How To Make A Wood-Gas Camping Stove

How To Make A Wood-Gas Camping Stove

Are you tired of cooking over a campfire and choking on the thick smoke? Maybe you are frustrated with large heavy stoves, and the accompanying bulky and expensive fuel? Let me introduce you to the Wood-Gas camping stove!

The Wood-Gas stove, also called a wood gasifier stove is relatively easy to build, cheap or even free to make, and both easy and reliable to use. Best of all, the fuel itself is absolutely free, provided for your use inevitably wherever you have chosen to camp. Though wood will be a common choice for fuel, any dense, vegetative based, dry fuel (often called biomass) will operate these units.

The smallest unit on the cover page was capable of perking a half-gallon of coffee using only nine pine-cones for total fuel. Wood-Gas stoves are by nature very efficient and economical in fuel use, emitting very little to no smoke during operation, and leaving a ridiculously small amount of very fine grained powder ash residue. Over all, a light weight, economical, and an overall worthwhile addition to any camping backpack, outdoors cooking set, or emergency preparedness kit. These stoves are good for personal use, make great gifts, and can even make you some extra cash if you so desire. They are so fascinating to see demonstrated that the viewer invariably wants one.

The cost to make a gasifier camping stove

The cost to make a wood-gas stove is negligible. When using cans found around the home, it is absolutely free. Though many may wonder about utilizing used materials, it in no manner creates an inferior product. It is a good and useful means of recycling the materials as well. Consider the stove in the photograph below:

Reliable Camping Stove 

This stove has been through numerous rain storms, camping trips, has made countless meals, and boiled numerous pots of coffee. I am showing pictures of old stoves throughout this book to demonstrate just how reliable they really are. All of the stoves pictured are beat-up, well used, and abused camping veterans of many years of camping service. Every single one of them still works as well as when I first made them. This stove was completely free, as the outer jacket started life as a steel No. 10 coffee can, and the inner combustion chamber was a steel infant formula can.

You may well even decide to buy brand new cans to make a stove. A new gallon paint can for an outer jacket will run about five to eight dollars at a lumber store, or even much cheaper on-line. A quart paint can may cost around four dollars for an inner combustion chamber at the same store. Total cost for a stove that will last for many years of hard use? Eleven dollars brand new, or completely free used.

Concerning a backpacking stove, a quart sized outer jacket is optimum for overall size/weight in a pack. For these I buy a quart paint can for the Outer Jacket and use a thoroughly cleaned recycled green bean can for the inner Combustion Chamber. Say what you will, but the lowly green bean can is optimum for a quart can Outer Jacket, and I have not yet found a new can for sale which serves the purpose better. The factory green bean cans are made of a decent quality mild steel, fit into the quart paint can perfectly, and they really hold up to constant use. Sometimes the free option can also equal the best option.

Tools and Materials Needed

The tools you will need are fairly simple, with the only power tool necessary being a hand drill. You will need:

  • 1 Sharpie permanent marker.
  • 1 Pair of leather gloves. Burrs and the edges of cut sheet metal are extremely sharp.
  • 1 Tape measure, ruler, or seamstress tape. I prefer a seamstress tape as the cloth measuring tape easily measures circumferences of round objects such as cans.
  • 1 Tin snips or small but heavy duty metal shears capable of cutting light gauge sheet metal. I use aviation style compound action tin snips.
  • A 1/8” drill bit to precisely start the holes for the larger step drill bit.
  • 1 Sheet metal step drill for up to 3/4” holes. The cheap ones work just fine, though the expensive bits do work much better. I use the cheap ones myself. *
  • 1 Hand drill. Cordless or corded either one will work, but variable speed is very handy.
  • 1 can for the Outer Jacket
  • 1 can for the inner combustion chamber, approx. 1 to 1-1/2 inch smaller in diameter than the Outer Jacket can.

* Note: Large drill bits could be used in place of the sheet metal step drill, but they will not come close to providing as clean of a hole. If using large bits, start small and then drill successively larger holes to the finished size. Be sure to de-burr the holes afterwards. As far as cost, a cheap three piece step drill set is only ten bucks or so.

The only limitations are that both cans must be steel, and the inner can must be between one and one half inches smaller in diameter than the Outer Jacket. Aluminum cans may melt due to the intense heat of the Combustion Chamber during gasification, so should be avoided. The diameter relationship of the two cans allows for proper spacing between the Combustion Chamber and the Outer Jacket. This spacing determines whether enough air flow is available, and whether said air flow is heated enough for necessary proper convection to occur. Too little of a gap restricts the air flow, while an excessively large gap prevents proper wood-gas/air mixture heating.

