GEK Wiki / Brian Gautreau, Colorado
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Brian Gautreau, Colorado

Page history last edited by bgautrea 15 years, 1 month ago

Brian shows how to build a GEK out of junk, using only stone tools and raw enthusiasm.  A sight to behold!






I began building the Stone Age GEK after being inspired by someone's gasifier that was running their truck.  I intially thought I understood what it was doing but quickly found out I needed to know more.  I attempted to build a small scale model, but the lack of knowledge kept it from working as I _thought_ it would. 


The SA GEK was built with as many "freebie" parts as possible.  Freebies, while not many, included the 30 gallon barrel, fan motor, and a 10' length of 1" pipe.  Parts purchased include (1) 4' x 8' sheet of 16ga hot rolled sheet metal, around 15 feet of 1/2" black iron pipe, (10)  1/2" elbows, (5) 1/2" couplers, (5) 1/2" x 2" nipples, (5) 1/2" 90 degree elbow reducers, 6 feet of pool vacuum hose, (1) 1.5" -> 1.25" bushing, (1) 1.25" x 3" nipple, (1) 1.25" -> .75" bushing,  (1) .75" x 8" nipple, (1) 1/4" NPT Stop Cock, (1) 1/2" -> 1/4" bushing, (1) dimmer swith, as well as numerous 5/16" nuts and bolts.  The documentation is here:




I had limited access to tools to begin with.  While I have a welding machine, I do not have access to oxy/acyt torch or plasma cutter, therefore I used a jigsaw and metal blade to do most of my cutting,


Initial Tools

Cordless Sawzall

Cordless Drill



4.5" Grinder

MIG Welder

Sledge hammer

Carpenters Hammer

Propane Torch

C Clamps

Vise-Grip Pliers

Cargo Tie-downs



Other Tools

10' Sheet Metal Brake

3' Sheet Metal hand crank roller


Crooked Reactor













Fabrication began by building the reactor.  It is a 10" diameter x 20" cylinder.  It was fabricated by beating and

pulling it into shape around a 10" form.  As can be seen in the photo to the right, fabrication of the reactor was difficult and not quite round in nature. I was able to cut and drill the bottom plate fairly simply, however cutting the holes for the reducer and couplers for the nozzles proved to be difficult as well.  I also cut flanges at this point for attaching the reactor to the cowling barrel. 


The air nozzles were connected to the preheating tubes using a series of elbows and nipples.  The preheating tubes were aligned and holes cut in the mounting flange for the reactor, then welded into place.  Seen here: .



The cowling was relatively simple, though adjustments were made later on.  I cut out the port in bottom of the barrel for ash removal and a hole was cut in the upper side where a 1.5" union was welded in for the output.  The barrel was older and rust and didnt weld nearly as nicely as the sheet so there was quite a bit of time spent fixing where I would burn through while welding the 2 different thickness materials.  A flange was also added to the barrel's top to support the reactor inside.  This again also caused welding burn through issues, though not as bad.


The 1" tubing was cut into 2' sections and welded to the bottom of the cowling for legs.


Holes were drilled in the mounting flanges of both the Cowling and the Reactor and bolts were welded into the flange of the cowling for securing the Reactor to the Cowling.



The cyclone and packed bed filter were constructed from the sheet metal as well.  These 2 pieces were constructed from 3 pieces of sheet, 1 for the filter, 1 for the upper cylinder of the cyclone, and the last for the cone of the cyclone.  The cylinders were rolled on the sheet metal roller then overlapped by about 1/4" tacked, and welded.  The cone was divided into 10 sections and bent on the sheet metal brake.  The cone was then overlapped, tacked, and welded.  A small circular plate was added to the bottom of the cone and the stop cock was welded in.  A hole was cut in the side of the cyclone and a mounting flange ( was attached on the tangent of the cyclone so the entire assembly can be attached to the cowling.  Intially I had the inlet attached to the Filter, but after learning more about the cyclone it was moved to the cylinder of the cyclone.


Fan and Fan Cowling

The fan was fabricated per the AutoCAD drawings at  The fan motor was salvaged from an old IT cabinet that was being scrapped.  It had a collar that was pressed on with an interference fit and it had to be ground off.  The motor is a 110V AC motor with a 3/8" shaft.  It's HP is unknown, it is labeled to operate at 1200-1500 RPMS. 



The reactor simply sits inside the cowling.  The Filtration assembly with the filter and the cyclone were all welded together and they bolt to the side of the cowling as well.  Weatherstripping was added around the flanges where the reactor sits on top of the cowling and around the mounting flange for the filtration assembly.




I have not lit or tested the performance yet.  I did add a vacuum gauge, however it is to large of a scale and does not register the vacuum (or it is not calibrated for the altitude of 6700 feet ASL

Update 1 YouTube plugin error

I got the gasifier lit and I've been able to temporarily light the produced gas in the swirl burner.  In my best case, I've been able to light the burner for about 18 seconds.  This seems to infer that I have a fuel/air mixture problem.  I also seem to have quite a bit of white "smoke".  I think I've read that white smoke is from moisture, but I can't confirm that.  When I put my torch to the white smoke, it ignites and goes clear, so I dont know if that is good or bad.

I've also built a make shift water column manometer and I'm measuring somewhere between 3/4 - 1 in H20.  This may be too low so I'm scrounging around for a new motor or a different idea on spinning the fan.  I've thought of a pulley system but I fear that the problem is simply the horsepower of the motor not being sufficient to spin the blades at full speed.





