Rocket Fuel is really only meant for a raw wood gasifier when you have a bunch of overly wet wood or just need a boost in efficiency.
Mixing in raw wood I think could really only work in something like the Double Flute if it’s sealed off like with Don and Bob’s versions, or with a Mako style charcoal gasifier. Something with a perifery of jets. Even then I’d only mix maybe 10% raw wood in a quick charring form like wood chips.
Rocket Fuel for a wood gasifier is usually 90/10 wood/char I think.
That’s my understanding too. I’ve tried it only a couple times but it seems a wood gasifier gets easily consipated if you overdo the char.
Is that because of the charcoal soaking up the tars and gets sticky?
Does that mean a WOOD gasifier don’t work on all charcoal?
This gasifier still isn’t dropping the charcoal down real good and I poke it down after almost every run and the level drops. The same thing happens with my simple fire and it has never had any raw wood. I assumed it was just too big of charcoal or maybe my flute nozzle blocking the charcoal from dropping. Not usually a big deal since I mostly only run an hour or less but sometimes a couple hours.
Brian, I think it has to with tar to a point. It turns to soot. Also, all the soot, char and ash from above have to pass a restriction in a wood gasifier.
Small fuel, extreemly dry fuel and char - they all contribute to a denst charbed. They all chatter down to small bits faster.
Hello Brian .
All what JO said plus a couple thoughts of mine .
Char along with small dry wood will catch fire and react much faster than raw wood blocks. As this char or dry small fuel burns it consumes the oxygen and leaves the wood gas flowing down through the remainder of the char bed and because of no oxygen in this gas the lower char will stay dormant and start packing up and get constipated.
I think I understand but don’t know how much I can explain because I found the information in the premium section.
https://forum.driveonwood.com/t/choke-plate-variables/709
Since I’m using just charcoal, I don’t know if it fully applies to me. I don’t really have a choke plate. I’m considering my stack of brake rotors as the fire tube with the nozzle right above it. I’d have to empty it out to get actual dimensions but should be around 5 inch diameter but maybe up to a foot between the nozzle and the grate.
I haven’t run it a lot and usually only an hour or two maximum at a time. My generator is only a 212cc engine so probably not a lot of pull. I haven’t gotten enough ashes or dropped char to bother cleaning out yet. MAYBE the distance/diameter is not allowing the oxygen to get close enough to the grate to purge the ashes?
I might be overthinking it. Charcoal only wasn’t supposed to need a restriction plate and it works good enough.
Yes to tight of a Charcoal bed is not good, I use popcorn size for my smallest Charcoal size, I like to use bigger Charcoal because it does reduce down in size quickly and fills in the voids in the brands above the nozzles. The charcoal picks up moisture quickly. Then when it burns it makes extra Hydrogen. But this is what I experiences with my WK Gasifier. We all know the gasifiers are all different in operations.
If we are talking just a charcoal gasifier bridging , then you will always have a collapse of fuel after stopping the machine as there is a cavity of sorts above the nozzle that falls once you poke down after stopping , over the years various contraptions have been thought of to over come this and also to move the funnel effect of the charcoal not flowing from the outer edges .
This is why its a good idea to get your fuel as small as possible smaller pieces flow better
Dave
I second what Cody says. You MAY get by by using a bit of torrefied wood but raw wood might be too much. Only the periferal nozzles will prevent tars sneaking trugh by the walls.
Raw wood and bridging is a recepie for tar. Imagine. A cavity forms because of a bridge. It collapses sooner or later, and now you have peaces of raw wood dangerously close to the grate… l have tared up engines before by just that phenomena, in a dedicated raw wood gasifier…
Speaking of bridging, a stiff connection from your generator to the gasifier shuld produce enaugh vibration to help it.
That is my experience as well.
Another hour+ run today.
Trying a different path for the gases and added the water trap.
Charged all my drill batteries and did some grinding and welding on the cyclone.
It run good but I found some leaks when I shut down.
The water trap didn’t catch any liquid but had some leaks which I kind of knew the jar didn’t seal tight. I have a rubber Fernco adapter ordered that I hope to use in place of the jar lid.
