#21  
Old 09-14-2009, 08:41 AM
Serf
 
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Location: portland
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Default Re: Steel Dome Oven On A Trailer

I'm too am going to build a steel dome pizza oven for a trailer,I will have a deck size of about 4x6'.My plan is to do a barrel vault style the arch and walls will be 1/2'' steel insulated base with fire brick on top.Then do a brick arch and mantel for looks,build a enclosure fill with loose perilite or equivalent 6'' on sides and back 12'' on top.does anyone see a problem with this design?
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  #22  
Old 06-26-2010, 04:35 PM
Grimaldi's Avatar
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Default Re: Steel Dome Oven On A Trailer

Finally done with the oven...more details need to be worked out concerning the trailer setup.

The project was difficult because I was working out in the open, and with no shop. I put up a covered shed and that helped keep tools and materials out of the weather.

I was wondering if I was ever going to get it done after awhile...then I decided I couldn't let it this thing beat me. Anyway, the final plaster should be cured enough in a few days to start cooking. I'm looking forward to that...a long time coming.
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  #23  
Old 06-27-2010, 10:20 AM
Master Builder
 
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Location: Washington State USA
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Default Re: Steel Dome Oven On A Trailer

Good to see you are back and enthusiastic! Here's a couple of photos I took yesterday at another gig "The Dented Bouy" catered. It was the Grand Opening of "finnriver farm and cidery" here on the Olympic Pennisula. If you closely you will see where the farm has it's own cob WFO...it can be seen just behind them in the first photo when they were still setting up. Finnriver farm and cidery is working with local farmers to bring back local wheat production and The Dented Bouy is using some of the flour from that local cultivation in their pizzas (as well as locally produced cheezes in the toppings).

They had already done the Quilcene Market in the morning and only had sixty skins left for this event... and sure to sell out. We had to leave early to attend another event but they were really cooking when we left. As you can see another day of contantly fighting the rain here in the Pacific Northwest (Not!)


Bests,
Wiley
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  #24  
Old 06-27-2010, 10:53 AM
Grimaldi's Avatar
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Default Re: Steel Dome Oven On A Trailer

Hey Wiley!

The Dented Bouy is a great looking beast of an oven...it looks like you could take it off road. The Finnriver farm sounds very cool. The cob oven looks like the orno's of the Southwest.

I've yet to test my oven, I built one fire in it after cladding it with 500 lbs of Heatstop 50, and before insulating and plastering...just to see if it would draw properly, which it did. Next, I will find out how long it takes to get up to temp and how long it will hold heat. I'm a little concerned about my High Duty firebricks (got them cheap off craigslist)...as dense as they are I'm hoping it doesn't take hours to heat them up. The firebrick are sitting on 3" lightweight insulating bricks which are sitting on 9" of perlcrete. 4" to 5" of ceramic insulation in the dome...no perlcrete. Time will tell.
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  #25  
Old 07-04-2010, 10:47 PM
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Default Re: Steel Dome Oven On A Trailer

I fired up the oven today and baked a few pizzas...not a stellar performance on either count, exactly. The oven floor didn't heat up very evenly...I couldn't reach the 750 degree level on the floor except right by the fire. I didn't build a huge fire, but it was pretty good sized...several good sized oak logs burning well.

I got more heat on the outside of the dome than I expected...as much as 150 degrees at the peak of the fire, around 130 on the rest of shell. It was at the heat of the day also, so some of the numbers could have been affected by the fact that the shell was already over 100 without a fire...just from the sun. The underneath stayed unchanged from the ambient outside temps...around 90...I think I over built on that count.

My first pizza wouldn't slide off the peel and ended up flopped over in a pile...as my 12 year old daughter would say - Epic Failure :]

I also got some cracks in the plaster...not a big deal, but the expansion of the metal inner dome did cause it, especially right at the bottom where the plaster meets the insulated perlcrete slab.

I've got more experimenting to do and see if I can work out what I see as deficiencies in the oven's performance. I'm using high duty firebricks, and if they are part of the problem, I can fairly easily remedy that with low duty firebrick or even step up and buy some fine looking soapstone at a local rockyard that I've been admiring...probably the low duty firebrick route for a 1/10th of the cost ;]

I may have unrealistic expectations, but I can hardly see the practicality of having a fire taking up half the oven floor to cook pizzas in a few minutes. Maybe an outside door will help some also.

I'll just keep on working on it and hope for the best.
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  #26  
Old 07-05-2010, 03:14 PM
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Default Re: Steel Dome Oven On A Trailer

Hi Grimaldi, Sorry to learn of your problems. I've gone back over your thread and I have some questions that perhaps will help in answering why you are having problems.

Starting from the inside of the WFO please list what the layers are from inside to outside of the WFO. And include the thicknesses.

You were talking about fixing the dome to the trailer at one point by welding it to the frame. Did anything happen regarding that idea? Or is the WFO sitting upon the high temp firebrick which is in turn sitting on the perlcrete/vermicrete? What is the bottom edge join between the base and the outer shell.

What is the outer shell: stucco or ? and is there any wire or expanded metal armiture?

What did you end up using in regards to refractory? Did you score it or cast it in sections or ? Just how did you provide for expansion of the inner steel dome? The list of layers will be most helpful and be sure to include any slip layers like aluminum foil over the steel dome.

