My 900F BBQ Mod

[TXCraig1]

Here is what I've been using to cook my pizzas for the past year or so. The grill has 3 heavy cast iron burners along the bottom and an IR burner along the back. I run them all together (the grill does say not to do this...) and also build a small wood fire in the back corner. With this set up and the insulation, I can get the air temperature over 900F (in the summer), though I generally bake my pies at 750-775. The wood fire adds some heat, but I mainly started doing it for the flavor - that's the theory anyway. I can't say for sure if it adds all that much. My typical cook time is about 2:00 - 2:15.

To get the heat up inside the grill, I use two insulating blankets. The red blanket on the bottom is a double layer of ADL Insulflex 32oz Pyroblanket. It's designed for very high temperature industrial applications (such as protection from welding splatters) and can stop open flames without a problem. It doesn't have a whole lot of insulation qualities, but it brings the temperature down enough that I can a lay a Kovenex Rapid Response EMS Blanket, folded into four layers, on top. The Kovenex blanket is pretty good insulation and keeps the heat fairly constant.  Neither of these blankets burns or gives off any fumes or smell when heated, however I found out the hard way that the Rapid Response blanket will darken over time and eventually disintegrate if placed directly on the hot grill.

The stone is a FibraMent-D grill stone. It is thick and holds a lot of heat, and it comes with a metal pan that not only protects the stone from the flames but also reflects some of the heat down and away from the stone which allows me to keep the burner directly below the stone on high without the stone getting too hot.

Here is where I got the blankets:
http://www.adlinsulflex.com/fire-blankets/pyroblanket-32-oz
http://www.thefirestore.com/store/product.cfm/pid_3033_kovenex_rapid_response_blanket_professioanl_ems_10oz_58_x73_/

[tommy]

good looking pizza.

how long do you generally have to cook in that set-up?

[TXCraig1]

how long do you generally have to cook in that set-up?

typically 2:00 - 2:15

[pizza dr]

Love it .... That is one good looking pie dude. 

[Tampa]

TxCraig1
It turns out we have the same oven.  Like you, I use the bottom burner and back (rotisserie) burner to set the temp for bottom and top of the pizza stone.  Having not seen your post, I approached the problem differently and put a barbeque lid inside my larger grill.  The result is that I can get a stone temp of 700F in 20 minutes using only one bottom burner and the rotisserie burner.  I also moved the rotisserie motor from a side mount to a vertical mount where the motor is inside the storage door below.  Here's a picture.
Dave

[Jackie Tran]

Wow awesome mods guys! 

Tampa can you give us a little more detail on your setup?  Is the rotisserie inside the smaller lid facing down?  Tampa, it also looks like the smaller lid is lined with something, is that foil?

How long do you cook your pies for?  Also are both the bottom and rotisserie burners going the entire time of the cook?

[flyboy4ual]

Here's mine....

[Tampa]

Flyboy4ual - I love the idea of using the grill warming rack as an automatic, self-leveling, hood over the pizza.  I'd be tempted to use a light metal cover (instead of stones) to reduce swing-weight and warm-up time.

Tranman - I posted the rotisserie concept previously here http://www.pizzamaking.com/forum/index.php/topic,10241.0.html.  Since that time, I made several modifications, but the most significant one was moving the drive axis of the rotisserie from horizontal to vertical.  The rotisserie motor is under the stone, under the burner, down inside the cool cabinet below.  What you will (hopefully) see in the picture is a pipe flange with a 3/8" steel shaft going down through the burner to the underside of the grill.  I used an Ace Hardware bronze bushing in the steel cross bar to minimize rotational friction.  Since the bushing is only rated to 650F-ish, I used a now-tarnished copper pipe to keep the flame off the drive shaft and bushing.  If it still isn't clear, let me know and I can supply more info/pics.

Dave

[Bob1]

Tampa,
That is slick, and so simplistic.  Great idea.

Bob

[Jackie Tran]

I agree, that's some slick engineering!  Very creative thinking Dave.  I really like how you can get up to temps so quickly.  It's one of the most efficient setups I've seen yet.

[Jack]

Dave,

Never mind my PM.  The pics are here. 

Very nice.  Eloquent Engineering Dude!; You rock!!!  Simple, effective, very few moving parts, judicious use of rebar; sweet!

Once I get a break from ski patrolling, building RC planes, old British cars and other hobbies, I may need to duplicate your efforts.  This is a quantum leap in design.  The bronze bush is a nice touch, as is it's custom heat shield.

I only have two questions:

1. What carries the weight of the stone?
2. Can you post your calcs?  <kidding>

Jack, PE

[Bob1]

I assume he is using the idler bushings from his previous post.

http://www.pizzamaking.com/forum/index.php/topic,10241.0.html

Bob

[Tampa]

Thanks for the kind words.

