Woodrunner Volvo's

Some building pic’s from yesterday evening work, i fell asleep with the phone on my chest, so i post them today :smiley:

Cutting some flanges, homemade magnetic circular cutting jig.

Next step cutting the center out.

Cut out holes through all three flanges, and welded pieces of stainless steel threaded rod in the upper flange.
My intention was to build a fully welded gasifier but not much more work to go this way, anyways this gives me a chance to disassemble it in the future.


Not much work done today, atleast i cut some parts, and got the inner piece of the condensing hopper welded to the flange.

Upside-down at the moment.

Snow melting is really bad around here now, if you look closely there are 2 inches of water on my shop floor. Atleast there are less risk to set something on fire when welding, but my right rubber boot started leaking, and i dropped my angle grinder, when picking it up i got a nasty shock, well grounded as i was, standing in water
Well, i felt it was enough for today, so now it’s time for the couch and a book. :smiley:


Water and electricity and a good ground can make for a deadly shocking experience. You know God just saved your life again. God is good. I got hit with 220 volts when I was younger, found myself getting up off the ground ten feet from where I was standing. I know God saved my life.


Yes, someone once told me, God gave me two guardian angels, He use to do that to careless people.


I have more than two for sure.


Got some welding time today.

Cut some holes for “steam circulation” in the inner fuel bin.

Welded a rim inside the outer shell of the fuel bin, for the top lid part to rest on.
Here the top lid part are inserted upside-down, for measuring.

Here’s top lid part test-fit, going to seal this with sealing compound against the rim, and bolt it in place with 3 or 4 small bolts along the circumference.

Outer and inner shell put together for welding.


“openings for steam circulation”,… I am still undecided about this, namely, if the moist gases had the possibility to circulate along the cold outer surface, they make a rather large effect of cooling the inside of the process, but if they do not have this possibility (or a very small one), but they make a layer of insulation against the cooling surface, where the steam turns into water and thus shrinks approx. 1500:1, this creates a large space for new gases,… I’m just thinking out loud :stuck_out_tongue_winking_eye:


1 liter of water expands when it boils and creates steam to 1:1250, well, this ratio changes upwards if the steam is heated to a temperature higher than 100°C, which happens in the gasifier, and the lower pressure increases the ratio even more… .

Goran, I’m still with you, let me tell you that my boss is on vacation this week and I can think more easily. :thinking::grin:


I know this has pretty much nothing to do with your build Göran so sorry if I am clogging your thread but it kind of fits with Tone’s thoughts earlier.
Just thinking out loud now, this could be an idea or just plain silly. But if one had WK tubes on the hopper and led the intake air as a shroud around one or two tubes in series and the condensing of the steam in the tubes should act as a ‘draw’ on the system thus releasing the heat (to the incoming air) that was required to boil the water in the first place and also pulling more steam through to condense because of the void created.
I realize that it is not enough to cool the hopper completely but my thought is that it would help with very slow driving or idling gas quality while the other tubes make sure to take care of the rest while driving.
I guess I am wondering about everybody’s thoughts on this, is this nonsens? Perhaps it is mentioned/covered on a thread I haven’t come across yet.


It should be more like a shower door, and it will condense in the outer surface and there will be a small region where it is cooler and the rest of it will remain hot. I wouldn’t think there will be significant cooling on the inside of the reactor at all. If anything, it should warm the hopper up.

If anything, i would be inclined to add fins to help cool it.


Sorry for a late response, here’s some thougts on double wall condensing hoppers.

This is about how i imagine the steam/moisture mowing in the hopper, i also base this on my experiences with the old volvo gasifier, and some research from SMP, and “Svenska Gengas” and like.

This is how i built it on the old Volvo gasifier, no holes for “circulation” in the lower part, condensed a lot of water, most after shut-down, possible to run it on “green” wood, don’t ran very well though, but could be done.

This is how i believe it would work with holes in the lower part, when low load, or just after start, like a “heavy”, saturated, “pillow” of moisture in the upper part, stops the flow up, over the edge, between the shells. Instead moisture pushes out the lower holes, to be condensed.

