Author Topic: Little Black Egg  (Read 355695 times)

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Offline chaspie

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Re: Little Black Egg
« Reply #1880 on: March 22, 2013, 07:05:19 PM »
Villa Roma's (formerly ronbro at the start of this thread) original LBE design had a top vent and no side vent.  The switch to a permanently open side vent and/or pizza launch portal and the subsequent abandonment of the top vent came along pretty early in the development of the LBE.   I think the side vent facilitates the effective use of a high pressure burner that is capable of producing an intense flow of air.  I just wonder if the original LBE top venting arrangement might still be capable of producing a 2 minute pie if a lower output heat source is used and radiant heat from above is more effectively harnessed, as in your MPO.  I'm just not sure if I can explore that avenue any better than those who started down that path in the beginning.



Offline chaspie

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Re: Little Black Egg
« Reply #1881 on: March 22, 2013, 07:16:14 PM »
I like the idea of using a steel plate underneath the bottom cooking stone to protect it from direct flame, so I have some questions for anyone who has gone that route. 

How thick does the steel need to be to resist warping?  I don't want any more weight or expense than necessary.  I know at least a couple of people have used 1/4 inch steel.  Would 3/16th's or even 1/8th inch work as well, or would the thinner steel be more prone to warping?  Is the thermal mass, conductivity, or emissivity of the steel important to consider?  It would take longer to heat the oven with 1/4 inch thick flame deflector than with a thinner one.  A thinner one would be lighter and cheaper, most likely. 

Next, how much of an insulating air gap should there be between the steel plate and the bottom stone?  Is 1/8th inch enough?  Is 1/4 inch too much?

Offline MightyPizzaOven

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Re: Little Black Egg
« Reply #1882 on: March 22, 2013, 07:38:18 PM »
What size of plate you are looking for?


do a search for "heat diffuser" on google, they range between 6" to 8"

https://www.google.com/search?q=heat+diffuser&rlz=1C1CHFX_enUS526US526&aq=f&oq=heat+diffuser&aqs=chrome.0.57j65l2j0l3.11484&sourceid=chrome&ie=UTF-8

Edited:  That's too small for what you are trying to do.



« Last Edit: March 22, 2013, 07:51:07 PM by MightyPizzaOven »
Bert,

Offline chaspie

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Re: Little Black Egg
« Reply #1883 on: March 22, 2013, 09:11:10 PM »
It's a 22.5 inch Weber, and what I'm thinking right now is that I want the sheet of steel to fit inside, sitting on a couple of horizontal lengths of rebar pierced through the kettle below the bottom stone location.   The bottom stone will be positioned above the steel with an air gap. 

I'll have a metal shop cut a disc of steel to my measurements and lop off a section (a chord).  The chord cut will be positioned at the back of the kettle opposite the side vent to force most of the air to follow that path to the top. 

Nothing new here.  This is how most of the LBEs I've read about in this thread were built, although not all of them use steel plate below the bottom stone.  Some use two stones, some only one with bricks or broken tiles or lava rocks below to break up the direct flame.

Offline Chicago Bob

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Re: Little Black Egg
« Reply #1884 on: March 22, 2013, 09:14:54 PM »
It's a 22.5 inch Weber, and what I'm thinking right now is that I want the sheet of steel to fit inside, sitting on a couple of horizontal lengths of rebar pierced through the kettle below the bottom stone location.   The bottom stone will be positioned above the steel with an air gap. 

I'll have a metal shop cut a disc of steel to my measurements and lop off a section (a chord).  The chord cut will be positioned at the back of the kettle opposite the side vent to force most of the air to follow that path to the top. 

Nothing new here.  This is how most of the LBEs I've read about in this thread were built, although not all of them use steel plate below the bottom stone.  Some use two stones, some only one with bricks or broken tiles or lava rocks below to break up the direct flame.
Brian uses a plate.
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Offline chaspie

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Re: Little Black Egg
« Reply #1885 on: March 22, 2013, 09:22:22 PM »
Would that be pizzaneer Brian?  I was just reading his build thread that he pointed me to yesterday.   Blue Bay LBE - in Baltimore MD.  What he did is exactly what I'm talking about and was my inspiration.  I didn't see in there where he mentioned the thickness of the sheet, but I know some people have used steel as thick as 1/4 inch.
« Last Edit: March 23, 2013, 08:32:44 PM by chaspie »

