Hey everyone, Chris was nice enough to set up this project space for small charcoal gasifiers. I am working on ironing out some details for a unit that I am calling the “Simple-Fire”. Will be making a video of it in a month or so, but until then, there is not much I am doing worthy of posting. In the mean time, get your wood split, stacked and under cover so it can dry out before turning it into charcoal :slight_smile:
Later, Gary in PA

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Great Gary! This deserves its own thread.

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The Simple-Fire is starting to pull together. I now have built a unit for my Gravely walk behind tractor as well as the log splitter. It has met my expectations so far and now feel it is time to “roll out the results”. Under the forum tab is one called “files”. If you go there, I have posted a document about the Simple-Fire, how it works and how its built. This unit is intended for use with small engines from 4 to 20 HP. Of course it could be scaled up, but my focus now is on small. This evening I fired up my Gravel. From a cold start, it took less than two minutes to start backing it out of the garage. I also made a 25 gallon batch of charcoal this evening using nothing more elaborate than a 55 gallon barrel with the top cut out. Using two screens, a shovel and some foot work, I will have that charcoal processed into usable fuel tomorrow. (Have to let it cool down over night, then go to work)
Charcoal isn’t the answer to everything, but it does have some advantages over wood. If you are anxious to get a unit together quickly and at a low cost, consider this unit.
Until later,
Gary in PA


Thats great Gary! I will have to try this at some point. Work before play…

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Hey folks, I recieved this email that I want to pass on as it may have interest to some of you.
Gary in PA
> Charcoal seems to be a good solution for smaller engines and mobile equipment that can’t
> carry a bulky wood gasifier. So I’m itching to try it… in my copious spare time of course (of which I have … none)
I have access to a lot of nail infested wood from a pallet mill nearby. Their procedure apparently involves cutting off the nail flush with the wood, which creates tiny bits of steel embedded in the wood usually 3/8" slats. Then they cut off and reuse the good parts, toss the nail-embedded bits. so I have a big pile of small scraps with a very high percentage of tiny bits of steel. I won’t put this in my truck and risk a plugged grate or other troubles. So I am wondering if I can make some charcoal, leave the nail bits in and run it in a Simple-Fire or similar. What would happen to the steel? There’s no grate, and you empty each load as a batch. Would it melt and puddle? Meaning I could grab a lump of steel and toss it in the scrap pile… Or will I get “nail-gravel”, lots of tiny steel bits that have to be sifted out, perhaps a magnet?
> I’m not going to pick out the nails, too many, too small. And my good wood is spoken for. But if nail ridden charcoal might be acceptable, I could give this Simple-Fire a whirl…

Well, here is my reply:
Nail infested wood will make great charcoal, but it will be nail infested. I recently charred some of my old pine (untreated) siding that had nails in it. After dumping the cold charcoal on a tarp, I stomp on it to break it up and used a high power magnet on the end of a steel rod to pick out the nails. Worked well but I had to make a checker board passes several times before I was satisfied the nails were gone. The reason for removing the nails is that this charcoal was put in the horse stall for them to trample, and then it is now being applied to my garden. Don’t want the horses to step on nails nor have one puncture my gravely tire.
Now you have wood scrap with short 1/2 or so long nail. When you make this into charcoal, some of the nails will stay in the charcoal and some will fall out. You could sweep a magnet through the pile but you will also pick up chunks of charcoal that have a nail in it. You can break the nail loose, but if you pick up a hundred pieces, it becomes too much of a bother.
Here is my recommendation. Char the wood with the nails. Place the charcoal on a concrete surface, spread them out and walk on the charcoal to break it up a bit. Make yourself a sorting screen with 3/4" mesh and another one with 1/8" mesh. I use old bee hive bodys. They are about 16 inches square and 6 inches deep. The screen is tacked on the bottom. Shovel some charcoal into the 3/4" screen and shake through anything less than 3/4" Put that back on the concrete for further stomping. When everything (nail too) pass the 3/4" screen, do the same process but use the 1/8" screen. I do this over a wheel barrow. Anything that falls through that screen goes in the garden. (Here you may want to sweep it with a magnet for nails) What remains in the 1/8" screen goes in a storage barrel as Simple-Fire fuel. (That includes the nails)
In the Simple-Fire, the nails will remain while any charcoal in the oxidation zone will be consumed. Because the temp in the oxidation zone is tempered with exhaust gas, the nails will never get hot enough to melt. At worst, they will oxidize into ferric oxide (black iron oxide) No big deal. Eventually you will get a pile of steel accumulation in the bottom of the reactor, but since the oxidation zone is above it, there should be no problem. My gut feeling is after about 5 fillings of charcoal, you should dump the contents of the Simple-Fire, and clean out any clinkers and “nail gravel”. With all this said, I have never run my gasifer with nail laden fuel. But I would not hesitate to do so. However, I do not know it all and always leave myself some wiggle room just incase something leans too far toward Fisher.
Do you have a small engine you plan to use this nail ladened fuel with?

