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  #11  
Old 01-15-2010, 09:47 AM
Journeyman
 
Join Date: Jun 2009
Location: minnesota, usa
Posts: 472
Default Re: Tips for Mobile frame for Pompeii Oven

Hi Dvir
Do you have any construction experience? I guess I'm not clear on why you'd want to use a wood frame in the first place, particularly when you want your oven to be mobile...?

Structural engineering 101, wood holds up wood, concrete and steel hold up concrete and steel.
Putting a WFO on any kind of wood base is ill conceived in the best of circumstances. Factor in that you want it to be moveable, and it's about 100x worse an idea.
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  #12  
Old 01-15-2010, 11:27 AM
Journeyman
 
Join Date: Mar 2009
Location: North Louisiana
Posts: 305
Default Re: Tips for Mobile frame for Pompeii Oven

Going against the grain here...

My oven is built out of castable refractory concrete. It weighs 600lbs before the 4" to 6" of perlcrete insulation another 200lbs.

I do have framing carpentry experience and I know I could build a wooden frame that could hold up 800 lbs easily.

Dvir, if you need any framing questions answered feel free to PM me.

Good luck with your build.
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  #13  
Old 01-15-2010, 11:57 AM
Journeyman
 
Join Date: Jun 2009
Location: minnesota, usa
Posts: 472
Default Re: Tips for Mobile frame for Pompeii Oven

Holding it up is not the issue. It's the flex and that wood is affected by changes in humidity, etc. vs. steel.
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  #14  
Old 01-15-2010, 12:03 PM
Journeyman
 
Join Date: Mar 2009
Location: North Louisiana
Posts: 305
Default Re: Tips for Mobile frame for Pompeii Oven

Of course steel would be stronger but I don't believe he wants to tow this oven behind a vehicle so a stout, wooden frame should be fine. mho
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  #15  
Old 01-15-2010, 12:04 PM
Laborer
 
Join Date: Mar 2009
Location: Monterey Bay, CA
Posts: 80
Default Re: Tips for Mobile frame for Pompeii Oven

OK, usually I keep my mouth shut when someone suggests building a stand out of wood, letting other people give reasons why it should not be done. First, a disclosure - I work for a building materials supply company, so anything that sells more wood is a good thing, especially in this economy. Having said that, I think that a metal stand is still a better approach, and the reason (in this case) being that you want to make it mobile.

Think about it, a 42" Pompeii oven kit ships at 2000 lbs. Add in the hearth, the stucco or walls and roof, chimney, etc. and you are talking over 3000 lbs. And all of this weight is sitting up 3 feet off the ground - a very high center of gravity. The static compression that a couple of 2x4s nailed together have to handle would not be the problem. The problem comes up when you introduce a lateral force to the structure - moving the WFO. Even though it is on wheels, that initial force will crumple your whole wooden base like a house of cards, unless you build it in such a way as to handle the stress.

How do you intend on joining the joists to the studs? Remember, lumber is relatively soft, so just nailing the wood together (or even using carriage bolts) will not hold up to the pressures. As an experiment, take 2-2x4's, 3 ft. long, and nail them together at 90 degrees, forming an "L". stand on the lower part of the "L", and push against the upper part. You will find it will not take a lot of effort to literally break the joint. Of course, there are ways around this - build the sides of the stand as walls (12" or 18" on center), using CDX plywood as sheathing. Now you need to figure out how to tie the walls together. And tie the walls to the floor. And we have not even started to discuss how to build the top of the stand that can support 3000 lbs of weight over about 16 square feet.

The point here being - you really need to engineer the stand right if you want to make it out of wood. Since mobile is a requirement here, you can relate the design to building a house that can withstand a substantial earthquake (look at the pictures from Port-au-Prince to see what happens when underengineered structures are subjected to large lateral forces).

Given all the other reasons, you might want to go back to metal - and just think, you can learn a new skill by welding!

