You can use a rheostat also called a dimmer switch to control your blower speed.
Rindert
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Daniel , great news you are now producing a good amount of gas , i suggest you play and play with that old mower of yours the time will not be wasted and you will learn so much from that first build of yours , if you see tar leaking or dripping from anywhere then , before stopping the mower engine maybe run some petrol through the engine for 5 mins or so and that should help burn off any tars around the valves also spray the carb butterflyās with some type of lubricant while its running on the petrol . Dave
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If using pine wood is your goal, then youāll want a downdraft gasifier. Making charcoal from pine is pointless, in my experience. Iāve only gotten very light, styrofoam like charcoal from softwoods. But thatās just me. Anyone who has made good charcoal from softwoods can feel free to share their secrets for doing so.
But softwoods seem to have a lot more hydrocarbons (including tar) than hardwood. This is great fuel, IF you have a gasifier that can efficiently crack all that tar. The Imbert is a good place to start for a downdraft gasifier.
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Thank you for the information! Going forward i am probably going to make another gasifier, this time a downdraft as suggested. And an imbert gasifier seems to be what most people recommend so i will probably start there.
Im totally hooked on gasifiers by now,
looking forward to experimenting some more with my current charcoal one, and definitly making a version two in the near future.
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Daniel, definitely look through other memberās posts here on the forum and see how their builds went.
What do you want to power first?
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Yes, i definitly have lots of interesting reading in front of me!
My goal as of right now would be to run my generator, which is a Stanley SIG 2000-1. Preferably on raw pine wood, since i have access lots of that stuff. But as of right now i will use an old lawn mower that i have laying around. Just to take my time and test the gasifier thoroughly before i ruin the generator.
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Just had a thought about how you could salvage your cross draft gasifier to run on wood. There was a design in the early 1900s that was essentially a cross draft wood gasifier fed into an updraft charcoal gasifier.
The unit consumed more wood than charcoal. Secondary air was added between the wood gasifier and the charcoal gasifier. The wood gasses were burned, which heated the charcoal to glowing hot. The hot char would crack any remaining tar as well as combine with the CO2 from the wood gas to form CO. The charcoal also functioned as a filter.
There should be a picture here.
Itās the one in the middle on the right.
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Iāve seen other gasifier designs that incorporate this double burn concept in various embodiments, as a way of dealing with tarry gasses. If youāre going to use pine, itās probably worth looking into.
Iāve seen a few variations that configure the air nozzles with a venturi that draws tarry gasses from near the top of the hopper. This helps make sure more of the tar is directed into the combustion zone. Itās basically burning the tar to heat the char, instead of burning the char to crack the tar.
Due to the venturi, some hot gasses will be drawn up into the hopper, pre drying the wood and extending the pyrolysis zone up higher.
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thatās cool. Something i will have to look into aswell!
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Hey again guys, long time no see!
Since my last post I have worked hard on my next attempt. This time I have gone with the imbert hearth design thanks to many suggenstions on here. Iāve tried upping my production quality a bit too, so it has taked a fair amount of time to build, but Iām pleased to tell you that Iām only days away from generator fire up at this point. Really exited to see how it goes.
The reactor is of imbert type and has a restriction of 115mm (same as the firetube) at the moment. But further restriction plates are easily added in less than an hour since I prepared mounts down there. The reasoning behind having the quite large diameter restriction is to avoid the wood hanging up and clogging. But I am a bit worried that this will result in a too high tar output. What do you think?
The fuel is stored in a 200l oil drum with gravity feed into the reactor.
The gas is then pulled through the fire according to the imbert plans. It further passes through a cyclone filter along with plenty of cooling pipe before entering another 200l oil drum where i plan on having multiple stages of filters.
Exited to show you the results in a couple days when the unit assembled fully. In the meantime i will add screenshots of my CAD sketch tp show how it is going together.
And If you see any obvious issues or flaws in the design Iād of course be happy to hear about it too! ( Most of the componets are fabricated already, so I hope notā¦ But itās never too late to ask I guess:-)
/Daniel
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Your hopper is way too big. That thing is going to make lots of tar and very weak gas. Because the hopper size there is more fuel that the hearth has to dry and it will. But the problem this will releese all the moisture in the wood and crash your reactor. Wood gasification is best for V8 engines. Inline four cylinder engines you may have marginal success and any smaller wood fuel is an absolute no go. It will be nothing but problems.
