Making my simple fire gasifier

Thanks Dave, I didn’t have any cheaper silicone but was wondering about that since none of these joints get very hot. I’ll keep that in mind for future needs since a big caulking tube of clear silicone is way cheaper than the little squeeze tube of the high temp stuff.

I am still using duct tape on some parts like the outlet of the gasifier where I put the hose since I remove it to start the gasifier. I used the duct tape to build up the diameter so the plastic pipe fits tight but can still be put on or taken off easily. That COULD still be a source of my leaks but I was kind of using that as a place that could be blown off just in case.

Another possibility, now that I think about it, is the 3 inch pipe cap where I fill the charcoal. Gary suggested putting grease on the threads but I haven’t done that yet. I’ve just been hand tightening it so I can usually get it back off without tools. And here I was bad mouthing duct tape. I never noticed smoke coming out of that fitting but there’s a good chance a little bit of air could be getting sucked in through those threads.

I haven’t added any kind of sealant to the inlet fittings but air leaks there shouldn’t be a big problem and shouldn’t be the reason I need to almost close the air valve on the mixer to get the engine to run right.


Hi Brian, have you tried the thin aluminum tape, hot-duct tape? I don’t know what it’s called in english, but it works very good, even at hotter parts. It’s very easy to rip and tear, but once in place, and “massaged” tight, it really seals, could also be tightened with some turns of binding wire, to tight it up even more.


I haven’t tried the aluminum duct tape on the gasifier but have used it for other stuff.

I tried the gasifier running the log splitter again today and split a fair amount of wood.

Got all of this plus some more that didn’t fit in the tractor bucket. I didn’t time how long I run the splitter yesterday and a couple times today but it made a noticeable drop in the charcoal.

There was a few knotty pieces that it had trouble splitting and I stalled it out once but it started right back up. On gasoline this splitter slows down but rarely won’t split even really tough logs. On charcoal gas I still got them split but had to let up to let the engine speed back up or even reposition the log to get through it. Most of them split without any real trouble.

All my silicone helped but I think I still have a leak somewhere.

I made a gasket for the jar out of a piece of inner tube rubber but I saw a little smoke coming out when I started it so I wrapped it with more duct tape.

The liquid it caught this time looks dirtier than last time. Maybe because the charcoal level had dropped more than usual because I didn’t refill it after yesterday’s run. Maybe I got too forceful when lighting it and forcing air into the inlet pipe.

I also misplaced the new pipe cap that I was using to shut it down so ended up putting aluminum foil in the pipe to block the air.

Yesterday’s batch of charcoal which should be the biggest batch I’ve made so far is still warm so I guess it needs another day before I can open it up and dump it out.


It is wery important for a Simple fire, or any updraft for that matter, to have your fuel as dry as possible. All the moisture in the charcoal WILL end in the gas. In the vacuum and warmth of the gas under runing conditions, the volume of water vapour can exceed 10% if l remember my calculations from way back. Doesent sound like that much but keep in mind you alredy got about 55% nitrogen in the gas. Those aditional 10% of a inert gas can literaly be the difference between good gas and not being even flamable!

Perfectly dry charcoal is preety much impossible to have as it will soon absorb 5-15% its weight of water from the air moisture. Its why l strongly stand by downdraft charcoal gasifiers. Then you can actualy intentionaly moisten the charcoal and the design will take care of all that water, giving you dry and rich gas. But l do understand its a bit more work and experteese so if you decide to stick with an updraft just keep your fuel real dry and you will be fine.


On the topic of fuel moisture. Not only will it creep in from the air at storage, but many times the charcoal making method can be the cause.

In short, as the batch cools down, any bit of uncooked wood will continue to expell moisture and also some tar and the colder charcoal will suck it all up. I admit being guilty of doing this on purpose sometimes when l cook BBQ charcoal. This proces of absorbing the gases of smoldering wood gives it some flavour. And about 10% more product to sell :wink:


All my brake times are coffee cacoa with pure tree sap maple. since i quit tobaco and alcohal 17 years ago- and sure happy i did quit- but now i am trying to trim back the caffene hot ones.Sorry to inturupt-I couldent resist the bragg- though i could not have defeet those habits with out the help from the man up stairs.


I think this thread has about gone as far as it needs to. I could keep documenting my experiences with it like today I sorted out another bucket of charcoal plus enough to replace what I used in the log splitter. Or, I think I finally found my air leak which was the water collection jar wasn’t sealing good enough.

I agree, my charcoal has too much moisture. Not really anything I can do to fix that other than get some better sealing buckets to store the freshly made charcoal and be more careful about letting all of the wood completely convert to charcoal before shutting it down.

