My bag material is some kind of upholstery, I got from a friend that worked in a textile mill. Feels like some kind of poly blend. I’ll take photos of it with light showing behind it.
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Jakob, you must have read that I use raw sheep’s wool for the filter medium. At the bottom of the container there is a grid to distribute the gas evenly across the cross-section, here I insert a layer of 20 cm of sheep’s wool, then a layer of 20 cm of sawdust, then a layer of fine hay and, finally, a layer of sheep’s wool on top, which surrounds the oval final filter made of felt. I can say that it works perfectly and the water drains nicely from the wool. The tractor has done 150 hours on wood gas and so far the intake line is completely clean. Let me not forget to say that I change the filter material every 40-50 working hours and what pleases me the most is that all the material is biodegradable and is not harmful waste, just like plastic or synthetics.
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I am planning on using a bag for the hay in the hay filter, with another bag of sawdust on top of it. @Matt only uses sawdust in his ammo box filters so I figure it must work pretty well.
GC
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Jacob, I use hay in a nitted wollen bag. Not perfect, but good enough for me. I believe it’s more important to prioritize breathing capability if you’re running a motor which you expect to operate within a wide range of power.
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What JO said ,
plus 20 characters
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Here’s my upholstery material, it’s rough on the outside, I leave that on the dirty soot side of filtering.
Here’s the pictures with light showing through it.
I use mosquito screen behind the sack filter to stiffen it so maybe the screen is also catching some finer soot, but I’ve noticed and as Kristijan has advised as the sack gets dirtier the better it filters. I never washed the filter only shook it.
It even worked for my 4.3, the sack was about 18" wide by 36" long when laid flat, hose clamped to a stand pipe.
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Tone,
I am interested in the sheep’s wool. There are many varieties by that name. Can you suggest a specific product available on-line which is similar to what you use and might be reasonably priced.
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He probably means raw unwashed wool, which still has lanolin on the hairs. Lanolin is oily so it would grab dust and repel water very easily.
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You could try a foam rubber, I use about 3" thick and get very little soot with it, and this has very little resistance, look at filters for lawnmowers, for example.
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Well sorry guys for not updating sooner. I hit the ground running after the conference in PA and today was the first day i was able to slow down and take a break.
We left out for P.A. on Tuesday two weeks prior to tomorrow. the conference was on thursday morning we got there early and set up our display booth. We had washed out the gasifier before we left so we brought it inside and set it up so people could see the inside of the firetube. Dad had a session right after lunch. he briefly explained the science, some of the people stated snoring through that part but as soon as he turned the videos on of it running everyone became very bright eyed and bushy tailed. The next Day over lunch break we set it up in the parking lot it. We lit it from empty as a display to running in front of an audience, I was bit nervous because as we all know they never work right when people are watching. But it turned over about five times and started. the next day Jesse and I and another young boy took it over to the lake and set it up. It took a little more there to get it going. I could not get enough water in it with my water drip. It would run but wouldn’t rev up enough to not stall when i put the prop in the water. After a few minutes of fighting with it i took a water bottle i had in the cooler in the boat and stabbed a small hole in it with my pocket knife and made a squirt bottle between it and the water drip i was able to get enough water in it to run well. Once i got it hot i didn’t have to use the bottle the water drip kept up. although i could get a very noticeable boost of power with adding more water. I think functioning here verses there has a lot to do with humidity in the air. We are close to tropical as far as humidity goes up there it was dry and cold. i think the air in the water here made up the difference that i had to add up there. I anyone has any other theories i am open to suggestions. After that demo we drove through the night back to KY for a wedding that next day, After that i left my siblings in KY and drove home that night and we showed the boat to a group of professors from Milligan University from up around Johnson City TN Who were here for a meeting. The Mechanical engineer, and the Journalist both went on a ride and drove the boat some. When they got back to the dock with it with it iding it had a backfire in the engine and blew the mixer box i had built apart. I tried to tape it back together but i think it blew the pipe off the carb itself so i didn’t get it to run after that, and i havent had a chance to look at it since but i know it will.
so that is an update of where we are. I believe now we have proven the concept that this will work. Now i need to design build and test the unit/ system to take to the Jungle. Right now i am trying to get more info of what exactly there drive units look like and what specific engines they are using.
But i have a few parameters i have to start with now. the number one right now is profile. I need to design a gasifier that is about 18" tall at the most it would be nice if it could be shorter. I also need this thing to be really light and easily removed so that when they have to take there canoes out of the water and carry them over the trees in the river and such it can be carried over, or be set down in the boat to go under the trees depending on the water level. I am not trying to go for a non welding gasifier but a design that uses minimal materials and welding would be nice. I am kind of asking for a brainstorm here. What do you guys suggest i start with here? I am fond of the down draft because of its forgiveness with wet char and up cooked char. I imagine in the rain forest keeping charcoal dry could be a problem. I am thinking about possibly running this unit down in the water to help with profile aside from the unit rusting do you guys think there would be problems from that? Cooling to much … ETC
Also we are tying to think of ideas for a very simple refuel on the go system so there could be very little hopper space and you just keep adding char into it.
I am also thinking for that sake of simplicity Would you have to9 have an air jacket around the firetube? could I Just run the 4 nozzles out into the air and have 4 water drips or would i loose to much heat from the gasifier? Has anyone tried anything similar ?
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4 water drips seems like a lot to look after and tune.
And then you’d have to cap off all 4 nozzles for shutting down.
You could make the air jacket external to the gasifier instead of internal. Take for example you use a barrel for the bottom gas exit area, take another barrel bottom and weld that above and you have the air jacket. You could braze the air jacket on instead of weld if need be.
