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My JABOD


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The first time it happened, it was still wet. I fired it up again last night with the dirt dry and lost another side of my fire pot. I also melted the air hose at the tuyere. The tuyere wasn’t hot but the air/smoke coming up it while inactive was enough to melt the thin plastic hose. When I rebuild the fire pot it, I’ll put a longer pipe in it. For now, I’m just holding the air hose in the pipe when I need air. 

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A longer steel pipe will have a stronger chimney effect unless it's long enough the hot gasses cool off before reaching the hose. If you have an elbow put it on your tuyere with a nipple aimed straight down. That will make the pump hose go down and hot gasses won't flow to your plastic.

If your "fire pot" sides keep collapsing make it more shallow. If the sides gradual all they'll do is settle where they are unless you scrape them out with a poker or piece of stock. 

Good luck with red brick, it's low fire clay as in cover it with cut brush sticks and light to fire from clay to brick. 

Try different things, you'll fid what kind of fire management works for you, it'll click one day.

Frosty The Lucky.

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Found some brick finally. My doctor, of all people, had several walls worth of it stacked up in his shed. Apparently the guy who used to own the house collected them. I got 12 bricks and the promise that I could come get more whenever I needed them. He will be getting a stethoscope bottle opener as soon as I figure out how to do it. Modifications are now under way. We’ll see how it turns out. I didn’t have enough time to finish it tonight. I don’t think the neighbors would appreciate me chipping brick at 10pm. I’ll upload a picture once I have it done. 

Frosty, thanks for the advice about the elbow. I think I have one laying around and they are cheap enough if not. I wasn’t looking forward to cutting another chunk of pipe with my hacksaw.

The problem with my current set up is that the sides of the “fire pot” melt into clinker and either wind up in the bottom or pull away when I clean it out. I’m currently having to rebuild the “pot” every time I want to use it. I tried lining it with clay from deeper in the ground (roughly 1 1/2’) but got the same result. It was wet when I started the fire, no idea if that makes a difference. With the humidity we’ve been having, I would have been without a forge for several days to a week if I waited for it to completely dry. 

I’m not expecting the bricks to last forever. I’m giving them a try because it’s what Charles used on his MKIII. I know they will melt at some point and I’m going to have to leave a layer of ash in the bottom to prevent the clinker from sticking. If it doesn’t work, I’m not out anything but a little bit of time. Plus, experimentation is half the fun. It’s got to be better than rebuilding the thing every time I want to use it though.  

 

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Modifications complete! The fire pot is ~8x4x4”. Tuyere has been moved ~1” backward with a hole chiseled in the brick. I put a 90* elbow and a short nipple on the pipe to hopefully prevent it from melting again (thanks again for the suggestion Frosty). It’s currently spitting rain and forecast to get worse so firing it up may have to wait until the weather improves tomorrow. Or, I may get impatient and rearrange the carport to make it work. 
 

The next modification will probably be wheels of some kind to make it easier to move around. I’m debating between casters on all four legs and an axle and wheels on one side only. 
 

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The weather died down and I was able to fire up the forge this evening. It works but just barely. The heat wants to sit way down in the fire. If I scrape the coal mound into a donut shape, I can see where the coal is a nice whiteish yellow. It’s ~2” below the hearth. 

I can push it up with enough air. It just takes a long time to get there and dies back down as soon as I quit pumping. After a couple hours, just getting 1/4 round up to a workable temperature was a beating. I’m sure clinker was a factor toward the end. I pulled about a fist sized chunk out of the bottom after it had cooled down. Getting a good heat was a struggle from the start though.

I can raise the tuyere some to hopefully solve the clinker blockage. I’m wondering if I need to reduce its size though. Going from a 1” pipe to a 3/4” pipe should increase my pressure with a given volume of air. I’m hoping that by increasing the pressure, I can raise the heart of the fire without having to pump so hard for so long. 
 

I’ll do a post-mortem on the brick tomorrow. I know some of it melted but I won’t know how much until the sun comes up tomorrow.

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5 hours ago, Bantou said:

I can see where the coal is a nice whiteish yellow. It’s ~2” below the hearth

Two solutions that I can think of is to lower the hearth or raise the floor of the firepot. My MARKIII firepot is only the depth of a brick in it's thinnest orientation in the front and back of the firepot I guess 2 3/4 inches. The tuyere is approximately 2.75 inches below the hearth. The thickness of a brick measured on its thinnest side.  It's oriented just like this one built by Charles R Stanley except I have tall walls on both sides and short ones in the front and back. It's basically a tiny japanese style trench forge. Mine is disassembled in my truck and it's 4am so this is the best I can do right now. 

Pnut

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Pnut, that’s probably what I’m going to have to do. I built it at ~4” deep based on this chart:

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It was part of Charles’s post about the anatomy of a side blast forge. He mentions somewhere that a coal fire needs to be deeper than a charcoal fire in a side blast. My, apparently faulty, assumption was that I would need a deeper fire pot since the MKIII was designed for charcoal. Hopefully, raising the bottom of the pot fixes my issue. This thing has been kicking my backside for going on two weeks now. 
 

