The idea started when I was going to discard a microwave oven I found in the trash. I dismantled it looking for the coil that some people uses to make a spot welder but this one had a small plastic version that does not look like it will generate enough power (some motors and switches in good shape from the oven will be used in future builds).
As I have no oven and want to bake some bread and pizza I though I could use the metal box with its glass door to make mine.
This took some old rusty metal laying around and lots of tools.
Step 1: The Frame
I made a frame so the metal box can be heated using wood or a gas stove I have to sterilize compost. To cut metal I installed a metal cuting disk in place of the normal toothed disk of my bench saw. As it did not fit I had to cut an acrilic ring in my laser cutter for the disk to fit firmly in the motor. To measure the screw size and disk hole I used a digital calliper. The frame design was so simple I did not even made a drawing. I welded several pieces of that rusty metal using my MIG welder. After I finished the frame I heated the metal box using the stove and as it reached 400F a stange smell came from the white paint. That disuaded me to eliminate the paint as I had gone some way welding the metal frame just for nothing.
Step 2: Paint Removal
To do so I used a torch and lots of patience. The heat from the torch made the paint burst in flames with quite some smoke so a mask and ventilation were crutial. The photos show how the paint burns and is removed from metal using a torch.
After the whole metal cooled down I brushed the carbonized paint remains and made a second test with the stove: the nasty smell was gone. It was time to weld the metal screen that I bought for one dollar at my neighborhood metal yard (I sell them aluminium beer bottles after parties for quite some cash).
Step 3: Insulation
In order to confine the heat generated by the wood I watered a sand/cement mix (3/1) instead of clay as I had a some cement and sand but no good mud.
Some wood board and clamps were necesary for the mix to stay in place while the mix hardens.
The whole process has taken me two days and I will need one more in order to finish all the sides.
I will update this post in hope it includes some great looking pizza photos taken out from this peculiar oven :)
Step 4: Heat Sources
Gas for heating the oven
The holeunder the metal box is big enough to let a stove get into the oven, the flames can heat the metal box over 400F very fast.
Wood for heating the oven
A couple of powdered milk recipients were used to make a rocket stove. the heat generated using one wood stick was 350F inside the metal box. The wood has to be pushed as it burns so not to stop combustion, this can be done using an elastic cable, like one in a bow to push the wood into the stove. It was necesary to block the space in the hole so the smoke only goes out over the hole on the top. To make it I used metal from a cassette deck rescued from garbage. It is hard and took some time to make a hole for the stove to pass through.
Now it is ready for cooking, only problem at present is heavy rain so this weekend I will not be able to cook something.