If you’d like a drawing I can see what I can sketch up for an idea.
I have the same idea that the humid air compensates for water drip. Water drip works best when it’s evaporated into steam, which I think the updraft flute has had a major advantage in that department since the water can just sit there and boil off.
Also for the air intake of the engine I guess it’ll be a good idea to make a puff valve. Maybe a pingpong ball? Or a plastic 1 way flapper valve could work, like the big sewage ones that Wayne has.
I’ve had a few puffs even with my updraft charcoal gasifier, but normally it’s when I gave it the beans from a dead stop. I never had a spring loaded lid so it just vomited sparks from the nozzle
Edit: here’s my drawing. Other essential components like ramping for charcoal to feed well not drawn.
Red is the hearth core, grate, and gas exit barrel. Can either be made of one drum or two if you don’t want to worry about a lid gasket. Or a solid drum.
Green is the air jacket, for simplicity I’d use a drum bottom or if you only have barrel sections, make a sheet donut.
Hopper is a drum top.
I’m using drum loosely, could be buckets or hand rolled sheet.
You really wouldn’t have to weld much on this design. Only the hottest portions like where the burn tube meets the gas exit, the nozzles, grate maybe.
Air jacket and hopper can be brazed if that’s more plentiful than welders.
The bottom of the air jacket will still be in contact with the hot hot gasses and will let moisture drip turn to steam vapors and the nozzles will suck in the vapor.
The idea I drew at the bottom was maybe having a big ash dump on the bottom, using a lid. I don’t know how hot it gets down there to know if a gasket would survive it.
Do they have access to air tools like zizz wheels or nibblers?
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Thanks for the update.
I too built the new tractor gasifier with simplicity in mind, so l tryed to avoid building the air manifold.
Why do you drip water instead of moisten the char? Its easyer. This sayd, too thod about having the nozzles just stick out. Its not a problem if you use wet char, no water drip, and the steam will slowly suffocate the flame at shutdown. I dont even have an air shutoff on myne.
The only reason not to do it in my wiew is fire safety. Flames sometimes shoot out the nozzles, char bits spit out… l cant afford that while in the woods or on a hayfeald with the tractor. But on a lake… you decide.
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Cody, that’s about the design we have now.
I think we’ll use a tennis ball for a puff valve.
I think doing away with the air jacket will rob us of power since it will be colder, it won’t crack as much water. But I’m hoping in wrong about that
I love the down draft… It’s so forgiving on char quality.
K. We tried pre mixing the water, but the best recipe our expert could give us was “just put as much as you want until it feels about right”. 
Lol. Thanks by the way. So we got it too wet and it wouldn’t burn. We didn’t have time to research moisture mixing sure to put deadline.
But now that we have more time, I am liking the idea again.
Trading apparatus for knowledge and application skill. If we can find a way to define the proper moisture ratio and then find a way to measure that and teach that in the jungle without advanced tech…I would very much prefer that to adding apparatus. Simpler is better for this application. But we have to find a measurable easy way to do and teach it. One of the principle objectives with this program is “multiplicability”. We would like to disseminate an apparatus and a process that can be learned and re taught by the end users. Tall order I know… To take more art out of gasification. But it is the only way we can affect masses of people. Make it a system that will spread itself…
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Moisture content I’d consider a benchmark of 10% by weight.
And to tell if charcoal has moisture in it after being stored, figure in the weight dry of the same volume and compare it.
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Jakob and Family… IMHO: You guys are awesome! 
I think you will need to carry two “fuels”: one, the bulk, moist charcoal. Two, a (much smaller) bag of charcoal that can be kept reasonably dry for first fill, lighting, and replenishing a "lost (burned up) " charbed. Your “operator” will just have to keep it out of the rain, and away from the damp charcoal. [ I am thinking about an overnight out and back hunting/fishing/gathering scenario trip on a river or lake]. I like the idea of a tennis ball valve. To minimize store-bought stuff, and it seems counter-intuitive, but could you make some components out of wood? like the air box cover, a pop valve, a hose coupler, etc.? what about leather, cork, tar, fibers, (hair, jute other veg. byproducts), if not right at the first run, then for field repairs. Don’t forget rivets, the whole 19th century infrastructure was built with them. You can hammer and anvil an awful lot of finished products. Outside housing or not, you will have to provide cool handles and heat shields so the thing can be taken apart, moved and stored safely directly after a power run. just my first $.02 payment! 
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We’re already using a wooden air mix box.
Not sure these people have scales to weigh charcoal. We need a simple, visual indicator or bench mark… Like when we say “if a flare will burn without a pilot light on a wk, then it will run an engine”. Something like that.
Still thinking…
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Maybe enough water until it stops being dusty when you’re pouring the charcoal?
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I like to start out with dry charcoal. Light the gasifier up. Get it going. Add some 10 % moist charcoal on top of the start up drycharcoal. If it feels wet it is too wet. Mix in the same amont of some dry charcoal with it in a bag and mix it. It should be ready to go. So having some dry charcoal on hand is a really good idea. Cody. Charcoal with 10% moisture does not feel wet to me. It will not have the white dusty ashes on it. This is the really nice part when pouring it in the hopper no dust fly up.
Bob
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The first simple fire I built, when I knew even less than I know now, actually flared as it condensed water droplets out of the fuel. Too wet char. It would hold a flare but wouldn’t run the engine.
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We had that problem the other day on this one. We were in heater mode. (Thanks Unruh). It would start on water but not run on char.
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