Making my simple fire gasifier

After seeing the simple fire plans and contacting Gary, I got to see his gasifier in person.

My first step was to make some charcoal.

I later found out that lighting the wood from the top instead of the bottom and adding a rusted out garbage can as a chimney made a lot less smoke.

After a number of batches I had some nice looking charcoal.

Now I needed the gasifier but didn’t have an extra metal bucket and tight fitting lid like Gary used. Another visit with Gary and his advice along with a 3 inch diameter pipe nipple on a metal lid that he kindly donated plus a pipe cap that I had to buy and I turned an old air compressor tank into my Simple Fire gasifier.

My first attempt at lighting it I just used random pieces of my charcoal and only got non-flammable smoke. After fixing a couple leaks I got my first flare flames by blowing air into the bottom nozzle pipe. The flame was hard to see being almost invisible in the sunlight but, being inspired and impatient, I found a section of plastic drain pipe and some duct tape and fed the gas to my generator. It took a little fussing around with the air/fuel mixture but it worked. I only left it run a short time since there wasn’t any filter but I was very happy and inspired to continue.

I needed to make “engine grade” charcoal instead of the random sizes I used for my first test.

This was the plan I drew up based roughly on Gary’s grinder but modified because I didn’t have a large piece of pipe. I also didn’t have the square stock (and didn’t want to go buy some for a test) so just used some nuts and bolts.

This crude device is what I ended up actually building as a test. I just set a bent up metal funnel on top to keep the charcoal from easily falling off and hooked a cordless drill to the shaft.

It didn’t work the best and it is a really dirty process but that got me the smaller sizes of charcoal I needed for the gasifier.

Running the crushed charcoal over a piece of screen got rid of the finest dust and that got thrown into my compost pile.

This mixture of dirt and biochar was made before I built the gasifier and seeing how nice it looked almost caused me to crush all my charcoal up into biochar and forget about wood (or charcoal) gasification.

My test plant is still doing alright so mixing the charcoal dust and dirt at least wasn’t toxic to plant growth.


Getting back to the gasifier, for my filter I just reused a previous, unsuccessful wood gasifier filter.

This one had leaking problems (fixed with duct tape) and still had tar in it from the failed gasifier attempts but it got me a quick filter to test the new charcoal gasifier better.

This is the adapter for the generator. The valve is to adjust the air mixture and it’s a little tricky to get set but it works. Again, more duct tape to hold the new gas line in place. I really should have an air filter but… (add excuse here)

It’s hard to tell from this picture but this is looking inside the gasifier after a 15 or 20 minute burn. It was full when I started and it is dropped almost 4 inches so it did use some charcoal but, to be fair, most of that charcoal was from soft wood. Some of the pieces might still be on the large size but at least it works.


Welcome to the forum Brian, nice to see that you already got your feet wet so to speak. Good job :smiley:


Oh trust me, if you make any serious amount of charcoal for this gasifier you’ll have plenty of biochar byproduct.


Welcome to the site Brian. Way to take the bull by the horns. Even a coffee filter tied over your air inlet would be enough to keep it from sucking in any dust since you are working on dirt.


Welcome to the forum. I started with the Simple Fire and will stick with it. It is a great way to start. I have praised Gary Gilmore many times for his contribution to the art, but I have not had the privilege of meeting him. You are fortunate.


Mix your char with anything organic and you need some acids to create the reactions. Just white ash, also dump your media from filtering in there with it. This should have natural acids from filtering.


Here is another idea… for breaking up the charcoal.

Problem would be the char would be wet after this process, but very useful for biochar…



Thanks for all the replies. I figured this topic might be of some interest to others.

I am amazed at just how SIMPLE this is compared to the methods I tried before. I guess using charcoal instead of wood was the biggest factor since the tars are mostly (if not fully) gone.

The difference between lighting the wood for making the charcoal at the top instead of at the bottom is another big difference although I still don’t have it perfected.

I assume this is from the branches being too wet or perhaps the “kiln dried” scraps of pine was not as dried as it was supposed to have been or too much sap. The smoke got pretty thick for a while but then it had an intense fire with very little smoke and almost invisible (in the daylight) flames.

I finally made an air filter for the generator to replace the one I removed when I adapted this for use on wood/charcoal gas.

I haven’t tested this air filter yet with the homemade fuel but I assume it should be much better than nothing. Just a cut off plastic drink bottle with a piece of foam from an old cushion.

I need to modify my grinder and build a wooden hopper for it so I haven’t ground up more of my charcoal to refill the gasifier yet but wanted to make another batch of charcoal from some dead branches that have been laying around for years.


I have not done this but from what I have read in other threads people using the tlud way of making charcoal usually tilt their drum up to 45˚ to get even better results.
Someone correct me if I am wrong, like I said, haven’t done it myself.


Tested the generator again. That foam filter was too restrictive.

Then my adapter plate broke again.

My poor brazing job just can’t handle all the vibration.

This was one of the parts from a wood gasifier that I paid a lot of money years ago for but never got it to work. It appeared to be assembled mostly using epoxy of some kind (which was fine) but I had to seal it better with high temperature silicone (again, probably common).

The main problem once I did get it sealed up as good as I could was the large amount of tar it produced even running it on wood pellets. It very likely was operator error but it stopped my wood gas experimenting until I found the simple fire design and seen that charcoal was a lot easier to gasify cleanly than wood.

Now I have to build a new adapter to get the charcoal gas into my generator. I guess if this was too easy everyone would be doing it.


Brian, one thing you can do is place the air mixer further away from the carburetor, it is likely all the weight stressing out your adapter. Connect the mixer to the carburetor using hose.


