Preparing for steel oven build.

[david s]

If that was my set up I'd be including some gussets or diagonal bracing on the stand legs that attach to the trailer chassis.

[Wiley]

Scarnucci,
Regarding the strength of the vermicrete: terrible in tension, better than terrible in compression but not much better. One could get really complex in designing so you have little or no heat loss in your hold downs/anchors.

Realistically (IMHO) what you want is something that will keep everything together when you are forced to do a panic stop. You most likely will be driving conservatively otherwise and so therein lies the grey area between what is enough and what is not.

An idea:

A plate of steel welded to the steel dome at each end of where the underneath supporting cross member is located. This plate is maybe something like six inches long by three inches wide and maybe 1/4 inch thick. It is welded horizontally up from the bottom of the dome where it will eventually be embedded in vermicrete. This small plate has a one inch hole drilled in it. The hole is located in the plate so that it will not be embedded in the thermal mass when the plate is welded to the dome. Thru this hole there will be a 3/8ths inch bolt which is welded to the tray support so the threaded end is upright. This bolt will be long enough so that when assembled it sticks up thru the hole in the plate by an inch (minimum). Locate the steel dome when assembling the oven so the bolt passes thru the hole but doesn't touch it. Once the dome is set upon the bottom bricks and before you pour the vermicrete thread a large nut onto the bolt. This nut can be constructed of a large fender washer welded to a regular nut, the idea is to make it so that the bolt cannot come thru the hole when attached yet the interstitial space between the bolt and nut assembly and the small plate is filled with vermicrete. Thus you have the thermal break and yet the dome is less likely to part company with the trailer when you (hopefully never) have to make a panic stop. The bolt should be a grade five...no need springing for the extra cost of a grade eight as when you weld it the heat treating will be lost and grade fives are basically grade eights without heat treatment. The weak point is the weld between the bolt and the support but hopefully some of the energy will be taken up by the compression of the vermicrete in the hole before the load is transmitted to the bolt, bending the bolt before transmitting enough energy to break the weld.

Just my thoughts and first thoughts at that. No liability as to failure, take it as worth what you paid for it...which is nada.

Hope this helps,
Wiley

Also, when I grind anything that makes a lot of dust I always try to set up my large shop vac so that the intake is where the grinder will be throwing the waste. Helps a lot to keep the dust from going everywhere.

[scarnucci]

Thank you for your comments and suggestions for welding the dome in place.

I cut some bricks today and picked up the dome from the fabricators.

Some pics of where I am at:

Bricks are not locked down yet, obviously. The 2X4s are in place where a vermicrete mix will go. I'll probably end up welding some bolts in the middle of that area and then some plates from the bolts to the dome, as per some suggested.



More or less where I want the dome at.







I stopped by a local refractory fire brick factory on my way from picking up the dome. Talked to them about layering the dome in two inches of refractory cement, then insulating it. He is also into pizza and pizza ovens and suggested that the refractory be on the interior of the dome. As this is mobile, I dont really want that. He doubted the effectiveness of any refractory on the outside of the dome, and suggested that I just insulate the hell out of what I have. That the insulation and shape of the dome will keep blasting the heat downwards towards the brick floor which will absorb and hold the heat.

So, I am considering building 4 walls up from the existing frame, and making a square enclosure for the dome. Wrap the dome in 607 super wool, then fill in the remainder of the area inside the enclosure with vermiculite. Wall it off, roof it, call it done.

Is there any chance at getting away without the refractory?

[Wiley]

"Is there any chance at getting away without the refractory?"

Little to none IMHO especially if you expect to produce pizzas commercially (ie: lots of pizzas baked one after another sort of rapidly). But no one here has tried it so if you decide it is worth the experiment let us know how it works out.

Looks good! I would suggest that you wire wheel (large cup brush on angle grinder) the inside of the dome. My WFO has had no problem with rust flaking down on what's baking inside but if one rubs one's hand on the interior surface one does come way with a red brown colored hand. I wire wheeled the interior (exterior as well, didn't want problems with paint burning off) of the steel dome when I built mine and have had no need to further address internal rust issues. It's a dirty task but IMHO worth doing.

Bests,
Wiley

[scarnucci]

Does the vermicrete border need to be of a refractory cement or will regular quick-crete work? I did pick up 3 bags of refractory, but at $30 a pop I wonder if the job will be done just as well with $5 bags.

[Wiley]

Scarnucci
Where I come from Quikcrete is a mix that when water is added makes concrete. It has gravel and sand and cement.

You do not have to use refractory (calcium aluminate) cement when mixing vermicrete, regular portland type 2 will work just fine. Probably portland type one or even "plastic" cement (which is plastic only in consistancy/flexibility not made of plastic) would probably work as well. There are a couple of good threads concerning how to mix so I would advise checking the archives. RTflorida (if memory serves) had a procedure for mixing and placing which allowed for high insulation with little cement and lots of vermicrete (9 or 10 to 1 vermicrete to cement ratios are possible). The threads are a couple or three years ago.

Hope this helps,
Wiley

[TapRackFire]

Scarnucci,

How did your oven turn out? I have poured my foundation and liked your version for a dome.