Author Topic: The Rotisserie Pizza Grill  (Read 16369 times)

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Offline Tampa

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The Rotisserie Pizza Grill
« on: February 09, 2010, 05:25:54 PM »
A standard gas grill can be easily converted into a great pizza oven.  In my case, I’ve been able to achieve stone temperatures up to 850 F in 40 minutes, using only two burners.  I posted two youtube videos, one shows making pizza, and the other shows the oven design.  Just do a search on "Rotisserie Pizza Grill" and both videos will immediately appear.  (Sorry, I tried to hyperlink but am not allowed as a "new member".)

By way of background, I love the “Little Black Egg” design.  I was about to build my own egg when I realized that it wouldn’t fit on the patio.  (But I still yearn for the sound of the LBE, roaring like a 747 at the beginning of a short runway.)

My neighbor buddy, “Bob, the Pizza Doctor”, has a professional Cecilware oven running on 220 volts.  But, I’m no doctor.  I’m more of a frustrated engineer, with kids in college (read: broke) and a big appetite for good pizza.

Here were my design goals
•   Use the propane grill I already have
•   Make it dual purpose (grill or pizza oven)
•   Inexpensive to build
•   Energy efficient
•   Short TTP – Time To Pie

After some experimentation, I met with success in “Rotisserie Pizza Grill 1.0”.  RPG 1.0 was simply a free Craigs List grill cover that fit inside my existing larger grill.  I used only one bottom burner plus the side rotisserie burner to achieve separate control of the top, and bottom, of the cordite stone temperature.  RPG 1.0 also included a pin mounted to the center grate to enable manual rotation of pizza stone.  In short, the pin sits slightly above the grill surface and, when located in the center of the cordite, it allows the stone to rotate freely.  Excellent results were achieved.  Remember: good enough is, good enough.  Stop reading now.

RPG 2.0 is where I got really stupid.  After days, and some sleepless nights, I fell in love with the idea of converting the automatic rotisserie motor into something that turned the stone at 700 F or more.  The design that finally worked reliably is shown in the videos.  With RPG 2.0 I cut down the oven hood and enjoyed a dramatic reduction in the TTP.  As an example, the original full-sized Craigs List hood took approximately 40 minutes to reach 650 F while this low-profile hood took only 22 minutes and I like saving propane almost as much as eating pizza.  I also added a door on the oven with 2.0, with a slot borrowed from the LBE, so that all the hot convection air would flow over the pie and out the front.  Where does one find bearings that operate in an open flame?  Good question.  It turns out that those bronze bushings at Ace Hardware, that spec out at 650F work fine (up to at least 850 F in my tests).

I’m trying to remind myself that I’m in the “pizza eating business” not the “oven design business”, but it’s hard not to think about RPG 3.0 and 4.0.  In 3.0, I’m thinking about the absolute minimum volumetric hood over my 16” stone – something like a round Weber grill lid morphing into a rectangular back so I can still use the rotisserie burner.  If done properly, I might be able to cut the TTP from 30 minutes to 20.  In RPG 4.0, I’m thinking about pizza parties with friends, and making a lot of pies in a short period of time.  In that case, I’m confident that rotisserie motor has more than enough power to turn two stones at once.  By locating two drive wheels where adjacent stones would (almost) touch, the stones would rotate in opposite directions (think crazy eyes in TV cartoons).  In this configuration I would have three underside burners available and one rotisserie burner.  I’m quite sure it would work, but I’m trying not to think about it and just enjoy the pie.


Offline Jack

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Re: The Rotisserie Pizza Grill
« Reply #1 on: February 10, 2010, 12:02:35 AM »
Dave,

Step away from the BBQ Grill.  You've gone off the deep end.  <Grin>

Hey, nice work on the Grill.  I'm impressed!!!!  I only found one video, and it didn't show a pie cooking, but I"ll you are having some fun with being able to hold that temperature.

Enjoy!

Jack


Offline mike_b

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Re: The Rotisserie Pizza Grill
« Reply #2 on: February 10, 2010, 12:00:29 PM »
Dave:

Very impressive! I like this outside-of-the-box engineering!

Jack:

If you want to see both videos, copy the following into your browser's address bar, and replace the [dot] with actual periods:

www[dot]youtube[dot]com/profile?user=MrTampaDave

I would have pasted a real URL, but I am still a new member.
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Offline Tampa

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Re: The Rotisserie Pizza Grill
« Reply #3 on: February 10, 2010, 04:51:22 PM »
Thanks for the kind words.

For those interested, here are a few pictures.

Dave

Offline Tampa

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Re: The Rotisserie Pizza Grill
« Reply #4 on: February 10, 2010, 05:03:17 PM »
View from outside, oven hood "on blocks" to aid view.

