I don’t think it will hurt to have a reduction as it will for sure help to concentrate a hot area if you were intending of mixing in some raw wood chips , with my attempt i lay a sheet of stainless steel to hold back the charcoal from the bottom of the drum and just drilled some 12mm holes in it at the far end to allow the gasses to flow down and out .
Dave
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If you haven’t seen this thread it will benefit you to look through it Brian.
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Forgive me if l sound critical, but unfortunaly this design achives the exact opposite as is the goal with a gasifier. You want to keep as much heat in the hearth as possible and prevent losses to the outside. Those rotors will work as heatsinks pumping heat from the inside out. But you answered all the solutions your self alredy. One brake rotor at the bottom will work just fine. By the time gas comes there there isnt much heat left and also it isnt needed anymore.
The gasifier will then form its own firetube, nicely insulated by charcoal and ash.
On this note, the grate can be a peace of 1/2" mesh. Used that plenty of times. A stiff rabbit fence even. Again, not much heat here to melt/bend it if the nozzle is at right height.
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Thanks Kristijan. That’s the answer I was hoping for.
As far as the nozzle height above the grate, I would like it to be as close as possible so I can use more of the fuel before it needs refilled.
17 centimeters = 6.693 inches which is where the 7 inches I drew on the tank came from. The 12 inches on one of my drawings came from looking at my simple fire and thinking about the fuel level when it quit making good gas. Maybe split the difference and put the nozzle 10 inches above the grate. Cutting the nozzle out, patching the hole, and moving it is an option if I get the height wrong but I’d rather get it in the right spot first try. Higher up should mean less heat at the grate and less heat in the gas but less space above the nozzle as the “hopper”.
My simple fire can run the generator at least 2 hours before needing refilled. I would hope to get double that time from this bigger one.
I would like to try mixing in some wood chips or charcoal that didn’t fully convert but the main reason for wanting to switch to down draft is the ability to use damp charcoal. My last few batches are still in the sealed barrel so should be pretty dry but all the rest of my charcoal is in open top buckets or containers that are not air tight.
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Not having super dry Charcoal will be always a problem here where I live. We only get 15% rain fall a year here, the reports say. But the moisture in my covered wood is about 10% , so I would say my Charcoal is about that all the time, I would think?
Over on the rainy West side of the Cascade Mountains where Steve U. and Marcus live in Washington State the rain fall is much higher.
So running my Charcoal gasifier with moisture Charcoal is good for me. So I just forget trying to keep the Charcoal dry as the desert in drought time. Keeping it in open containers is good enough covered with a board and plastic over it. I put holes in the bottom of my containers too, to make sure no water can fill them. Besides moisture in the Charcoal keeps the nasty black dust down when hangling it. Like KristijanL said no sign of dust is good, it has about the right moisture content in it for use in the gasifier with out water drip being added to it. A win, win in my opinion.
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I’ll admit, the last couple days I’ve been running the generator on GASOLINE. Partially because I took the filter apart on the simple fire and partially because I was welding and wanted to make sure I got good penetration welding the tank back together.
Took about a gallon of gasoline to do a few welds and some grinding. Makes me realize how much I was using that gasifier. A half hour here, an hour there adds up. The generator manual said 10 hours per 4 gallon tank at 50% load if I remember right. At full load it obviously uses considerably more.
Welded in a fitting for the nozzle and a ring of sheet metal around the lid.
Now, I need to refill my filter so I can stop wasting gasoline and get back to charcoal.
One more run on gasoline to make some planer shavings. These are two of the birch boards I made on the sawmill thread.
These were sawed at 1 inch minus the blade thickness and they finished at 3/4 inch.
My filter now has a layer of gravel on the bottom, and a couple pieces of felt over that.
Then a layer of the planer shavings. This was fresh cut boards but the log had been laying around for a long time so mostly dry.
Another layer of felt on top to keep from sucking up planer shavings.
Should be ready to run again as soon as I fill it back up with charcoal. I’m going to get my tools set up ready to use before starting it but I expect it to work. This is the first time running with the rocks and new gasket on that filter.
This is the ash clean out port for the new gasifier. The old simple fire powered the grinder to cut off this big piece of pipe and did most of the welding although it complained about that. This is way thicker than the welder was made to do and the generator running on charcoal was giving it everything it could. I’d be really surprised if I don’t find some leaks here but that’s one more step closer. The inside diameter is around 4 inches and the outside lip is around 6 inches with a groove to put a gasket.
The simple fire got really hot and ate a lot of charcoal. I didn’t time the run but it was working pretty hard most of the time it was running.
I refilled it and I’d guess it took about 3 gallons of charcoal.
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That filter should work really good with those rocks to help coalesce moisture, and the planer shavings. Felt will help too.
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One more step before I call it a day.
This is the idea for the nozzle. As marked, I’m thinking about 5 holes in the flute and will have them pointed down. The simple fire has 4 flutes if I remember right so this will be one extra unless I change my mind before I drill them.
Not sure what diameter I’ll make the holes but probably smaller at the end.
It’s a 1/2 inch diameter pipe 11 inches long.
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If you have the ability to take it in and out, start small and make them bigger if it’s not running the generator.
Edit:
I’d say 3 holes at 1/4" to start. I ran a 2 liter with 6 holes at 3/8" for reference.
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I drained out maybe a tablespoon of water out the bottom after the run. I opened the top and there was some condensation on the lid but the felt looked clean and the planer shavings were a little damp but not wet like before I added the rocks.
