Fabricated a Pizza Oven using old computer for Weber Grill

[petef]

My latest project here. I purchased a new Weber Genesis gas grill and then designed and fabricated a pizza oven using heavy guage metal from an old computer case and some unglazed quarry tiles with an aluminum frame to hold the tiles in place. My first few pizzas came out great! My initial attempts resulted in a 5 minute bake.

First some pics of the Weber Genesis pizza oven...

[petef]

Ok, now some pics of my first attempts at using this setup.

With the lid closed, I preheated about 30 minutes with 3 burners set on LOWEST heat. The tiles measured about 550 Deg F. using an IR digital thermometer.

I loaded the fully assembled pizza to the tiles, closed the lid and raised the 3 burners to MED heat. I opened the lid at 4 minutes to check for browness and removed the pie at about 5 minutes.

In one pic below you will notice that half the pie baked faster than the other half. This was due to having the tiles positioned all the way to the rear of the grill resulting in less heat to bake the rear half of the pie. I fixed that problem by positioning the tiles such that hot air could circulate evenly around all 4 sides of the tiles.

Immediately after baking a pie, I tried measuring the tile temperature but my IR thermometer can't read over 600 deg. F.,  so I was not able to measure the temp. In between pies, I'd lower the 3 burners to LOWEST heat and waited about 5 minutes before baking the next pie.

As you can see, I'm getting excellent browning on both the bottom crust and the top crust and i still have margin to raise the temperature from MED to HIGH to achieve a faster bake than 5 minutes.

[scott123]

Hey, that's pretty creative with the old computer.

Are those 6" tiles?  15" x 18" hearth?

The tiles seem a bit on the thin side- when you crank the burners to high during the bake, there's a slim possibility the intense heat might make it through the tiles and burn the bottom- even in 3-4 minutes. Even if the heat doesn't travel that far, the next pizza's going to get scorched.  You might be better off with firebrick splits. It's a shame this grill can't handle 18" x 18"/8 firebricks.

You may not need clearance on all sides. If I were working with a genesis, I might go with a hearth that's 17 x 19 and make 16" pizzas.  The 17" dimension won't allow much air to flow, so the rim in the front and back won't burn and the rim that's 1.5" in from the sides of the hearth should be far enough in to shield the pizza from the intense heat wrapping up and around from below. I know 17 x 19 isn't all that practical, but it gives you the largest possible pizza without exposing the rims to too much heat. 17 x 18 with 15" pies would also probably work well.

It looks like the tiles are getting a bit hot around the edges.  Firebrick should help with that also. 

[petef]

Hey, that's pretty creative with the old computer.

Are those 6" tiles?  15" x 18" hearth?

Yes it is.

The tiles seem a bit on the thin side- when you crank the burners to high during the bake, there's a slim possibility the intense heat might make it through the tiles and burn the bottom- even in 3-4 minutes. Even if the heat doesn't travel that far, the next pizza's going to get scorched.  You might be better off with firebrick splits. It's a shame this grill can't handle 18" x 18"/8 firebricks.

If bottom burning becomes a problem, I'll try adding a metal plate or maybe switch to a store bought stone.

You may not need clearance on all sides. If I were working with a genesis, I might go with a hearth that's 17 x 19 and make 16" pizzas.  The 17" dimension won't allow much air to flow, so the rim in the front and back won't burn and the rim that's 1.5" in from the sides of the hearth should be far enough in to shield the pizza from the intense heat wrapping up and around from below. I know 17 x 19 isn't all that practical, but it gives you the largest possible pizza without exposing the rims to too much heat. 17 x 18 with 15" pies would also probably work well.

Good suggestions, but 14" is about the largest I'd like to go. Mainly because the way I store my pizza 
and how it fits into the plastic containers that I use.

BTW: If you remember this.. http://www.pizzamaking.com/forum/index.php/topic,18385.0.html
That was the thread that led me to buying the Genesis Grill and helped me design the pizza oven insert. Thanks again for all your help and suggestions!

---pete---

[atom]

That is beautiful and looks much more simpler then what i was thinking of concocting. I'm gonna keep my eyes out for some type of chassis to do something similar.

[bfguilford]

That's really ingenious (that kind of thinking kind of reminds me of kits that converted the first generation Mac to a small aquarium). I guess it wouldn't work nearly as well with an old laptop.

I'd really like to get out of the kitchen for summertime pizzamaking.

[pizzaneer]

Very creative use of stuff!  My wife yells at me whenever I bring home junk, but after I turn it into useful things, the yelling stops.  Nice job.

Your next step may be to add some thermal mass to the top, and increase your density on the bottom, per Scott's suggestion.  Try filling the oven area except for the rear, leaving about a 2" gap.  This will allow airflow to heat the top mass.