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So, the more fuel drying up top the more moisture is going to be pulled through the reactor. Gotchaā¦ might need to size it down abit 
, maybe possible to make a smaller insert for actual wood inside the large hopper, which would also help with insulationā¦
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Yup or make it into a monorator hopper and do both add the insulation on the inside. This will help keep the chamber outside the hopper cool along with outer shell. Keep the core hot and cool the outer chamber to get the moisture rich gas to condense and drop the icky stuff out. lol .
If this unit makes tar, there is room for you on the darkside. Most of us have been there thinking wood fuel was the easier path and charcoal is very very bad. But that is not really the case; Charcoal units are far less complex, fuel production is much easier, more viable, more reliable, gas quality is beyond superior, stronger more engergy dense, plus water is added as a fuel reclaiming most of pre process energy losses.
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I can show how many people do in Sweden, I have one that gives gas to a 1.5 liter engine, but has had problems, but probably mostly due to my welding.
Think you can translate with goggle, table 1 shows the dimensions of the hearth, Knv is how you calculate how much gas the engine needs. K= 0024 at idle K=0094 at full throttle n= engine speed v= liters of the motor
http://www.gengas.nu/byggbeskrivningar/smp/kapitel_2.shtml
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You need some way to catch moisture in the hopper, and a restriction for tar cracking, otherwise no problem, but if stationary you need some (agressive) shaking for fuel flow.
I drive inline 4 with 100liter hopper-no problem, and 400cui v8 with around 300 liter hopper, no problem. Both may run on raw wood, in emergency.
All can be doneā¦
Edit: i forgot, for your first attempts, all small hopper will be easier, make it easy to replace.
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Hi Daniel! This is what caught my attention.
The firetube seems very small. You would be limited to marble sized fuel to avoid bridging above the nozzles. A wider firetube will always have better flow. My first gasifier had a 200mm (8") firetube and I believe even that is borderline too small. Further down, once the wood has turned to char, a restriction doesnāt cause bridging - only a healthy ash cone that will provide insulation and keep the heat in.
What size engine will you be feeding? I believe a 4-cyl around 20-30 hp would be doable with wood chunks, but anything smaller is better suited for charcoal.
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Yes! Believe it or not, this is actually the site that I have based most of my dimensions upon! (har faktiskt svenska som modersmƄl sƄ har lƤst orginalet ) I have gone for the 300/80 hƤrd design.
Woud be interested in what kinds of issues you have been facing, as my setup currently has more or less identical proportions to the ones described on gengas.nu. (specially after adding an restriction cone)
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Thanks for the info! I have a big shaker motor attached to the hopper. As for the moisture I havent added anything yet, but will have to do so.
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I have lots of engines to choose from, but was thinking of something like a 0,6l twin or similar. The thing about charcoal for me is that I feel like it is just a lot of work. Burning, washing then drying, so I would much prefer to run of wood chunks or chips if physically possible. Iāve seen lots of videos of it being done, which is probably what has misled me into thinking it is a good choise. The thing Iām slowly starting to realize with them videos of course is that people can cut out all mistakes, and only show the best 3 minutes of the run.
As far as the firetube goes, you are probably right. But the thing that kinda confuses me is why it matters what the diameter is up at the nozzles, when there is a small 80mm restritciton just a few more centimeters down. Surely this is going to be the real bottleneck? Or can someone try to explain why not, so I can understand it better? This is the main reason i made away with the restriction in the first place. But apparently i got this a bit wrong.
and yes, I do realize that many of you are suggesting charcoal, but Ive watched lots of videos of people making DIY charcoal n all, but to be honest Iām just not really feeling it. It looks like quite the hassle. Please convince me otherwise, or else I will forever try justifying wood chunk gasification for small engines
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I made one for my ferret 1.5 liter saab v4, core tube 34cm (30cm would have been enough) choke 65mm, but I didnāt weld the cone to the core tube that the choke is on, so I think gas went past the choke, causing tar in the engine .
The choke is there to increase the gas velocity and thereby increase the heat that breaks down the tar.
I had 21cm core tube first in the Chevan, it caused hanging and a lot of hassle.
This time it went well.
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