Domes

[nmich_mason]

I want to build an oven but i wanted to do it all out of steel, i work for a guy who builds outdoor boilers for home heating and we use propane pigs, we cut the rounded ends off and we have lots of them around, usually we scrap them. i could build a perfect oven out of the 'pig end' ? is this a bad idea?

[hodgey1]

Re: Domes

Hopefully some of the members here that are more experienced than I will chime in but here is my $.02. The key to your build using steel will be two very important things.

1. Thermal Mass "the ability for it to hold heat"
2. Insulation " helps holding in the heat you created"

I think because medium duty fire brick hits the thermal mass part perfectly and is relatively cheap is why it is the primary building material. Since you have a free source of steel, your challenge will be to figure out if it will retain the heat necessary to reach and maintain the pizza oven temps you wish, 500-600*F for NYish style pie or 750-1000*F for Neapolitan'ish pies. My guess is that if the thickness of steel is great enough it will work fine, but what that thickness would have to be I have no idea.

On the insulation side, using steel I think would have the same needs as the brick and that is to insulate the heck out of it. The FB plan spell that out pretty clearly and are free to download here.

Good luck!

[deejayoh]

Re: Domes

There is an oven on the site built out of a similar sounding steel dome. Think it is Wiley's? Try a search on that. It's a nice build, and AFAIK works well

Edit: found it myself. it is exactly as I thought, same thing - http://www.fornobravo.com/forum/f43/...oven-3717.html

[fornax hominus]

Re: Domes

Could you not thickly mortar the heck out of the dome exterior and add mass that way before you , as usual , insulate, insulate , insulate .

[stonecutter]

Re: Domes

Could you not thickly mortar the heck out of the dome exterior and add mass that way before you , as usual , insulate, insulate , insulate .

Not unless you reinforce,reinforce,reinforce the mass layer. Otherwise the thermal cycling will crack it apart in short order.

[TropicalCoasting]

Re: Domes

Check this out
http://www.fornobravo.com/forum/f43/...oven-3717.html

[nmich_mason]

Re: Domes

Hey gang! thanks for all the comments, now that i know someone made one, i am going to make an AWESOME one! the Wiley guy had a cool design, i am going to fab a sweet stove, think i will use one of the commercial oven designs. I will keep eveybody posted

[wotavidone]

Re: Domes

Not unless you reinforce,reinforce,reinforce the mass layer. Otherwise the thermal cycling will crack it apart in short order.

Agree. Having seen the efforts we go to get refractory liners to stay in place inside steel vessels, I reckon a steel oven with the refractory over the outside won't have that refractory in place for very long at all.
Just regard it as an oven you must use with the fire going, and accept that while the oven won't have much thermal mass for retained heat baking, it will be very quick to heat.

[david s]

Re: Domes

I can't see that a lot of cracking in the refractory layer would cause any problems in this case. It is held in position by the steel inner dome and insulated over the top of it. It could crack as much as it liked without altering the performance of the oven.as it is not added for strength, only thermal mass then it shouldn't matter.

[stonecutter]

Re: Domes

I can't see that a lot of cracking in the refractory layer would cause any problems in this case. It is held in position by the steel inner dome and insulated over the top of it. It could crack as much as it liked without altering the performance of the oven.as it is not added for strength, only thermal mass then it shouldn't matter.

It could cause a problem if he planned on using insulating concrete ( perl/vermicrete) because the cracks will transfer through the insulation layer into the finishes. A blanket would solve that problem...but why skip the reinforcement? It's not like it adds a huge expense or time to that step. Anything worth doing is worth doing right. Personally, I know I wouldn't want a layer of busted up mass under my insulation layer.

[fornax hominus]

Re: Domes

can you make a sandwich ? a layer of blanket to absorb the expansion , powder the outer surface with dry portland , lightly spray it and let it harden ..then chickenwire and vermicrete or just mortar .. This was how I finished off the vermiculite insulation on my oven and after it set I could stand on it ! 5 years in - no cracks .. i did leave a port /vent in the top and after a year I opened it and topped up the vermiculite where it had settled . just a thought ..

[wotavidone]

Re: Domes

Personally, I know I wouldn't want a layer of busted up mass under my insulation layer.

Me either.
I've been re-reading Wiley's thread. Seems like it can be done, and he doesn't seem to have had any trouble. Appears his thermal mass is calcium aluminate and crushed basalt. With reinforcing as you recommend, stainless steel I presume, then it seems like it would be reliable?
I like wiley's oven - its a pity propane tanks aren't anywhere near as readily available here in Oz.

[TropicalCoasting]

Re: Domes

Wileys oven would be a good way to make a portable oven.

[stonecutter]

Re: Domes

Me either.
I've been re-reading Wiley's thread. Seems like it can be done, and he doesn't seem to have had any trouble. Appears his thermal mass is calcium aluminate and crushed basalt. With reinforcing as you recommend, stainless steel I presume, then it seems like it would be reliable?
I like wiley's oven - its a pity propane tanks aren't anywhere near as readily available here in Oz.

I was thinking along the lines of small grid welded wire..like hardware cloth, but I don't see why other kinds of reinforcment wouldn't work. Even crushed basalt will act as reinforcment if it's well graded : fines-1/4" or 6mm. There no question that cladding with reinforcment is superior to one without it.

Sure a layer of cracked, and separated mass will 'work' but my point is that doing it right isn't difficult at all.

I haven't read that thread but I'll take a look. I like the idea of the steel shell with some masonry cladding for a fast heat up oven. It would be great if wood was scarce or expensive. Maybe I'll build one someday.

[david s]

Re: Domes

The power of a fairly thick expanding steel dome will crack just about anything reinforced or not. It is probably more important to maintain good contact between the refractory cladding and the steel dome. If the cladding layer cracks into three or four pieces this will allow the steel to still have good contact and therefore conduct its heat through to the cladding better. Stainless steel needles are the recommended reinforcement for castable refractory but they don't come cheap. Chicken wire will rust out (I've tried it) heavy steel reo expands too fast and cracks the refractory that surrounds it too, hence the recommendation for ss needles.

Here's Wileys link
http://www.fornobravo.com/forum/f43/...html#post28632

Wiley has considered this issue and his solution is shown here
http://www.fornobravo.com/forum/43/s...html#post36926