Converting down draft wood to charcoal

I mentioned earlier that some years back I built a downdraft gasifier from the WK book. Had to make a few modifications due to material availability but it was fairly close to the build shown in the book other than it was built to run a generator and only had an 8 inch fire tube. I ran it once back then and it made gas. Not knowing anything about gasification I figured that was all that was necessary and it got pushed to the back burner. Now I want to build a utility vehicle for around the homestead. I’m low on obtainium right now and the original unit is overly large and cumbersome for a vehicle like that. I’m thinking it would be easier for me to just use some of the components, which may not have worked all that well as a wood gas unit anyway, and build another charcoal gasifier. It will take a while to go through the build pictures of the original. Here is the unit as it exists right now.

I recall someone posting about using old acetylene tanks for builds. The casing for the firetube for this unit was made from one. Won’t be doing that again.

I expected to find just a empty tank. This was filled with something. Took a long time to burn it all out. more to follow.


This confirms what I had been told about those tanks. Thanks for the pictures

Fire tube with holes drilled and welded to a wheel.

Top view.

From my previous posts you can tell I’m real fond of building with wheels.

All covered with two five gallon metal buckets cut down.

To be continued.


You either a brave-man, or a xxxxxxx one TomH.; dinking around with an acetylene tank.
Liquid acetylene-acetone mix in an inert porous filler-buffer.

Thanks for putting this up so others will see and avoid.


When I was doing structural Iron we didn’t have heaters to warm up with in the winter. Common practice was to take a metal can the bolts came in. Fill it half way with gasoline and light it. As long as no one knocked it over it was fine. When I cut up propane tanks I just fill them with water once. Drain it and cut them. None of my ugly came from blowing myself up. The sad thing is that I still have four more of those small acetylene tanks and one large one and have no idea what to do with them. Makes me crazy to see something like that sitting there with nothing I can make out of it.

I only have a couple more questions about this conversion but not sure what is out of bounds. I probably should just let it live as it is and build something new. I am thinking of trying a bigger firetube made out of sections of five inch channel, which I still have a small supply of, and welding them into an octagon to bring this thing up to vehicle standards. I’m thinking round or octagon should not make much difference. I’ll chew on it awhile. I think I’m going to start on the greenhouse water heater and charcoal maker next. I have a design that I believe will work.

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That is exactly what i am doing. The pellet stove is the proof of concept and I do plan to build a dumbed down version of a down draft unit with an active passive grate for bulk feeding chip fuel. I think something like this will allow lower cost box store chippers a viable solution. I will let you know as I have one.


Hi Matt, I remember a active passive grate that @gasman Max came up with. It was like fingers that were put together like rakes and would move. It would keep fines from clogging it up by the way it would move. I thought it was a really cool design. Not sure if anyone tried to build a grate like it. Maybe someone knows where it was posted on the DOW site.


Hi, Bob!
Chris played a bit with it and probably built it in the “plank” gasifier.
It was not fulfilled, as he got the new farm to build up …
Hopefully he fulfilles it, as there are 2 “new” items and two internal cyclones to evaluate…


Thanks Max, I go and look on Chris threads and see if I can locate it.

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Yes I remember the twin cyclones. They had a common clean out on them. I think for them to work correctly each cyclone clean out needs to be isolated from each other.
Hopefully he will find some time in the future. I miss his project innovations that you two would come up with, like the plank gasifer. Thanks again Max for all your input.


Today we built an indoor charcoal Kiln heater. Doing some testing outside and so far I think we have a winner. It is sort of like a rocket stove, the kiln is made up like the one I showed in my last video but with a 55 gal drum to serve as a bell. So the gas is not just exiting the top it has to migrate back down and then exit out the chimney. We will be installing it tomorrow for our shop heat.

Here is a link to my latest post on the Thrive Forum. Easier for me this way verses reposting everything.


I’m going to reassemble this gasifier and run it on charcoal. If the fire tube melts out so be it. I just want to see why this would happen. I’m going to cut chunks to make charcoal out of to try and keep it as close to the fuel size it would have if it was raw wood.


You could always buy some ceramic wool and just line the inside, maybe a 1/2" thick piece will do. I’ve made a charcoal fueled foundry using an old helium tank lined with the really thin ceramic wool simply laid on the inside with a steel pipe to funnel air from my fan into the lit charcoal.
Either that or paint the inside with refractory?

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Tom, if you moisten your charcoal just abit, say 15-20% by weight, you will lower the temperature conciderably while achiveing much better gas, more hydrogen.


It’s already only an 8 inch fire tube Cody. I wouldn’t want to decrease that size. I do have ceramic blanket. I just got a new supply this week because I want to wrap the base of my Don Mannes gasifier. 1 inch by 24 inches by 25 foot . 99 dollars. They also have bulk fiber. 25 pounds for 50 bucks. Home Depot.