Portable Wood Fired Pizza Oven/Patio Heater

Although there are already many instructables on the topic of stoves made from old propane bottles, I thought I would try to come up with something a little more usefull in the cooking department. This all came about when a chunk broke off of my beloved pizza stone and I had to think of some way of repurposing it.

The theory behind it is as follows:
A fire is built in the main fire pot, and the air is drawn up through an adjustable flue in the bottom which also serves as an ash egress point. There is an upper chamber for cooking which the hot smoke passes through before exiting out the stove pipe. The temperature can be regulated both by controlling the air through the flue, and also by rotating the top chamber so that the hot smoke has less distance to travel from the fire pot to the stove pipe.

To be used as a brazier or patio heater, the top chamber can be lifted off and the stove pipe fits directly to the fire pot. The Kettle boils quite nicely on the stovetop, or even a wee frying pan works well.

Materials:

• Tall Propane tank
• Steel door hinge
• 4" stove pipe
• Grate of some description
• BBQ & Stove paint such as Krylon
• Exhaust cement
• Oven Thermometer
• Old pizza stone

Tools:

• Drill & holesaws
• Angle grinder & many cutoff wheels, alternatively plasma cutter (I wish!) or gas axe
• Welder

Note: I'm trying to present these steps in a more logical order than which I actually did them, so pay no mind if you notice differences in the pictures.

Step 1: Cut Up the Tank

The first order of business is to get your hands on an old 33kg LPG tank. I got mine from the good blokes at National Gas for a whopping $6NZD, and they were even kind enough to purge it for me. That's easy enough to do yourself though, just fill it up with the garden hose and then drain it out before cutting into it.
What was originally the top of the bottle is going to be the bottom of the stove, so stand it upside down and scribe a line all the way around where you want the top to be. I used a few sheets of paper taped together to get as accurate a line as I could. Cut along the line using whatever implement you've got, it uses the better part of a 100mm x 1mm cutoff wheel to get all the way around, and makes one heck of a mess. Now lop off the foot ring of the tank so you're left with a clean dome for the lid. Try to keep it on one piece, you'll need it later. Also cut along just above the seam of the dome to remove it from the rest of the bottle.

Step 2: Make the Door

Draw on the door where and how you want it. I positioned mine so it cut out as much of the side and lower seams as possible. Next drill out the corners with a 2" holesaw, and connect the dots with the angle grinder to get your door opening.

Cut your door out of the leftover metal, being sure to make it a little oversize, especially on the width. For example, if you made an 8x10" door opening, cut a 9x12" door (HxW). Take your door hinge and edge weld it to the edge of your door.
Note about welding gas bottles: I don't know if this is the norm, but it turns out that my gas bottle was covered in some sort of incognito galvanization, which gave me a hell of a time trying to weld it. Give the area a good thrashing with the angle grinder before you try to weld anything, to make sure you've got clean metal.
Next clamp the door on so it covers the hole, and weld the other side of your hinge to the body of the stove.

Fashion some sort of latch out of the scrap metal to hold the door shut. I found that a countersunk 1/4 20 screw and a bit of hardwood makes a plenty heatproof handle.

Step 3: Make the Flue

Cut a flue hole in the bottom the same way you did for the door. To make the flue sliding door, cut a piece a little larger than the hole again. To get it to fit the curve of the dome I employed my classic bash-it-with-a-hammer-until-it-fits ploy. I was surprised at how easy it was to form considering how thich the metal is. If this doesn't work for you, just use a bigger hammer. Once you've got it so it sits flat over your hole and can slide straight sideways without lifting off of the bottle cut a couple of rails out of angle iron or whatever you can find to hold it in place. These will have to be curved to the shape of the dome as well. When it all fits and slides without binding, weld your rails down.

Add a handle of some description so you can operate the flue when it's hot. I made mine out of a rod from an old dead printer. If you look closely at the last photo, you can see the nub I welded to the inside of the flue once it was installed, to keep it from opening or closing too far.

Now is also a good time to fit your grate. Mine was a cast iron affair, trace the inside circle onto it, cut it up with the angle grinder and fit it into the bottom of the stove.