The lid still isn’t sealing right probably because the little springs aren’t strong enough. Didn’t seem to be a problem with vacuum on the system but leaks when there is any pressure. I didn’t check around yet to see if I can find an old valve spring to make a different hold down.
The rubber connector from the gas output to the cooler was stopping some of the water and not sealing tight. Probably not enough slope on that pipe which also explains why the jar didn’t catch any water.
The filter did catch some water but I didn’t measure how much.
I tested the cyclone with a shop vac and some dirt and it did catch the dirt. Not sure if it caught all of it because I had wood shavings in the vacuum container which I didn’t realize was there. The plastic Cyclone either missed some or I used it without that filter. I’m not sure if I will add the cyclone to the gasifier or not but it was nice to see the design might work.
I thought the water problem should be going away. It is getting a lot less but still getting some. The generator is running good and the charcoal didn’t get the big pocket like it had been even though the level dropped noticeably on this run. It wasn’t completely full when I started though.
All in all, I’m still happy with it but there is still work to be done to improve it.
Pressure brings smoke and vapors to the outside where we can see it; vacuum brings it to the inside and I’m not crawling in there to watch. 
By vacuum I meant from the engine. It likely could have also been leaking (especially at the jar lid) but I hoped the lid was being sucked down making a better seal until the engine was shut off. I haven’t had any more poofs at the lid since my first test where it blew the lid clean off. It does sometime shoot flames out the nozzle inlet pipe when I shut off the engine.
The strange thing is the smoke at the top when I have opened the lid right after shutting down doesn’t ignite even if I stick a burning torch inside. Must be mostly water vapor?
I’ve been refilling it with freshly made charcoal that should have been dry so it must still be moisture from all the damp ashes I used to seal the brake rotors and that moisture soaking into all the charcoal. I don’t really want to have to add a monorator to this one and don’t want to make charcoal in it again to try to dry it out and burn off all the paint. It is getting better each run. Maybe just keep running it without adding fresh charcoal until it uses up as much as it can. I haven’t run this enough to know for sure but I think there’s probably another hours worth of fuel before it gets to the nozzle.
Maybe light it, open the top and send the heat, smoke, and steam out the top for a little while?
Now that I think about it, I haven’t emptied the ashes from the clean out port. Could be the water is collected in there and slowly coming out with the gas.
Sounded possible but probably not the problem. This is what I got out of the ash pan. Slightly damp but not wet enough to wet a paper towel when a handful of it was squeezed in it.
I opened the top and the remaining charcoal feels dry. Probably a little damp but shouldn’t be the problem. The top of the lid is slightly damp but even that barely dampened a paper towel.
I guess it works. Just accept the little bit of moisture that it collects and hope it continues to get less each run like it has been doing.
Brian , i am at a loss regarding your constant water problem , i live at a high altitude where some days clouds are at ground level here and yet i have never had a problem with my charcoal , i have had the odd crackle from the nozzle when first lighting up but that soon passes , i do not think that the ashes you mention around the brake rotor will be the cause as it must be at least the 3rd lighting and the brake rotor would have gotten hot enough to dry out those ashes i am sure .
Still i guess the only way is to start all over again with new coals and new dry ash and look into how you are storing your charcoal between using it , do you store in metal drums or plastic drums ? maybe condensation from the metal drums ?
Dave
I was considering that but that’s NOT the answer I was hoping for.
Not only has this been run multiple times running the generator, I also filled it with long pieces of wood and burnt it to coals so it’s hard to believe that the ashes wouldn’t have dried out.
I was just reading the FEMA plans looking for the fire tube dimensions they recommend. Probably doesn’t relate to mine but for an engine the size I’m running they call for around a 2 inch diameter or maybe slightly bigger.
A fire tube with an inside diameter of less than. 6 in. would create bridging problems with wood chips and blocks. If the engine is rated at or below 15 horsepower, use a 6-in. minimum fire tube diameter and create a throat restriction in the bottom of the tube corresponding to the diameter entered in the above table.
Without scrolling back up I think my “fire tube” area is around 5 inches diameter the whole way down to the grate. Using all charcoal I thought I didn’t need a restriction but now I wonder if I do need a restriction to stop the moisture from passing through since my diameter is twice what it maybe should be.