Yes what Cody said.
First externally support to the generator set frame all of your incoming gas hose, fittings, Tee, and air valve and air filter.
Second then attach to your adapter using spiral spring reinforced vacuum cleaner hose. Or similar wire reinforced will-not-suck-flat pool hose.
Goren “woodsrunner” on his Woodsrunner Chevy topic latest pictures show that you CAN clamp those down air and gas tight.
These both will tell you if you are allow the devoured gas to be still too hot by melting.

You are correct . . . your brazing needs help.
Both the flat plate and the threaded fitting appear to be silver colored anti-corrosion plated. Brass will not stick to that.
Power grind/flap-disc grind that off on the areas to be brazed to the true underlaying steel/iron metals.
Your previous brass looks to have been too direct flame hot and have many flux and oxides inclusions.
You braze like you would solder. The material to be joined are heated and then they melt the stick/filler materials adding.
Using an oxygen-acedelyn torch set use a larger welding tip with low flow heating set a bit gas rich. Fuzzy soft flame core. Not a sharp pointy oxidizing flame core.
Using a hand held propane type torch defiantly use the hotter yellow bottled MAPP gas.
Heat the areas to be braze joined to a dull red. A heat that will melt the touched brass filler rod by contact. One-thousand-one; one-thousand-two; melts! Helps to torch heat the filler rod too. Hold the flame away from the area to be brass added. Angle aimed at the advancing area to be worked to keep adding heat but directing the exhaust gases away for the work area.
Myself I will not use the blue pre-fluxed brass brazing sticks. Too much flux and not able to control the flux to my style.
I use the bare rods, steel wool scrubbed clean, then flame heated and dipped into a can of powered flux. Then I can control the amount of flux used.
Brazing the flux should flow see-thru-clear over the top of the molten brass and flow off, outward carrying all contaminates with it. The puddle of molten brass must be a consolidated liquid enough to allow the flux and contaminates to rise up thru, out ,and away.
Your’s clearly did not do this and had flux and contaminates inclusions throughout.

Takes practice. Do this plate flat down. Fitting supported standing up. Flame heat always directed mostly towards the thicker more mass part.
Save horizontal brazing for later when you become very, very good.
Steve Unruh


I wonder if a floor flange and with pipe nipple screwed in would work as an adapter for the engine gas inlet?


Yes SteveB. this has been done. The problem is weight-mass of those thick heavy parts. Those doing this way have had the carburetor studs threads pull out of the aluminum cylinder heads damaged. Very hard to repair.

Instead buy/get an SS handrail. Give you two very light-weight true welded end-flanges:



The piece I tried to braze I think was made from electrical conduit fittings and I had tried to fix it before. I think it was galvenized and wasn’t very clean plus I was using propane and oxygen which some claim doesn’t work to braze with.

I remade the piece out of heavier steel which was welded together instead of brazing it.

I like the idea of separating the weight of the mixer valve from the carburetor but just fitted and duct taped it back on similar to what it had that was working.

I also added a piece of hardware cloth to the bottle air filter to keep the foam from being sucked into the end.

That worked better.

I relit the gasifier and hooked it back up the the generator. I didn’t time how long I run it for and didn’t measure the temperature but shut it down when my duct tape going to the bucket gas filter was starting to melt.

It just doesn’t have enough power to run the air compressor but this 3200 watt generator has trouble running that on gasoline.

It did run a miter saw, an abrasive cutoff saw, a wood planer, and other hand power tools. I did try it with the flux core welder and it would run it if I kept the power turned down low. Again though, that generator will run the welder on gasoline but it isn’t happy about it.

There’s lots more to do to the gasifier setup to make it more convenient and I’d like to add either the exhaust gas or a water drip to keep it cooler.

I did notice some water come out of the outlet pipe of the gasifier when I shut it down and unhooked the hose so my charcoal must still be damp. The bucket gas filter had some liquid in it and the cloth final filters were dark and damp.

The gas input at the engine was a little damp but clean. No sign of tar there so must just be moisture from the charcoal.

I opened up the top of the gasifier and the level of charcoal went down but not real far. I didn’t dump out today’s batch of charcoal yet but I expect there to be more than enough to refill it again.


Important notice: as you mention my clamped down hoses, the red one used for woodgas is’nt spiral spring hose, it has rings for reinforcement, where it clamps to the pipe it’s perfectly round, this hose is used turbocharging/ intercooler hose from big trucks, used v-band clamping original but that is taken off.
The yellow and black hoses (for air, to mixer, and to carb) is spiral spring hose, i use to put a small amount of sealant, the stuff little harder than silicone, inside to smooth out the surface where spring passes. :smiley:
If done right, letting the sealant harden just enough before mounting, it’s possible to take it apart without ripping it.


Tilting the barrel is different from TLUD Johan. It’s something Chuck Whitlock developed. Does cut way down on smoke but it’s not load it and leave it.


That is a clever solution. Good idea.


Thanks for that explanation on brazing. I’m assuming my flame probably had too much oxygen and I definitely used too much flux.

I always use bare rods and powdered flux mostly because they are way cheaper than precoated rods but I heated the rod and dipped it in the flux several times on the job that broke.

For practice I brazed a couple nails together and, if my brazing job would have been better that adapter shouldn’t have cracked.

These nails were flat when I brazed them and I pounded and bent them with no sign of cracking.

I used the grind and paint method on my last welding job to make it look nicer and I’m pretty confident that adapter won’t break but, with clean metal, brazing should have been plenty strong enough.