Though not technically a woodgas stove, this does do some woodgas
conversion as it burns. In reality it charcoals first, burning the
vapors produced in a secondary burn below the grate. Though there
is bound to be some producer gas after it heats up and charcoals, my
primary aim is just an efficient, controllable stove which will burn
small wood scraps.
It is efficient, and can do a nine-hour burn putting out good heat
the entire time. It also does a great job burning the small scraps,
ranging from 12" 2x4s down to 2x2x1.
What I do not have is control. Enough air to get it started is
enough to turn the entire stove orange as the outgassing starts.
Even less is required once the wood is charred through and we are
burning charcoal. Part of the problem has been caused by using a
flat piece of stainless for the cover. If fire gets into the fuel
magazine it tends to warp the stainless, giving way too much oxygen
in the wrong place. The whole stove has turned orange a couple of
times, which seems to distress my wife almost as much as the charred
spot on the floor.
Primary air is two 3/8" standpipes teed about 4" above the burn
grate. They come up from a 2" piece of exhaust tubing with 28 1/4"
holes drilled into it for the secondary air supply. Regulation is
via a snug-fitting aluminum can with 2 Vs from the open end. Moving
can out exposes more of the Vs to let in more air.
Observation so far says I should increase the primary vent sizes.
Also, there is a good possibility that the door gap lets in enough
air to fulfill secondary needs so I could plug more of the holes in
the exhaust tubing. I tried to make it fairly tight, but even a
1/8" gap all the way around would be 5 square inches of vent.
My biggest problem has been the top warping. My brother is bringing
me some disks off of farm implements which are dome-shaped and will
not have the warp problem flat metal presents. The disks will be
given a lip, an inner collar, and a stove gasket, which should
pretty much eliminate the leaks.
This is a batch stove, although the lid may be lifted to add fuel
either while there is still plenty in there or after the charcoal is
almost gone.
Sorry for the long post, wanted to include as much information as I
could. If you have suggestions I'd be glad to hear them.
This same question will be posted to the Yahoo Woodgas group for the purpose of eliciting suggestions.
Rex