Gary in PA

Good info feed back GaryG.
You going to be know as the fellow dragged engine exhaust control from out of the 20th century into the 21st century.
Fellow I write with who has chemical engineering knowledge is real excited about what the engine exhaust CO will do to the energy balance especially factoring in the fine char dust and soot into his calculations. Ha! Ha! Told him to get Real and subscribe to your group.
Me; I like the fact that it then ties in the effort to an actual engine and makes it real world based uesable.

Back when I was considering charcoaling my soft wood Douglas Firs fuel stocks I ran across a fellow named James Hookway.
He had two videos up and later wrote a construction manual. I bought the manual.
I’l try a video link:

If this does not work a person can youtube search for “The Best charcoal retort in the world?”
Don’t let the title fool you he is a very modest humble man. Construction is barrel based with only one jobbed out weld joint. Processing very gentle on fragile softwood char. This was his 2nd video. Shows advancement from the 1st “Smoke Free” to the 2nd one. Last I spoke with him he had advanced farther yet.
His stuff is worth looking at because he designs in the UK in crowded sensitive populated areas. Not rural US smoke 'em out like most here able to charcoal make.

Steve Unruh

i like the kiln approach a little better since you are using the burned off gas to drive the reaction. It just seems like a waste of gas to burn it off the top like that. something sorta like this(you can see the design in the first 40 seconds the rest of it is blather.):

Would you need the pipe coming off the top and then going under? If the barrel is sealed everywhere couldn’t you just poke holes in the bottom so the gas if forced out the bottom of the barrel right into the fire?
I don’t see how it could explode if it is air tight except for the holes.


I would guess the holes might get clogged with char/tar/etc. I read after I posted it, it isn’t a very efficient design either. This one looks a lot better, but they didn’t show quite enough of the design to reverse engineer it nor have I found any plans.

They monitor the temp to keep it in the 400C range, and trap the bio-oil, tars, and extra gas coming out of it.

Good man SeanO!!
Yes you figured out the failure points:
Boiled off pyrolisis gases/tars and steam have to be kept hot or WILL condense, coat and clog. JamesH insulates his piping internally.
Putting the heat UP on the center of a rounded surface actually is the distillers secret for very efficient heat trasnfer - ONLY works for this efficiency if the vessel is full of a convection circulating capable liquid!
Again JamesH figured putting the heat into the center of this mass. Then figured to insulate the outsides to conserve the process heat. Go back and watch all four of his videos in sequnce of release and see how he is quoting decreasing fuel stocks weight cost to heat drive the system with a higher net weight yield result. The forth one he says he is able to stop adding combustion wood fuel once up to heat and then have it just heated by the driven off gasses and tars.
It IS his chimney that creates the draft to get the heat up to make a secondary combustion zone to not have visble smoke and makes his system a much quicker processor.

Your horizontal barrel vidio did show me a way around the top un-loading weakness to the Hookway and most all vertical barrel systems. Centerpoint mount these on an A frame to tilt unload like friend AleseyA does with his gasifiers to be able to horizontal dump and rake out.

I offered up the Hookway system as the only thing that I’d seen that could be trasported and used at suburban and even some urban construction, de-construction and transfer clean up sites and used in place to clean up “Dispose” of woody debris and scraps directly without having to double energy fuel and labor load and move scrap wood. Just as bad labor and enrgywise chipping up good charcoal convertable woody debtis/scraps and then hauling it away s-o-m-e-w-h-e-r-e to mixing it into shredded compost-able leaves, needles and twigs.

