One problem that often comes up is that people don’t have the ability to weld. To solve this problem I created the “Constance” gasifier. She is built with nothing but pipe fittings and a grate made of steel mesh cut with tin snips. The best description I can offer is the following set of videos:
Being a cross draft machine she will never be as clean as something like the two stage Victoria or even the Anastasia, but it is MUCH cleaner than a FEMA of a similar size. It also makes faster burning gas resulting in more power because the flame has time to cross the cylinder before the exhaust valve opens.
Parts List:
Here is a list of parts which make up the Constance and their McMaster-Carr part numbers:
3/4 X 1/8 Pipe coupling (McMaster-Carr P/N# 44605K386)
1/8 X 1.5″ Pipe nipple (McMaster-Carr P/N# 44615K421)
2 X 1/2 Pipe Bushing (McMaster-Carr P/N# 44605K295)
1/2 X 1/4 Face Bushing (McMaster-Carr P/N# 44605K259)
2″ Pipe Tee (McMaster-Carr P/N#44605K159)
2″ X 12″ Pipe nipple (McMaster-Carr P/N# 44615K549)
2″ Pipe Cap (McMaster-Carr P/N# 44605K657)
2″ X 3/4″ pipe bushing (McMaster-Carr P/N#44605K294)
Expanded metal grate sheeting (closest McMaster approximation P/N# 9302T636)
or use the Lowe’s grate material I ran Hillman Group P/N# 11786
Northern Self Reliance 
This is genius! Thanks for this.
If you’ll put this into a PDF with simple assembly/operating instructions, I’ll add it to the Free Gasifier Plans page at DOW. – Chris
Hi Chris. I’m glad everyone has enjoyed it. I will get the PDF together but it may be slow coming. I am knee deep in getting the Arduino mixture controller working. I need that to be working well before the fair season and the Gas Station gets seen by the general public.
Dear Stephen:
Thanks for the weldless design. I have cobbled together a charcoal gasifier for classroom (outside) demonstrations, based roughly on Gary Gilmore’s Simple-Fire. Mine’s simpler than his, since it’s just a pipe with a hole low down on one side for the jet. The advantage is that students can see a little more of what’s going on, since I was able to scrounge a piece of 5.5″ fused quartz furnace tube.
The point of the long-windedness is that I’ve been asked to put together a wood gasifier as well. I built a near-copy of Constance, and am learning. Southern California is not a great place to buy wood pellets, so I sliced up hardwood pallet into 3/8″-or-so cubes. The flare looks like I’m ready for making ham or jerky, and there’s some bridging, so the pellet advice seems sound. And speaking of sound, with about 3/4″ h2o draft (
Dear Stephen:
Second try after hitting wrong key (sorry).
Thanks for the weldless design. I have cobbled together a charcoal gasifier for classroom (outside) demonstrations, based roughly on Gary Gilmore’s Simple-Fire. Mine’s simpler than his, since it’s just a pipe with a hole low down on one side for the nozzle. The advantage is that students can see a little more of what’s going on, since I was able to scrounge a piece of 5.5″ fused quartz furnace tube.
The point of the long-windedness is that I’ve been asked to put together a wood gasifier as well. I built a near-copy of Constance, and am learning. Southern California is not a great place to buy wood pellets, so I sliced up a hardwood pallet into 3/8″-or-so cubes. The flare looks like I’m ready for making ham or jerky, and there’s some bridging, so the pellet advice seems sound. And speaking of sound, with about 3/4″ h2o draft (which is about the best I can do with an airbrush compressor), there’s an organ pipe resonance in the fuel hopper, which blows smoke out around the nozzle. If I remove the pipe cap, and cover the hopper with my hand, it’s really clear what’s happening. have you ever seen this with a Constance or Anastasia? Maybe pellets would pack closely enough to prevent this problem also.
Any advice (beyond using the right fuel 🙂 you may have would certainly be welcome.
Thanks again,
Kent Potter
Hi Kent. If I were to guess, I bet the organ tone is detonating tar gas in the hopper. Once it builds up enough it detonates and the cycle stars over. If I am correct I would cement in the nozzle as the first fix. If that doesn’t work try using a bigger compressor and see if the problem goes away. I honestly didn’t do a lot with Constance simply because the fuel hopper is too small to do useful work. Even tiny Isabella has run a 4kW up to 1800W before the cycles started falling off. That’s a lot of performance for a $350 gasifier.
Hi wanted to say thanks for sharing with us it sure makes my life easier to get started.
