Charcoal gasifier prototype for 5-7HP lawnmower engine

Alright, after standing at my work bench for a while and worrying over all the details that I did not have answers to, I decided to just get started and see where it takes me.

I started by deciding I was going to test the firebrick nozzle idea, and maybe eventually wedge a tungsten wedding band in there and see if that makes any difference. I did not want any air leaks, so I thought I would weld a threaded pipe section to the bottom of my very thin pail… It sounded like a fun challenge, but it wasnt. I did grind the threaded pipe down to a very narrow edge, and very carefully added some steel to the edge of the hole, but it was not ideal. After filling over some burn-throughs I went back and covered it all with some bronze braze to seal all the pinholes. Got it on there, and I think it is pretty well sealed. I think the bronze braze starts to lose strength at about 500 F, but since the welds should hold it in place It shouldnt fail until it reaches more like 1000F. I am hoping it will never get that hot.

I also put together a little stand so that If this pail doesnt pan out I can swap it for another one. I threaded on a T just to get a sense for how much space I need below, but I was wondering, how far can you “reach” with a propane torch for lighting? I was thinking that I would light from the bottom, and plumb in the EGR to the side of the T.

I set up a filter in an ammo can, and it has much thicker walls, so it was easier to work on. I made a wire cage for a wool sock filter, and put the outlet at the opposite corner. I sewed up a little bag that slips on to the cage, and which I will secure with a hose clamp. I got some wool batts for the filter media, and will put a cloth over top of it all.

the smallest ceramic hole saw I had was 3/4 so that is what I will start with for my nozzle. My plan is to bed the brick down in a little refractory cement, then fill the areas around the edges with ashes to keep any air from leaking around the bottom of the brick.

I also made an outlet pipe at the top that will suck the gas from just under the lid. This one I brazed on, and that was Much easier. I figure since the top of the reactor should not be getting too hot, brazing should be fine. I am using a heavy PVC spa hose for my tubing, which with a 1" ID fits well onto 1" OD thin walled tube. It will get hose clamped on once everything is up and running. The reactor lid came with a clamp, but I am a little leery of using it on account of the risk of a backfire. I am thinking I might secure it with a handful of those little document clips - and maybe devise some spring-loaded setup later. maybe connect it down to the stand somehow.

I have ordered a thermometer and an 800C thermocouple probe that I will thread in to the side of the reactor part way up the side to get a relative temperature reading of the reaction, and I will probably put another probe on the outlet pipe.

So, a couple questions:
I want to eventually put a cyclone right on to my outlet pipe - can anyone point me towards the dimensions (diameter, height, taper, etc) I would want to use for a 1" inlet?

I looked at the muffler on the donor engine, and it does not have threads, but bolts on. Could I drill a hole in it for the EGR, or weld a pipe over part of the outlet, or do i need to fabricate some sort of manifold?

I am going to work on my blower next, and see if I can get this thing to flare.


Carl that looks too easy i like it, so i hope someone else with charco exsperiance chimes in too help, i want too build one for small moped and generator soon myself, keep us posted.

Looking good can’t wait to see the flare

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Carl I would not worry about a puffer lid on a charcoal gasifier but be aware that if it does have a hiccup it will likely spit some sparks out of the air intake.


I think you have done a great job, and the ammo can filter and should work really good .
If you decided to make another one with thin gauge containers its far easier to get whatever size you want in a pipe nipple with threaded ends so you can just use a couple of nuts either side of the container and then tighten it down with a little silicon ,i am a terrible welder at the best of times so this way i dont have worry about air leaks and have built at least 4 gasifiers this way so far .
Cant wait to see the smile on your face and your flare when you light this unit up , hope you have the engine ready and waiting sitting in the background .
ps what is the size of your container from the top of the fire brick to the gas outlet ?

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to chime in with Dave, use electrical connector nuts that come in various sizes. To spread out the load on the thin metal, others have used pipe flanges that have 4 mounting holes. They can be used on both sides to really beef things up. These solutions are easily moved to new vessels.


nice work! if you plumb the filter in the opposite direction, you can inspect your filter and clean by brushing or blowing air into the sock. this would also allow you to cover the sock with perlite or charcoal granules for even better filtering.

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I am alway on the look-out for any type of buckets, plastic or steel. Where do you all find these steel buckets in such good condition? I have collected quite a few old six gallon (20 pound?) used propane tanks and they are easy to weld. Fill them with water and use a cut-off wheel to cut them open.

The bucket is not very deep, so it maybe only has 12" or so of height. It remains to be seen how much run-time I get before it starts to overheat.