I didn’t empty the charcoal from before so it had more moisture than it should have had. Still run OK but probably would have run better if I would have changed it to dry charcoal. Hopefully the new gasifier isn’t so picky about the fuel.
I’m still happy with the simple fire and will continue to use it but will probably dedicate the down draft gasifier to the generator and use the simple fire for the log splitter or maybe a different generator at another location.
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Looking around for a cover for my ash clean out port I might use an old circular saw blade.
This was just a thought before it gets dark here. Pretty close the right size and flat.
The square tube I have isn’t big enough so I’ll probably use angle iron to bolt this in place using the flat bar as support and to block the holes in the blade.
I still have more to do before I need to worry about that so I might find something else that looks nicer but this should work.
Next step will either be the gas outlet pipe or the grate as well as welding the end of the flute nozzle shut and drilling some holes.
That flute nozzle should be easy to get to as long as the charcoal is not in the way so I’ll start with less holes than I originally thought and drill more or enlarge them if needed.
Oh yeah, I forgot to mention but the bottom of the tank is rounded and my clean out isn’t at the lowest point but I figure I will just leave some ashes in it to help insulate the base.
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Looking great Brain, nice workmanship on your build. Yes use your simple fire on your more portable stuff. And like the bigger gasifier handle the generation part. I like the saw blade idea, I have a few old blades on the wall. Put them into a new use as hatch covers for clean outs.
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This doesn’t really have anything to do with this build but kind of related to the saw blade and I didn’t want to lose this video just in case I needed another project someday.
On the comments Kristijan said it was a sawblade 2 or 3mm thick but should have been 4 or 5mm.
Mounted directly on the PTO of a 70hp tractor at idle.
I haven’t looked to see if there was any more information on this here but doesn’t look complicated to figure out just from the video.
EDIT:
EDIT AGAIN TO ADD:
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Looking good. You might run in to some problems with the nozzle overheating (heat rises up) but definitly go small on the nozzles. Like Cody sayd l wuld go 3 6mm for a start.
Problem also with a down facing nozzle is molten slag drips down the nozzles and plugs them. Atleast it was in my case…
The chunker was stupid easy and cheap to make and worked good, apart from the disc being too thin. Only aditional talk about it was me recomending to Cody to change the geometry of the disc from this snail shape to a more rounded shape for extra strengh.
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Hi Kristijan, I plan to use 1-1/2 inch schedule 80 pipe passing entirely through a 100 pound propane tank. I want to try two 6mm nozzles inclined 20 degrees down from horizontal. Nozzles pointing away from 4 inch perforated grate on opposite side 10 inches below nozzles. The tank is 15 inch diameter. I plan to line the tank with 1 inch refractory insulation. I plan to place the nozzle holes 7 inches apart drilled at 45 degrees facing toward each other. 45 degrees points the two hot zones into the center and allows easy cleanout from each side opening. Do you see potential problems with any of that? Thanks in advance for your thoughts.
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Correction: to 3/8 inch nozzle size 8mm or 9mm?
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I’ve been thinking to just sharpen a disc and adding the hub off center. Fluidyne’s manual chipper is essentially just that. All you need is the curvature to slice without the entire edge going in at once, and like you said a more rounded shape is stronger. The shark fin design I think would eventually snap at the tip.
http://www.fluidynenz.gwprojects.org/simplechipper.gif
I have a 9" diameter steel disc at 1/4" thickness right now, haven’t sharpened it yet. I’m hoping to run it slow enough I can automate it to cut with an angled hopper like Patrick did with his.
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Here is my pto chunker:
I wish my pto turned slower but it chunks a lot of wood in a short time.
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Thanks for the information and links to the simple chunkers. Someday I might try making one.
Today I fired up the simple fire again and did some more work on the down draft gasifier.
First I set the chop saw up to cut some pipe.
Thought I’d try less sharp bends this time. The simple fire I just cut 45 degree angles but this time I set it at 22.5 degrees. Took extra welding but might have less restriction for the gas flow.
Just about finished another 2 pound roll of flux core wire.
Now, I could have hidden this lumpy mess but I wanted to show good and bad to encourage others and show that you don’t need to be a professional welder to do this.
I wasn’t happy with that lumpy mess but I could have tested it for leaks and put some silicone or JB Weld on it to fix any leaks and called it good enough but decided to grind it off and see what it looked like under all that weld.
Not real bad but found some places I’m going to weld up.
This is a temperature reading just after shutting off the simple fire. I guess it was time to shut down. This burnt a lot of charcoal (probably a bucket full) but was running good. I think I’ll let it cool off and empty it out tomorrow to get rid of ashes and to check on the nozzle.
Closer to the nozzle the outside of the tank was over 450 degrees F (232 degrees C) but the temperature after my cooler was still under the boiling point of water. I didn’t check how much water it condensed but today’s charcoal should have been drier than yesterday’s run.
I probably should have shut down and refilled it sooner but it was running really good and I was almost done.
I didn’t time this run but it must have been a couple hours or maybe a little longer. It run long enough to cut the pipe pieces, grind the edges, weld them together, and grind the lumpy weld back off. I was going to weld some spots that looked like they might leak and grind those welds back down by my uncle came and offered to take me to get some firewood slabs.
This is all hemlock so not the best firewood but a local sawmill told me to take as much as I wanted. This will likely be just burnt in the furnace but I might try turning some into charcoal.
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Hi Brian. I have been reading and watching you closely. Hope to start building soon. My experience is that hemlock burns with as much heat as fir but it doesn’t smell as good and must be really dry.
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