I do have a question what would happen if I used 2 1/2 or 3 inch pipes instead ???
Hi Hugues…The short answer is I don’t know. I suspect you would have more tar and potential for plugging because the gas flow speed could spread out too much and not blow the ash through. There would also be more room around the combustion zone for the tar to escape.
If you did do it, I would recommend going to a 1/4″ pipe nozzle to make the combustion zone larger.
If i were to use a 3 inch pipe, how many hp would i be able to run? Same with 4 inch pipe
Hi Bob..Going with bigger pipe will only allow the tar gasses to have a larger path around the combustion zone and out of the machine. The gas could get dirty fast going larger. If you want to scale up go to an Isabella. That is 4″ in diameter, makes very clean, potent gas and is only $350. I’m not sure 4″ fittings would be a lot less than this.
Also, how do you start the fire in the constance?
I just turn on the ejector and blow a propane torch in the nozzle for a few seconds.
where did you buy the bushings. I can’t find them
Hi Bob…They came from McMaster-Carr. The 2 X 3/4 is:
http://www.mcmaster.com/#44605k294/=vebq6g
The 2″ X 1/4″ may have been discontinued. I can’t find it either I would just put a bushing in the 2″ X 1/2″.
i am sorry for bothering you so much but i have 1 final question. What would happen if i made the outlet 1 inch instead of 3/4 of an inch.
Hi Bob…Not a problem. Probably nothing. That reducer bushing just gives the grate support from falling over.
Ok this is the final question. i promise, probably. Would a battery powered air mattress fan be ok to start this unit? Also, is this unit capable of powering a 1500 watt generator? lastly, I’m thinking of getting a 2 inch pipe thats 12in long and filling it with sawdust and using that as a filter. ill put reducers on the end and connect it to the constance gasifier. I’m thinking of running 5 ft of automotive exhaust pipe from the gasifier to the filter to cool down the gas. then, ill use 4 ft of sump pump hose to connect it to the generator. what are your thoughts on this?
Air matress fan?? I would need a part number to know. Doubtful. Maybe a 12V tire inflating compressor pushing through a .063 orifice.
It would probably run a 1500W generator if the generator is a four stroke.
Regarding cooling…you are still going to need a cyclone to remove the charcoal bits entrained in the gas. You would be better off cooling at the cyclone. I tried fan cooling 4ft of 3/4″ pipe and could only get down 150’ish degrees. I was limited by the internal convective heat transfer.
I have never tried sawdust filtering. Sounds a scary to me. Lots of pressure drop, there is a possibility of particles coming loose, pyrolysis gasses being generated if things get too hot, condensation soaking. I know it has been done, but I wouldn’t based on what I have seen.
I tried sump pump hose and it was a no go. If it gets even a little warm it collapses due to vacuum. It was meant for cold low POSITIVE PRESSURE. Get 1.5″ blue pool hose and banjo couplings. It works much better.
Ok thank you for your suggestions. i really appreciate it!
If I have a fan not powerful enough for the suction draw method could I attach it to the fresh air intake and would a small burning charcole be enough to start it since there would be no were for a torch ignition
Hi Callum…Without enough flow you will not reach reduction temperatures or blow the ash through so starting it will be irrelevant. Stephen
hi Sab
wanted to know if the constance could be powered by a fan forcing air into the nozzle rather than it drawnig air though it.
thank you Callum
Hi Callum..Pressurized gasifiers never work as well as suction models. I know, I tried to go with pressure for about a year before I gave up. The best explanation I can give is to imagine the incoming air as a string. In a pressure model the string goes in and bunches up until it finally falls out in a wad. Not exactly the best for ensuring complete tar combustion. If you suck the flow through, the string is tight from the nozzle to the exit making the pyrolysis zone smaller and more predictable. That makes it burn cleaner. Stephen
How well would charcoal work with this unit?
Hi Kevin,
Charcoal should be fine. You will just have to grind it to the appropriate small size, probably about .25″.
Stephen
Hi Stephen
At About what tempature dose this gasifier start to reduce and for you how long dose it usually take. Would it be OK if increased the the injector size to 3/8 and left it a open bushing and couple away from the T so no pellets fall out?
Thank you callum
Hi steve
Also dose there need to be adjustable fresh air or additional air to produce a clean flame, and when I did try my fan sucking air, it heated up after a fairly smokey start and started to go clear with these bisrts of smoke, could it be ash not being pulled through because the fan is to weak. I tried lighting the exaust then and nothing, any suggestions is much appreciated!
Thanks again Callum