I cleaned out the pot this morning. The bricks held up better than I originally thought. The two on the back of the pot took some damage above where the tuyere comes in but not a significant amount. There is some clinker adheared to the bricks but I should be able to chip it off without an issue. ABDBE9B5-2087-4311-A459-D824393F0984.thumb.jpeg.4bb41eb9e2141ad07a18b593343b8450.jpeg

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Having the tuyere closer to the hearth will raise the hot spot and having the two bricks standing up will allow you to mound up the fuel. I have bricks standing up on both sides of my fire pot. Since I have dry fill I can easily rearrange it though. I primarily burn charcoal in mine but it works with coal. I'm just too lazy to drive the ninety minutes to Louisville to pick any up and I have a source for free wood to convert to charcoal. 

That's the one great thing about a jabod is you can easily tinker with it until it's working for you. I swear no two seem to work exactly alike. 

Pnut

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Man, that is just silly deep! I've never made a coal fire deeper than a fire brick standing on it's side, 4.5" and usually laid flat, 2.25" and if using a side blast I aim the tuyere down the length facing me. In the side blast forges with bricks standing on end they are the "Fire Back." The blast aims at the fire back across a shallow trench, maybe 2" or so deep. The trench being 4-5" wide max. 

This allows you to modify your fire by how close and high against the fire back you place your work as well as how much blast you apply. 

My preferred side blast is a trench with longitudinal blast though the fire back has advantages for different uses. With the air blowing lengthwise in the trench you can see the zones, even covered by: ash, embers, breeze, pyrolizing and green coal. The harder the blast the longer the fire and heart (sweet spot). 

Placing the tuyere cross wise across a trench is better for making a small fire, and is my preference when I need a tea cup size heart for small pieces or close heat isolation like setting rivets or collars. 

I love the JABOD though I've never used one as such. I certainly wouldn't have made one from 2X' lumber nor so deep. The couple times I've made a trench forge at comfortable working height, I did it on an old wooden kitchen table. I just dumped a couple couple buckets of barely moist soil on it and hammered the mound hard with a 2x4. I say mound but it was maybe 6" and flat, wide and flat. I scraped a shallow wide V trench, a couple 3 inches wide and maybe 2 deep. The tuyere was just a piece of pipe and the end didn't last long, I hadn't done this before but it lasted a while. In a ground forge I stop the tuyere a few inches from the fire and make the final "nozzle" from broken fire brick. The table top forge worked fine for a couple hours which is what we needed. The table top didn't show sign of heat though it got plenty warm.

I've never had soil fire very hard but unless you're really lucky we don't get clay here and I'm not driving to the coal mines for fireable clay.

I don't know what's going on with your Gumbo but the real problem looks to be structural. Steep vertical sides that deep aren't going to last. It's not like you're treating it like pottery and following the specific necessary steps to get clay to fire, even brick fire. 

I'm not trying to nit pick you, you haven't made a mistake we haven't though you've maybe packed in a few more in one project, maybe not. I know I've made record numbers trying to make or do some things. You get used to it after a while, it should NOT bother you any more than having to try something else.

Charles has a LOT more experience with coal and charcoal than I and his JABOD thread is a proven fire back design. Stop trying to improve on it, just make it look like HIS pictures. Go to the first couple, the first one works just fine, later refinements are but they're not necessary for a functional forge. Keep it simple, forget all the discussions on the thread, you get involved in other people's confusion and problems which causes YOU to think you have the same problem to solve. 

Lots of suggestions are from people who are still trying to figure out how to make them work which is a good thing if there are 3-4 of you trying to make one work in person is somebody's back yard. Online you get hundred of guys suggesting unproven IDEAS, sometimes laughably unworkable ideas. You don't need any of that. Just follow Charles long time proven JABOD. If you run into a problem you cant winkle out yourself maybe ask CHARLES in a PM so you don't get flooded with helpful but confusing, conflicting ideas and suggestions. 

Recently guys have made solid suggestions though they vary between them, mine included. You don't need to pick and choose or worst of all mix and match until you know how the things work. 

Frosty The Lucky.

 

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Frosty, I shallowed up the fire pot this morning. It now sits at 2 1/4” (roughly the same as the short side of a brick), which is about what Charles’ is. I kept a slight downward angle on the tuyere. I’ll post an update with pictures after I get it fired up. 

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On 4/24/2021 at 4:04 AM, pnut said:

My MARKIII firepot is only the depth of a brick in it's thinnest orientation in the front and back of the firepot I guess 2 3/4 inches

 

1 hour ago, Frosty said:

laid flat, 2.25"

That's the correct measurement. My masonry teacher in highschool would be mortified that I couldn't  remember the thinnest measurement of a brick hahaha. 

Pnut

That should do it for you. The fireball should be level with the surface of the hearth now. I'd bet you'll have better results. 

 

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I might have if my air pump hadn’t broken on me... the o-ring gave out after less than a week of use. Looks like I’m headed to Wally World for an electric pump.

