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Old 03-15-2008, 07:07 PM
Doug Lester Doug Lester is offline
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Cool Charcoal coal forge problem

I'm having kind of a love/hate relationship with my charcoal forge. It's a bottom shot forge made out of a charcoal grill that has a fire pot about 16" long and probably 6" wide, there is about 3-4" of space above the black pipe twyere and the top of the pot. The refractory is a mixture of kitty litter, sand, and straw which was covered with a bit of left over Mizzou. The air source is a 80cfm blower that I run with the choak plate closed down. The problem is heat can be a real iffy thing. Sometimes I can get a bright yellow and at other times it seems that I'm pressed to get cherry red. I burn lump charcoal in it.

Some things about it make me wonder. I have used the length of the forge for heat treating but I use my heat treating oven made out of a kiln more and I do have a 18" deep gas forge that I can also use so I really don't need that long of a fire pot. It seems to me that I may be burning more charcoal than I'm actually using. I am also thinking that I might not have enough charcoal burning underneath the work.

Here's the plan. The mom-and-pop hardware store near me frequently gets in a 3 gallon galvanized tub that I could line with a refractory and feed with a side shot twyere. With a smaller fire to feed I might be able to bring my double stroke raft pump out of retirement and use it until I can afford to send off my hand crank blower to be repaired. I think that it has a bad bearing. Any suggestion, feed back?

Doug Lester


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Old 03-15-2008, 07:50 PM
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prizzim prizzim is offline
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Feedback: If you're welding, you want a good amount of air pushing through a deep pile of fuel in a tight spot. If you're forging longer pieces, you want air distributed over a longer area, so you can work more inches per heat. For heat treating, you want to get enough charcoal hot enough to hit the critical temp for a few minutes, without overheating anything before quench. The last two share pretty much the same geometry. A bottom-blast, or side-blast coming out of a single pipe will not give you any length to work with at higher temps... but tend to save fuel because you're only feeding a few square inches at a time. Burning a Lively forge (18 inches of hot charcoal) eats a lot more fuel if you load it up, but I find I can weld in it if I get a tall pile on one side only, thus saving fuel by not running the whole length. 2 to 3 inches below, and a good inch plus on top of the work is essential, as is the state of the fuel... smaller charcoal bits that have burnt down for a while tend not to generate the same heat as freshly cherried fuel, so I reccomend before doing any high-temp work, you refresh the forge a bit, let it work for about 10 minutes or so, then crank it up.

As for the pump, I suggests slave labor. Got kids?


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Old 03-16-2008, 08:56 AM
Tai Google Tai Google is offline
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It should be deeper in general for charcoal. You need at least few inches of coals under the work AND over the top. The closer to the tuyere the work is the more oxidizing. If the work is resting on the tuyere it won?t heat up well at all.

About the only time you might need that 16 inch length is for heat treating. However, you normally need the fire pot to be longer than the blade you are doing, to get an even heat. For forging you only need 4-6 inches of length or so, and you can do any size blade.

I usually set up a muffle tube over my side blast, and am able to get 12-14 inch heats nice and even for H.T.

One problem with the pipe at the bottom with a series of holes is that if one or more gets clogged, you get uneven heats. That's why I stopped using that style,... burnt the points and tangs of a few nice pattern welded blades, and learned the hard way.


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Last edited by Tai Google; 03-16-2008 at 09:01 AM.
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Old 03-17-2008, 02:41 AM
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NuViking NuViking is offline
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One problem with the pipe at the bottom with a series of holes is that if one or more gets clogged, you get uneven heats. That's why I stopped using that style,... burnt the points and tangs of a few nice pattern welded blades, and learned the hard way.[/QUOTE]
Ive been having that problem too.


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