DIY BB aka Gasified Wood Stove

First, my stove is based as near to possible to the authors original design with a fosters can and bean can.

It's not a huge deal but the internal can fractured and fell off.

Ironically it fractured above the air holes I drilled in the bottom sides. Meaning they were not the week point.

Not sure if this will be a repeated problem but I'm going to continue to experiment with the design.

My big problem with this design is still the airflow problem. Since I'm not using it for cooking I'd like it to burn for prolonged periods of time with as little maintenance as possible.

When it's fairly newly lit and hasn't yet clogged with ash I can put quite large sticks in about the diameter of a quarter and it'll burn them surprisingly well. In fact better then small sticks. It only requires 3-4 of these larger sticks to produce a good flame for prolonged periods.

I suspect they burn well because of the focused heat of the stove design and large amounts of airflow around them which is impeded when you fill the can with smaller sticks.

What's more though I can't break these sticks down very small I can leave them hang out as much as six inches and they slowly settle as they burn.

The problem is it does start to clog eventually, airflow is restricted and the fire starts to smolder instead of burning hot and clean.

BTW, it's important to note that when you leave larger sticks poking out the top they are at least impeding the gasification process a little as they block the holes around the top. Thus they increase the smoke a little.

This is an acceptable trade off for me since I'm not using it as a cooking stove. Being able to use quite large sticks increases the burn time and lowers the maintenance a lot.

O ther things of note.

1) the bottom of the stove doesn't get to hot allowing the stove to be used on a picnic table with very minimal marking.

2) the stove is a little top heavy and tips over a little easy, though not disastrously. A few big rocks around it can help steady it. Obviously this is because I'm using larger sticks.

3) The stove doesn't radiate much heat out away from the can, just up. Meaning it's not great as a warming fire. Unfortunately the vertical structure is the key to getting air to flow up through the can.

4) The heat around the top of the can is pretty intense and focused… which is probably what makes it great for cooking. I find that placing a large stick or two across the top of the can that are to long to fit in it or break by hand works well. It actually seems to intensify the ossification process and quickly burns the stick through enough it can be easily snapped. This process of breaking down and burning larger sticks seems to be a great process for burning the stove long and hot… which is probably why the internal can cracked. It's possible to quickly produce an abundance of six inch sticks of 1" to 1.5" in diameter that can burn for hours and hours.

So, I think what I'm going to try next in no particular order.

1) experiment with a computer fan to increase airflow on this or another design.. Brush Buddy inspired

2) make the entire bottom half or 1/3 of the internal can absolutely full of holes to increase airflow

3) possibly leave a big gaping hole in the bottom of the internal can so that more ash falls through (if a tiny bit of still burning wood).

4) make the outer can out of a Heineken can so it's stronger.

P.S. It has occurred to me that I don't necessarily need a woodgas stove if I'm not using it for cooking. Am thinking I might try the Nimble Will Portable flat pack stove design for potentially better radiant heat… but not until I'm finished experimenting with this design.

I made several versions of this, but was never satisfied because all needed too much attention to keep burning. I finally settled on this copy cat version of a TD Caldera Ti-Tri Inferno, made from titanium foil and weighing in at 2.15oz…

…more details at this link;

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=25085&skip_to_post=205299#205299

Have had a chance to experiment quite a bit with this design.

When I started I was just planning on using this as a winter heat source, however my last two experiments have produced some rather amazing results.

My current version now uses a tiny 12-volt computer fan at 6-volts and produces both tremendous heat and a good movement of air.

Basically the thing is like a heat gun.

Bloody amazing.

Because of the fan it now burns extremely hot, clean and consistently particularly when material becomes charcolized. The fan keeps the charcol materials red hot producing tremendous heat with no visible flames and absolutely no smoke.

Seriously… it becomes *absolutely sootless*

As long as you use dry wood of course.

It's hard to believe so I will continue to test it.

I haven't done boil tests yet but I expect they'll be very fast. Maybe rivaling iso-butane stoves like the Jet Boil.

The only negative is this sootless mode does require some time to burn down some good materials into charcol/ embers.