And lastly the exterior cracks: are they shrinkage wherein they remain open after the WFO cools or do they expand and open when the WFO is hot and close again when it is cool?

Bests,
Wiley
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  #27  
Old 07-06-2010, 12:20 AM
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Default Re: Steel Dome Oven On A Trailer

Hi Grimaldi, It's late and I see you are still up and so I'll be quick with some first thoughts.

I don't see a venting space where the trapped air between in the insulation can escape. Perhaps if the refractory is not fully dry there is water heating and becoming water vapor which would lessen the effectiveness of the insulation and so cause the stucco to heat and expand. With 4 plus inches of InsulFrax I would not expect much heat loss thru the insulation in so short a time and that is the first possibility that jumps to mind. I'll sleep on it and perhaps come up with another possible reason overnight.

If it is trapped moisture continued firing will eventually dry it out. Like I mentioned I do not see a vent area where the insulation can "breath" hot air escape and so not cause internal pressures beneath the stucco. Creating such a vent area might speed up the drying out process and remove the possibility of heated air causing any pressure.

Bests,
Wiley
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  #28  
Old 07-06-2010, 12:59 PM
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Default Re: Steel Dome Oven On A Trailer

Grimaldi, After reading thru my thread (Steel Dome Oven)I finally came across a posting that is relevant to this discussion. I thought it was there but it took some time to find it. And in retrospect I perhaps should have placed more emphasis on it. It's post #52 and I mention that I have had some fires in order to dry out the refractory and was making use of the heat doing some cooking.

From rereading your posting it would appear you had but one fire to test the draw of the WFO before continuing the insulation and stucco. If that is the case (and I didn't miss something) I suspect you have water/moisture trapped between the inner steel dome and the outer stucco shell. The moisture is/was in the refractory. Water when it converts to water wapor increases massively in volume. Remember back to the lab in high school where the teacher placed a one gallon can with a little water in the bottom over a bunson burner? After the water was boiling he screwed the lid back on and removed the can from the heat. As it cooled the can buckled and compressed as the water vapor converted back to water with diminished volume and the can was then crushed by atmospheric pressure. Well just the opposite is happening to your WFO. The trapped moisture is making a huge volume change when it converts to water vapor. That is what is causing the expansion of the outer shell and consequent cracks. It is also lessening the effectiveness of the insulation making the outer shell hot to the touch.

Good news is I think you haven't done any permanent damage to the insulation. The bad news is you are going to have to open a hole in the top of your stucco dome to let the water vapor out. A significant sized hole of a couple of inches diameter should do the trick and then build a smallish fire and keep the WFO hot for several hours....maybe longer. I would use a mirror held over the hole to detect escaping water vapor. When it is no longer condensing on a cool mirror then you can call it dry.

I suspect at that point you will find a fire will heat the WFO in a manner more to your liking. And that the heat will be held by the WFO. At that point you can more accurately determine the merits of the higher temp bricks used in the floor.

When you reseal be sure to incorporate some sort of weatherproof/rainproof vent either to the top or elsewhere on the WFO so that pressure from heated air inside does not cause cracks on the shell. In the case of my WFO I have a gap between the chimney and the exterior shell.

That's my suggestion and opinion as to what is happening with your WFO. And I hope it solves your problem.
Bests,
Wiley
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  #29  
Old 07-06-2010, 01:16 PM
david s's Avatar
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Default Re: Steel Dome Oven On A Trailer

http://www.davespizzaovens.com.auWiley,
I would agree with your assessment. I had thought that was the problem also. Too late now but it's better to do the curing fires before the stucco layer.Have a look at my website to see how I've designed a seal around the flue that allows the oven to breathe.
If you just keep firing the oven it will eventually dry out and then you can deal with the cracks in the outer shell.
Good luck,
Dave
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  #30  
Old 07-06-2010, 08:19 PM
Grimaldi's Avatar
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Default Re: Steel Dome Oven On A Trailer

Wiley, thanks for giving these issues some thought, I really appreciate it.

Your explanation makes a lot of sense, I'm sure there is/was a lot of water vapor forced out by the high temps in the recent cooking fire. Just to note, the one other fire I had when I tested the draw was a modest fire, but the cladding was steaming and water droplets were running out from under the cladding and sizzling on the metal...I'm sure it wasn't hot long enough to fully dry out all the moisture before insulating and plastering, but quite a bit did expel.

After insulating and applying the base coats of plaster, it stayed covered in 90 something degree heat for at least 2 weeks before the finish coats. After applying the 2 finish coats, I kept it misted and covered for a few days, and then it rained for a week (covered). So, when I finally fired the oven, I'm sure there was quite a bit of moisture in the layers.

On the subject of cracks, the dome itself did not crack, it was around the bottom where the surface bonding cement connected to the perlcrete (and some minor cracks around the chimney). I troweled the surface bonding cement on the dome and the exposed surface of the perlcrete in each application...but not with the base coats of stucco...the base coats were on the dome, entrance, and chimney transition only .

Do you think moisture will be an ongoing problem between the Heatstop50 and the steel dome? I'm a little hesitant about cutting in to my plaster shell since the shell didn't crack exactly...I don't think I was clear about that in my previous post, just the joint where the 3 materials met around the bottom (steel, perlcrete, and surface bonding cement) and around the chimney.

What is your method of venting moisture in your oven? Did you create a specific venting space?

Thanks again,
G
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