My plan is to fill the filter with a piece of folded up wool batting, which being white, will give me an indication of how much junk I am catching. If I reverse the plumbing, gravity is going to be working against me, letting everything settle down towards the outlet, but I might play around with it.

I dont have access to much of a junk pile, so I end up getting a lot of my project components from Amazon. Here is a link for the bucket:

The lid was like 20 bucks more, hence my reluctance to put any openings through it. I figure this first bucket will serve as my prototype. I had originally been thinking about attaching a tube to the bottom, and just using the pail as the fuel hopper, but right now i just want to get it running.

OK, I have produced some gas!

I started by testing the little mattress inflater I got, but it blew like crazy. I did not have a good way to step it down from 12 volts, so I figured, why dont I try that silly hand-cranked blower I wasted so much time building. And sure enough, it worked! I never did bother sealing it, so I think I might put some more work into and actually make it my primary blower. It only has 4 vanes, so and it might do better with more.

I will say that it probably took a good 5 minutes or so of cranking to get the flare to stay lit, and I suspect it has to do with the firebrick I am using as my nozzle. It has been sitting out all winter, so it is probably saturated with water.

Also, as you can see in the video, there was a pile of charcoal forming under the lighting port, and every so often more would come tumbling down. Is my grind maybe too fine? Is my nozzle too big (it is 3/4" all the way down)? I ordered a tungsten wedding ring, so that might make more of a proper nozzle.

I sealed the port when I shut it down, and the outsides of the container were barely warm. Seems like after a while the top started to get hot, then it seemed to cool off very slowly, this is normal right?


Hi Carl thanks for for letting me know the size , i can give you a rough run time on a say 5hp engine with no load using that size container with very small sized charcoal should keep the engine running for around the 40 min mark maybe even an hour depending on the revs , but as soon as you load the engine up you will notice the heat on your outlet pipe within maybe 10 mins .
That size container though is great for getting your hands dirty and getting to play with your new toy and will have loads of fun showing it off to friends and family .


I figured as much. I recall Koen suggested 20" of charcoal above the nozzle at all times, and I have about 10". My thinking at the start was to have a long tube coming out the bottom to serve as the reactor, and the pail welded on top to be the fuel hopper. We will see, Maybe if I made a flange instead of trying to weld anything to that paper thin bottom it could still work. I have plenty of work to do before I get anywhere close to doing real work!

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Congrats on getting a flare.
I’m wondering if you screen your charcoal? Some pieces look a little big? I could just be an illusion.

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Way to go, Carl!
Simple setup and beautiful flare – with a homemade hand crank. This is now my go to video to show how simple it can be to get good gas.


Congrats Carl, on your flaring and with your home made blower too.
If you want more charcoal capacity you could just add another bucket on top of the lid. Bolt it and Seal it together. In the bottom a 6" hole . You now have twice as much charcoal capacity to run on.
Simple add on.
Some of the gasifier have a bowl under the nozzle with water in it . It catches the coals and makes steam for more cracking H2O into hydrogen power. It also puts those hot coals out for safety.
Looking forward to seeing the engine running on chargas.

My one version back seems to do that. Maybe engine pulses lower the temp.

I screened it through 3/8" expanded mesh, the 3/8" being the narrow dimension of the little oval openings. Then it was further screened over 1/8" hardware cloth to get rid of the fines.

As I was cranking, little piles would come raining down, maybe a teaspoon at a time. Could my 3/4" nozzle be too big? I had thought of making it smaller, but that was the only size of hole saw that I had (more are on the way). Tomorrow I am going to have some more time to work in the shop, I think, and I can maybe get some more work done on it before the holiday craziness descends.


I run a two inch grate but the grate would block some of it. I have just used a hole about 1 inch to about 3/4 inch but that was years ago and the brain fog is setting in.

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As you run a few more times you will probably build up a slag volcano that should slow down the stuff falling through the 3/4 inch hole. You could also move to a 1/2 mesh so some of the pieces are more then 1/2 the diameter of the opening… just ideas to think on.


Hi Carl , the 3/4 nozzle is just fine for what you want to do , even on my 1 inch nozzle and a 7kw generator pulling on it i sometimes get the odd small lumps of charcoal drop down , and as Robert said just have a small bowl with water in it to keep it from setting fire to anything and to make a little hydrogen at the same time , your charcoal looks great and will make some great gas i am sure .

As for your mattress pump/fan i am surprised its not working for you ,even on a small set up i have , my mattress fan never really seems to over pull and i just use it with the in built battery , but you could always block of a little of the intake hole so it wont suck as much ,its a quick workaround and save you having to hand crank .
Great job so far !

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