Lets make a stove!

Now, let us determine what your needs are, which will determine the relative size of stove you need to make. You may decide you want to make more than one sized stove. This is not a problem as the exact same techniques are used are used to make a small one, as an extremely large one. It is also much faster to fabricate two stoves simultaneously rather than separately. Therefore, if you want one for personal use and a larger one for family use, I would advise building both together.

The first choice which must be made is for the size of the stove. The over-all size of the stove is determined proportionally by the size of the outer jacket. A description of the capabilities of each general size is in order. First, here is a small list of approximate can sizes.

  • 1lb (small) coffee can – 3 X 5 ½
  • 2lb (medium) coffee can – 5 1/8 X 6 1/2
  • 3lb (large) coffee can – 6 3/16 X 7 (same as No. 10 tin)
  • 1 qt paint can – 4 3/16 X 4 3/16
  • ½ gal paint can – 5 7/16 X 5 7/8
  • 1 gal paint can – 6 5/8 X 7 1/2
  • 5 qt paint can – 6 5/8 X 9 1/2

Cooking with small camping cooking cups or mess kits works well using a smaller backpacking size stove. The entire stove is small, compact, and very lightweight weighing in at only a couple of ounces. A good outer jacket for this stove would be about quart size, and I regularly use either quart sized paint or stain cans for the purpose.

A stove capable of easily cooking with larger family sized cookware, is a medium sized unit utilizing an outer jacket of a half-gallon paint can, or a 2lb. Coffee can. The wider based can will be more stable for full size cookware, will still fit in a backpack, but is twice the volume of the quart sized. It is still very lightweight at much less than a pound as well.

For group cooking with large cookware such as stock pots, a large outer can should be used for stability, as a wider base is less prone to tipping. Heat between the medium and large sizes are approximately the same, but burn time increases due to a much larger volume in the Combustion Chamber for the larger stove. For this purpose a 3lb. Coffee can or either a 1 gal or 5 qt paint can should be used for the Outer Jacket. This unit is too large for practical backpacking, but great for ordinary camping.

Now that you have decided which stove size you need, then it is time to start marking out the cans. Marking shall be followed by drilling the holes, cutting, and lastly by the final assembly. Much thought has gone into the manner of conveying the necessary information to the reader. Pure text leaves everything widely open to confusion. Photographs of one being built leave much to the imagination even with explanation, though this tends to be the common approach. Therefore I have chosen to use a combination of photographs, explanation, and illustration type diagrams to show the process as the most effective solution to the problem.

Marking the cans

The first step to make a wood-gas camping stove will be to mark out the outer Jacket. If you decide to change the size or spacing of holes, you need to understand that the cold air inlet holes need to be at least 3/4” in diameter to allow enough cold air flow into the stove for a proper wood-gas/air mixture, so 3/4” x 2 + 1/4” (to retain material strength) is at minimum 1-3/4” spacing. Concerning the Combustion Chamber holes, leave at least 1/8” gap between holes.

The various hole relationships are as follows: The Outer Jacket cold air inlet holes must be greater in surface area than the combined bottom Combustion Chamber wood-gas escape holes. The surface area of the Outer Jacket cold air inlet holes must also be at least equal too, but not less than, the combined surface area of the upper row of wood-gas/air mixture Combustion Chamber inlet holes. The surface area of the ring between the cans must be at least equal to, but not less than the combined surface area of the upper row of wood-gas/air mixture Combustion Chamber inlet holes. These relationships are necessary for proper convection, and for proper wood-gas/air ratio and mixing.

Outer Jacket

Camping Stove Outer Jacket Markout Diagram

The outer Jacket provides two functions. It is the outer jacket which forms an air chamber for the cold air input to mix with the wood-gas before combustion. It is also the structural wall which carries the weight of any cooking implements and/or food which are placed upon the stove if a pot-stand is used. This section will demonstrate how to mark out the jacket for cutting and drilling.

This is the only part of the unit that requires any cutting, as the Combustion Chamber is inserted through the hole cut in the top of the Outer Jacket. Examine the following diagram for an overview of the Outer Jackets side marking. A separate diagram will be provided later for marking out the top.

