Brick Oven Exercise Ball Build?

[darkjester95]

Im about to start my first brick oven build and since I've never attempted any masonry work, I wanted to do it for a relatively low cost. If this build goes well, I plan to save up and do a real one based on the experience I have here.

I've seen a number of builds that include an inflatable  excise ball, or bosu ball as the form for building the dome. Every build I've seen has been from heat tolerant concrete (actual name escapes me) and i've only seen firebrick included as the floor.

Well I have a bunch of firebrick so I was curious how well this would work, I imagine it would be too much weight for the ball to support as you got close to the top so I figured the "form" would collapse, hence the reason why I havent been able to find any such attempts.

Has anyone ever heard of, or saw a video or an attempt at anything like that?

Any help would be amazing! Thanks in advance!!

[wotavidone]

The ball is OK for a cast oven, as you can make a table with a hole in it so only half the ball is sticking up above the table, mould the dome then lift it off and move it to its permanent home.
That'd be a pain in the butt with a 4 inch thick heavy brick dome.
Either lay you cooking floor, then make a dome shaped mound from damp sand to lay your bricks against, or do what I do - use a stick on a swivelling hinge. It is known as the Indispensable Tool on Forno Bravo.
Here's one I prepared earlier.
You should be able to work out the indispensable tool from this photo. The longest part of making that one was me explaining to all the "helpers" why it did not need to be adjustable.
Once you grasp the concept, this really is the easiest way to go.
You never find yourself crawling in through the arch trying to point missed mortar or scrape off excess, because you have access to the inside to clean up as you go.
This photo also explains how simple it is to marry a hemispherical dome to an arch.

[vtsteve]

The longest part of making that one was me explaining to all the "helpers" why it did not need to be adjustable.

I made mine adjustable.   

I shortened it by about 4" as I built up the dome, so it's flatter than a hemisphere (42" diameter, 17" height).

[wotavidone]

I made mine adjustable.   

I shortened it by about 4" as I built up the dome, so it's flatter than a hemisphere (42" diameter, 17" height).

The issue I had was the number of people on that job who thought the angle of the little L-bracket on the brick end had to be adjustable.
On that oven the customer wanted a full height hemisphere. It now has a 1 inch layer of mesh reinforced homebrew mortar over 3 1/4 inch thick brick, 3 inch bricks on the floor, and the whole lot is encased in 6 inches of aerated concrete blocks. It holds heat well.
That is a 34 inch oven BTW, it happens to be about 17 inches internal height, too. 

When I want flatter than a hemisphere, I will set the hinge pin further away from  the centre pivot, so the stick is shorter than the radius.