My Muddy Box

[4seasons]

After spending the last month extracting clay from my dirt and last week mixing and mashing a clay, wood ash, sand, and grass string cob I finally got it some molds yesterday. Not sure if I can post photos but this is what I have so far:

I sat it about 3 feet from my current wood stove to speed up drying.

This is a 4 inch core.

And the heat riser.
I slapped the molds together out of some scrap plywood I had laying around and used coffee cans to form the round openings. I filled bags with sand and stuck them in the coffee cans so they wouldn't get crushed by the mud. I figure if I can't just pull the cans out of the mud once it dries then I can punch the tops and bottoms out and pull out the sand bags one by one. I also used a solid block of wood for the port opening so that will have to be drilled out before I can burn the inside mold out. I used 2 inches of mud on all sides including the top. Not sure if that will hold up as most of these I have seen used bricks or a piece of refractory over the top of the box. I'm also not sure what ratio my clay/ ash/ sand mix is as I kinda just went by feel. If I had to guess I would say 10:6:3 clay/ash/sand with very little grass string in the mix to give it some fiber. I think my clay was a bit wet as my mix seems a bit runny. It can be rolled into a ball but it sticks to my hand so much it comes off my hand teardrop shaped and lands with a bit of a splat. Hopefully setting it this close to an active wood stove while get it to dry out.

[mannytheseacow]

Cool! I can't wait to see how it turns out! I've got a 4 incher in the works too. All ready to cast as soon as the ground thaws a little to dig some dirt for cob to build the surround. I'll bet you'll have to do some major firing to dry that block out! Your current wood stove will certainly aid in drying too. Good luck!

[matt walker]

Super cool! One thing to avoid with any casting, but especially the mud ones, is any banging or rough handling. I'm telling you now, so you can take the path of least abuse to get the stuff out of the mold. I would probably gingerly drill to open up the passages a little, then burn everything out, cans included. Tugging on any of that is almost sure to break it, especially once it shrinks around all of that solid stuff. It's going to be cracked already, so tread lightly. Awesome little project! Can't wait to see it burning.

[4seasons]

Good tip Matt on the banging the mold. I figured it would be kinda fragile so all am planning on pulling is the coffee cans. Anything more than a light tug and I will be reaching for the drill. That's why I bagged my sand so I could get it out easily if the cans wont pull. The heat riser is already cracking. Since it weighs about a third of the core though I would expect it to dry much faster. I also lined the core with plastic to keep it from filling up the seams in the plywood but just taped up the joints in the riser. I would imagine that the riser is losing some moisture to the wood where the core can only loose moisture thru the top.

[4seasons]

Well I took it out yesterday to burn the core out. It was still very wet. So wet that it took 2 hours to get a fire going in the mass of mold that had formed inside. I could not drill out the port opening as the extension on my drill broke so I thought it might burn out. No such luck. Even after getting all the sand out of the coffee cans and getting a fire burning in both sides, the plywood was just to wet. Even a 6 hour long fire was not enough to get the wood in the port dry enough to burn. I did get the top and sides to dry but the bottom is still pretty spongy. Today is another rain/freezing rain/snow day so I brought the core back in to set next to the wood stove. The heat riser seems to be in the same shape, to wet to do much with and I didn't even try to burn it. So I learned a couple of things. First my cob mix was to wet to start with. Second even sitting in the house next to a hot wood stove, 200 lbs of mud will not dry much in a week. Also the parts that did get dry were starting to crack pretty bad. Not sure if that means I needed more sand, wood ash, straw, or just that it wasn't packed in enough. Even if the whole thing crumbles on it's first real burn I can still call it a learning experience. Anyway this project is back on hold until the weather clears up.

[4seasons]

Time for an update. Spent Friday and Saturday Trying to get this thing to rocket without much luck. I did finally get the port drilled and to burn out enough to pull the rest of the wood out. Tons of cracks around the back of the box and p-channel. So I decided Sunday to try to seal all the cracks and gaps up with some more cob mix. It wasn't pretty but after lots of plugging gaps and sealing the heat riser to the core with cob I started a fire. My first impressions were not good. I got tons of smoke, had flames lapping around the front of the box and smoke rolling out of the p-channel, front of the box and heat riser. I played with the air in, and closing and opening the P-channel. Nothing seemed to make it burn clean. I could not get the cyclone of fire up the heat riser. So I went to get the camera so I could show you guys what it was doing and get some advice. That is when things started to go right.

[4seasons]

Well here is the first video of my muddy box. It had burned down to hot coals and the smoke cleared up.

So I loaded up some wood on the bed of hot coals and set the air back where I had it.

As you can see it started to smoke within a minute. I played with the air a bit to try to clean it up, but by the time it was clean it was down to coals again. So I reloaded and tried again.

[matt walker]

They are always difficult at first. It looks like it's working in the video, or, starting to anyway. It looks good man!

[4seasons]

Well after loading the next load I again got a bit of smoke.

I am wondering if this is normal or if my design is slightly flawed. I used an offset riser to create a single cyclone rather than a centered riser for the ram horn effect. The single cyclone finally started working here.

As you can see I still have a little smoke and the remains of my coffee cans have not fully burned out of the riser yet. I will keep burning and see if it clears up.

P.S. I would imbed the videos in the forum but I cant seem to get the youtube tab to work. Any tips on how to get the videos posted here instead of having to link to them?

[matt walker]

It should go smokeless once all the stuff is burned out of the mold. Remnants in the riser can for sure choke the stove. I think your offset entry into the riser should be okay, but the standard "ram's horn" mixing pattern is a good one.

You've got the Https link to the videos. Go to the video and copy the link right from your browser window and put it in the youtube tags. If it is a secure Https link, delete the "s" so it's just Http. That should work.