Offline Chicago Bob

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Re: Little Black Egg
« Reply #1886 on: March 22, 2013, 09:56:55 PM »
Would that be pizzaneer Brian?  I was just reading his build thread that he pointed me to yesterday.   Blue Bay LBE - in Baltimore MD.  What he did is exactly what I'm talking about and was my inspiration.  I didn't see in there where he mentioned the thickness of the sheet, but I know some people have used steel as thick as 1/4 inch.
Yes pizzaneer....Brian is very helpful to others.  I believe he used something quite thin chaspie...hopefully he will be here soon and clarify this(I don't mean to be sending you on a search mission ;))

Bob
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Offline shuboyje

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Re: Little Black Egg
« Reply #1887 on: March 22, 2013, 10:07:58 PM »
If I recall correctly from a few months back, Marsal and Sons Deck ovens use 10 gauge deflectors between the burner and the stone.  That is a quality commercial oven. 
-Jeff

Offline chaspie

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Re: Little Black Egg
« Reply #1888 on: March 22, 2013, 10:35:29 PM »
OK, 10 gauge is a bit more than 1/8th inch (0.1345 if steel).  The Marsal and Sons deck ovens are natural gas fired from a 3/4 inch supply, so probably some hefty BTU, and engineered for their ovens.  I wonder how it compares to a high pressure propane cone burner?  I know that propane burns hotter than natural gas.

Offline Chicago Bob

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Re: Little Black Egg
« Reply #1889 on: March 22, 2013, 11:07:24 PM »
OK, 10 gauge is a bit more than 1/8th inch (0.1345 if steel).  The Marsal and Sons deck ovens are natural gas fired from a 3/4 inch supply, so probably some hefty BTU, and engineered for their ovens.  I wonder how it compares to a high pressure propane cone burner?  I know that propane burns hotter than natural gas.
Actually, there is a big misconception about that.....propane is only about 45 degrees hotter....but in the realm we are discussing(1150)aprox. degrees) propane's advantage is insignificant.

However...natural gas can cost up to 1/6 less.  ;)   Most LBE units are portable and thereby necessitate the expensive propane tank, unfortunately.

Bob
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Offline chaspie

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Re: Little Black Egg
« Reply #1890 on: March 22, 2013, 11:45:51 PM »
Bob, as it turns out, I'm planning on firing mine with natural gas.  My main reason is the lower cost of NG versus propane, plus the convenience of not having to fill tanks.  I don't have any plans to use it outside my backyard, so it doesn't really need to be portable.  But I have a couple of propane burner stands too, so it can be portable if I want that.

Offline pizzaneer

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Re: Little Black Egg
« Reply #1891 on: March 23, 2013, 12:37:45 AM »
To finally supply my missing datum - sorry for the omission - my stainless steel plate is 1/8th thick, and is reinforced with the cooking grill. It has held up very well with minimal warping.

In my setup, it is not intended to be the sole support of the stone, but to channel the heat flow to the back of the LBE.  I didn't really want it to be a large thermal sink - I leave that task to the stone.

You could probably get away with using a large (22") round kiln shelf and cutting off a chord.  Support it with rebar if you like, or reinforce the original mount points for the cooking grate.
I'd rather eat one good meal a day than 3 squares of garbage.

Offline chaspie

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Re: Little Black Egg
« Reply #1892 on: March 23, 2013, 02:53:06 AM »
Brian, thanks for clarifying the thickness of your steel plate.  I'm glad to know that a thin sheet works well for air shaping and flame protection.

I am planning to buy a thick round kiln shelf for my bottom stone.  A kiln shelf can probably take direct flame safely, but I may be able to even out temperatures across the stone with the steel plate below it serving as a flame guard.  If there are cool spots, for example, I could perforate the steel under those areas to let more heat get through. 

I'm not clear about whether an air gap between the steel and the stone is necessary or advisable.  An air gap will act as an insulator.  It seems likely that it would increase the time it takes to get the stone up to target temperature.  If the stone is in direct contact with the steel, it should heat up more quickly.  But if the steel warps, it might stress or break the stone.  What are your thoughts about an air gap between steel and stone?