The high ground in my opinion for charcoal making and using is in the Urban/Suburban areas.
CANNOT have any soil, water or visible objectionable air pollution.
This is why charcoaling has always been a rural production activity (pollution) and an urban consumption “Luxury” fuel.
THIS is what needs to be fixed.

Steve Unruh

Got a video made tonight of my Simple-Fire in action. It is on youtube at

About 7 minutes long but will let you see it in action.
Gary in PA


Great video!! Thanks for posting.

Gary, Nice!! You deserve SAG (Screen Actor Guild) credits for that. :slight_smile: Seriously, I love watching your video presentations, you are extremely good in front of the camera, and your presentations are informative and to the point. The camera work is also actually really good. I don’t know where you picked up that skill, but don’t lose it. :slight_smile:

hookway just added surface area to the heated surface. A 6" pipe has more surface area then the bottom of the barrel. I do like how he ran the return gas pipe on the inside. In the later video’s you don’t see the gas losses and he makes more efficient use of it. But from what I can tell, is it is essentially a rocket stove that isn’t heating anything.

Also while I agree, smoke is a huge conern, I would still get a ticket for the Hookway design. My house is in the city.

I really enjoyed talking with you at the Indiana meetup. I like the the charcoal route and find the simple-fire very interesting. The picture of your Gravely mower has got me wanting to convert my Grasshopper over to charcoal. It has a 25hp gas Kubota on it. I think it will be easy to switch between gasoline and gas because it has an electric fuel pump and a shutoff solenoid on the carburetor that I can shutoff when the gasifier is up and running. I know this engine is a little bigger then what you list for the simple-fire. Do you have any recommendations for hopper and inlet nozzle size. The mower has the perfect place to mount the unit right behind the motor over the back wheels (close to the muffler).
Thanks for all your experimenting and willing to share your knowledge.

Hi Phil, I’ll look up what a Grasshopper is, but your engine is a 25HP and let me assume it is a two cylinder. Let me also assume the largest passage way through the carburator is less than 1". If these assumptions are correct, then my feeling is the pipe dimensions used for the Simple-Fire (1" pipe size) will work, Since only one cylinder fires at a time, there should be enough gas availale to keep the gas manifold filled with charcoal gas. I’d recommend you use the tallest steel reactor you can find and fit on the Grasshopper. My Gravely unit is a 6 gallon pail and will last 30 minutes on the first run. After refilling it, the second run only lasts 15 minutes before the gas outlet temp hits 130F. I am playing around with higher temp radiator hose since the cut off temp of 130 is where the sump pump hose starts to melt. Here is the bottom line. The simple-Fire is simple, but needs tested in other applications and situations. I’d encourage you to help us move this concept ahead! Come on board!
Gary in PA

gary this is a nice thread, for a novice at woodgas i had not known the trade off’s between wood and charcoal fuels, this is a great way to get that out there and even gives alot of people something to do with their gasifier coals, i look forward to seeing the kind of charcoal my unit produces and making something similar to your simple fire for a generator i have. i enjoy your youtube videos and think this simple fire is a great idea

Gary, The Grasshopper is a zero turn mower, about 60" deck. It is actually a three cylinder motor and the carburetor is about 1" dia. I did a walk around of my resources, the scrap pile, and found two water heaters 40 to 50 gallon, two 20 pound old propane tanks and a air compressor tank (20 to 30 gallon). I thought WOW I’ve got what I need to build a simple-fire. I’ve got a couple old 55 drums and plenty of limbs and brush. I need to start making some charcoal. I’ve got a few small motors to play with and get my hands dirty with before I take on the bigger motor. The water heaters are about 4’ tall, a little big for the mower. I’m looking at the air compressor tank for the mower. Fit the mower better and maybe run for an hour??? I need charcoal!!! This could get addicting.

Here are a couple of photos of my version of Gary’s Simple-Fire. It uses the 1" inlet and outlet ports, as well as the spacing Gary specified. My spray can of 500 degree engine paint was almost empty, but I did get some color on it. I can get my arm in through the 4" hopper to remove the input air nozzle.


Looks real good Ray. Do you think you will need that puffer lid with charcoal, or did you do that for easy opening? What did you use for a gasket? I can’t remember what you plan to run with this setup or did you say sidecar on a moped?
Don M