Looking forward to seeing your further efforts, your pies look great!

[Chicago Bob]

What does the "sear station" knob do Petef?   Thanks!

[petef]

What does the "sear station" knob do Petef?   Thanks!

If you look at the pic of my grill you will see 3 large knobs where the 3 main burners are located.  So you have 3 flavor bars over those burners plus 2 additional flavor bars between them. The concept for normal grilling is that the additional 2 flavor bars get hot and radiate heat even though there is no flame burning directly under those 2 bars. This results in fairly even heat across the entire grill surface. For EXTRA intense heat there is a 4th burner where you see the SEAR STATION (smaller knob), which puts a flame under the second flavor bar. This means the first 3 flavor bars have a flame burning under them, resulting in very intense heat for used for searing meats.

---pete---

[petef]

Very creative use of stuff!  My wife yells at me whenever I bring home junk, but after I turn it into useful things, the yelling stops.  Nice job.

Before I throw something out I look at it for it's value in raw materials. I'll keep or cut out the valuable materials and scrap the rest. I had saved that old computer case because it had large flat areas of heavy gauge metal. I know if I had to buy similar metal at Home Depot, they don't even sell that heavy a gauge sheet metal and the thinner stuff they do sell goes for about $30 for one just one sheet about 15" by 24".

---pete---

[buceriasdon]

Pete, I too wanted to commend you for the great looking pie and grill mod. Nice job all around.
Don

[PizzaHog]

Brilliant, cost effective, simple, and earth friendly too!  Can't wait to see what you try next.  Too bad "Pizza Hacker" is already taken.  Well done!     

[petef]

This is my second try using my custom pizza grill oven. This time I documented the temperatures at various locations and changed the burner settings shooting for less heat directly under the hearth and more heat for top side baking.

This Weber Genesis grill has 3 main burners that run front to back, enabling me to lower the center one for reduced hearth temperature and raise the outer ones for increased top side baking. Using an IR thermometer, I measured the temperatures at... Hearth center tile, and Top center surface of oven sheet metal.

Process as follows:

Note: Mainly for flavor, prior to baking, I brush the outer rim of
the dough with an emulsion of olive oil, butter, and garlic.

1.) Set 3 burners to MED/MED/MED heat for 30 minutes with lid closed.
Hearth=645 F, Top sheet metal=535 F

2.) Set 3 burners to..  HIGH/LOW/HIGH for 10 minutes with lid closed.
Hearth=650 F, Top sheet metal=580 F

3.) Load pizza to hearth and bake 4 minutes with lid closed.

4.) Open lid to check for browning and bake about 1 minute more
with lid closed.

5.) Remove pie and immediately measure hearth center tile.
Hearth=550 F

Excellent results, no bottom burning and top bakes well on this 12 inch pie.  

[pizzaneer]

For just a second attempt, your pie looks great!  Nice spring, decent crumb, evenly cooked - you had a win!

I'm curious whether your grill has a front vent in the hood.  In the LBE setup, without a vent to set the airflow, the hot air essentially gets trapped, ruining the convection aspect that provides the top char.

Could you take a pic of the grill with the lid shut?

Would you be willing to make a vent in the lid, or fabricate some skirts that would allow you to prop up the lid about 1", but seal the grill except for a 1" high by 3" long gap in the front?.

Not that I'm encouraging you to have the same issues that everyone else has, since you are meeting with such good results already - I just wonder whether you could achieve a NY/NP hybrid.

[Chicago Bob]

Pete
Fantastic hack...you have ingenuity plus!

Brian,
You crack me up bro!    The man has a brand new Weber Genesis an already you want him to go cut'in on it...    you gonna get that boy in trouble   
You guys are great fun, thanks!!   

[petef]

I'm curious whether your grill has a front vent in the hood.  In the LBE setup, without a vent to set the airflow, the hot air essentially gets trapped, ruining the convection aspect that provides the top char.

Could you take a pic of the grill with the lid shut?

Would you be willing to make a vent in the lid, or fabricate some skirts that would allow you to prop up the lid about 1", but seal the grill except for a 1" high by 3" long gap in the front?.

Not that I'm encouraging you to have the same issues that everyone else has, since you are meeting with such good results already - I just wonder whether you could achieve a NY/NP hybrid.

Here's a pic you can zoom in on.
http://www.hayneedle.com/sale/webergenesise330gasgrill.cfm

I'm still not done experimenting, and I would like to see if I can get more heat to the top side. I'm thinking that a vent in the grill lid is not going to help all that much if the internal oven I created is the main bottleneck for air flow. So I could test your theory about air flow by boring a vent hole into sheet metal of the oven I created. I could also attach some sheet metal to the front of my contraption and then simply lift the Weber grill lid to facilitate air flow.