Offline solorbob

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Re: The Rotisserie Pizza Grill
« Reply #5 on: April 13, 2010, 11:23:14 PM »
Great idea.  We just got a new gas grill about two weeks ago, so I think it is time I turn this baby into a pizza making machine.  I'm guessing a lower profile inner cooking chamber will bring the temp up quicker, and since I'm planning on making my own inner piece, it should be no problem.

I was toying with the idea of a temporary brick pizza oven just to do something quick, but this looks much faster and cheaper.

I'll keep you posted on my progress.

Offline Tampa

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Re: The Rotisserie Pizza Grill
« Reply #6 on: April 14, 2010, 08:45:13 AM »
Thanks Solorbob.

I've improved the simplicity and reliability of the rotisserie design.  Pls take a look at this thread:
http://www.pizzamaking.com/forum/index.php/topic,9614.0.html

In addition, I've run a bunch of temperature tests using only the bottom burner, only the top IR burner, and combinations of both.  When time permits, I'll post the data in the hope that it help others predict how their grills will perform.  With a little luck, someone will improve my grill implementation.

Dave


Offline Tampa

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Re: The Rotisserie Pizza Grill
« Reply #7 on: April 30, 2010, 01:06:09 PM »
Hopefully this note will post and be comprehensible.  I've run a lot of tests of various grill configurations and have simplified the data down to a few pictures and a graph to illustrate the results.

Offline Tampa

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Re: The Rotisserie Pizza Grill
« Reply #8 on: May 18, 2010, 05:14:03 PM »
Time to fess up.  I need to make another change to the RPG.  It turns out that the 3/8" drive shaft, made out of mild steel, has a nasty habit of oxidizing in 700-800F temperatures.  I heard it squeaking the other day and saw that rust was interfering with proper operation of the bronze bushing.  There are two ways I can see to resolve this.  Either use a stainless steel shaft or rely on a simple thrust washer or two and remove the bronze bushing.  I'll probably try both.  For starters, I've got some stainless steel coming off ebay for $12.

Offline Tampa

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Re: The Rotisserie Pizza Grill
« Reply #9 on: June 07, 2010, 05:27:16 PM »
I think the stainless 3/8" drive shaft is a winner.  I've cooked a dozen or more pies at 700-800F since replacing the mild steel with stainless, and there aren't any signs of oxidation - a bargain for $12.  The rotisserie is so quiet that I don't know if it is turning the stone unless I look under the lid.  Thanks to all the borrowed ideas from contributors to this forum, I'm very happy with the reliability of this system.
Dave


Offline Jackie Tran

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Re: The Rotisserie Pizza Grill
« Reply #10 on: June 07, 2010, 05:46:58 PM »
Dave, any pictures of current pies?  We'd love to see them.   ;)  Your gadget is definitely one of the coolest pizza ovens I've ever seen.  Bravo!

Offline Jack

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Re: The Rotisserie Pizza Grill
« Reply #11 on: June 08, 2010, 03:26:57 PM »
Dave,

Again, nice work. 

FYI - While I'm sure my build is a ways off, I've started acquiring parts in a box in the garage.  <Grin/rolls eyes>  I'll have to incorporate some Oxy/Actelene jets for faster warmup.  <kidding!!!>

Jack

Offline Tampa

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Re: The Rotisserie Pizza Grill
« Reply #12 on: June 08, 2010, 06:08:53 PM »
Jack - you had me all excited for a second or two!

Tranman - we'll be having pie tomorrow & I'll snap a picture or two.

Dave

Offline Tampa

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Re: The Rotisserie Pizza Grill
« Reply #13 on: June 09, 2010, 07:24:11 PM »
Here are pictures from today's pizza.  These are "Mellow Mushroom" type pies w/ a bit of molasses in the dough.
Dave

Offline widespreadpizza

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Re: The Rotisserie Pizza Grill
« Reply #14 on: June 09, 2010, 07:29:01 PM »
Tampa,  I finally had the mellow mushroom pizza a couple months ago and was not very impresssed.  Yours looks much better,  is it whole wheat based?  -Nice job  -marc

Offline Tampa

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Re: The Rotisserie Pizza Grill
« Reply #15 on: June 10, 2010, 08:59:37 AM »
Thanks Marc.

I appreciate that not everyone likes the "Mellow" pie.  For most folks a great pie is based on a pizza experience at some prior time, so it is naturally different for different folks.  For me, I've had a lot of good pizza over the years and the Mellow Combo pie was a good one.  (BTW, the Mellow folks don't use whole wheat flower, only molasses to achieve the darker color.  Also, they 'paint" garlic butter around the rim when it comes out of the oven then dash on grated parm.)

In fairness, I made two pizzas yesterday and the photos above are a hybrid of the two, taking only the best shots.  Like others striving to create the ideal pizza, I've got "issues".  In this batch, I didn't get as much "poof" as I would like especially on the first pie and the underside was a little over-charred on the ingredients side.

