#11  
Old 05-18-2011, 01:22 PM
david s's Avatar
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Location: Townsville, Nth Queensland,Australia
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Default Re: Kettle bbq with refractory cement walls and dome

Hi tinkerric,
This is an interestingbbuild. I am a bit mystified as to why you used an insulating refractory. Generally the inner dome needs to be a dense material. By adding perlite to the mix you are also weakening it. The idea is to have a dense material to give you sufficient thermal mass to store heat then insulate all round it. Not saying your idea won't work, I think you should proceed and see how it goes. I think small is good, less cost, less time, easier stand etc. And most folk only cook one at a time anyhow.
Dave

Last edited by david s; 05-18-2011 at 01:25 PM. Reason: Thought of more
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  #12  
Old 05-18-2011, 05:23 PM
Serf
 
Join Date: Sep 2010
Location: Western MA
Posts: 20
Default Re: Kettle bbq with refractory cement walls and dome

Hi David,
I agree with both of your points.
I will probably end up casting the next one with just dense refractory.
But, the pizzahacker's lightweight dome is what got me moving on this project.
His oven gets up to temp and his pizzas bake pretty fast.
Maybe it will work. I can't wait to try it out.
My dome is probably more dense than his so I may need insulation anyway.
Then I might as well omit the perlite. Its an experiment.
I was all set to build a 28" oven but after seeing your oven, I went small again.
Thanks for all the information you've shared.
Rich
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  #13  
Old 05-18-2011, 05:35 PM
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Default Re: Kettle bbq with refractory cement walls and dome

A few more pictures of my molds.
The entrance was to be cast as a separate piece if I had had enough material.
Attached Thumbnails
Kettle bbq with refractory cement walls and dome-dscn1585.jpg   Kettle bbq with refractory cement walls and dome-dscn1587.jpg   Kettle bbq with refractory cement walls and dome-dscn1590.jpg  
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  #14  
Old 10-31-2012, 01:00 PM
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Location: Salt Lake City
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Default Re: Kettle bbq with refractory cement walls and dome

Hi Rich,

I'm new to this forum, but what you did here is exactly what I've been investigating. Unfortunately I have no experience in working with cement and forms. Is there any way I could get more details on how you set this up? Was this last post your final product or did you try any additional attempts?

I have a ceramic grill that I was thinking about trying to build a "pizza dome" for that would look very similar to your creation. It would set on the bottom half of my Big Green Egg.
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  #15  
Old 10-31-2012, 03:20 PM
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Location: Western MA
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Default Re: Kettle bbq with refractory cement walls and dome

Hi Tailbiter,
Here is another thread where I detailed my build and posted some pictures.
http://www.fornobravo.com/forum/f2/p...ble-16351.html (Perlite/Mizzou castable)

I've been making pizza in my oven for over a year and there are no cracks in the dome.

It gets up to temp in less than an hour with very little wood. I can bake pizza all night as long as I keep a fire on the side. I cook in the oven as it is heating up, and bake bread after I'm done with pizza and the oven is cooling down.

I added 2/3 by volume of coarse perlite to ks-4 castable refractory. It has performed fine and is very strong. The only advantage is that the dome is lighter. It probably doesn't perform as well as a dome cast from straight castable refractory. my dome still needed insulation. This dome might be awkward to take on and off your green egg.
If you have any specific questions I will do my best to answer them
Rich
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  #16  
Old 11-06-2012, 02:27 PM
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Location: Salt Lake City
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Default Re: Kettle bbq with refractory cement walls and dome

So this idea of building a dome for the big green egg (BGE) would constitute a smaller dome that what you put together using the Weber kettle lid. The diameter is about 20 inches. If I did it out of straight castable refractory it might not weigh much more than the standard BGE lid.

Would straight ks-4 be stronger?

Now I just have to figure out how to come up with a form that size.. ??

Thanks for your input.

Eric

Last edited by tailbiter; 11-06-2012 at 03:12 PM.
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  #17  
Old 11-06-2012, 03:59 PM
Serf
 
Join Date: Sep 2010
Location: Western MA
Posts: 20
Default Re: Kettle bbq with refractory cement walls and dome

I used the bottom of a weber kettle for my form. It is pretty much a half sphere , 22 1/2 " diameter. I think you can see pics of it in these threads.
It might be easier to just make a sand form. Look at Kiko Denzer's book, Build your own earth oven.

Whether you use straight ks-4 or mix in the perlite like I did, you still need an insulation layer. I used Perlcrete, 10 parts perlite and 1 part portland cement.

How much weight do you thinks the big green egg can support?
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  #18  
Old 11-09-2012, 12:04 PM
Serf
 
Join Date: Oct 2012
Location: Salt Lake City
Posts: 4
Default Re: Kettle bbq with refractory cement walls and dome

So my green egg sets in what they call a nest. it's a fairly sturdy metal frame to support the weight of a 155 lbs ceramic base, and dome (lid).



I removed the dome piece yesterday and weighed it. It's 38 Lbs. It's about 1" thick ceramic. I'm guessing the frame could support and additional 50 lbs. If needed I could build a wood table that would support much more weight.

In this model (using the big green egg) all heat is generated below in the firebox. A "platesetter" shields direct heat, and then my stone is raised above the platesetter using a couple of trimmed fire bricks.

http://sphotos-a.xx.fbcdn.net/hphoto...12664878_n.jpg

Therefore direct heat does not come in contact with the dome. I'm wondering if this might reduce the need for this additional insulation layer.??

Here's a couple of more questions related to the insulation layer you mentioned..

When you mention the extra insulation layer of "Perlcrete" is this poured after the initial shell is dried and cured?

Is the perlite the insulation material that is held together with the portland cement being the cohesive agent?

Would you apply this with a chicken wire mesh and trowel like the WFO's I've seen posted?

Thanks

Eric

Last edited by tailbiter; 11-09-2012 at 12:10 PM.
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  #19  
Old 03-14-2013, 07:25 AM
Serf
 
Join Date: Mar 2013
Location: Valdosta, Georgia
Posts: 1
Default Re: Kettle bbq with refractory cement walls and dome

Rich,
Thank you for being so generous with your knowledge and experience. I am in the beginning stages of planning a build similar to yours. The link to the youtube video of the ripoff build of the Franken-weber won't let me access the video, stating that it's private and requires a password. Do you have another way to access the video?
Thanks
-Andy
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