understand some basics, have a little bit of first hand experience and am able to weed through the mass amount of information easier. It kind of hit me one day watching a video of someone "teaching " how to forge some random object, and I said to myself 2 minutes in, "this guy doesn't know what he's doing." A year or two ago I would've not been able to tell the difference. I'm not saying I'm an expert of anything, I certainly am not. My long winded point is that it is easy to get misguided when you don't know where you're going.  And the learning curve is exponential.

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"Why so many burners" is a question it takes a look back in time to answer. Over twenty-five years ago guys were experimenting with naturally aspirated propane gas burners that were basically an imported Australian design; these were competing with better gun burner designs that were mostly limited by the use of natural gas for a fuel source. The average NA burner wasn't all that hot, and guys, who were after all groping in the dark, concluded that "more might be better" and loaded up oversize gas forges with too many burners, hoping to overcome problems the didn't understand very well...wait a minute; guys groping in the dark with a bunch of half baked ideas? That sounds more like current events, doesn't it!?!  
 

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There's also the hard wired instinct that tells us, "more is better." It's a survival trait from oh I don't know Homo Habilis days? Maybe farther back, the more food you gather the longer you can go with a guaranteed meal and that's better. More of any necessary resource is better and it spills over to everything we do, look at a fast food burger, enough food to feed a couple people. It applies to everything and it takes knowledge and experience to overcome.

Why shouldn't it apply to forges, anvils, hammers . . . well every darned thing.

Exercising my experience with forges and burners how many and what size burners have pretty well set parameters. #1. The hot volume determines burner output (tube size). PERIOD.

The number of burners is dependent on the hot volume shape and the needs of the user. Shape first, long and narrow needs to spread the flame out IF the user needs even heat. More smaller burners or a ribbon. Personally I LIKE a hot spot in my forge for general work it lets me work one area more easily without having to baby the rest. So, one larger burner.

A LITTLE bigger than you need is a good thing for a couple reasons. You might want to make something bigger but more likely the less crowded you are in the forge the less likely you're going to bang up the liner.

My new forge is half the size of the shop forge and it's still too big. That darned human nature and survival instincts get us all. Where's Spock when you need him? <sigh>

Frosty The Lucky.

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My own desire for multiple burners at first was for flexibility.  Being able to run 1 or 2 to get that localization that you're talking about Frosty, if I needed it. But groping in the dark, as Mike said, I still made it too big, and one burner will not keep the whole forge hot enough. I have experimented with a firebrick baffle as described in another thread here. It helps some. Someday I will probably experiment with ribbon burners and make the interior dimension slightly shorter. Right now I'm content with the smaller one. I have jabbed the kaowool a couple times since it is so narrow. 

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On ‎8‎/‎13‎/‎2016 at 3:06 PM, Frosty said:

Exercising my experience with forges and burners how many and what size burners have pretty well set parameters. #1. The hot volume determines burner output (tube size). PERIOD.

I would add that it is not just the interior volume, but also the type and thickness of the forge insulation as well as the door construction/configuration, but I see where you are coming from Frosty (for sufficient insulation that the side walls are not bleeding out all your heat and reasonable door openings the critical parameter is the forge volume).

I have also made the mistake of having my first two gas forge bodies a little too large.  Now on my third, which will have a ribbon burner, and hope to correct this.  Forge design is a bit more critical when you are heating with residential pressure natural gas.

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Latticino,

I hope, since you are employing a ribbon burner, that you won't go to the other extreme by making the forge undersized. Yes, I am one of the loudest voices baying "smaller is better." But, I believe the central point of ribbon burners is are their ability to hold a high heat in a larger interior volume without breaking the bank.

Do to "economies of scale" factors, I think that mounting a ribbon burner on a miniature forge is to miss the whole point of them; your thoughts?

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Well, I think the forge is hardly what I would call miniature, just about 2/3 the size of my current forge.  The  new interior is right around 340 cubic inches, configured as a half cylinder (hemi-cylinder?);  a "D" shape with the flat side down.  Saw that configuration in other's forges and when our local group had a workshop making same I had to sign up.  Most folks used a pair of full hard bricks for the floor (backed by 1" of kaowool) I used a high alumina split brick floor backed with a bit more thickness (as far as I'm concerned you can't have too much insulation).  The design standard was for a single 3/4" NA propane burner, and reportedly others have achieved welding temperatures with same.  I use low pressure natural gas in my shop, so I decided to try a ribbon burner instead.  My logic, and it may be totally off kilter, is that the ribbon burner will permit me to add the same amount of heat (combusting air/gas mixture) to the forge interior at lower flame velocities and greater spread to initiate the radiative heating process used to actually heat the metal.  Hopefully this will give me a couple of positive outcomes:

  1. Not overtaxing my smaller blower (would rather keep with the Kane Bros 140 CFM blower than go up to my Dayton 1/2 HP high pressure blower, which is rather oversized)
  2. Reducing the noise level from the gas forge
  3. Reducing the effective forge heat lost via the combustion products venting

The last one is a bit questionable I agree, but my theory is that my door openings typically are not optimized during forge use (larger than needed) due to my negligence in closing the doors and/or stock considerations.  With a door that is too open, high velocity flame fronts (from conventional stable burner outlets) could lead to high velocity flue gas exit, or even portions of the flame existing the door itself.  The higher velocity at the same door opening size would result in a higher heat loss.  Basically the slower the flame moves inside the forge the more time it has to heat the forge interior and the stock. 

Now I'm not a combustion engineer, and have been quite impressed with the design information for forges and burners you have shared with us on the site.  The natural gas/forced air ribbon burner I have is 9" x 2" Mizzou with 15 crayon sized holes.  What do you think?

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I think you have everything well in hand; this is the size and shape I would go for. If you later decide your choice of fuel doesn't supply all the heat desired at times, enriching it with a small percentage of a second fuel gas is quite easy; in fact fuel enrichment done this way would give you the most bang for the least bucks and the least wear and tear in your equipment this way.

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