Before I go to all those extremes, I have some other possibilities:

* Remove the flavor bars on the outer 2 burners to allow heat to flow upwards more freely.

* Raise the hearth towards the oven ceiling which will be hotter for top baking.

* Begin the baking cycle with the hearth preheated to a lower temperature and then put all 3 burners on HIGH for the bake.

* Add more mass to top of the sheet metal using plates of steel, or iron or even tiles as a means to hold more heat in.

* Add insulation or some kind or heat blanket over top of the sheet metal as a means to hold more heat in.

* If the above 2 experiments resulted in very little change for increased top heat, then it might make sense to add top venting to my oven contraption.


Ok back to the airflow issue of the LBE. Can you point me to a thread that has pics and discusses that venting solution?

---pete---

[pizzaneer]

sure, I'll do my best to point you to a post that has all the info you need -  the thing is, the entire thread is basically about solving that issue.  Like your setup, bottom heat is never a problem.  It's getting more heat to the top that is the big deal.

What we found over the course of 7 years of tinkering is that:
1. you MUST have a vent in order to have good airflow from the burner to the top of the cooking chamber.
2. You CAN direct that air using baffles, or let the air heat a top stone.  Baffles work better in getting the heat down onto the pizza.  The shape, size and direction of the baffle are entirely up to you - seems like everyone who builds an LBE has come up with a different shape.  They all serve the same purpose, so it's hard to point one out that is "best".

Like you have theorized, we basically let the stone come to baking temp, then launch the pie with the gas turned up to provide more top heat.  The top heat should be about 20% higher than the stone temp.  If the air is coming straight from the burner at high velocity, no problem.  If you have slowed it down by not providing a path to follow, it will cool off by the time it gets to the cooking chamber.

Here's the thread... like I said, the issue has been discussed ad nauseum, over and over.  Skim it if you like.
http://www.pizzamaking.com/forum/index.php/topic,4753.0.html

[petef]

Here's the thread... like I said, the issue has been discussed ad nauseum, over and over.  Skim it if you like.
http://www.pizzamaking.com/forum/index.php/topic,4753.0.html

Thanks, for anyone else following this issue, I think that REPLY#20 on PAGE 2 of the thread above best describes the air flow issue on a LBE pizza oven. The video below best demonstrates it.  

<a href="http://www.youtube.com/watch?v=T1maPZLe_zo&amp;feature=relmfu" target="_blank" class="aeva_link bbc_link new_win">http://www.youtube.com/watch?v=T1maPZLe_zo&amp;feature=relmfu</a>

pizzaneer, after quickly reading the thread and watching that video, my impression is that the LBE is much more sensitive to the "air flow" problem than my Weber Genesis is. Reason being, you can literally hear the fast moving rush of air on a LBE, whereas, on a Weber Genesis there is no sound that I can recall. I'll pay closer attention next time.

With all that in mind, I'm thinking that adding a top vent into my pizza oven contraption might help a bit to increase air flow and top baking temperature, but the affect might not be as dramatic as is with a LBE pizza oven. That's my best guess, but perhaps someone else here has experience or first hand knowledge who can shed more light on this "air flow" issue as it applies to my Weber Genesis pizza oven contraption.


One after thought... I just looked up the BTU rating of my Weber Genesis 3 main burners and the combined output is 38,000 BTUs. The burner in that LBE grill is 117,000 BTUs and that's all concentrated into a tiny egg style oven. So I think we are just kidding ourselves if we think we can get similar results in my grill. There's just not enough BTUs to do the job.

---pete---

[Chicago Bob]

Sorry, I can't remember his name right now but you might be interested in his mod....removed the rotisserie infra and put it face down in the middle of his brick ceiling. Those things don't work well anyway for the use they were intended. Actually, I have one an never used it....it's yours if you want to play. Jus let me know....

Bob

[petef]

Sorry, I can't remember his name right now but you might be interested in his mod....removed the rotisserie infra and put it face down in the middle of his brick ceiling. Those things don't work well anyway for the use they were intended. Actually, I have one an never used it....it's yours if you want to play. Jus let me know....

Bob

Bob, I think you hit the nail on the head! More BTUs is what my system needs in order to get results similar to that LBE pizza oven. I appreciate the offer. Thank you. I'll keep it in mind.

At this point in time, I'm just happy to get a 4 to 5 minute bake and the results are better than I ever got in my home kitchen oven. With some more experimentation, I may still have some room for improvement on my Weber grill. I'll keep you posted on my progress.

---pete---