Feasibility of Rectangular Charcoal Gasifiers

We are exploring the practicality of a rectangular solid-shaped charcoal gasifier that would be an 8"x3’x3’ rectangular container that would strap on to our cubic-shaped open source micro tractor. The Microtractor has a 28 hp Briggs and Stratton 2 cylinder engine. See http://opensourceecology.org/microtractor-workshop/ .

Does anyone have any insights on what would make this work - or why this may not be a good idea? Is there any reason why rectangular-form gasifiers would not work? We would like the rectangular shape since that would fit well with our cubic open source Power Cube, which is a hydraulic power unit.

I could see one issue with the burn zone getting too hot and melting the sides of the container if the container is only 8" wide. Any suggestions? 8" wide appears to give us approximately 4 gasoline gallon equivalent (after engine derating) in terms of run time, so it’s a nice size that would make our machine practical while allowing the gasifier to take up little space. We are considering placing the gasifier on the back of the walk-behind MicroTrac.


Hi Marcin,

Don Mannes just built a rectangular unit for his lawn tractor. The Garringer gasifeir was rectangular. No issue there.


@marcin_ose Welcome.

I love your mini-tractor design/concept. I’ve been brainstorming similar ideas for a while now. Any guesstimates on the rough cost of one of your units?

As for the charcoal gasifier… I’ll start by saying that I haven’t run one yet… But I think that 8" wide would be more than enough, assuming yous were using proper exhaust recirculation/water misting to temper/enhance the reaction zone. Even without zone cooling, I’d guess that your specs should be good for at least a few hours of use before the walls got too hot.


Total bill of materials is $5k. If you have a Power Cube already - then it’s $3k in materials. You can see the rough BOM here - https://docs.google.com/presentation/d/1w4SvUnHZLBcpEVHb8repIji6MMjIuLAK2NHSaxcXSHQ/edit#slide=id.g9a9986240_0_72

If you’d like to be inolved in design - you can join our design team. We have the file on the http://opensourceecology.org/wiki/MicroTrac_2015 page.


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Hi Marcin,
I have to say I really like what I’ve seen of the open source tractor. I like the idea of an all hydraulic prime mover and have wondered if overheating issues have come up with heavy use. Tractors with hydraulic drives used to suffer from that. Anyways, your unit should work but there might be a few bugs to overcome. Off the top of my head
The narrow unit might cause you to lose too much heat from the sides so you might have to insulate or go wider and let the charcoal do it for you.

Be sure to position the nozzle centred if from below or extended into the ggasifier about 1/3 if from the side. That way the charcoal will slope down as it burns down from both sides so your charcoal will go further. Also remember that you will only be able the consume 1/3 to 1/2 of your total volume before refilling so work that into you range numbers. I calculate 2-3 cubic feet of useable charcoal. What density are you using?
Good luck, David Baillie


Hi Marcin, I am afraid your narrow charcoal generator will get red hot along the sides. Not enough charcoal to provide insulation between the really red hot oxidation/reduction zone and the generator walls. I am using a 14" diameter drum and it can get hot enough to burn the paint. A 1" nozzle will take care of your 23HP engine, but there will be a lot of air being sucked in which enlarges the oxidation/reduction hot zone making it more necessary to keep it surrounded by a thick layer of charcoal.
Are you thinking of fabricating this generator? What thickness of steel? There is a possiblity of bringing the nozzle in from the bottom as Luk Koen and Jeff Davis do, or you could bring it in from the corner.
As David noted, you can only burn about 1/3 of the charcoal before needing to refill so the generator height is also critical. Will catch up with you later this week.
Gary in PA


We aren’t making charcoal yet - just design phase. All details to be worked out.

We were thinking of welding 12 gauge steel for the container. Dan Hartman of the Chevy Lumina charcoal conversion and I were thinking of a soft fire brick for an extended “ceramic nozzle.” We are open to ideas. Bottom entry sounds right of we go vertical.