It would help if I had more recipe experience and expertise like Pete-zza and others.  I'm still more of an Oven Head, trying to figure out how to map and visualize convection currents.  If anyone knows the answer, let me know.  I know that a smoldering cigarette shows a little bit of current and have heard of smoke producing items for parties and such, but none of those seem appropriate for oven design.

Offline Jackie Tran

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Re: The Rotisserie Pizza Grill
« Reply #16 on: June 10, 2010, 10:19:51 AM »
Very Nice Dave, thanks for the pics.  Gives us all an idea of what is possible with a modified gas grill.  I can see the crunchiness of the crust and the cheese is melted perfect.  Nice work! 

Offline Jack

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Re: The Rotisserie Pizza Grill
« Reply #17 on: June 10, 2010, 01:07:38 PM »
a bit of molasses in the dough.

Dave,

It's good to know I'm not the only one cooking with molasses.  I use a lot of it in my fish and fowl brine solution to prep them for my smoker and the flavor is great for all sorts of cooking.  While I hate to admit it, because we are pretty health conscious family, I buy molasses by the gallon.  <blush>

I'm still more of an Oven Head, trying to figure out how to map and visualize convection currents.

While I've used cigarettes and punks for figuring out air current flow in a house with a wood stove, I attribute most of the heating in a oven to radiation and conduction, especially if you have a stone or two in there blocking a lot of the flow.  I just don't see convection making a big impact in in an oven. 

Since I've started using a top stone, for heat only, it's been far easier to manipulate the finish on my pies top to bottom.  I am trying to emulate a typical pizza oven.  I started with one stone on the bottom and one on the top rack.  I've moved them both up and down, but settled on the top and bottom racks.  It gives me a nicely finished crust and gets the top fully cooked at the same time.  This is at 525F in an electric home oven. 

Do you have room for a second stone on top, inside the inner lid?  Your foil liner reflects heat, but when you slide a room temperature pie in there, the foil has very little heat to reflect, so you are relying on conduction through your stone and whatever convection is available to get heat to the top of the pie.  See if you can't get a top stone in there somehow, even if it's a thin one attached to your inner lid, because without the chilling effect of placing a pie on it, it should stay pretty constantly hot throughout your cook.  You could try getting rid of the foil.  If that inner liner is hot, it should radiate.  The foil may be insulating the inner hood from the pie.

Jack
EDITED for clarity, as English is a second language to an engineer.
« Last Edit: June 10, 2010, 01:46:58 PM by Jack »

Offline Tampa

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Re: The Rotisserie Pizza Grill
« Reply #18 on: June 11, 2010, 03:35:25 PM »
Hi Jack,

Punk - that's a great idea.  Hadn't thought of that.  BTW, I saw another post somewhere that you were near Seattle.  Although I now live near Tampa, I went to high school in Bremerton.  Filippis - back in the day, that was good pie.

I've got room for all kinds of stuff in that grill, including a top stone.  But I'm an impatient tree-hugger and 25 minute "go time" and two burners of propane is my current benchmark.  You are right that conduction and radiation seem to dominate pizza cooking, IMO.  (I have to add IMO these days b/c I keep finding out that my college grades were generous given my oven skills.)  The bottom of the pie experiences conduction from the stone and the top of the pie experiences radiation from the upper IR burner in my case.

If I put a stone on top, it will take time to warm up.  I've read through a lot of the LBE information and believe that a top stone isn't necessary if you just properly convect the underside burner heat over the top of the pie before exiting the egg.

Although I'm happy with what I've got, it bugs me that there may be more optimization if I could just see the heat flow.

Dave

Offline Jack

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Re: The Rotisserie Pizza Grill
« Reply #19 on: June 11, 2010, 06:15:30 PM »
I'm right there with the generous grades.  <grin>

So the egg folks cook pizza before the sides and top of the egg get hot, i.e., within the first 30 minutes also?  Hmmmm.

I forgot, you like to emulate The Flash, while making pizza. <grin> I also forgot you use a side firing radiant burner.  Unfortunately, it's not angling much heat at the pie; mostly straight across the grill.  At a minimum, get rid of the foil and see if that helps.  If it does, try a piece of sheet steel as a radiating panel.  Something that will catch the extra heat from the side burner and angle it down at the pie.  All you need is something up there that will radiate when it's hot.  While it would be a bonus if it retains heat, it does not have.  Basically, bring the insde of the lid closer to the pie, to get the maximum radiant heat to the top of the pie.

Any chance you can top mount that IR burner, or maybe lift it up slightly and angle it down towards the pie, so more of the heat is impinging directly onto the pie.

All of this is theory.  I am a ME and a PE, but I don't do thermo for a living and only played with burner for a few years.

Jack
Now in Covington, WA - 1 1/4 hour SE of Bremerton, via the highway, not the ferry, but born in NYC
« Last Edit: June 11, 2010, 06:44:08 PM by Jack »