Starting to wonder if the pump hasn’t been half of my problem 

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1 hour ago, pnut said:

My masonry teacher in highschool would be mortified that I couldn't  remember the thinnest measurement of a brick hahaha.

So long as he won't strike you off for it! A course as laid is 2.5" because it has been mortified. Now forgetting THAT 1/4" is a pointless mistake. 

Frosty The Lucky.

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Eureka! It works. Eats coal like a wild thing but I can work metal at least. Finally finished my set of tongs and got started on a hot cut hardy tool. Unfortunately, I missed a strike while upsetting and the hammer handle suffered a catastrophic failure. Took me forever to find the hammer head. It wound up a full 18’ away from the anvil behind me. I had a spare hickory handle that fit it. I just need to sand and finish the handle. 
 

I need to turn it around though, the tuyere angles a little to the far side and the fire follows. I could pull the bricks and shift everything over but it’s a lot easier just to put a brick in the “cold” side and turn the forge around. 
 

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Fuel does not make the fire hot, air makes the fire hot.  Add gentle air and only as much air as you need to get the heat you want. It eats coal because that is the setting of the air flow. 

Put a on/off switch in the electric line and turn the blower off when you do not need it, like when you are working at the anvil.  You can mark the air valve for two positions, one when you are heating metal, and two for when you step away to the anvil.  You may need to take the air valve apart and apply a little lubricant to make it turn more easily.

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I’m planning on tinkering with the air later. I know I was probably running it hotter than necessary. I was just happy it was actually working for today. I had the valve at about 3/4 open while heating and then shut it when I wasn’t using the fire. Half open wasn’t enough to heat the 3/4 piece of sway bar I was making the hardy tool out of. I’m sure there is a sweet spot in there somewhere. It will just take some playing with to find it. 

I’m not sure if I can take that valve apart or not. I’ll look at it tomorrow and see. It would definitely benefit from a shot of lube though. Worst cast, I can squirt some silicone up in there with the ball closed and then wiggle it back and forth some to work the lube around. 

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13 hours ago, Frosty said:

So long as he won't strike you off for it! A course as laid is 2.5" because it has been mortified. Now forgetting THAT 1/4" is a pointless mistake. 

Wish I had a witty reply but it's too early in the morning. So I'll just TUCK my tail and POINT my feet towards the door. 

Pnut

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Posted (edited)

Fired her up again today and got the air just about dialed in. My mark for the “sweet spot” on my valve is just a little bit off. I need to move the handle just past the mark in order to get it right. I let the fire get too big a couple of times thinking I had the valve on the money.

I wasn’t able to disassemble the valve. It is a pvc ball valve meant for water lines and is formed to be a solid unit. Interestingly enough, squirting PB blaster into it just gummed it up worse. PB is supposed to be safe for pvc but I had to put vise-grips on the valve to comfortably adjust it after adding the PB. I’ll probably wind up changing it for a brass valve at some point. Right now I’m saving money for a post vise. 

I changed the way I stack my coal. Instead of one big mound, I built a small mound over the fire and piled the rest beside it; close enough to coke up but far enough away to not fall in. I keep just enough coke on top of the fire for it to stay black. With the large mound, I was disturbing the fire too much and putting green coal in it every time I added or removed stock. With this method, I can easily rake the coke back onto the fire without mixing in a bunch of green coal. I tried two different methods of putting the stock in the fire (stabbing it in and working it in from the top) with similar results on the large pile. 

Between the two changes, I was able to reduce my coal usage to about a scoop’s worth over 2 1/2 hours (I use a medium sized Folgers can for my scoop). I could have reduced this some with better fire management. It’s a learning curve and will be a bit before it all becomes habit I’m sure. 

Clinker build up on the bricks over my tuyere is becoming interesting. The hottest part of my fire is against the brick. After about two hours of forging, there was close to a half inch of clinker built up on the brick.   I had to chip it off to access my best heat. It was easy enough to chip off with my rake but I need to remember to keep an eye on it or figure out how to stop it from sticking. 

I also need to find a way to quiet the mattress pump. I think Charles mentioned a way to do it somewhere but I can’t remember it now. I’ll try and dig it up before I fire the forge up again. 

Edited by Bantou
Grammar
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The more you know lol. I always assumed Pam was vegetable oil. I wonder if Moly would solve my clinker issue. It’s melting point is well over 4,000F and there doesn’t seem to be any health related issues with heating it. 

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Picture of approximate coal consumption for 2 1/2 hours of forging. I seem to be burning roughly the same amount of coal per hour as I did when taking my class. 
 

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The straps will work great to hold down your anvil, so long as you keep them near room temperature. I wouldn't be able to manage that long enough to make it worth using straps to me. Don't breath the fumes when they burn. 

I recommend putting bolts through the foot holes, or screwing metal strapping down over the feet, or bolting bars over the feet, or bolting eyes down to the spool and using chain and turnbuckles to hold it to the eyes, or... anything else that is non-flammable. :)

 

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