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  #101  
Old 02-27-2009, 07:49 AM
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Join Date: Feb 2009
Location: Quilcene, WA
Posts: 11
Default Re: Steel Dome Oven

Hi Wiley,

Thanks for all the info! They are cutting the tank either way as they sell them to folks for BBQ's. I think I may hold off and go for a smaller one, 40" or so. All your points are convincing and I do want to consider firing time for a larger oven. Once I get the bug for something, such as this and start looking I usually find just what I need. Fun poking around all these yards as well. I wouldn't be suprised to find what I need tucked away in the woods around here. Plenty of people seem to have an obsession with collecting "stuff", piles of it. I was thinking of this as I lugged my new buoy, chain, a huge block, and other stuff associated with the buoy back to my home. All treasures I say! This is what I told my wife.

Keep your eye out for domes...

thanks,
john
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  #102  
Old 02-27-2009, 08:26 PM
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Join Date: Nov 2008
Location: Collierville, TN 38017
Posts: 9
Default Re: Steel Dome Oven

John, I have a 41" OD with the backer ring on it that I would sell for a $100 but I'm a long way from you so I'm not sure what shipping would be. My zip is 38017
Wiley, thanks for that very detailed explaination of the thermal break and rim.
After reading a few times I think I understand fully.
Also, still thinking about what you said on the steel floor welded to the dome. My wood stove is build like this and it gets much hotter without warping. Of course the floor is smaller. I make fire pits from these domes and never leave the backer ring and cut flames in the sides and I never had any of them become distorted so I don't think anyone needs to worry about it much.
Randall
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  #103  
Old 03-05-2009, 03:47 PM
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Join Date: Nov 2008
Location: Collierville, TN 38017
Posts: 9
Cool Re: Steel Dome Oven

Wiley, does steel hold heat longer than the refractory? I was thinking of making the dome 2 layers thick. One dome on top of another then add the refractory. Of course I would need to slit the top dome 3 or 4 times to let it slide over. What does the aluminum foil do that you put on top of your dome before the refractory?
Thanks,
Randall
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  #104  
Old 03-05-2009, 09:12 PM
Master Builder
 
Join Date: Mar 2008
Location: Washington State USA
Posts: 780
Default Re: Steel Dome Oven

Randall, Although I do not have any figures to prove this it is my opinion that steel does not hold heat longer than firebrick, I believe that it conducts heat faster and that a solid steel oven would actually cool down sooner than a totally brick WFO. That's given that insulation would be the same etc.

The purpose of the aluminum foil was to cause a slip surface between the steel dome and the refractory molded over it. I don't have the calculations at hand but if I remember correctly if the circumfrence of the dome was a straight length of steel and if one heated it from a reasonable ambient tempreature to around 900 F degrees the length would grow something on the order of 1/2 inch. Pi x D gives the circumference so the diameter would grow something on the order of one third of one half inch or one sixth inch. Not much, however, that expansion is real and needs to be reckoned with. The refractory is going to expand as well but the steel will heat faster as it's closer to the heat source and I don't have any figures as to how much the refractory will expand. So by creating a slip surface between the steel dome and the refractory (and segmenting the refractory) I can control more or less the expansion. As the oven heats and everything expands the cracks between the segments grow and as if cools they contract. I think I included photos of the cracks somewhere in the thread. I heat cycled the oven several times to prove to myself that the oven was "working" as I wanted before continuing with the kaowool and etc. covering. I also placed strips of aluminum foil between the segments so the expansion cracks were more likely to form there than elsewhere.

I will admit I had some concern that the oven would expand and when it cooling the refractory would hangup and remain in the expanded shape leaving a gap betweeen the steel dome and the refractory. In my case the refractory cycled as I wanted and expected. I'm not sure if it had hung up there would be a problem with heat transfer to the refractory from the steel dome or not, but the worry turned out not to be warranted on my oven. I add that because I don't know of another WFO like mine and one is a pretty small sampling from which to make a definite statement.