Step 4: Cut the Top

If you've got some spare 1/4" plate steel lying around, feel free to use it for the top, but I wasn't so lucky, so I used some of the leftover steel from the bottle.
I cut off as much as I needed, put it in the parking lot, and ran it over with my bus a few times to flatten it out, and then finished it off with a sledge hammer.
Put the stove on the plate and trace the circle, I would highly recommend borrowing a plasma cutter if you can find one to cut this out with, it was quite a niussance trying to cut a curve with an angle grinder, lots of corners.
Once you have your circle cut out , clean it up and weld it to the top of the stove, making sure your grate is in the bottom first.

Make a ring out of a 2" wide piece of scrap, just big enough for your stove pipe to fit into. Cut a corresponding hole in the top of the stove opposite the door, and weld the ring in place. If you don't have a holesaw the right size, just use the biggest one you've got, and grind out the difference. I didn't have any grinding wheels small enough to fit in the hole, so I sandwiched together a few of the cutoff wheel stubs leftover from cutting up the bottle, as you can see in the last picture.

Step 5: Make the Lid

Make another stovepipe ring, this one about 4" tall, and fit it into the dome lid, just like you did for the stovetop. It will be a little harder of course, due to the curvature of the dome, but I found that 2 offset holesaw holes got it pretty close and the same grinder ploy worked out well.

The oven thermometer is optional, but I find it very handy for making a good pizza. Mine was the garden variety than hangs from a rack in your home oven. I cut off the sheetmetal housing, drilled a hole in the top of the dome lid, and glued it in place with some exhaust cement.

For the handle I used a section of an old shopping trolley which I rolled up and welded on. It actually dissipates heat quite well, and although you'll see me wearing a glove in the video, I've since discovered that it's not necessary and it can be touched even when the thermometer is reading 500°F+.

Step 6: Handle the Jandal

For portability I added some handles made out of some 4" tall sections of scrap. Bend them into a "C" shape as shown, cut halfway down at the corners, and roll the middle secton over using the same hammer trick as you did for the flue. Round off the corners, weld them to the sides, and you've got it handled.

For stability I also put the foot ring back on the bottom by welding some tabs between it and the original top of the bottle, as you can see in the last photo.

Step 7: Test Fire!

Before painting the stove I thought it might be a good idea to bake the old paint off. It didn't work entirely, but did make it considerably easier to remove with a wire wheel. You'll notice it's a bit darker in the 2nd photo as the stove begins to heat up.

Also pay attention to how the door and flue operate when hot compared to cold. I noticed they were a bit tighter and I had to file a bit off of the door latch.

Step 8: Painting/Finishing

Once you've got everything how you want it, give it a good dose of BBQ & Stove paint. Once it's dry, fire it up again before you cook anything in it, to cure the paint.

Step 9: Cooking

Once you're ready to cook, fit your pizza stone to the top. Mine had conveniently broken with a nice chunk missing where the hole comes up out of the fire pot. But then the lid wouldn't close quite, so I had to fine tune it a little. I would recommend investing in a ceramic cutting wheel for your angle grinder if your stone needs any fine tuning. I thought I could do it with a few judicious blows of a rock chisel, but in fact all I accomplished was shattering what was left of my precious pizza stone into half a dozen more pieces. No worries, a bit of exhaust cement and it was as good as new.

In order to regulate the temperature for cooking, first build a good hot fire in the stove, and let it burn down a bit, you don't want any flames shooting up into the upper compartment. The smoke imparts itself to the pizza quite well, so it's best to use some nice hardwood for the fire. I've used both Macrocarpa and Eucalyptus Gum wood so far, and they both work great. Whatever you do, never burn any pressure treated lumber, especially if you're cooking over it.
Start out by positioning the lid over the pizza stone so that the stove pipe is 180º from the hole in the firepot. Now adjust the flue to get the temperature somewhere between 400 - 500°F. If it goes over that and you're not a fan of crispy pizza, close the flue down, and if that doesn't do the trick, rotate the lid so that the smoke egress is closer to the point of ingress, and the temperature should drop low enough. You'll get a knack for it, I wound my thermometer all the way around back to 0°F (~750°F) before I had it figured out.

When the temperature is right, get the pizza on the peel with plenty of cornmeal, open the lid, and slide it right onto the pizza stone. Give it about 5 minutes, more or less depending on your taste.

I haven't tried it yet, but I reckon that this would also work well as a meat smoker with a rack in place of the stone. If you build one, try it out and let me know how it goes ;)