This really old tank has already provided the metal for some projects so I’m tempted to cut a piece out and pound it into a tube shape for my burn tube.
I hope everyone isn’t getting tired of my posting all my crazy ideas while I try to build this gasifier. I’m trying to post the process I’m going through (good and bad) instead of just waiting till I have a working gasifier and edit out all the problems and mistakes along the way.
I’m trying to design this so, when it doesn’t work right, I can easily take it back apart to make changes. I’m also trying to do it with what I have available. I have way more time than money so can’t go buy everything I’d like to use.
This is my idea for a fixed grate. It will likely get plugged up but might do as a test. I can always pull it back apart, cut out the bottom, and add a movable grate later if it actually produces usable gas.
A lot of mass here that might cause problems or make it take a while to get hot enough to produce good gas but it all comes back apart so nothing is permanent.
About 8-1/2 to 9-1/2 inches from the top of the stack of brake rotors to the grate depending on how I stack them which is a little higher than Giorgio’s version but smaller diameter.
The nozzle will probably be a little higher and removable so I can get these back out when it doesn’t work. The whole stack will be covered with ashes to insulate it and seal the spaces around them.
This was a sketch I made last night. Not exactly how I will probably build it though. Hopefully there isn’t much condensed liquids so the drain from the condenser could probably just be a plug in the lowest point.
The way my filter from the simple fire is made I used the original threaded opening for the propane valve as the drain. It only catches a tablespoon or so of liquid depending on how damp my charcoal is.
This hasn’t been tested yet. I filled the bottom of the filter with gravel. My thought is this will help condense any moisture that the gas contains and keeps my planer shavings from sitting in that liquid. Obviously, using dry charcoal in the simple fire should eliminate most of the moisture problem and hopefully the down draft won’t have as much problems with less than ideal fuel.
I could change my design and just try the stainless steel tube but it’s really thin metal but bigger diameter.
In the grate plate you need a lot more holes so it does not plug up. All the rotors will take time to heat up but will hold the temp inside and give you a good turn down ratio. But this is need in gasifiers that are not stationary and are not run at a constant velocities like running a vehicle engine. This will will be running a generator right. Some sort of a cone will be need to funnel the Charcoal into the smaller fire tube from the hopper, I like 60%. It should work if it is sealed up air/gas tight.
Thank Bob. There’s still a lot left to do so I’m sure this isn’t the final design. I’ll probably make an actual grate of some kind or at least cut the holes bigger in the fixed one.
Yes, my plan is to use this to run a generator. It’s going to be too big and too heavy to easily move around especially if I stick with the stack of brake rotors.
I was hoping I could just stack/compress ashes to make the cone funnel but I suppose that would be above the main heat so sheet metal should be good enough.
If you can I would put a grate in that will hang by chains, then you can reach in through the clean out hatch and give it a bump or shake to clear the ash off the grate and out of the fire tube or linkers that might form above the grate. Leave 1" to 1 1/2" of space above the grate to the bottomof the fire tube. Make your grate larger than the opening of the fire tube by at least 2" in diameter. If the grate plugs up the gases can still go out the side of the Charcoal pile. This is great for a standing gasifier stationary unit. Some people put grate shakes on their units. I have never put any on my Charcoal gasifiers.
Thanks again Bob. I made some notes for what I’ll look for to make the grate. That grate will need to fit through the opening I just welded in place. Might make it a little tricky to go at least 2" bigger diameter but I could either cut the opening bigger or make the grate in pieces that can be assembled in place. Will depend on what I find or build for the grate.
I still need to make the clean out hatch and the gas outlet.
Even though this is supposed to be charcoal only, I probably should make the lid able to handle a poof. I would like to try Rindert’s idea using square tubing idea to hold the ash door closed.
Might be able to add springs to those brackets to allow the lid to lift if it needs to.
Hi Brian , I’m no expert when it comes to downdraft but i am pretty sure just ash pressed around the outer diameter will work on top of the brake rotors just fine , also the charcoal will naturally form a cone of sorts .
I have read comments from other people that have had much longer run times of there downdraft compared to me i have only run maybe 40 hours , but if what everyone else says about no need for a reduction as such them maybe just use the 1 brake rotor that way at least it will make it a lot lighter to move around .
Dave
PS there is no such thing as crazy idea’s and your posts will help a lot of people new and old that follow you through your journey so keep on doing what you are doing is what i say .
I was wondering about that. Just put the nozzle at a height that gives enough space for the reactions to take place and use it basically like an upside down simple fire. Sounds like a good idea unless someone disagrees.
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