Hi Marcin,
I’m more awake now.
If you are running a 28 HP engine take a look at my tractor; it is rated at 28 HP. The air intake is angled at 45 degrees from the side at the bottom. The nozzle is just some refractive cement poured into a disk in the bottom with a 3/4" hole. The unit gets quite hot at the bottom but the top remains cool; height is your friend. Consumption ranges from 7.5 to 10 gallons per hour of softwood charcoal depending on load. I’m sure you will make it work but think wider and taller if possible.
Best regards, David Baillie


Here is how I did it on my 9 1/2 inch wide container.

I only ran it for a little over a half hour or so yet but it does not burn the paint off the container yet
I did put in a close nipple instead of the 3 inch nipple like Gary Gilmore suggested.


Do you have anything holding the refractory bricks in place? or did you just set them in? I would be worried about them shifting with the bouncing of the tractor, but that won’t happen as much if they char is packed in tight enough to hold it in place. Trying to get a bracket to hold them roughly in place through the hole would be kind of like building a ship in a bottle though…

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I used that high temp latex fire stop caulk that Tom C recommended. Also the bottom firebrick are cut between the vertical ones for a wedging effect and like you say the charcoal also has some effect in holding them in place. Time will tell. So far so good.


That should last for a while, save the patterns for the bricks, I have a feeling you will need to replace them at some point.

Bigger tires will help too, they smooth out the ride. Turning it into a “Monster Char” especially with a glossy black paint jobs with flame detailing, is more work then I would put into it though. :slight_smile:

Hi Don,

Was the 1/2 hour time the run capacity of the gasifier? What are your tank dimensions?


the bottom of this thread has the tank used. Although he gives the dimensions earlier in the thread.

My tank is the same as Sean pointed out, 16 1/2" wide, 9 1/2" deep and 28" high. There was a depression in the charcoal after a half hour run time about 6 inches in diameter and tapering down about 3 1/2" and then a gradual rise to the four corners. I would estimate that I burned up about a gallon plus or minus in that half hour. This depression was pretty close to straight above the end of the nozzle which tells me that I could have used a little longer nipple to center the burn cone better. Without a lot of experience using charcoal I would say my setup would give 1 1/2 maybe 2 hour run time before half the fuel is used which I hear is a good time to refill.


I’m glad to report that we are shooting for the 8"x36"x36" gasifier, and we are moving forward with the gasifier workshop - https://www.facebook.com/OpenSourceEcology/posts/10153945206771562 .

Does anyone have technical plans available for a continuous DIY charcoal production system? I’ve seen the discussion at Making charcoal continuously . We are considering a taller system that augers wood into the top, and augers charcoal out the bottom. But at the same time, it would be nice to wrap a helical 1/2" pipe heat exchanger around the flame for house heating. That would be great for winter house heat with combined fuel generation for MicroTractors and MicroCars.


Hi Marcin, do you have a sketch up of why the unit must be that narrow. At that horsepower you will be bleeding a lot of heat that could be used for more productive purposes. Good luck with the build.

Hey Don,
I am just now getting caught up on all the post from Argos meet up I was camped next to you in the Aline camper I was so busy trying to see every build that I didn’t ask enough questions or get enough details of your tractor .I brought some tig nozzles to experiment with in Garys’ gasifier and my 100# propane tank gasifier we both had failures due to heat and the only thing I could find to match up with black iron pipe and the nozzle was a brass nipple the brass can’t take the heat so I am wondering if I wrap the nipple and nozzle with stainless or I bought some fire clay make a cylinder over both I am looking for longer run time
Thanks, Dan Moore

Hi Dan, I remember Gary waving a melted Tig nozzle in front of me at Argos but we didn’t talk about it only to say that he was disappointed with them aqnd would be using stainless after that. How long did the Tigs last before they melted? Did you use exhaust to temper the heat? I am still using the first nozzle I put in when I built the tractor. I use exhaust to cool and add CO2. I rode around a lot at the steam and gas show Friday and have maybe 7 or 8 hours run time on it so far.

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