Wood-burning stoves aren't technical machines. A firebox with a door and chimney flue are the main components. Used oil drums, metal buckets and other items have been recycled into workable stoves. There’s no reason a 20-pound propane cylinder can’t be pressed into similar service with a little work, a bit of ingenuity and be the perfect size for heating a tent.
Before you start drilling, cutting or welding on a used propane cylinder, be sure the cylinder is empty. On cylinders with the old-style valves, this was a simple chore. These are identified by having only internal threads on the valve at the top of the tank where the gas hose attaches. Open the valve at the top of the tank, and all the propane will quickly vaporize away. On cylinders with the new-style valves, it’s not so easy. These cylinders, identified by having both internal threads to accept the old-style hose ends and external threads onto which the hose from the propane grill or heater attaches, won’t let the gas escape by simply turning the valve to release it to the atmosphere. Check this cylinder by attaching to a grill or outdoor stove and then try to light the burner. With either style the valve will have to be removed to make the stove, so starting with what you assume to be an empty bottle, use a heat gun (not a torch) to heat the area where the valve threads into the cylinder. This will soften the thread sealant. Hold the cylinder in place, then use a pipe wrench to slowly unscrew the valve. If, when you have the valve mostly unscrewed, you hear any hissing or see any vapor blowing out, stop and wait for it to quit before taking the valve completely out. Once the valve has been removed, it’s safe to weld or use a cutting torch on the cylinder.
Horizontal or Vertical
The stove can be made with the bottle upright (valve hole at the top) or lying horizontally. Constructing the stove will be somewhat easier if it’s to be an upright model. A horizontal model will burn wood slightly better and will accept chunks of firewood slightly longer in length. It’s your choice.
In an upright stove, cut a hole in the side of the cylinder, six inches square. Use the metal you cut out of the side to form the door. Weld hinges onto the cylinder and door so it can open and close. On a horizontal stove, cut a round door at the end of the cylinder where the valve was located on the inside of the safety collar. Weld a hinge onto the tank and to the piece you cut out to make the door. With either style, make a latch to hold the door closed, using a piece of flat steel bolted to the door.
Fabricate a set of legs to hold the stove up off the floor of the tent. The wider the stance, the better the stability of the stove.
Cut a hole in the center of the top on an upright stove or toward the rear of the stove in the outside of the cylinder wall on a horizontal stove where the flue will attach. Flue flanges are available most places stovepipe is sold, or use a length of flat steel, bent in a circle and welded around the flue hole to mate with the stovepipe. A 3-inch-diameter stovepipe is suitable for a stove of this size. A flue damper isn’t necessary but will help optimize the heat output from the stove. Adjust the amount of air entering the stove by opening or closing the door.