Hope that answered your question, if not ask again and I'll try again :-)
Wiley
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  #105  
Old 03-05-2009, 09:38 PM
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Join Date: Nov 2008
Location: Collierville, TN 38017
Posts: 9
Default Re: Steel Dome Oven

Thanks, Is that just regular cooking aluminum foil or thicker stuff? If so, where do you purchase it. Approx. how long does your oven stay hot? say from 700 to 250? Once you remove the fire.
Randall
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  #106  
Old 03-05-2009, 11:48 PM
Master Builder
 
Join Date: Mar 2008
Location: Washington State USA
Posts: 780
Default Re: Steel Dome Oven

Randall,
It's just regular aluminum foil, I used the widest my wife had to minimise joins.

I haven't had time to build what I consider an insulating door so how long the oven holds at what heat are figures I do not have. There is very little heat lost thru the insulation on my oven and I suspect that when I have a proper door it will retain heat as good as a brick oven. There may be a bit more loss as the flue is steel and connects directly to the inner dome, however, my "proper door" will seal the flue when in place. Any door that doesn't close off the flue allows the chimney to work and transfer heat away via convection from those non-insulated surfaces. As for the rest of the dome, the mantra of Forno Bravo Forum is "insulate, insulate, insulate". After several hours of running my WFO at pizza temps one could not detect heat thru its outer dome.

Even without a proper door I have not had problem cooking a single loading of bread (didn't bake enough to require a second loading) and it roasted a Thanksgiving turkey without dificulty as well.

Bests,
Wiley
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  #107  
Old 03-21-2009, 07:34 AM
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Join Date: Aug 2008
Location: Peculiar, MO
Posts: 1
Default Re: Steel Dome Oven

WOW! What a thread! I'm worn out! NICE build!!!
Something I have seen no mention of -
The aluminum foil is serving two purposes, it's intended original purpose and as an infrared reflector. Infrared is heat. In the infrared world there are emittors and reflectors. Flat black is an excellent emittor, allows infrared to easily pass through. The foil, applied bright side in, would be an excellent reflector, driving heat back into the oven and improving efficency.
I build meat smokers and use a bright silver paint as a base coat when painting them for this reason. It makes a difference.
I am a FLIR certified thermographer.
Again - NICE BUILD!
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  #108  
Old 04-08-2009, 02:41 PM
Serf
 
Join Date: Nov 2008
Location: Collierville, TN 38017
Posts: 9
Default Re: Steel Dome Oven

Wiley, Where did you get the Frax paper and what thickness did you use? I can only find this paper in 100 sq.ft. rolls which is mega $. I will only need a small strip. Trying to gather all my supplies before I start.
Thanks,
Randall
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  #109  
Old 04-08-2009, 09:18 PM
Master Builder
 
Join Date: Mar 2008
Location: Washington State USA
Posts: 780
Default Re: Steel Dome Oven

Randall, If memory serves it came either from Seattle Pottery Supply or from one of the Seattle art glass suppliers. It is commonly used in slumping glass. I used to do alot of enamel work and SPS used to carry alot of stuff for enameling. If I were searching out a source today I would try them first and if no luck try a local glass blower or bead maker. I've seen bead makers use it to set their finished beads upon when annealing.

The thickness I used was about the same thickness as thick blotter paper. I'm sort of surprised they are only offering to sell it by the roll. When I bought mine it was so much per foot, they showed me what they had and I selected and bought. Then again, I was purchasing from a retail not wholesale outlets back then.

Hope this helps,
Wiley
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  #110  
Old 04-14-2009, 09:58 AM
Serf
 
Join Date: Nov 2008
Location: Collierville, TN 38017
Posts: 9
Cool Re: Steel Dome Oven

Seattle Pottery does carry.
They have 1/32, 1/16", 1/8" 1/4" Would thicker be better or does that cause other issues? Thanks for the contact.
Also, did you install a thermometer in your oven or do you use a laser non contact thermometer?
Randall
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