First post, looking for advice

hello community, newbie here.

WARNING, stupid questions will follow.)))

i am trying to build a wood gasifier for a small engine to run 4kw generator in winter months, when the solar energy is insufficient, also wind does not help much.

some pics of how it looks like at this moment

overall view (parts are just stacked together)


my first question is about location of ignition port relative to air nozzles. should it be on level with air nozzles, above or below?

thank you!


All of us were/are newbies. There are people here that have more experience with wood/ charcoal running small engines than I do so much I will defer to them. But I can give you a big Welcome to the DOW


Welcome to DOW, I see that you are quite far along in your build. Did you build it from plans? Can you give us a drawing of it, a side view of the gasifer? Many of us do not use a lighting port. We light it from the opening into the hopper by checking our charbed below the nozzles into the charbed at the grate. We use a rod to feel down into that area. By pulling the rod out slowly we make a hole down where we can light it. Some want to light it from the out side so you can put a lighting port in line with one of the nozzles so you can see straight into the nozzle hole. After the light up you can cap it off screw cap plug. Just looking at your welds it looks like this is going to be a fine gasifier. Is it a charcoal unit only? Or are you planning on burning wood too.
Looking forward to it running making good gases.


Tom,Robert, thank you for warm welcome.

i build it according to inverted cone gasifier dimension table i found in DOW library. 5x 7.5mm nozzle and 80mm restriction.

cross section looks somewhat like this

i hope to run it on wood chunks.
there is one image per post rule for new members and i have a few more photos, i will post them in my next replies. ))


view from above


heat exchanger - 4x one inch plumbing pipes.


Oh yes very nice build you are doing there. Many gasifiers that run on wood have been built this way. I take it you sized you restiction opening inverted cone and nozzles size according to the tables for your generator engine size you are using.
You should be able to post more pictures after we have made a comment.


If you really want an ignition port, you could make a plug via the air jacket lined up with a nozzle and light from there. But like Bob said most light from the top by rooting out a hole in the fuel and using a blowtorch.

Are you planning to make a monorator hopper to extract moisture from the wood?

The ash cone design works very well, it utilizes the ashes to insulate the hearth. It would be helpful to preload with ashes from a fireplace.


Wellcome Andris! You built a fine gasifier. This will work great. Just remember to prime it, first with ash and charcoal mix (to fill the cone) and then with good charcoal the size of a hazelnut. Doing this l guarantee you will make clean rich gas in seconds after first lightup. And your weld job shows its gonna stay working without problems.

I do have two concerns thugh. 80mm is a tad big for a 4kw generator, but with good air preheat and dry wood you shuld be ok. More problematic is the cone… looks like stainless? If so, its not the preffered metal of choice in a gasifier. Stainless actualy has a lower melting point thain steel and it oxidises even faster. Plus its a bad heat conductor and has bad thermal expansion.
Even if its not stainless, it looks too thin. There is hell going on right at the rim of the cone. It will likely erode or warp fast. Usualy we put massive, and l do mean massive chunks of steel in there. And usualy they are still regarded as consumables.
Good news is you can still add this, now or later. Big bearings work great, l have also forged my own before, or just a cut off section of some thick wall pipe. Just put the ring over the cone and tack weld on two or 3 places.


I agree a 100%. Good points to point out Kristijan. It is best to get the proper starting up instructions so you get good clean gases on the first time running.


so much great advice already, thanks!

yes, it is 3mm stainless, unfortunately.
but as Kristijan said, it is not hard to reinforce cone rim, i will definitely do it.
and if the cone goes completely bad, i can cut it out, leaving little rim ant put a new cone on that rim.

although the generator is only 4kw, the engine is 12hp rated 2 cylinder soviet уд-25 (UD-25).


yes, i am going to make outer shell for hopper to gather condensate.

improved cone




Oh yes thats more like it! If you insulate the cone well with ash from above it will last a long long time!


Andris, I would try firing a propane burner directly into your air port. In any case, hot gases will warm up the layer of firewood. Another question is that it will take a little longer than lighting firewood through the bunker. But it will be much cleaner and neater to do it outside.

P.S. Please show in the picture how your heat exchanger is connected. It’s not at all clear from the photo.


Marat, i think i will cut ignition port in through air jacket, maybe i will try to use a tractor glow plug for ignition. these glow plugs are placed in intake manifold of diesel engine, they ignite diesel fuel and the flame then is sucked into cylinders.

here is cross section of heat exchanger

gas flows up trough pipes and air flows down through space between outer shell and pipes.

plus some more photos ))

making tube from a sheet
bending contraption
progress at this moment


Hi Andris, i read about your ignition ideas, i use one of them plugs you mention, in a separate ignition port, it works very well for me anyway, i use 50% barbecue lighter fluid and 50% gasoline mix, ignites easy and burns slow (no boom).
About 1tablespoon needed every lightup, one can use one of them rubber priming bulbs to squirt some fluid for the igniter (i use an electric in-tank fuel pump, runs 1,5 second).
Them ignition glowplugs should be mounted so there is’nt to much draft, and near, slightly higher than one of the nozzles.
Just some tips.


andris, your roller…fantastic!!!


@Göran advice from experienced people is what i am looking for. thank you very much for sharing.

@giorgio that is an improvisation, i made it in couple hours from scrap metal and it turned out better than i expected. ))
i am glad you like it.


I would really like to see some details on how you made that, Andris. Some detail please, especially about how the roller or rollers are driven. Big thumbs up. I’ve been wanting to build one like that for years.


hi Tom

some photos of roller:
2 inch plumbing pipes fit loosely on 60205 bearings, no machining needed.

upper shaft has knurled surface,i am not sure whether smooth shaft would have sufficient grip or not.
i just found a knurled shaft in scraps.

lover pipes tend to push against one side, there is need to limit lateral movement.

now about gasifier.
progress at this moment: