#1  
Old 04-05-2010, 08:29 AM
Peasant
 
Join Date: Apr 2010
Location: Tucson, AZ
Posts: 44
Default insulating gas grill lid?

Would it be possible to simulate some of the effects of a WFO by insulating the lid of a propane grill and leaving the heat on during coking? I have about 1 1/2" gap between two layers of stainless sheet metal that make up the lid to my grill. I could insert either kaowool or insulafrax blanket in this gap which may help to distribute the heat evenly from the top and bottom. I would leave a pizza stone on the grate and get it to probably 700+ degrees prior to cooking. What do you think?
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  #2  
Old 04-05-2010, 07:44 PM
Laborer
 
Join Date: Mar 2009
Location: Monterey Bay, CA
Posts: 80
Default Re: insulating gas grill lid?

From one Davis to another (and from one former Tucsonan to a current one), I think it is a good idea...

http://www.fornobravo.com/forum/f43/...sion-9229.html (Forno Clamshell - Another Charcoal Grill Conversion...)

Mind you, I took a charcoal grill and converted it to propane. With a round grill, it made it easy to mount a pizza stone on top, to provide radiated heat from above. Also, I found I was cracking (cheap) pizza stones right and left that I had sitting on the grill grate - the solution was to invest in one of the FB pizza stones.
Ed
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  #3  
Old 04-07-2010, 07:16 AM
Peasant
 
Join Date: Apr 2010
Location: Tucson, AZ
Posts: 44
Default Re: insulating gas grill lid?

thanks for the tip!

I'll look into the Forno Bravo blanket and see how much insulation that gives me. Do you think I can do without a chimney since I'm not burning wood and generating smoke? There are air intake holes in the bottom of the grill, and the lid doesn't seal air-tight so there is no chance of pressure buildup.

I noticed in your thread that your temperatures were getting too high. You can probably add a gas regulator right at the propane bottle and slow the flow all the way down to a trickle. Check Grainger or a welding supply shop.
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Old 04-07-2010, 08:31 AM
Laborer
 
Join Date: Mar 2009
Location: Monterey Bay, CA
Posts: 80
Default Re: insulating gas grill lid?

Tyler,
A roll of the FB blanket will be more than you may need - I bought a roll, and used only a few linear feet of it, about 1/4 of the roll used. Now, I am (eventually) going to build a Pompeii 80, so I figured I could always use the extra insulation on that.

I added the chimney in order to ensure good air flow. The hole in the bottom does draw up fresh air, but I also wanted the heat to be drawn up around the lower stone and then around the upper stone, maximizing the heating of the stone itself. And during cooking, it provides a good heat by convection. With the cap in place, it seems to be the right balance for my setup. I have never tried it with a regular gas grill, so I can't comment.

The burner I have does have a knob that allows me to adjust the gas flow. The problem is I need to turn it way down, so I am not generating too much heat. And I need to be careful at that low flow rate, so as to prevent the flame from blowing out. A smaller burner would allow the flame to be adjusted more in the middle of the range, rather than at the low end. But hey, that is all part of the fun of prototyping, right?

If you do put this thing together, please post some pictures. I think it has some good possibilities as an alternate, portable way for making pizzas.
Ed
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  #5  
Old 04-07-2010, 08:46 AM
Peasant
 
Join Date: Apr 2010
Location: Tucson, AZ
Posts: 44
Default Re: insulating gas grill lid?

thanks Ed

I only need < 10 sq. ft. so I won't be buying a full FB roll. I am looking at other blanket materials which sell fractional sizes.

Any thoughts on kaowool vs. insulfrax vs. isofrax? I'm not worried about safety, as the blanket will be protected from mechanical damage and water damage (trapped between two layers of sheet metal).

I have a little more than 1/2" gap between metal layers to insert the blanket. would it be wise to buy a thicker blanket and compress it to fill the gap? Or should I buy exactly 1/2" thickness. I know with fiberglass insulation, you ruin the airspace properties by compressing it, but I'm not sure how these woven alumina blankets perform....
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  #6  
Old 04-07-2010, 07:35 PM
Laborer
 
Join Date: Mar 2009
Location: Monterey Bay, CA
Posts: 80
Default Re: insulating gas grill lid?

Tyler,
I think any one of the three would work. Don't compress the insulation more than you have to, to keep the insulating properties. Good luck with it.
Ed
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  #7  
Old 04-11-2010, 10:29 AM
Laborer
 
Join Date: Mar 2009
Location: Monterey Bay, CA
Posts: 80
Default Re: insulating gas grill lid?

Tyler,
Here is something along the lines of what you may have been thinking - just add insulation...
YouTube - Rotisserie Pizza Grill - Design.mpg
Ed
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  #8  
Old 04-11-2010, 10:46 AM
Peasant
 
Join Date: Apr 2010
Location: Tucson, AZ
Posts: 44
Default Re: insulating gas grill lid?

yeah, now we're talking

the spinning seems silly/unnecessary, but as a fellow engineer I can appreciate the geek factor in installing bronze idler gears in your grill!

personally, I just rotate it 180-degrees with my pizza peel 1/2-way through cooking

I did a test run last night, while waiting for lid insulation (I posted a request n the Barter forum for 10 square feet of leftover insulation). With all 3 burners on full blast, I got a lid temperature of 650 F sustained. I'm sure I can get at least another 100 degrees after adding lid insulation. I managed to crack the Home Depot tile I was using as a "pizza stone" in the process, so I plan to pick up a thicker quarry tile in the near future.

The pizza cooked in just over 4 minutes, and it was delicious

Not a bad start for investing zero dollars/hours so far....
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  #9  
Old 04-12-2010, 06:28 PM
Peasant
 
Join Date: Apr 2010
Location: Tucson, AZ
Posts: 44
Default Re: insulating gas grill lid?

so I have experienced and read others with the problem of insufficient heat from above (since there is no refractory dome). How do others arrange the heat/stones to try to equalize the large amount of heat coming from the underside of the pizza?
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  #10  
Old 04-12-2010, 09:07 PM
Laborer
 
Join Date: Mar 2009
Location: Monterey Bay, CA
Posts: 80
Default Re: insulating gas grill lid?

Tyler,
In my case, I do have a single pizza stone mounted to the lid. And since this top stone is at the top of the lid, this is where all the heat rises to, it does heat up quick. As far as the lower stone is concerned, I use two stones, doubling the mass, which is mainly heated from below. I also use a perferated pan right over the flame, to help disperse it around the bottom of the lower stones. Remember, you have reflective heat from the dome, radiated heat from upper stone/mass, direct contact heat from the lower stone, and convective heating from hot air flow.

What does this all mean? - I have not a clue! Seriously, it does all seem to balance out well (in my case).
Ed
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