My stored charcoal is mostly in open top buckets and not sealed up but the last couple times I added charcoal it was freshly made so there SHOULDN’T be much moisture in it.
I really don’t like the thought of taking all the charcoal back out and starting over when, aside from the moisture problem, it is working and seems to have the same power as the simple fire does. The ability to use damp charcoal instead of a water drip was the main reason I wanted this down draft and the last run I’d estimate I drained out at least 2 ounces of water from my filter and what was stuck in the cooler pipe. That’s way less than I was getting but Kristijan said:
I either have too much water in the charcoal or the ashes or the water is finding another way past the hot zone.
You don’t need a restriction, but you should probably open the lid after a run to evacuate any moisture.
Don’t disturb anything in the bottom, it will eventually cement the ash into something more sturdy. Just give it time.
Are you keeping your gasifier out of the weather? Maybe it’s getting rain and snow inside from the lid. Toss a tarp over it.
Are you still using a stack of brakes or did you revert to just one brake? Kristijan had warned a stack of those brakes would rob the heat away from the reaction.
You might have just solved the mystery. Yes, I put the whole stack of brake rotors back in so created a big heat sink.
It must still be making good gas right in the center (the engine has been running good) but the cooler edges near the brake rotor stack wouldn’t be hot enough to crack the water so that would give it a path through as steam. That would explain why the drier charcoal and ash produced less liquid in my filter and less making it all the way to the engine.
When I get a chance I’ll take it back apart and take out all but the last brake rotor. That one has my grate attached to it.
The weather should be nicer tomorrow so I’ll probably try to get more free slabs but now I’m curious if this solves the moisture problem.
The gasifier is exposed to the rain and snow but the lid shouldn’t let any water get in. I do want to get it under a roof and off the ground so I might be able to use it over the winter. I haven’t used the simple fire since this new gasifier was working but I should get that one moved somewhere that it doesn’t get froze to the ground. It would still work. It just isn’t as easy to fill through the 3 inch pipe on the top as the bigger down draft where the whole top comes off.
You solved it your self. I had a feeling the rotors arent making you any favours but it didnt occur to me what you just wrote. And its the most likely cause indeed!
You might however still see moisture when you eliminate the stack, at least untill the dust plugs the walls of the new “firetube”.
I emptied everything out and only put the single brake rotor with the grate back in. Then I cut off a piece of stainless steel tube from the soda container and put the ashes back around that.
I don’t really expect that to hold up long but it will get me back to about what I had minus all the mass from the brake rotors.
I’m still running it as I type this and it does seem to be running smoother but it might be wishful thinking.
The glass jar water trap has maybe 2 ounces of dark water in it and I don’t know what the filter condensed yet.
I did notice the flute nozzle is not really a flute anymore but put it back in anyway.
So far I’ve refilled my air tank (but it wasn’t empty), run the miter saw a little bit, charged my car battery, and am now charging the drill batteries while I let the gasifier dry out and waste some charcoal.
I don’t really have any projects started right now but hate to shut it down with it running so smooth.
The gas outlet is 233 F or around 110 C. The bottom of the cooler is 150 F or 65 C and the top is about 108 F or 42 C so it should be condensing most of the water vapors.
The generator started sounding different and my bigger drill battery was charged so I shut it down.
I opened the gasifier top and got smoke and then flames. The charcoal level was getting really close to the nozzle and I could see glowing coals so it was probably time to shut down. I hadn’t added any more charcoal before today’s run. It got the same charcoal I had in it from yesterday so my hour estimate was probably close.
The filter did have an ounce or two of condensed water and the grass/straw was really damp.
It will take another run or two to see if the moisture problem goes away and I’m going to need to make another nozzle but probably going to continue using the melted one a little longer.
Is that a 3/4" or a 1" pipe? You could nest a 3/4 into a 1" pipe to make it thicker. Weld it at one end and cap it off, then drill the holes.
eBay has lots of thick walled DOM tubing that you could weld a pipe nipple onto. That’s what I used for all my flute nozzles. 5/8" thick walled 2" OD tubing.
