Design criteria

I have seen all kinds of tables for calculating the dimensions of wood gasifiers.
Is there a similar set of tables to design a charcoal unit?

My engine is a 600cc twin

So how do I calculate the tuyere size, the distance between the tip and grate?
And how large should my grate opening be?

Thanks in advance.

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Hi Wallace
I have tried many sizes of nozzle tips from 1/4 up too 1 inch and have managed to run every engine size, single and twin cylinder up too 750 cc so far on the 1 inch nozzle with no problems .
Not sure about distance from grate though as non of mine have a great as such , just a bed of char in the bottom .


Hi Wallace, the most important dimension is the size of the charcoal. About the size of chashew nuts. I only have a grate and no nozzles so can’t help with much. Charcoal gasification is like stepping into the wild wild west.


I have been giving this some thought.
How would make I a tuyere that I can adjust in depth, or remove to quickly adjust size or make any other adaptation to the needs of the day?
I need something that I can swap fast.

I took a piece of 1 inch conduit and slid it into a Tech connector ( Teck cable is a common armoured cable in Canada with steel armour covered by PVC on the outside covering a inner PVC jacketed cable ).

If I remove the rubber sealing ring and replace it with a graphite packing ( like a pump gland ) then I have somethig I could weld into the gasifier tank that gives me access to the system without having to stop and wait for cool down to make a change.

I have yet to crack an easy water cooled tueyer solution yet but putting conduit in conduit and welding up the ends for a steel prototype seems to be the direction I am going )

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Use a JIC tube adaptor

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I have something better than that for my specific application Matt.
The inner pipe does not need a flare for this.
It slides in and out to the depth you want.

I have to make a up a prototype.
For the time being look at the pump gland and imagine the shaft you see is the pipe, the body is the stuffing box and tech connector nut is the glad.

I do like you JIC idea however and plan to use it in another place where I do not need the depth adjustment.

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Neither does the JIC adaptor its an adaptor to for straight pipe made out of SS. This does not have any flange and you can get the other end in NPT thread. Its works much like a cord grip like you have shown


Too me this is a JIC hydraulic fitting

I don’t think we are talking about the same thing.

I kind of get what you are talking about though.
Cord grip?
Not familiar with that term.
But I suspect you are talking about a very similar fitting used on “Cab tyre” rubber jacket cables these fittings are usually zinc

I use something very similar on large rubber insulated portable power cables ( about as big as 2 or 3 inches in diameter ) they serve mostly the same purpose.
The advantage of the fitting I suggest is it can fit pipes in diameters as large as 3 or 4 inches.
This would leave room for a pipe within a pipe for a water cooling jacket of some kind.

Yes I know what they are, they make special ones to adapt straight pipe and other things. In my previous life my career feild was special automated machinery building from scratch from the ground up. My background ranges from automated farm equipment, manufacturing and process equipment, (automotive product lines) robotic assembly, solar panel production, extreme precision machine tools etc.

A (cord grip) there many names for many things. Im refering to a bulkhead type fitting for routing and sealing cords and cables entering an electrical enclosure It is much like the conduit bulkhead fitting you had shown. JIC is just SAE standard and typically refers to the flange angle however, other fittings to made to adapt other things. They make an adaptor to mate a straight cut tube and it has a steel collar to reinforce the tubing with a step in it much like the cord grips to lock and seal it in place.


Maybe a giant compression fitting is better comparison.


I understand you.
I run into this when getting technical with other people who are in similar lines of work in different countries
Different names for mostly the same product, often more confusing the same name for completely different products.

Yes my idea is a giant compression fitting would have been simpler to say I guess, but with the graphite rope packing instead of a metal to metal seal.
This way I can use heavy wall pipe instead of tubing.


Here is a thought to interchange nozzles quickly. If you use a pipe union and weld the outer nut or collar to your drum, the inner parts can be loosened and pulled out replaced. If you have several inner parts of unions with different sizes of nozzle it would be really quick to change.
Don Mannes used this for his thermocouple installation, and I copied it. Pictures he shared on my build thread. You could if you wanted bore out one side of the union and screw one of your big compression fittings into the other if you wanted also to slide in and out.


Great ideas here.
Thanks guys!

I have a plan coming together.
In my head it looks something like this design bit with a side grate and ash pit under it all.

I think a propane tank for the body with larger charcoal hopper on top.

There seem to be a fair number of designs that look like this modified down draft with grate.
It just required more fabrication than the simple fire.

Next things to crack are the steam injection system tied to the throttle position and a means to insulate the reactor to conserve as much heat as possible, then heat exchanger for the gas to try and transfer as much heat as possible to the incoming air.
I am thinking of some sort of counter flow heat exchanger for air and perhaps use engine exhaust to boil my water then use the steam to cool the tuyere.
I do not know if the last part is practical.
I want to try and super heat the steam but this might not provide enough cooling to protect the tuyere.

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I have been playing with Gary Gilmore’s design that is patterned after a forge with a few of my own modifications…
I used a 30 gallon gas water heater as the container and a brake rotor that covers the water sump with steam slots that introduce steam in the center of the hot zone
Here is a slideshow of my build steps so far.


i look at it “case by case”
many ways to “protect” the nozzle, one i also use is not preheating the water prior the injection, ( no steam coil, just straight water drip)
in fact, you can play with any endothermic reaction to control the temperature and size of your “hot zone”
Airspeed at nozzle, size of your charcoal, the kind of charcoal used… endless list, endless fun to find things out…


Thanks Koen:
I am trying to think of as much possibility for adjustment and change as possible in the build with the least amount of cutting and welding for each modification.
I have 60cm of snow on the ground only just starting to melt so I have time to plan this out.

The link asks me to sign in to google video?
That’s strange I never had that asked of me before…
Maybe you have a private video?

Don I see that link now.
Very impressive build I will have to refer back to that for ideas.
Thank you.

What we do on the micro is we weld pipe couples into the hearth. We cut them in half and face them to so that they accept the pipe from the outside of the hearth. Then when we build the jets we use a reducing bushing that inserts into this. Ok now in order to install a jet into this from the side that is not tapped for it. We ram a pipe tap into this side so it can accept a pipe to create the jet tube. Smell what Im steppin in??


Yes Matt, I follow.
That is a very good idea I plan follow as well.

I wonder of there are some large diameter red brass pipes and tubes I could use to make the tuyere from?


Yeah I dont know, I use mild steel and they hold up just fine in a gasifier. Easy replacement and tuning ability is what that system is all about. It it really nice to be able to remove those jets from the outside of the machine.


Yes Matt that is a very slick feature.