I find the bigger the materials… ie. 1" or 1.5" sticks the better they charcolize and the longer they'll burn as charcol.

What I found most interesting though is i could stuff (and I do mean stuff) a bunch of leaves into the stove and after smoking a whole lot, then flaring up a whole lot the leaves would become charred and produce a tremendous amount of heat for as much as 10-15 minutes with little to no smoke.

They reminded me of a mantle on the old Coleman propane lamps.

That is as long as you didn't throw anything in on top of these charcolized leaves they'd continue to burn for extended periods of time.

However if you did throw something in on top of them they would collapse into a fine powder and go out.

That said this may in fact be the quickest way to get to a clean near sootless cooking fire.

It's unbelieveable how long and hot these leaves would burn but I think I'd still prefer to cook over some much bigger chunks of charcolized wood.

Other things of note.

1) I put in a double row of hole punch holes as close together as possible around the top of the inner burn chamber.

This not only produces tremendous effective gasification (a wall of flame instead of just jets) but also in combination with the fan seems to move a lot more air in general making it a nice warming fire instead of just a nice cooking fire.

2) I put a lot more holes in the bottom of the internal can/ burn chamber. In fact I completely removed the center 1.5" of the can bottom. I then drilled holse all around this, and used a can opener to open up large triangular holes all around the bottom walls of the internal.

In my non-fan tests I actually had three rows of holes around the bottom of the internal can beause it would fill up with ash and clog. However with the fan small particulate seems to burn more quickly and thouroughly so te stove is less likely to clog with ash.

3) I switced to a heinken can.

The Heineken can holds up much better to packing and the additional heat caused by te addition of the fan.

4) How I mounted the fan.

I basically cut a 2"x2" square hole in the side of the outer can wall and then used a bit of aluminum flashing coiled into a cylinder to both hold my fan and channel the air into the wood gas stove.

5) Inner can still cracks

BTW, still having problems with the inner can flaking / cracking and eventually breaking. I may have to come up with a different alternative burn chamber.

6) Batteries

The tiny little CPU fan is 12-volts, but I am only using it with 6-volts. Specifically I'm just running it off my battery pack for my headlamp.

Have not done efficiency tests yet but I suspect te drain on my headlamp battery is negligible.

All in all my experiments have been a huge success. Though I'm still looking for ways to make a stove that packs smaller (i.e. flat pack) I've come to realize that this stove might well be able to function as both a cooking stove and heat source simply by how I use or don't use the fan.

What's next:

I intend to go through a few more iterations before posting pictures and documentation. Mostly I want to refine my craftsmanship (protypes are rudimentary), but I also want to try a 9-volt battery and see if I can't come up wit any oter improvements.

Pictures and videos to come.

I made my fire box out of paper thin titanium (0.005") from TI Goat. It's had countless fires in it. No sign of cracking or flaking. It's amazing stuff.

I'm using a 5 volt, 1.5 W fan rated at 10 CFM. I think it's way more than is necessary. I plan to try one with half that power next summer. Even so, it uses very little power. Conservatively, I can run it for 2 hours on my 2 AA NIMH cells and voltage booster.

I only use the fan until I get a boil. Then I turn it off. The natural draft is more than enough to keep a simmer going and it simmers longer without the forced draft.

I get a boil almost twice as fast as without the fan. It's not quite as fast as a canister stove, but it's close.

Looking forward to the pics and videos.

"I only use the fan until I get a boil. Then I turn it off. The natural draft is more than enough to keep a simmer going and it simmers longer without the forced draft."

What kind of boil times do you get?

I'm honestly hoping I'll be able to boil about 16oz of fluid (half a Heineken can pot) in just a few minutes.

As mentioned I was definitely not expecting this stove to be practical (clean enough or hot enough) to be useable as anything more then a winter heat source. That said using forced air has blown away my expectations of how clean these things can burn and your above discription is exactly how I'm now hoping to use my stove.

I'm an alcool fan and a tiny bit of alcohol seems to get it off to a good, clean, fast and hot start with the fan which may allow me to cook on it immediately with no priming. (Just beginning to play with it.)