Offline pizzaneer

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Re: Little Black Egg
« Reply #1893 on: March 23, 2013, 06:37:54 AM »
I currently don't have an air gap under the stone.  So far so good.  I can only think that a cordierite kiln shelf will be even stronger than my soapstone slab, and better able to stand up to direct flame.

But as you noted, the steel likely serves to even out the impinging flame footprint.

You could refer to Boatman2's setup.  He incorporated all these current mods and nailed the results the first time out.

I'm certainly not going to discourage trying anything new - check out this mod: http://www.pizzamaking.com/forum/index.php/topic,23731.msg241031.html#msg241031
I'd rather eat one good meal a day than 3 squares of garbage.

Offline chaspie

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Re: Little Black Egg
« Reply #1894 on: March 23, 2013, 02:28:36 PM »
For reference, I found boatman2's build described back at reply #1824 in this thread. 

That wok burner setup in the link you posted is very cool too.  A successful build that doesn't utilize side venting.  I'm leaning toward the more typical side vent though, as the construction is a bit easier.  Still, the results were impressive with that configuration.
« Last Edit: March 23, 2013, 08:30:52 PM by chaspie »

scott123

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Re: Little Black Egg
« Reply #1895 on: March 23, 2013, 05:05:56 PM »
I'm not clear about whether an air gap between the steel and the stone is necessary or advisable.  An air gap will act as an insulator.  It seems likely that it would increase the time it takes to get the stone up to target temperature.  If the stone is in direct contact with the steel, it should heat up more quickly.  But if the steel warps, it might stress or break the stone.  What are your thoughts about an air gap between steel and stone?

Chuck, it depends upon the style of pizza that your striving for, but if you ever want to hit a 60 second bake (the holy Grail of LBE's), you want the air gap between the steel and the stone. In all 95 pages of this thread, no one has ever complained about too much top heat. The insulating effect of the air gap takes heat from the bottom and channels it up and over the stone. The hearth pre-heats just fine with hot air flowing over it as opposed to heat conducting through the steel below.

This hasn't been spoken about a great deal in this thread, but in recent months a lower conductivity firebrick has come to our attention.

http://www.pizzamaking.com/forum/index.php/topic,23596.msg240081.html#msg240081
http://www.wgpaver.com/firebrick-2/

The additional mass of the firebrick split will suck up a bit more fuel, but the lower conductivity will further handicap the bottom bake in such a way that it will go even further towards the 60 second holy Grail.  Cordierite kiln shelves are readily available and thermally durable, but they are, in my opinion, too conductive for bottom heat scenarios.

« Last Edit: March 23, 2013, 05:08:18 PM by scott123 »

Offline chaspie

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Re: Little Black Egg
« Reply #1896 on: March 23, 2013, 06:27:04 PM »
Scott, that discussion about the Whitacre Greer light duty firebricks in An Open Call to Ceramic Engineers- Reverse Engineering Biscotto di Sorrento is very interesting.  If I were to use some of those instead of a cordierite kiln shelf for my pizza stone, I'd need to devise a means of keeping them perfectly level with an air gap between the stones and the steel sheet below.  Aside from using two sheets of steel separated by an air gap with the bricks placed on the upper one, I can't think of a good solution.  Or do you suppose that the lower conductivity and thickness of the W-G splits would allow it to sit directly on the steel plate without an intervening air gap?

Edit:  fixed linked
« Last Edit: March 23, 2013, 08:31:29 PM by chaspie »

scott123

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Re: Little Black Egg
« Reply #1897 on: March 23, 2013, 07:01:56 PM »
Chuck, because of the potential for warping, I'm not a big fan of putting anything on steel. If I were doing it I'd put the firebrick splits on the Weber grate and suspend the steel deflector below it.

You might be able to, like Brian, sit the fire bricks on the steel, and the conductivity might possibly be sufficient, but I think hanging the deflector is a better bet. The most important aspect is that the deflector is larger than the firebrick on all sides so that the edges of firebrick don't superheat, and that there is a hole in the back/on the non-vent side to channel the heat up and around.

Offline Chicago Bob

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Re: Little Black Egg
« Reply #1898 on: March 23, 2013, 07:34:18 PM »
Is it me or are Chucks blue highlight links dead ends?
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Offline chaspie

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Re: Little Black Egg
« Reply #1899 on: March 23, 2013, 08:31:52 PM »
Bob, I fixed the links, I think.  Try again.


 

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