My main purpose was to prove to myself that the simple fire gasifier would run my engines and it does work even if it isn’t perfect. I’m not sure if I will just continue using it as it is and eventually build another better gasifier or keep adding to this one. I’m thinking that it might be better to keep this as a usable gasifier and start looking for other materials and possibly even build a different style (down draft) or even try building a wood gasifier instead of charcoal.

On one hand, it would be nice to be able to start from raw wood but that still requires cutting, chipping, or chunking the wood into uniform pieces plus the more complicated design to deal with tars. The other problem, as far as I can tell, is that most wood gasifiers should be used on much larger engines than what I want to run. On the other hand, the charcoal takes time to make and process but I have other uses for it as well as the “waste” biochar and it looks like I can use things that wouldn’t be practical to use for heating like small branches or boards full of nails since I don’t need to cut those into shorter pieces to fit the furnace risking damaging the chain or blade by hitting nails.

Basically, this build has been a fun learning experience and I have ideas of things I would change on the next one. I used (or reused) a lot of parts just because that’s what I had and I’m sure future builds will be done the same way but this build has many “problems” like the nozzle not going to be easy to change, there isn’t any real base so it just gets propped up somewhere to use it, and most of the pieces are welded or brazed together so cleaning, dumping it out, and even refilling it keeps getting harder the more I add on.

I hope this encourages others to get started making and using a gasifier. Even if the simple fire design isn’t your final gasifier, it can be made fairly quickly and is a good way to get usable fuel. I do intend to keep using mine at least until I build something better or might dedicate this one to one engine and build a more portable version to use for multiple engines as I wish.


And thats exactly the point of this gsifier. In your case you fulfilled its purpose 100%.


One last thing.

As I said, one of my main uses for my generator is to run my air compressor and the gasifier just couldn’t run it from my generator.

I had another smaller electric motor and a smaller pulley but in my selection of v belts I had some too long and some too short.

I cut one and spliced it back together with a piece of brazing rod.

Not sure how long this will last but it saved me from buying another belt to find out if it would work. I didn’t fire up the gasifier but the generator run it with no problem which even on gasoline that generator struggled to do before. It’s slower to fill my tank than the bigger 220 volt motor run the compressor but it should work on the gasifier powered generator and better than switching to a tiny air compressor which would be fine for blowing stuff off or to light my gasifier but about worthless for most air tools.

If/when this belt breaks, I can measure it so I will know what size belt to buy.


I like using the linked belts. Very customizable for size and when one link breaks you can replace it. I think they come in 4ft lengths.


I considered ordering one of those linked belts when I didn’t have the right size belt but the price that I saw was considerably higher than a normal belt. I had seen the video about splicing a belt and had some old belts that were too long so figured I’d try it since I wasn’t even sure the motor would run the compressor. I was using a 2 HP 220 volt motor and changed to a 3/4 HP 110 motor and a smaller pulley to turn it slower.

I knew it wouldn’t pump up as fast but, once the tank is full, I can use the impact wrench or die grinder for a little while before needing to start the generator to refill it. I had a 100 pound propane tank hooked up to it which doubled my capacity but I didn’t put a drain on it yet so I unhooked it because I’m afraid it would rust from the inside and I just used pipe fittings where the original valve was and didn’t flush it out with water so I’m hesitant to drill and tap it for a drain. My original plan was to use it upside down with a drain on a “T” fitting but I never built a stand to hold it upside down and was using it standing upright so any water it collects would be stuck in the bottom.

Those linked belts would be nice for things that the engineers decided to build in a way that you have to rip the machine apart to change the belt.


The upside down idea is good, just need to make some legs to hold it up. Something you could ratchet strap down. No need to drill and weld a new fitting and risk the integrity being tampered.

I was thinking of doing that with a few 20lb propane tanks, mounting them to the wall and have a length of pipe where moisture will drop to.

Is there any way to alter the regulator to kick the motor on sooner, like say regular max pressure is 130PSI but kicks on at 80PSI, could you raise it to kick on at 100 PSI so it has less catching up to do?


I generally incorporate an idler pulley in to belt driven things I build. Especially if there is any distance between the other pulleys. I have never seen a belt spliced like that. I have collected so many V belts over the years that it would take me an hour to sort through and find a particular size. Smarter people would probably have stored them sorted.


Hello BrianM.
I agree much with the conclusions you have reached here.
Except for your most recent foray into small engine charcoal usages I’ve had the same frustrations with raw woodgasing small single cylinder engines.
And getting a operable IC engined electrical generators to operate my relatively small true portable air tool powering air compressor.