A. The first set of marks bisect the top into four equal parts. Place a single mark on the rim, then follow it across to the other rim dividing the can top in half. Mark the middle of this line, then rotate the can 90 degrees and repeat. You may not be exact, but you will be extremely close.

Camping Stove Outer Jacket Lines

B. Transfer the lines from step A to the outside of the can at the rim. Hold the can perpendicular to your body, then place the point of the marker on your mark. Slide your hand straight back towards your body, and you will have a nice straight line down the side of your can.

C. The line around the circumference of the can at the base is made in a similar manner. Measure up from the bottom (open end of can) one inch, and place a mark. Place point of your marker on the mark, with the rim of the can resting solidly on your palm. Hold marker steady, and rotate the can until the line is completely around the can.

Camping Stove Outer Jacket Top Markout Diagram

D. For the final set of marks, hold the can with the bottom towards you. The line going around the can is perpendicular to the four marks down the side of the can. Divide each section between the four lines into three equal parts by making a short line across the main line around the circumference of the can, as demonstrated in the following photograph.

In the photo, the lines are all laid out and marked. The vertical lines in the picture, where they intersect the horizontal lines around the can will be the points for drilling each cold air intake hole. Now lets work on the top. Consider the following diagram.

A. Place you combustion chamber can upside down onto the top of the jacket, and use your marker to trace around the rim.

B. This circle does not have to be exact. Freehand draw it inside the first circle by one half inch.

Camping Stove Outer Jacket Marking

C. These black triangles will be cut out to form the tabs. These will be the tabs that hold the combustion chamber firmly in place. Once folded down at slightly less than 90 degrees to the vertical, they will press against the combustion chamber like little one half inch long spring teeth.

The top should look similar to the preceding photograph when the top marking is finished.

This photograph demonstrates what the Outer Jacket should look like after all marking has been completed.

Combustion Chamber

The inner combustion chamber has no cut-outs requiring snips, just holes. First, consider the following diagram.

 

Inner Combustion Chamber Diagram

A. In similar manner as the outer Jacket, the first set of marks bisect the bottom, instead of the top, into four equal parts. Place a single mark on the rim, then follow it across to the other rim, dividing the can top in half. Mark the middle of this line, then rotate the can 90 degrees and repeat. You may not be exact, but you will be extremely close

B. Transfer the lines from step A to the outside of the can at the rim. Hold the can perpendicular to your body, then place the point of the marker on your mark. Slide your hand straight back towards your body, and you will have a nice straight line down the side of your can.

C. The line around the circumference of the can at both the top and the base are made in a similar manner. Measure up from the bottom (open end of can) five eights of an inch, and place a mark. Place point of your marker on the mark, with the rim of the can resting solidly on your palm. Hold marker steady, and rotate the can until the line is completely around the can. Repeat this procedure at the top.

 

Inner Combustion Chamber Dividing

D. On the bottom line going around the circumference of the can, divide each section between the four lines into two equal parts by making a short line across the main line around the circumference of the can, as demonstrated in the diagram.

E. On the top line going around the circumference of the can, divide each section between the four lines into four equal parts by making a short line across the line centered between the two vertical lines, as demonstrated in the diagram. Now, divide the distance between this line on each sid in two again, placing a mark at each point.

 

Inner Combustion Chamber

The preceding photograph demonstrates dividing the can bottom as in step A.

This is what the combustion chamber should look similar too. I have chosen on this model to divide the bottom line into three equal parts between each vertical line instead of two, as I intend to use 3/8” holes instead of 1/2”, therefore need more holes to achieve the proper surface area ratio.

Inner Combustion Chamber Grid

And this is what the grid looks like. This grid does not have to be precise, as its only purpose is for an ash grate after final drilling. You can measure and mark out using a ruler for a straight edge if you prefer.

This is the last of the marking. Now, we are ready to cut and drill the stove in preparation for final assembly.

Cutting and Drilling

The outer body will be the fastest to complete, with only a few holes to drill, and some cutting which will go fast on the very top. The combustion chamber has many holes, and will be the slowest to manufacture.No photographs are really necessary at this point. All of the drilling is already precisely marked out on placement, and is merely a matter of drilling the right sized holes on the numerous Xs formed by lines crossing each other.