All of the pizza and stone load is carried by the single cross member made of 1" square steel tubing.

I got rid of the pesky idler wheels & complexity in going vertical.  There is one trick that isn't obvious from the pictures.  The flange that carries the stone alone doesn't feel secure when placing a pizza with the peel (the whole thing feels tipsy).  I used a masonry bit to deepen the centering hole about 1/2" into the stone.  Since the drive rod is 3/8", the hole is 3/8" as well and the two fit snugly together.  The combination of the extended rod and mating hole, plus the flange, really does the trick in keeping everything stable while allowing a free flow of the underside burner heat to the stone.

The rebar may be a little confusing as well.  It doesn't have anything to do with the pizza rotisserie or hood.  The rebar is a substitute for the framework that held the stones in place (which rusted out).

If you see an improvement, pls post so we can all benefit.

dave

[Jack]

Ok, so it appears that it is the bushing transmitting the loads to the 1 inch square tube.  Good, I was hoping the motor shaft was not carrying the load into the motor bearings.  Is the bushing a tophat bushing; i.e., shaped like an old fashioned top hat, so it not only has the vertical cylindrical section for the rotation, but also a flat on the top to take the vertical load?

Having a well centered, snug fitting hole appears to be just one of the important criteria.  I wonder if you might be better off with a larger diameter flange. . . . . but if the stone is stable with the putting on and taking off of the pie and functions fine with some off-centering of the pie, the flange is big enough.

I guess my only point of confusion right now is what takes the load of the flange and transmitts it vertically into the 1 inch square tube.

Again, beautiful work.

Jack

[Ronzo]

The ingenuity of the folks on this forum is absolutely amazing and inspiring.


You folks ROCK!

[Tampa]

Jack - the tophat bushing, AKA flange bushing, is indeed taking the entire (~3lbs) load.  Of course there is only a gravity load from the stone and pie, and thus no side load, to speak of, on the bushing.  I kind of liked how the bushing drops into the steel cross member, and then expands w/ heat to snug up, so I stuck with it.  Alternatively, you could just buy a couple of bronze washers to take the load (and save a dollar or two) then drill a 3/8" hole for the shaft through the cross member.  I had a flange bushing, so that's what I used.

Also, everybody's pizza stone is a little different, but you might notice in the underside picture above that my stone has a thick spot in the center that is about 3" in diameter - a good fit for the pipe flange.  For me, a larger flange wouldn't help because it would extend past the support area of the stone.  The hole works great.

All - enough with the compliments.  I've got all kinds of hours doing stupid grill tests to try various rotisserie designs for simplicity and reliability.  Somewhere in a drawer, I have a degree which says I should be much smarter.

[Jack]

Jack - the tophat bushing, AKA flange bushing, is indeed taking the entire (~3lbs) load. 

Thanks for the confirmation on the top hat. 

I have a degree which says I should be much smarter.

C'mon, even Edison had a few permutaion on his designs.  The bottom line is that your design, the result of an evolution of ideas, is an effective design.

Perseverance - It's what keep Mechanical Engineers designing better weapon systems and Civil Engineers designing harder Targets!

Jack

[scottfsmith]

Tampa, you should check out the 2stone if you didn't see it already, your concept looks similar.  I have the grill version and have no problems reaching 900F to cook pies.

Scott

[Tampa]

Thanks scottfsmith.  I saw a 2stone video a few months back - at least I think it was 2stone's.  They must be putting out a lot of BTUs.  I see that flame impinging on the stone underneath like the LBE's jet powered backyard bayou burner.  For now, I have to lick my lips with envy.  Their 15 minute warm up time bests me by five minutes, and their max temperature of 900F scorches me by 50F (850F for me).

My best spin is a BOM under $20 (bill of materials) including the craigs recycled hood.  With all the experiments and modifications, I've reduced the inside volume as much as possible and think the upper limit in my grill is 850F.  If I were feeling rich, I guess I could turn on another underside burner.

[gtsum2]

wow, I just saw these mods and they look like they work great!  I seem to be a day late and a dollar short lately it seems!  I had a Lynx gas grill (if you know what they are, then you know how good they are and how hot they get ) and I sold it and my Stumps Smoker and picked up a Primo Ceramic cooker.....mainly to consolidate my cooking, but also thinking that I would be able to create great pizza's on the Primo!   Needless to say, there are some drawbacks using a BGE or a Primo as a pizza oven, and here I could be cranking my old Lynx up to 1000 degrees and for a few bucks had a great pizza oven!   I am almost tempted to pick u p another gas grill but I think the wife would about shoot me...she already thinks my LBE project is way out in left field!