#11  
Old 01-20-2009, 04:50 AM
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Default Re: concrete weight

A friend has suggested a steel plate but I didn't like that idea. And as for modular, I am beginning to suspect I may have to consider that, though well more than half the thrill here was in the building of an oven. At least I still have a back yard that doesn't seem to be going anywhere...

Back to the hearth... Can I use the board insulation under the oven as suggested by Jed? I'd need the insulated hearth regardless of modular or brick, right? So do I have to do it with Portland & Vermiculite (or Perlite)?
Thanks all
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  #12  
Old 01-20-2009, 05:21 AM
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Default Re: concrete weight

You definitely need some kind of support under your oven. Neither the insulating board nor the vermiculite concrete has any strength at all.

The insulating boards and the vermiculite concrete do the same thing. The boards do the same thing in two inches that the vermiculite concrete does in four, and it's lighter as well.
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  #13  
Old 01-20-2009, 05:45 AM
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Default Re: concrete weight

Oh I am certain I need support, but must it be 7" of concrete? My question has more to do at this point with insulation. Would the board under the oven floor be enough insulation regardless of support? So, if I had four elephants holding the oven up for me, or had it dangling by chains from a crane and had the insulating board under the oven would it still be insulated enough to retain heat for pizza? It occurs to me (a complete newbie on most of this) that if I had a frame to support a steel plate and then had sufficient insulation, the steel "potato chipping" due to heat might not be a factor and would be sufficient support. I'm just trying to lose weight (for the oven project. My own weight is another issue) wherever possible. I read that 3" of concrete and 4" of concrete w/Vermiculite is the norm. (Or the other way around). If I had enough support why not just the concrete/Vermiculite layer? Why not just the board and maybe a layer of concrete/Vermiculite? How about the bat insulation Jed suggested? Why not that as well? Why all this concrete once the support issue is dealt with? Provided it is dealt with separately from tons of concrete?
Thank you for your patience and help.
Kim
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  #14  
Old 01-20-2009, 06:10 AM
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Default Re: concrete weight

=Disclaimer= I'm no expert.


Kim,

FB actually sells a metal stand. I've seen pics of an all wood stand. Concrete is not essential from a structural POV.

As long as the insulation isn't crushed by the weight that also should not be an essential function of concrete.

Since it's on a moving platform vibration is a big issue - especially for brick. That's where the rigidity of concrete and rebar may prove to be the best way to minimize the flexion of the platform (hearth) itself. I'm dubious that 7" would be necessary for that but I have no idea how much would be.

That said, it's been done before so it's certainly possible.

Invest in really good shocks. Invest more in the best brakes you can possibly buy.
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Old 01-20-2009, 02:42 PM
Jed Jed is offline
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Default Re: concrete weight

Kim,

You might consider building a structural steel structure for your oven (possible a bit more consistent and less weight then four elephants..). For this, I would suggest finding a civil engineer to confirm your structure is sufficient to support the weight; a civil engineer who can advise on the details of what is appropriately strong. The details are significant. The potential loads for this structure are significant, particularly as part of a moving vehicle.

Use an appropriate rigid insulation for under the oven - this will keep the heat in the oven, away from the supporting structure, and avoid compression from the weight of the masonry in the oven.

Use a cast or modular oven.

Use bat insulation over the top of the structure.

Metal venting ducts to pull the smoke from the oven and venting the smoke to the outside (you can still expect to fill the room with smoke, as my experience says that most of the smoke goes up the chimney, but not all).

And a perlcrete or vermicrete layer to finish the exterior. This will contain and protect the exterior insulation, and provide a surface to hold paint or some other light weight finish.

This combination of materials might provide the lightest combination of materials to build a retained heat oven.

With a firm plan on materials, prepare a complete weight analysis; how much do all of these materials weigh?

If the total weight of this structure exceeds the allowable design capacity of your vehicle - find another vehicle or reconsider your idea.

Keep up your planning!

JED
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  #16  
Old 01-20-2009, 03:23 PM
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Default Re: concrete weight

Well, at the least I feel this conversation has steered me to thinking about a modular. Much as I really, really wanted to build, I recognize there are two separate concerns here: A business need with a plan vs. the love of the oven and the hands-on building experience. The former needs the modular but the latter can still be done. I have looked into FB's Ristorante 120. It weighs about 1,200 lbs. The hearth for that, assuming about a 70"x 70"x7" hearth, by my calculations is about 20 cu. ft. So a 7" slab of only Portland @94#/ Cu. ft. = 1,865lbs. That's about 3,000 lbs. Seems a bit much to me without actually having real numbers for the bus itself available yet.

I know I have some research to do re: the bus's capacity. I have decided to scrap the elephants.
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Old 01-20-2009, 05:26 PM
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Default Re: concrete weight

Awww, I would have driven up there just to see the elephants...

You know, you still have that back yard... Wouldn't an oven look just perfect next to the deck/patio?


Um, rethink your calculations. I know it is counter intuitive but the cubic feet are actually 5 times that - 105.864 cf. I seriously doubt 7" is actually essential though.

Here's an online calculator for concrete: http://www.concrete.com/calculatorsmaterials.htm#volume
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Last edited by Archena; 01-20-2009 at 05:31 PM.
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  #18  
Old 01-20-2009, 10:07 PM
Jed Jed is offline
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Default Re: concrete weight

Quote:
Originally Posted by kimemerson View Post
That's about 3,000 lbs. Seems a bit much to me without actually having real numbers for the bus itself available yet.

I know I have some research to do re: the bus's capacity. I have decided to scrap the elephants.
I am sorry to see the elephants go...

Maybe the helium balloon variety of elephant ... two benefits: they hold up the oven, and with the helium, reduce the weight...

I went over to your blog, and if the picture of the bus is the one you are planning to use, my guess is you will need some weight reduction to this developing plan..

The bus is posted with a '9 passenger' limit. If the designers used an average of 200 pounds per passenger, and one 'pilot', that is 10 at 200 or a total of 2,000 pounds design capacity...

2,000# - 3,000# leaves and overweight condition of a noticeable amount...

Helium balloon elephants might help.....

JED
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  #19  
Old 01-20-2009, 10:20 PM
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Default Re: concrete weight

Hey Kim - don't get discouraged. If they can build these things on towing trailers - and they do - then there's a way to do it in a bus.

I suspect that with some careful design and a lot of insulation a metal stand can be made to work for you - then you can skip the concrete altogether.

It can be done - it just may take some creative designing. You're already creative so you're ahead of the game!
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  #20  
Old 01-20-2009, 10:29 PM
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Default Re: concrete weight

Or you can just buy one of these...

Forno Bravo Cucina Pizza Oven Stand


-slaps forehead- I should have looked that up earlier...
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