Comments (8)

(account deleted) said

at 1:09 pm on Mar 4, 2009

Great Job so far Brian G.!!
You haven't said what fuel type you intend to use. This will make a difference with how you configure your reduction tube/air jets/grate height. The default GEK has a 6" high reduction cone with the"ash" grate set 1.5" below. This results in an inverted cone shaped column of char/charcoal 7.5" high to create the thermal/chemical reduction area ( all of the produced gases must pas through this area). You could probably used a piece of 3-3 1/2" SS exhaust pipe of a late model diesel PU to make this. You Will need a grate to hold the charcoal up and out of the ash that will settle to the bottom. It Will have to be rotatable or shake able to sift the ash through the charcoal.
Keep it up. Looking real good. Steve Unruh

bgautrea said

at 2:56 pm on Mar 4, 2009

Thanks Steve.

I intend on using pine wood for fuel. Pine is quite abundant in the national forest and with a $30 permit from the forest service I can cut 3 cords of timber. I haven't figured out yet how fine it needs to be cut though. I can chop down to 1" blocks fairly easily, but having seen that many people are using wood pellets it had me thinking of trying to shred it in some fashion. Again... I haven't thought that far into the future yet.

I have a 3" x 8" reduction area, though it has no taper. It can be seen in the background of my picture with the fan above. As for the grate, thus far I have not built one however I'm going to get to working on it soon. Since the reduction area is a 3" diameter, I have it sitting ~4" below the center line of the nozzles. Also, my nozzles are on a diameter of ~6" and I plan on getting the grate to sit ~4" below the bottom of the reduction area. All those diameters are loosely based upon Table 5-2 "Imbert Nozzle and Hearth Dimensions" in the Handbook of Biomass Downdraft Gasifier Engine Systems.

Thanks again!

jim mason said

at 4:29 pm on Mar 4, 2009

brian wins the prize for most produced with the least resources. so i'm going to send him the new stainless sheet reduction bell and tar fence. it only seems fair . . .

his currently straight pipe one will be really senstive to flow rate. even with the cast 3" top 4" bottom bells, they are somewhat easy to overpull. you can tell when you are overpulling with the long TC probe that comes with the kit. poke it in under the reuduction bell. if you see the temp go over 700C, you are starting to pull your redution down onto the grate, as it is not fiinishing in the bell. if you really overpull, the temp will cliimb further. you can also see this by your paint burning off the gas cowling at the grate level.

jim mason said

at 4:31 pm on Mar 4, 2009


remember, the notion with the bell taper is that the taper outwards compensates for the reduced cross-sectional area as the fuel size is reducing. the goal seems to be to keep the velocity about constant, while the porous structure of the pathway is reducing in area. thus your flow potential / pressure drop through the bed remains about the same across all parts of it.

my current best guess on the taper that achieves this is a 1:2 taper, over a length twice that of the top constriction diameter. i think historic bells are too open, and thus result in flow favoring the walls, losing more heat than necessary. the fluidyne straight tube i believe is too far in the other direction, and thus has little potential for flow rate variation.

we've built a bunch of different proportioned bells to test this. but have yet to get to the testing.


jim mason said

at 2:10 am on Mar 12, 2009

brian, if you are pulling 3/4-1" of h2o vac, you have plenty of vac for a first one. or to clarify, if that is the vac after the reactor, adn before the filter, then you are ok. actually, i think it might be a bit high, given the straight reduction tube you are using. those are easy to overpull. they have a narrow band of proper flow it seems. you might have anemic gas as you are overpulling and reduction is not finishing. or it could be a ton of other things. you are starting with a charcoal prefill, right?

and yes, the white is steam. you always get this on start up as the moisture is being boiled out of the charcoal. then you will continue to get it if you fuel is too moist. anythign other than very dry fuel will greatly complicate your early runs. new pellets straight out of a new bag will work, but you will likely get quite a bit of tar. such is the usual experience. but you will get gas.

to make things easier, you can also start it by putting a cup or so of diesel fuel on the charcoal prefill stack. light this, let it get glowing, then fill biomass on top. the diesel will continue to vaporize off for a bit, which will help your flame strength in the beginning, and better transition into your regular gas. you can see this very clearly by the color of the flame.


jim mason said

at 2:19 am on Mar 12, 2009

to clarify, the diesel vaporizing off is into your gas stream, not out the top of the reactor. this is the cheating method of starting. you put enough liquid fuel on the fuel stack that as it heats up it just vaporizes and goes out your gas out. a very crude vapor carburetor. yes, a bit embarassing. but it works nearly everytime.

just don't use gasoline. the whoosh on starting is more than you want. alcohols can be similar. diesel or kerosene are nice. store bought charcoal lighter would work too. that really what its doing too. it vaporizes with heat and then burns, creating more heat until proper pyrolysis begins, and then those gases burn. so using it to light a gasifier is nearly a label correct application!

while doing this, point out to the newbies gathered around your fire, how vaporizing is different pyrolysis, though the products of both are burable gasses. this is the core of understanding the difference between the combustion of liquids and the combustion of solid biomass. two very different routes. but both lead to gas.

Mark Peiffer said

at 6:14 pm on Jul 27, 2009

Hi I live in denver, I have lots of metal working friends and spare motors and such - how are you doing, could I help? I would love to see one of these things working.

lazerwolf said

at 7:14 pm on Jul 27, 2009

Hi, I live in Fraser (next door to Winter Park) and I bought a GEK 3 from AllPowerLabs. I have been working on assembling it, and then am going to use it to power my 1974 VW Thing. I can hardly wait to see this one of these things working too. Making enough right size charcoal granules for the filter bed is the last major thing on my list, plus a details list. With any luck, I might fire it this week!

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