You can google exercise ball pizza oven to get a variety ways to proceed. A key to building the pizza oven is design it so the deck runs about 200 degrees cooler than the dome. That is dictated by the height of the dome and the height of the door. Your door height inside should be 63% the height of the inner dome.
You can watch the below video so see most of the form construction details which I will not include here
https://diyprojects.ideas2live4.com/2016/06/30/wood-fired-pizza-oven-exercise-ball/
I chose to go with a heavy non-portable solution that would give me a strong dome able to withstand a lot of repetitive heating.
So for the dome and the deck to hold the fire bricks I used the following combo
to make the refractory mix:
2 parts silica sand
1.5 parts Porland cement
1.5 parts Perlite (available at Home Depot in the gardening dept)
2 parts Fireclay(available at select Home Depots) This stuff
http://www.homedepot.com/p/H-C-Muddox-50-lb-Fire-Clay-100011882/100321936
When mixing this mud use the least amount of water possible as you do not want it runny and you want to reduce the shrinkage
So, the first step is to get an exercise ball. I believe mine is a 26inch but I inflated it to 29 and inserted it into a 28" hole cut into the 3/4" plywood. I made this handy dandy compass and I used it a lot during the process of making the form and the final table.
I then made a beefy frame out of 2x4's as that will be what the oven is on when finished. After making the oven on the frame with the hole in the plywood, the oven will be lifted off and another solid piece of plywood added. I then moved the frame and new plywood top to its final resting place. So here is a sequence of pictures and events.
OK, here we are ready for mud. The chimney is a key part to get the air flow going. 18" above the top of the door works great for me. What you see is not the final chimney. When the mud dried I pulled it straight up and then removed the door form
I used about 3" of mud all over. It helps if there are 2 people doing this. One making the mud and one applying as you really don't want to put wet on top of dry.
Note than when mudded and dried for 3-4 days the exercise ball is deflated and removed from underneath and the doorway frame is pulled out from the front. Gives this lots of time to dry before moving it. Covering with dampened towels will help with the shrinkage. So, a week later 3 strong guys lifted it off and set it on the ground.
More to come.