Voltage and flow:

I've run the 12-volt CPU fan on 6-volt and 9-volt. I don't think it takes much air volume at all. The 9-volt may be to much. Indeed with the 9-volt it started throwing sparks everywhere.

No idea whatsoever how much it flows in CFM.

I may one day actually put a dial on it to adust the flow and heat, but right now it's to early to speculate where this will go.

I am hoping btw, I can get MUCH more then two hours burn time.

I would have expected your fan to be more efficient, but I must say… my CPU fan, which I didn't think was very efficient still sounds much more efficient then your fan.

Perhaps yours is much bigger and produces much more flow then I'm picturing.

Am just about to post pictures.

Going on an overnight touring trip tomorrow and may take it as my only stove. The only thing left I have to do is create a pot holder on the top and do some testing with my Heineken can pot.

I love the my Heineken can pot as I have wrapped the whole middle section in fiberglass wicking/ insulation and can easily firmly grasp it with one hand even when boiling hot.

It's not yet good for drinking out of because I haven't figured out how to put an insulative lip or outward rolled edge on it. But it is nice to eat out of.

The only problem i've had with it is it doesn't boil or heat as fast as a wide bottom pot… meaning more fuel spent. The woodgas stove changes this equation though as I no longer need to worry about every ouce of fuel.

Packing:

I'm starting to realize if I can find the right size pot (hopefully a snowpeak titanium) I may be able to practically store the whole stove perfectly inside it so it packs compactly and well protected.

(Yes, this is to imply it's a little delecate in the pack.)

Taking into account the fact that I would no longer need to carry any fuel this makes it about half the size… maybe less then any other cook kit I've had. Even smaller then my ISO butane cook kit.

Not to mention lighter.

It's just unfortuneate that I can't store a Heineken can stove in a Heineken can pot. :( I thought about spliting one side of the stove so it can ingest the pot, but I just don't think I can make it latch together strong enough after that.

This idea that a wood stove setup could actually pack up smaller then an ISO butane setup is going to take some getting my head around.

Right now though I don't have the right pot to store my Heineken can stove in so I'll be carrying two separate little packages.

UPDATE: crap, never posted this. Sorry, running out the door.

protype: http://www.flickr.com/photos/mmeiser2/4078664881/

Video: http://www.flickr.com/photos/mmeiser2/4079433096/

finished product:

sorry for the lack of proofreading

I was able to boil a liter of 20 C water in a broad pan in 5.9 minutes. I think any inefficiency in my fan is due to the fact that I’m moving much more air than is necessary with my 1.5Watt fan. It creates so much surplus heat that the plastic insulation I put on the lid of my pot melted inwards about an inch.

From what I’ve read, about half a Watt would be sufficient. That would give me six hours of run time on the battery.

I don’t care about soot on the pot. I pack my pot in a plastic grocery bag. The pot gets very sooty because I turn off the fan once I have a boil.

Click here to view the thread on my fan setup. That’s a two liter pot. I cook for two.

I concur on the fan power.

I don't know how many watts it is but I'm using a 12 volt microprocessor fan. It's as small as they come. Furthermore I'm running it at either 6 or 9volts. At nine volts it's to much for te fosters can. 6-volts is more then plenty.

What I notice is these tiny round little wood gas stoves are extremely efficient with air.

In my tests I've made muc larger wood gas versions and made them square as well.

They were nowhere near as responsive to the little fan.

Furthermore i have no complaints about the heat of these small 32oz beer can wood gas stoves or their burn times.

I have therefore gone back to a much smaller sizes and embraced the round size.

Something else I've noticed. Though the outer walls can be made of anything canned good cans make absolutely superb burn chambers. I think it's because of their corugated side. It seems to really really generate a lot of heat both in the burn chamber and superheat the air.

What's more I like using them as a burn chamber becuase you can throw them out and make a superb new burn chamber with a can opener and the appropriate size canned good in a matter of minutes.

I may… may… use one in my final design, or at least design the stove around a standard can size so you can optionally use a bean can.

BTW, have read your thread multiple times… great design.