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What do you guys think of this forge design?

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I was thinking I would run a full length of C channel all the way down the bottom of my forge to support the 2.5" thick firebrick floor. Also do you guys see any problems with the inswool keeping to the shape of the roof wedged in like it is in my drawing? This will be my first gas forge so I've never worked with fiber blanket before.

I'm going to make a moveable back wall to block off the back section I'm not going to be using. With my math a burner spaced about every 6" using the 350 cubic inch per 3/4" burner rule of thumb could bring the entire 24" length up to welding heat, not that I'll ever need that much heat.

What do you guys think of the interior detentions? Should I make it taller inside?

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You need to encapsulate the ceramic blanket. Ceramic (read glass). Do you really want to be breathing small particles of glass? Think Asbestosis. Some just coat the blanket with Plistix, Metrikote, or ITC-100. The problem with this is that the Infrared reflective products to not impart any strength. Every time you hit the wall with a piece of metal (and it will be often) you will poke a hole in the IR coating.

The fire brick is a heat sink.

I suggest casting over the blanket and casting the floor with Kast-0-Lite castable refractory about 1/2 inch thick then over coat that with Plistix or Metrikote.

Attached is my tutorial for building a gas forge.

Building a forge with that many burners is way over kill. When forging you will only be working about 6 inches. The additional heated metal is just causing additional scaling. Burners costing from $50.00 to $150.00 each is always a consideration.

Of course a long heat may be needed if heat treating a sword.

And then there are exceptions to every rule.

Builld a Gas Forge Tutorial1.pdf

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"Should I make it taller inside?

*YES*---*NO*---*MAYBE*!

How should we be able to know that without knowing what you plan to do with it!

"I plan to forge ornamental work that will often exceed the 7" limit"
"I plan to only make knives and so the 7" limit is really too high..."

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OK, I can do a castable floor, doing the ceiling looks kind of tricky but maybe if I cast the ceiling first in a few different pours it would go alright. I see a lot of guys using firebrick to build forges out of though, I take it none of those forges will be as efficient at retaining heat as one made from Kast-0-Lite?

A far as burner placement, I really only want to be able to get welding heat in the first 10"-12" or so which brings the volume to 582-698 cubic inches I'll put 2 burners in that area for sure, but will one burner for the last 12" or so be enough to evenly distribute temperature without any colder spots?

Mostly I make knives, and lately all I have been doing is heat treating in my forge. But I do a little blacksmithing too, and sometimes when family pester me enough I'll get into ornamental work; but I always have a coal forge too so that 7" will work.

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The castable will not stick to the blanket so you have to do it is serveral castings. You can cast a portion, wait about an hour for it to set some then rotate it and pour another portion, working the joint to make a monolithic pour. Most fire brick forges are made using the soft light weight bricks which are not heat sinks to the extent of the hard brick, however, they are soft and break down after repeated firings.

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I think you should build it. Taking pictures as you do of course. Fire it. Heat metal in it. Then do a post on your results and what you like about it. What you don't like about it, and what you would do differently next time.

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If you are doing mostly knives, it is way too big and will use more fuel than you can imagine. As Thomas said, plan your useage. If you look back at some of myn older posts building blown forges, they are smaller than than your drawing. If you look at my website, you will see I build lots of stuff out of a smaller forge. Unless you plan on doing very long stuff, just built it 12 inches or less. I am using a newly designed blown system, outside dimensions is 10" by 10". inside dimensions are 6 1/4 wide", by 3 3/8" high, 10" long. I can make axes, all sorts of things, it uses less than 1/2 gallon propane per hour and the interior is a hard ramable (plastic) refractory covering the blanket that is between the shell and interior, it is impervious to flux enough that when doing a lot of welding, the flux puddles on the floor. It is also very resistant to me banging into it.

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Well my plans were to use soft fire brick for the floor, I didn't take into account the softer bricks breaking faster though. I'll have to figure up how much Kast-O-Lite I'll need.

I do make longer 12"+ blades so I defiantly need a forge that has depth to it so I can heat treat longer stuff. I'll be using a moveable back wall and will be able to turn burners off individually so for just regular work I can have only one burner running and the back wall pushed close to the front creating a smaller chamber to heat. That's a really nice looking forge Jymm. I'd be interested to hear more about that ramable plastic refractory covering, I don't think I've ever read anything about that stuff before.

I'll be sure to put some pictures of the build process together, I should be done before the end of the year.

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You might want to consider using a kiln shelf for the floor. You can cut it to size with a masonry blade on an angle grinder. It is hard enough to withstand
almost anything you put on it. I put mine over the soft fire bricks and lined the forge with 2" of ceramic. I coated it with kiln cement and then ITC.
You dimensions for your plan are about twice as big as it needs to be.

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I used to only put the ram refractory in the bottom and coat the blanket with 3,000 degree mortar, thinned down. It was cheaper than the ITC stuff. However, it eventually cracks and flakes off, pulling blanket with it. When I switched to using Dixie Refractory products, I also got a salesman that stops by my shop on occasion. He suggested trying using the ram to cover the entire inside. I really like it.
The advantage of using a ram refractory such as Thermogen 60 (listed in the above article, I now use instead of Plastek 85 due to pricing,) is you can easily put it in cold, molding like clay to any size or shape. Tricky part is putting it on the ceiling. With a couple of hooks in the top, or even without, and using some sheet metal clamping it in place, you can fire it up and set it. I have taken flat bar and made simple "C" type holders for the firing process. One thing I have learned is to not make it too thick on the top as it does slow down the warm up time. I use no more than 1" on the top, 1/2" to 3/4" works well. I make the bottoms about 1" thick. While straight fiber blanket may initially be faster, the combination of radiant heat and reflective heat can work in your favor. If you use straight blanket and put a large piece in, you can see the cold metal pull the heat out of the system of straight blanket. I don't have that problem with the combining of materials I use. Plus the longer my forges run, the better they perform.

I have the more complicated I make things, the more problems I have. So I keep coming back to the philosophy of keep it simple.

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