And here it is in full power, moisture travels up by heat, condenses between the walls, some moisture goes out the lower holes to be condensed, due to air draft around the outer wall, the condensing decreases the volume between the walls, which supports the “circulation”, mowing of the “steam”.

All this could be just wrong, but my earlier attempts, and some research reports seems to support my “fantasies” :woozy_face:


Oops, almost forgot Johan, i think your theories are correct, the condensing of the steam should act as a kind of “vacuum” to draw more steam from the bin (this is somewhat how a condenser on a steam engine works), but, i believe it’s better to just use the wind draft to cool the tubes, using the intake air would probably be too cumbersome, and more of use on a stationary gasifier, even then i think a fan as Tone uses would be more helpful.
Another thing if using the intake air (primary air) would be it’s necessary to shut it off the condensing heat exchangers when shutting down, otherwise the “after-smoke” would soon tar up the tubes, lowering the heat transfer remarkably. As they absolutely become “tarred” on the inside already, hard to avoid.


Goran, nice drawings and good explanation, well, my idea is a bit different. I think that a column of the hottest gases forms in the middle of the gasifier, which are therefore also the lightest and force upwards, the temperatures are already lower along the walls of the inner container and thus the conditions for the descent of cooler, heavier gases, it is especially cold near the wall of the outer container, where water vapor and also tar gases condense, well, some gases do not condense (e.g. CO), which would cool well against the outer wall and fill the space between the containers, so it would be good if there were smaller openings in the wall of the inner container, which would served to move these gases inside, I can say for sure, the flow of colder, heavier gases will be downwards and lighter, hot gases will flow upwards, such is physics.


Yes, it would be some work to make it and as I wrote, I was not really sure it would even be a good idea. Just a thought :smiley:

This is an answer that came from experience, why not to do stuff. Good point, thanks
KISS - Komplicera Inte Simpla Saker


Some update pic’s.

The double walled fuel bin is welded together, a little grinding and it will look acceptable.

From top, the inner cylinder is’nt that thick it looks like, it is cut through a weld.

Some welding on the hearth.


Hello Tone,
Not to interfere but take your last drawn illustration and add an upper and lower condensate catching gutter . . .
Stand out and separate the outer downward cooling flows from the inner jacket wall . . .
You will have just re-created the W.K. external tubes condensing hopper system.

And it for sure does wring out the wettest types possible input woods.
It definatly does down thru it’s lower fingers slits cone setup an inwards upwards; accross the top; then down the outsides cooling; back lower inwards, doughnut circulation flow.
Recycling the gaseous volatiles until they are drawn down thru the Oxidization/Reduction. Eventually collecting non-vaporizable heavy asphalt-like tars in the gutters.

You’ve seen the pictures on the WK Premium side.
This phenomena is indisputable.

I have come to believe one of the real hold backs for getting wood-for-power results is those who try for too many "benefits’ out of a single system.
You want to make charcoal, then make a dedicated charcoal maker.
You want to make wood vinegar and light wood tars make a system specifically biased just for that.
My multipurpose Leatherman tool on my belt is just for convenience. Not the best tool for any specific purposes. It’s value is always being on-hand, good-enough, usually.
Steve unruh


Sorry for all boring pic’s…

Hearth is fully welded, some work with nozzles and restriction left.

Gas outlets, i want them as high as possible, to leave some heat to the charring zone. I also want 2 of them, to avoid uneven draw of the gas.
Welded some pieces to fit a 2 1/2" pipe.

Had this exhaust parts laying around.

No work of art, but gas-tight. :woozy_face:

Gas piping going to a hot-filter, which i probably place in the trunk.

Cut out these lid’s to save some weight, heavy cast-iron, even if i weld fast and clumsy, i dont think the welded in sheets are going to be as heavy… :crazy_face:


Goran, while I don’t find these boring, sometimes the boring pictures can be the most educational.


It is more artistic then you realize. The exhaust reminds me a lot of a double flagellated protozoa. :slight_smile:


Double flagellated protozoa? I don’t like the sounds of that. Sounds like porn for biologists. That don’t make it art.