I am thinking of making a cloth filter, do you have any ideas on how this should be done, to get as small a box as possible for the largest filter surface.
It should also be easy to get tight, I think I need to have about 4m3 filter area.
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I use filters like these at work and although I never made one like it I did ask for some used ones to experiment with.
Another thing I tried was reusing truck filters.
After a point they become too restrictive for use and get scrapped but they are so large that at low flow rates for a small engine they can be used.
Maybe you can reuse something in place of making it?
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Well, I was going to make a filter of fiberglass fabric, because Swedish machine tests got such good results, I was going to test,
Göran also had good results, it would be nice to avoid soot in the cooling pipes, the oil and the intake pipe, the engine does not wear more than with petrol.
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I made a filter out of a sock stuffed with dog hair Jan. It was for a simple fire so not a test of how well it would work, but considering how much dirt my dogs bring in the house in their hair I think it would be good. 
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Hi Jan, great topic, it’s good to share ideas about filters, they often tend to be complicated, and i think many good ideas could be shared here.
Have you looked at the filters at Gengas.nu, or Vedbil? They are very easy to build, and should work great, only drawbacks is there are places for soot to gather, cannot fall down.
If you want to make some kind of cage inside the fabric, to hold the fabric, and stop it from get sucked together, you should look for stainless net, like chicken- fence, but with square holes, much sturdier, and the normal zinc-plated fencing rusts really bad due to acid’s in woodgas.
I used net for reinforcement of plaster-walls, (don’t remember if it was Bauhaus or K-rauta, or something like that) i bring a magnet when shopping some stuff, to check if it’s stainless.
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Stainless colanders are a good place to get something with small holes. you can cut out the rims and pound them flat if you need to or leave them intact and find the right size container to fit them into.
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Yes, I have looked at them, but as you say, the soot sticks to the top, I think your model seems better.
Have you made a form of iron on which you have the weave?
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Yes, made of net as i mentioned above, in the center is a pipe with holes drilled, this pipe holds up the net and fabric.
I think i made a sketch of it in another thread?
The net is secured on the pipe with stainless wire.
Im going to disassemble the filter to check it up, and patch some leaks, i can take some pic’s if you want? But i don’t know when I get the time to take it apart, has just started with the gasifier.
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Some pictures I would appreciate a lot, yes I saw the sketch, but can not find my way back to it.
I have been looking for a fire blanket, but how I should know if it is good or not I do not understand.
I started with canvas when I started building, but had one that I understood after a while was gas tight to put out fires, it did not work.
So from what I understand, it’s just buying one and trying, found 2 that I’m thinking about.
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Jan, just curious - do you plan for a fabric filter on the tractor or the truck?
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I thought of both, maybe do not need the cyclone then either, will be quite simple, unit, cloth cleaner which cools the gas quite a lot and then clean cools pipes, hope it works, just, a little afraid that my gas in the s10 will be too hot just …
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Jan perhaps this is overcomplicating, but maybe have a single run of cooling rail to reduce temps before the filter, then the rest of your rail will be Post Filter.
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I’m pretty sure Max would say keep the cyclone to spin out any live char.
Btw, I think there is contact info to a dealer of high temp fabric on gengas.nu , but maybe no longer valid.
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Yes, it seems like they did it in the 60’s when they did these tests, but at the same time I think it seems like the rest of you have a lower temperature out of the unit, and the only thing that can lower the temperature there is the reduction, so possible that I may extend the fire tube during the choke.
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Yes, they had small cyclones before the filter in the book, mine is quite large, so it might actually put up too much resistance, but Göran drove without a cyclone, so that would be the best thing.
I was looking for fiberglass filters when I started with this, it did not exist then either, Niklas has tried to get hold of new fiberglass but did not succeed.
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Jan; What do you mean you can’t get firerglasss? You can’t get the cloth or you can’t get FG filters. TomC
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I can buy fiberglass cloth, but do not know if it lets through too much or too little, that is the problem.
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Jan, I agree. I have a large cyclone and no hot sparks come out the other end. Now if your gases are coming out the bottom of the gasifer are hot this is good. But hopefully it is not because you are running your gasifer in heater mode or over pulling on your gasifer. This will cause weak gases. Charcoal reserves being used up is the cause and this equals high heat.
Okay, so now we know that is not happening let’s go on. You can cyclone filter your gases then go into cooling rails and then into a filter. I have done this with my charcoal gasifer and I was using socks for filters. Later made towel socks for filter. Not problem with any hot sparks burning them up.
Now wood gas is a much wetter gas. This is where the drop box effect comes into play, just reduce the velocity of the gases and the gases cool down quickly, vertical cooling tubes do the same thing.
The temperature at my grate can be 1700 f° or 926.67 C° and in the distance of 3’ or 0.914m it is at 400 f° or 204.44 C° loss velocities of the gases and contact with metal pulling the heat out of the gases.
Changing the fire tube length can help with charcoal gasifer’s charcoal reserves but this is the gas production area not the cooling of gases area. You need the heat here for this. So it is better to cool the gases after they leave this area, not before. I hope I made it clear to you. Production area of the gasifer, after that cooling of the gases areas, Dropbox, slyclone, cooling tubes all by slowing the velocities of the gases down and coming into contact with metals. Removing the moisture is the other prosses that are being preformed. All of this is to help clean the gases up before going into the gas/air mixer and into the engine.
Bob
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Jan, you should try double walls or a damper plate on the filter housing, dont let a “stream” of hot woodgas directly hit the fabric, this also helps to evenly heat up the filter fabric.
I have had gas temperatures reaching 400°c sometimes and this welding blankets have survived the heat.
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Kristijan used that to great effect in his double flute downdraft for charcoal. I don’t think he even needed a cooling rail with all the added surface area, though that’s only speaking for charcoal.
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