How To Make A Simple Wood Gas Stove (Large Version)

Wood Gas Stove -

Coaxial Downdraft Gasification 

This stove is based on the downdraft principle and typically built with nested cylinders which provides high efficiency in the burning process. Combustion from the top creates a gasification zone with the gas escaping downwards through ports located at the base of the burner chamber. The gas mixes with additional incoming air to provide a secondary burn. Most of the CO produced by gasification is oxidized to CO₂ in the secondary combustion cycle, therefore gasification stoves carry lower health risks than conventional cooking fires.


Getting Started

Materials:

•  (1) 4 Liter/ 1Gallon Paint Can - Plain, Unfilled Type ($3-$5)
•  (1) 1 Liter Apple Juice Can ($1)
•  (1) Adjustable Metal Hose Clamp ($1.50)
•  (1) Printed Template Of Drill Holes (Optional) (Basically Free)

Tools:

• Power Drill 
• Step Drill Bit (1/16" to 3/4")
• Sharpie Pen
• Measuring Tape 
• Can Opener (The One That Cuts On The Inside, Not Around The Outside)
• Screw Driver or Driver Bit

Step 1 - Marking out the circles and cut lines on paint can lid

Take the lid of the paint can and use the apple can to trace out the centered position with your sharpie pen, like illustrated below. Now create a second circle inside the main circle you created with the apple juice can. Make this second circle smaller by 1/2" or 1-1/2cm.

Now draw lines connecting the circles together. Cut out the inner circle and then proceed to cut the lines up to the main circle. This with create tabs that will create a compression fit when we insert the apple can.

 Step 2 - Marking the drill holes in paint can & apple juice can, then drilling them out.

 You will only need to drill 14-3/4" holes just above the lip of the bottom of the paint can. You will need to use a step drill bit to cleanly achieve this. I recommend that you mark (14) 1-1/2" on center dots with your sharpie. This should give you approx 1/2" to 3/4" spacing between holes.

 Your holes should look something like this, these are 3/4" holes. I didn't measure exactly, so my spacing was off a little bit and this doesn't affect performance. 

You will need to take your can opener and open one end of the apple juice can, I would only use the can opener type that cuts open the top and not the side of the can, if you cut the side of the can you start to loose strength and can bend out of shape easily.

At the top of the apple juice can you will mark out  35-40 dots (1/16th drill bit holes) and mark them 1 inch down from the top to allow for the hose clamp and tabs from the paint can lid.

Now mark 8 dots (3/4 inch drill bit holes) spaced out approx 2 inches apart around the bottom side of the apple juice can.

You will need to make 60-80 dots (1/16th inch drill bit holes) on the bottom of the apple juice can. I wasn't able to make them perfect here but as long as you make a lot of them.








Step 3 - Putting It All Together

You will need to push the bottom end of the apple can through the top end of the paint can to make the tabs of the paint lid to catch and create the compression fit. You can do 1 of 2 things here, I seen people use cold weld compound to secure the lid to the apple juice can or like I did, I used a metal adjustable hose clamp. This way I don't have to worry about the compound break down over time or burning away after multiple uses at the camp site. Since the hose clamp is circular it holds the lid to the apple juice can very tightly and you can also swap out the apple juice can if it starts to get to rusty or fall apart after hundreds of burns.

After that you are pretty much ready to start your first fire in your new Wood Gas Stove!

You will need to hammer or pound in the lid to the paint can to securely fit into place.

 When you start to place your wood you want to layer them by thickness. Place thick sticks approx. 1 inch thick and 2 inches long on the bottom. Then the next layer of sticks should be only 1/4 inch thick and the rest small twigs. To achieve the best results do not fill above the holes at the top of the can. These are the jets for the wood gas to feed the fire.

You will need to just start your fire from the top and not from the bottom as the heat from the fire on top will help release the gas from the wood and help draw it through the top holes to efficiently burn the wood inside.  

As illustrated here you can start to see the wood gas coming through the top holes of the apple juice can.

Once you get the fire fully burning you will see all the jet holes burning nicely and effectively increasing the fire temperature and cleanly burning the smoke, wood gas and wood in your stove.  

   *******Notice Of First Time Burn********

Most paint cans these days come with a grey paint liner in them, so the first couple of burns you will need to burn off this grey liner and by doing so will produce a lot of black smoke. It took me approx three full burns to completely get rid of the liner. You may try to sand blast it off or use some kind of paint remover.

Tapping The Birch Part 2

After checking the trees in my backyard I found one Birch that was flowing extremely well. You don't need much in tools and materials to collect sap from the birch tree, and any tools used in collecting maple syrup can be used as well.

Here is a list of the following items I used;

1. Hand Drill Brace (power drill will work as well)
2. Knife
   
3. Bottle or Container (I used a Pepsi bottle)
   
4. Rope (strap, wire or anything that will secure the bottle to the tree)
5. Branch (hose, tap, metal tube can be use to direct the flow of sap to your container)
6. Rag/Cloth
   

You need to first clear away the bark from the spot where you intend to drill your hole. Either peel or scrape away the bark with your knife. Use your knife to make a cut into the truck of the tree to make sure that sap is flowing.

I then found a branch and whittled down with my knife to fit my hole that I will make with my drill bit and I also notched out a small channel on the top to help direct the flow of sap into my bottle. My branch/twig measured approx. 4-5 inches and I scraped all the bark off so that it was smooth so there would be no resistance.

I drilled my hole with my brace (hand powered drill) at a 10 to 20 degree angle to further effect the direction of the flow of sap. I drilled my hole to a depth of 1-1/2" to 2" and continued to hammer/pound in my branch/twig until it was fully inserted.

I recommend that you bring a rag or cloth to wipe the area around your new branch spout as liquid tends to take the path of least resistance. It also helps to use your finger to wet your spout down the shaft with the sap to promote direction of flow. I found that the sap ran down both the bottom side and in the channel on the top and they both met at the tip to forum a drip.

Next I secured a length of rope around the neck of the bottle and left approx. 8 to 10 feet of slack so that I could wrap it around a couple of time so that it would not fall under it own weight when the bottle started to get half full.




You need to wrap the rope around the tree and with every second wrap I found I needed to wrap the rope over the top and then under the neck of the bottle on every second wrap to hold it in place and prevent the bottle slipping down the tree. Alternatively you could use straps or strips of Velcro to secure it to the tree.



I was in luck that a fallen stump was laying right next to the tree and I found a flat rock to make a stable base for my bottle. The roots of this stump laid right next to the tree and made things a lot easier.

I was able to collect 1750ml of sap in about 6 hours and filled the bottle in about 8 hours. After changing the bottle I was only able to get another 1/4 liter of sap in 12 hours. I proceeded to drill another hole 6-7 inch around the other side of the trunk and had similar results.



I would only suggest tapping the tree twice as you do not want to harm the tree and disrupt the natural flow of sap that the tree needs to grow and sprout leaves for the summer.

Please note that you need to remove the spout and stop the flow of sap by placing a plug made from a branch or twig. Your plug should be a larger than your hole to create a compression fit so that no sap can leak out. I never seen a tree die (bleed to death) from a open hole but if you want to tap the tree year after year a little prevention couldn't hurt. You also need to make it long enough to fill the cavity as well.





So what plans do I have with my collected sap, well I was going to try making Birch syrup but at this time I haven't collected enough, as the ratio is 100:1 for birch and only 40:1 for maple syrup. I plan to drink my 4 liters which is packed full of vitamins.

I will plan for next year harvest and try both maple and birch syrup processing. I hope this will help anybody looking to tap the birch tree in early spring.