Raw wood gasifing for small engine becomes practical if you just oversize the engines to at least a minimum 500cc. Preferably a dual or twin cylinder engine. The electrical generators those power are all on gasoline/propane in the 8500-12,000 wattage ranges.
Takes a solid good 6500 watt gasoline generator to restart up my air compressor gone down to 85PSI back up to 125psi to make my air tools work-sing. And be work-fast and predictable.
Yes. 8500-12,000 IC engine generators are transportable. On wheels. Big wheels. Not man packable.

Your other alternative is to phase out your familiar air tools and go with one of the newer battery electric systems. Milwaukee. Makita. Ryobi. DEWALT. Porter-Cable. They have gotten better. Much better than in the past.
Still . . . when you want to the most tight getter-in air 1/4", 3/8" air ratchet . . . air with a slim handle; and a slim whip hose; and a good 120 degree coupler can do what the heavier bulkier electrics still cannot.
And when I really want to shear off truck chassis rivets heads and then flat nose punch out their expanded shanks . . . give me my air chisel!!

As you have found charcoal gasification does have it place to keep existing small four cycle engine still working with some power.
Just the charcoal making: smokeless; fire season safe; all of the grading and sizing . . .
honesty I’d rather be sweating over heat canning foods. With all of the steps there.

Keep working on your brazing. A great way to make things out of steel and iron basic skill. “You control the flux. Do not let the flux control you.” Work until you are getting true puddles of the brass filler. And that brass is being capillary sucked into the iron and steel grain structures. The lower heat of soldering and brazing not so much changing the parent metals grain structures. Much hotter parent metals melting welding does.

Best Regards
Steve Unruh


Tom, that last statement. People smatrer thain me… story of my life :smile:


I tried the gasifier again today mostly to check if it would now run my air compressor and it does. Just a quick test of maybe 10 minutes.

I looked to see if the cut in pressure could be adjusted but I only found one adjustment which changes both the cut in and cut out pressure. I had previously turned it down and I think it has a maximum pressure of around 135 PSI now which is plenty for what I do. I think originally it was 150 PSI.

Fixing that last leak made a big difference in the speed of the engine. I still plan to build another, better gasifier but it looks like there isn’t any big rush. This simple fire gasifier is working better than it ever did.


In the realm of more cylinders is better I started thinking about those 1 liter geo engines Marcus is playing with. Small and could be adapted for powering equipment like a compressor. Crap on a cracker. I could buy a good 5.3 LS for less that they are advertising those for, rebuilt or used.


Brian & Cody,
The upside down idea has worked fine for my 100 LB cylinder on my air compressor. With limited skills I reasoned that I could pump air in, let it out and drain the tank from the one hole already in the tank.


Just a quick update in case anyone is curious. My spliced V-belt using brazing rod broke. I assume the brazing rod was a bad choice and replaced it with electric fence wire which can handle the bends and twisting better than the brazing rod. That fix was still working but I had ordered a V-belt the right length so replaced the spliced one but kept it as a backup.

Putting the smaller motor on and slowing the compressor’s RPM down seems to allow the generator run on charcoal to fill the tank but it did very noticeably lengthen the time it takes to fill it. I haven’t hooked the 100 pound propane tank back up yet because I don’t have a drain valve for it but I do plan to hook that in eventually. Of course, that will make it take even longer to fill up but I shouldn’t need to run the compressor as often.

Testing the compressor and some other tools with the charcoal gasifier powered generator used about a quarter of a bucket of engine grade charcoal but I was pushing it pretty hard to see how much it could do. Looks like it would run the air compressor at the same time as the wood planer or miter saw now which it couldn’t do with the bigger motor on the compressor. Ever an angle grinder along with the old compressor motor could blow the breaker.

I started cutting up a couple trees to use the log splitter again but didn’t make it to to the lower sections that will need split yet. Between running the generator and the log splitter I think this gasifier will be useful but I want to try a wood chipper to see if it can power that.


Future fuel.

I’m not a good judge of how much charcoal this will make but I’m hoping this small pile of sticks and slabs gets me enough to run my small engines for at least a couple hours once it is crushed and screened into engine grade plus it should make some more biochar.

This is going to be my next batch but it’s an example of the kinds of wood that I have been using although I’ve also used much smaller branches too.

This is another example. I’ve only converted some of this into fuel since it is loaded with nails and some tarpaper. It isn’t very good for heating firewood because it’s too long and risks damaging the saw chain or blades to cut it. It still takes some effort to separate the nails from the finished charcoal but it can be broken up by hand once converted to charcoal so little cutting if any is required.