Oil Tank barrel oven plan

[mendozer]

I obtained one of these recently and I was going to try building a simple oven design. Initially I was going to copy the popular portugese portable oven with steel inner with an insulation layer in between, etc. But now...I just kind of want to cover this in perlcrete. My plan was to cut this tank into fourths so you end up with 4 half barrel shapes, domed top, closed back and open front for a refractory insert I'm going to make. I was planning on doing the same dome to opening 64% as on dome ovens whether it's important here or not. I also prefer (the way I'm thinking about this) to keep the steel on the inside vs the refractory mix bc I want it to heat fast and steel conducts. Then the perlcrete would be my insulation layer plus add some heat retention a bit. But to be fair this is not going to be a traditional oven you fire up and cook for 2 days. It's an oven for coming home, firing it up, start stretching pizza and making toppings, then bake.
Input I was hoping for from the pros was...
1)do barrel styles need the same top to opening ratio?
2) should the chimney be at the edge of this dome vs over the opening like a dome style?
3) is there a benefit perhaps mixing refractory types, say castable refractory first along the metal THEN Perlcrete?

I was going to do firebrick bottom regardless for cooking surface, or maybe a thick baking steel, not sure yet.

any other input?

[mendozer]

https://youtu.be/ZzMjcHsI1Ck

this guy lined the inside of the steel with firebrick. Obviously we know firebrick works great for refraction, but I wonder why he didn't keep steel as the inner liner since it conducts so much faster.

I also thought...what about brick/castable inner liner, metal arch for structure, then insulation outer. Or would the metal expand faster than the castable things and crack? I'm approaching this like how Alfa builds their ovens, mixing steel with refractory. I want fast heat, more spade than my current Bertello WFO (which I love, still gonna be the portable thing to take places), and has some retainaed heat for prolonged cooking. I even thought about making a simple pipe burner since I have propane plumbed to the backyard deck and it could go along the long side of the oven for evening temperatures and prevent corner cool spots. Or i could use some castable mix to fill in the corners and make an "elongated dome" design. I was planning on doing this for the edges of the barrel shape anyways for more of an arching design. The flue gallery can either be casted over foam/sand or bricks, haven't decided yet. if I was limited to space, I'd put the flue gallery within the metal framework and put some sort of structure on the inside to deflect heat down so it'd be a shorter arched inner chamber. If not limited, then I'd make the flue outside the metal framework and this would allow me to not need to deflect he front down as the size difference of the gallery and arch would give me the natural draft pattern already.
As for the external materials, was going to do the typical ceramic fiber blanket/chicken wire/perlcrete or vermicrete.

[david s]

If you want the oven to be portable, then skip brick or castable because they're too heavy.
The problem with steel is its conductivity coupled with expansion. Highly conductive means faster heat up but also faster heat loss. Expansion at the inner surface is going to crack the cooler brick or refractory that surrounds it.
The other problem is corrosion. Heat and moisture accelerate corrosion and the thinner the steel the greater the problem. This can be mitigated to a large extent by using thicker steel or better still by using stainless.

I'd be doubtful if that oven in the video is still operating in two years time.
All WFO enthusiasts have found that if cooking more than a couple of pizzas, they need to maintain a live fire during cooking. More so if the oven mouth is as large as the chamber and neither the floor or chamber are insulated. I'd suggest you read plenty of builds on this forum before going further.

[mendozer]

Hey David. This one won't be portable. My other one is. sorry about that confusion.
I understand the risks with the expansion of the metal. So I'm gathering that metal would be better served on the outside of the oven, not the inner lining. The ceramic blanket would allow some give between the insulating perlcrete layer outside of that right? Or are you saying the expansion would also compromise the mortar/brick layer on the inside?

[mendozer]

Seems like no matter how much i try to find new ideas, there is no happy marriage of quick + hot + durable design. Only two of the three can be satisfied.

[david s]

Hey David. This one won't be portable. My other one is. sorry about that confusion.
I understand the risks with the expansion of the metal. So I'm gathering that metal would be better served on the outside of the oven, not the inner lining. The ceramic blanket would allow some give between the insulating perlcrete layer outside of that right? Or are you saying the expansion would also compromise the mortar/brick layer on the inside?

Yes, the blanket will work as an expansion joint, if the metal is on the outside. Most small kilns employ this method with the outside skin just holding stuff in place. However it will corrode unless it's stainless. Brick and refractory will both absorb moisture from the atmosphere. so when the internal heat pushes it out, it will hit the cooler outer metal skin, condense against it and accelerate any corrosion. with its hot moisture. When receiving instruction about camping as a teenager we were always told to "burn, bash and bury" our tins, which causes rapid destruction.

The more common method is to either build an enclosure (dog kennel) or a cement rendered igloo, neither of which will rust and don't trap moisture as readily.

[mendozer]

i would be painting the metal with high temp for proection. or do you mean it would transfer moister to the inner side of the metal frame? How long would this realistically take to corrode too?

[david s]

My experience with kilns tells me that any steel apart from stainless will corrode and becomes a primary cause of their demise. tHowever, a kiln is subjected to double the temperature as well as corrosive gases from the clay and glazes, but the same principles apply to ovens.
Also before the advent of Weber (and their knock offs) which employ alloy and stainless, the older steel 4 burner BBQs rusted out within about 5 years and they operate at lower temperatures than a WFO,

Try it and see. If you crete a simple cheap build it may be easier to get out of it what you can and just build another when it fails.My own build is 15 years old, fires as good as when new with no corrosion issues because the only steel is the stainless needles in the casting, the stainless flue and cowl and the stainless bolts holding the door insulation panel to its timber face.

[mendozer]

yeah i gotcha. i'm just trying to think of a way to use this tank haha. Originally I was just going to copy the Maximus Arena oven style which is a double walled steel oven with fiber blanket. Hot and fast but minimal carryover, which for me just doing pizzas in it isn't bad. I know it's more fuel consumption than a good refractory, hence why i thought of the hybrid idea. I mean the worse thing that can happen is i lose out on what $300 of castable mix or homebrew and bricks. I would want to make a real Igloo castable oven too for parties and such, but for just the pizzas I think not.