Good luck, whichever way you go!
Ed
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  #16  
Old 01-15-2010, 01:20 PM
Serf
 
Join Date: Jan 2010
Location: New York
Posts: 8
Default Re: Tips for Mobile frame for Pompeii Oven

Hey and Whoa!
First of all - I'm not going to drive with my oven on the highway. I just want to be able to move it around the yard/house as needed.
Second - the frame is going to be 5X5 ft. with 9 or more legs that every leg is going to get a wheel so all the pressure goes to the ground directly (nothing is holding).
Third - I am working in construction. My specialty is heavy duty concrete jobs. And where I come from (Israel) we build the house from concrete and we use the wood to put the concrete onto. This is tons of pressure that is put onto the wood which is only 1x4". so doubled 2x4 will be much stronger.
Fourth - regarding the insulation from the wood frame - it's going to be a layer of 1-2 inches of salt (insulates very well) on top of that there are going to be 2-3 inches of concrete and then I am going to build the oven.
Fifth - I'm not going to do a house shape for the outside, I am going to keep the igloo shape so that means only 6-8 inches of insulation.
Thank you very much. I've been enjoying debating with you guys!
Have a good weekend!!!
Dvir
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  #17  
Old 01-15-2010, 01:24 PM
Serf
 
Join Date: Jan 2010
Location: New York
Posts: 8
Default Re: Tips for Mobile frame for Pompeii Oven

Insulation Correction:
Fourth - the Insulation is going to be 2 inches salt, a thin layer of metal and then the concrete because the salt absorbs water so it will take all the water from the concrete.
Again, Have a good weekend!
Dvir
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  #18  
Old 01-15-2010, 04:24 PM
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Join Date: Jul 2005
Location: New Jersey USA
Posts: 4,216
Default Re: Tips for Mobile frame for Pompeii Oven

Quote:
Fourth - regarding the insulation from the wood frame - it's going to be a layer of 1-2 inches of salt (insulates very well) on top of that there are going to be 2-3 inches of concrete and then I am going to build the oven.
Whoa! Stop! Salt is not an insulation! Neither is sand, gravel, broken glass or any of the dozens of things that people try to use! We have one motto here at Forno Bravo: Insulate! Insulate! Insulate!

I really think you need to download our plans (Pompeii Plans Ready for Download) and read them carefully. They are the result of actual experience of building hundreds of ovens, as well as hearing about numerous ones that DON'T work.
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  #19  
Old 01-16-2010, 04:51 AM
Il Pizzaiolo
 
Join Date: Mar 2009
Location: USA
Posts: 1,436
Default Re: Tips for Mobile frame for Pompeii Oven

Dvir,
Would love to see a drawing or pics of your base... Or how you plan to tie it all together ? Have you begun yet or are you still in the design stage... I have seen an oven built on a wood base, but it was not made to be mobile.. You may want to consider using 4 x 4 and some half lap joints. And like EADavis said plywood on the outside.. I would never do it... Im sure it can be done... and you really need to think about a better insulation plan for the base.. If you are going to go forward with this plan, you are going to have enough difficulties and you wouldnt want to have to take it apart to reinsulate... also understand the reason we insulate is for heat retention.. I have no knowledge of salt and its use as an insulator, nor could I find any on the internet,, It may (may) provide enough insulation to keep your base from lighting on fire, but I doubt it will retain enough heat for you to bake a good pizza.... With all that being said... Good luck with this
Mark
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  #20  
Old 07-04-2011, 04:43 PM
Apprentice
 
Join Date: Jul 2006
Location: Dorset, United Kingdom
Posts: 149
Default Re: Tips for Mobile frame for Pompeii Oven

My oven weighs 1400kgs and was built on a bench with 4 legs of cheap softwood 4x2.
The concrete was vibrated and at times I have had to stand on the oven and that would add another 210 pounds plus the weight of the forms, wet sand dome inner and tools I have on the bench, If it seemed a bad idea i would have never stood beside or on it believe me. I guess the trick is to design the bench with a lot of thought
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