Please wear your gloves for all stages of machining and assembly work which remains. Drill bits and tin snips can leave razor sharp burrs and edges capable of cutting clean to the bone without much pressure. It really is a matter of safety. Have a few band-aids ready anyway, as it is better to have them and not need them, then to need them and not have them. As careful and conscientious as I am concerning safety, I still invariably encounter a sharp edge somewhere myself, the difference being that I rarely suffer a deep major injury.

Outer Jacker

I will start with the cutting section as it will teach a simple solution to a sheet metal work brain puzzle. The puzzle is how to start cutting with tin snips in the middle of a piece of sheet metal without cutting in from the edge.

Cutting:

What needs to be done now is to cut out the inner circle, and then cut out the triangles to form the tabs. Do not cut out the outer circle! It is there to mark the inner edge of the tabs as a guide mark only, and is not a cut mark. When cutting out the triangles, stop each cut as soon as it hits this line.

After reading the instructions above, you may well be looking at the top of the Outer Jacket with the two circles and the pattern of triangles while holding a pair of tin snips wondering if the author lost his ever-loving mind. How are you supposed to cut out the circle, without cutting up the whole can?

Easy! Use the step drill in the very center of the can top to drill out the very largest hole on the bit to give yourself a place to start cutting. Now comes a note about the use of tin snips. Using snips to cut out a circle can be fairly easy IF you know what to do. Otherwise you will fight it.

Aviation tin snips usually come in a pack of three, and the handles are different colors. You should have a red, green, or a yellow handled pair. Yellows and reds cut left hand while cutting out a circle, while greens cut right hand. What this means is that the side of the snips in which bottom side of the shears is bolted is on the left for yellows and reds, but on the right for greens. Cut to the line from the center hole, then turn left for yellow or red handled snips, or turn right for green handled snips. The material the snips push up will then be the center circle can material being removed. Otherwise the snips will want to bind, and you will experience a hard time cutting it out.

Drilling:

There are 12 holes which need to be drilled, all marked on the bottom line going around the circumference of the can. If unsure which line is referenced, see Outer Jacket Marking Diagram, and accompanying explanation C.

Start drilling using the 1/8” drill bit. Drill a hole everywhere a vertical line intersects the bottom line, which should leave a single row of holes (cold air inlet see diagram) around the base of the can. Follow this by drilling all holes with the Step Bit, carefully enlarging the holes to 3/4”. Every step on the bit is marked as to size. Make sure to follow safe drilling procedures, as outlined in your drill manual, and in the usage sheet provided with the step bit.

Combustion Chamber

Now, for the time consuming drilling. Drilling is the only sheet metal work that is required for the Combustion Chamber.

Drilling:

  • The grate on the bottom of the can should be 1/4” holes (Grate pattern on last photo of previous chapter).
  • The bottom row of 8 holes around the can should be drilled to 1/2” (Item D. in Combustion Chamber Mark-out Diagram).
  • Last but not least the top row of Combustion Chamber inlet holes should be drilled to 3/8” (Item C. in Combustion Chamber Mark-out Diagram).

Start out your drilling just as with the Outer Jacket, using the 1/8” drill bit to drill all of the spots where one line crosses another, followed by the step bit after all holes are pre-drilled. After these holes are all drilled, the only detail remaining is to bend down the tabs.

On the Outer Jacket top, all of the tabs are pointing towards the middle. Using your fingers, bend them down a little bit until they almost form a 90 degree angle to the can top. The Combustion Chamber needs to slide against these tabs tightly as the unit is assembled.

Assembling the parts

Wood Gas Camping Stove Diagram

Everything at this point is finished according to the metal-working aspect of the project. You are ready now to assemble the two pieces into a functioning stove. Make sure at this point that all the holes are drilled on both cans, and that the top of the Outer Jacket is fully cut out and the tabs turned down. Please refer to the following assembly diagram.

The Combustion Chamber should appear to not quite fit the hole. This is exactly what you want, namely a solid friction fit. You want this as the factory rim of the Combustion Chamber will not easily pop through the hole in the Outer Jacket, and the stove will be both sturdy and solid. To start the Combustion Chamber into the hole, hold the Combustion Chamber at an angle to the hole, then start one edge, pressing the can in until half of the bottom factory can rim has popped in. Next, wobble the Combustion chamber in a circular manner to work the rest of the can rim into the hole. Once the factory rim has started all the way around, simply press the combustion chamber down until the top factory rim touches the Outer Jacket top all the way around.

You are done. It is now time to fire up the unit for the first time.