Weight of dome on board insulation

[Travelinman]

I have started my forno, due to concern over the weight of the dome compressing the hard board insulation.
I drove my car over the sample hard board and parked it for a few days. The board compressed 3/8 to 1/2 inch.
i do not the weight of the 42 inch finished dome. Is the front tire of a highlander the right weight to test the compression. Too much or too little?
I read that you should should build dome over the insulation.
I started this project three years ago, had to stop. I am back!

Thanks, Chris

[UtahBeehiver]

Floor insulation should have about 70-75 PSI strength with 5% compression to support a WFO (expand on what you mean by "hard board insulation, IE CaSi board?) The oven needs to be isolated from the hearth so both the floor and dome need to be on insulation. I am going to move this post to the Pompeii Construction thread rather than the Newbie Section

[Travelinman]

Thanks. It is 2" CaSi. I will look at the suggested forum.

Chris

[rsandler]

To your original question, I think putting a wheel of your truck on it was significantly more weight than the board needs to handle. From the calculator on the forum, the dome of a 42" oven weighs around 1440 pounds (180 full sized fire bricks at 8lbs each). That weight is distributed around the circumference of the base, around 650 square inches (the area of the outer diameter of the dome footprint, less the area of the inner diameter, 25.5^2*pi - 21^2*pi = 657.4). So, about 2-3 PSI. A quarter of the weight of your truck (per a google search) will be over 1000 pounds, but you put all that weight in the contact patch of the tire, which is around the size of your hand--call it 20 square inches, so more than 50PSI of force at a minimum.

[Travelinman]

Wow! That is great information. Lots of details.
Now I can go back to building it.
Thanks.

[MakaDemian]

Sorry but when you say the dome of a 42" oven, do you mean the measure of the interior dome (cooking area) or the whole external dome with all the insulation on it ?

[Giovanni Rossi]

Hello Demian, When oven diameters are posted, the number typically refers to the internal dimension unless otherwise specified. Depending on brick or cast dome construction and how much insulation and render/stucco are used, the finished outside diameter could be 12-20 (or greater) inches larger.

[MakaDemian]

Hello Demian, When oven diameters are posted, the number typically refers to the internal dimension unless otherwise specified. Depending on brick or cast dome construction and how much insulation and render/stucco are used, the finished outside diameter could be 12-20 (or greater) inches larger.

Ah ok, Thanks Giovanni, I asked about it coz someone says that you need 180 fire bricks for a 42" oven, so i wanted to calculate the amout of bricks i should buy for my oven coz its gonna be 37" inside.