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Friday, September 11, 2009

Wood-gas Stove for the BPL Trapper Mug, Prototype 1 (mini-me1)

So I've been eyeballing wood-gas stoves for awhile and even came across some great plans on BPL MYOG forums for a 5.5oz wood-gas stove. The problems for me was it was on the heavy side, materials weren't going to be cheap, and it suggested I buy some special tool from Harbor Freight. Granted the special tool would of made my job of tinkering easier and cleaner, but I didn't have the money or time to buy the extra expenditures. The other problem is that it wouldn't nest in my Trapper mug or a Tibetan Tiatanium 700ml mug, which is what I'm contemplating getting for longer trips. Therefore it would take up even more space in my preferred little pack. The thought of going on a long trip and not having to carry any fuel really intrigued me. I could start gathering sticks along the trail on the way into camp or wherever I was going to be cooking.

The project started with scouting out the cupboard for any combination of cans that might actually nest into the mug and would be able to be fit into each other to create the stove. I didn't really have a weight that I was shooting for with this project, but I wanted it to be light and functional. Since I haven't really played with wood-gas stoves I also didn't want to be out a lot of money if I didn't really like the idea.

I found a Hunt's Tomato Paste can and an Alberstson's Peaches can. They seemed to be about the right dimensions to work and the large can would nest into the Trapper mug. Did I know if the tomato paste container was really large enough for a burn box... nope... but that is what tinkering is all about, finding out what works and what doesn't. You have to try it to find out for sure.

The final weight is 2.5 oz. without the pot support. I haven't made one that is staying yet, so it could affect the actual final weight.

Cost:
A couple dollars worth of cans and some of your time if you already have tools lying around the house.

Materials Required:
2 nestable cans
A plan
A cutting tool (dremel or something that you can use)
Possibly some JB weld
A drill or some form of metal punch
A side cutting safety can opener

The Hunt's Tomato Paste can on top of the Albertson's Sliced Peach can. Here I traced out the small can onto the lid of the large can to mark the hole for cutting.
Here I cut off a lid off of each can. The lid that was removed from the large can do not discard! It was the one that the smaller can was traced onto and it will be reused.
I set the lid that was removed from the large can back onto the can and used a cutting wheel on a dremel to cut just inside of the line that was previously drawn onto the lid.
The center was then removed from the lid. Since we cut to the inside of the line we allowed room to trim the lid to form fit to the small can. You can discard the center piece that was cut out.
I than trimmed the left over portion of the lid ring from the small can's open side.
Using a small grinding adapter on a dremel I slowly smoothed out the cut from the large can's lid until it was just at the inside of the line I drew. Don't remove too much material, because you want a tight fit with the little can.
When you get the cut smoothed out to the line, start test fitting sliding the small can into the hole. At the first sign that it will fit very snugly slide the 2 pieces together. Remove the parts and drill the holes as stated below for the small can, than you can cut off the other lid remaining on the small can. At this point if you made the hole tight enough you don't really need to epoxy the 2 parts together. If you didn't take your time to make the hole tight you can use some JB weld or any other chemical that you feel safe with to bond the 2 parts together. I used JB weld even though mine was a very tight fit, but I got hasty and lit it way before the JB Weld was dry and it cracked, dried up and did not bond. I won't be re-bonding it because I made it such a tight fit.
I left out the cutting of the holes because that is what I will be playing with until I get this guy to burn well. Basically I found the largest size drill bit that I had, measured out 1" intervals along the top side of the small can just low enough to be just below the top of the small can. I used a punch to mark the holes and to keep the drill from wobbling. I started with a small bit and slowly stepped up the size until I finally reached the largest size. I did the same with the large can but moved the holes up from the bottom of the can so that 3/4 of each hole was above the base of the inner can. After the holes are drilled remove and discard the other lid on the small can. Than remove the bottom lid of the large can and keep it. The large can's lid will be used as a base to protect the ground from the fire and will make the stove self contained during the burn. Which will help reduce the chance of catching anything else on fire along the way.

First ignition.
A makeshift pot support, which will not be used in further testing. I need to get a wire mesh pot support that allows the air to flow a little. The closed off design helped stifle the flame at times.
The stove nested into the BPL Trapper mug.
All the parts disassembled after the hour burn. I didn't take a close up of the wire mesh that was put on the base of the small can to hold the wood inside the burn box. The reason for that is that it was a very makeshift assortment of metal fencing rods and it will not be in the final design. I'll be using the same wire mesh that the pot support will be made out of for the bottom of the small can.

Far left is the inner burning box, in the middle is the large outer can, on the right is the trapper mug and the base of the wood burning stove.
As stated previously this is prototype #1, I still need to play with the holes on the outer can to try and get a more efficient burn. I will be changing the makeshift pot support and the wire at the bottom of the burn can. I also noticed that the type of wood also made a large difference on how it burns. The small twigs don't seem to matter when burning through the bark, but the slightly larger sticks need to be stripped of bark. Another idea that I will be investigating is finding an aquarium tube and using it to help blow air into the fire when it starts to smolder or die down so that I'm not huffing in the smoke fumes. After a couple more burns and some more dialing in I'll post another thread on the revisions and further thoughts on the mini-me wood burning stove.

Warning! Playing with fire and tools can be dangerous! This post is for informational purposes only. Using any of these methods, or using a fire, a stove or tools can cause health hazards, injury or death!!! Use this information at your own risk.

1 comment:

  1. cool stuff, may try this out once you get the design finalized (i'll let you do all the R&D)...

    http://www.poormansheli.com

    ReplyDelete