Author Topic: Oven dimensions / ratios  (Read 2716 times)

0 Members and 1 Guest are viewing this topic.

Offline biggrigg

  • Registered User
  • Posts: 12
Oven dimensions / ratios
« on: October 11, 2013, 01:35:13 PM »
So, I plan on adding more depth to this question as time goes on; but wanted to get some opinions on basics first.   I am designing a metal framed mobile WFO, to be insulated with ceramic board/rolls and small scale brick hearth.   Since my welding / metal work skills are yet to be developed I want to keep the design simple but not loose tract with proper oven dimensions .   I am thinking of a hybrid approach of a barrel dome the has been 'squared' off to octagonal arrangements.   Hopefully links below will illustrate what I am trying to achieve.

I building this on a Jamco service cart:
http://www.amazon.com/gp/product/B002TSAUHO/?tag=pizzamaking-20

that gives me a foot print of 24" x 36".   Looking at other smaller residential metal fabricated ovens, I am thinking that on overall interior dome height of 13.5".   That being said, a true octagon looks too boxy, and think I need to elongate the side to get more proper dimensions (does that make any sense?).  I but some links below to help with my lack of proper terminology.

so big question I have is,   if want to have a 24" wide, 13.5" tall semi octagonal dome;  what should the overall height of the sides be, what length should the top be, and what angle should the beveled sides come up as?  I guess the simplest way to say is, if I had proper dimensions of a true barrel oven, what the best way to square it up to ease fabrication but not loose ratios of a proper oven.

Any thoughts on this are welcomed.  Thanks for taking the time to help out.

-Rigg


examples:
This would illustrate roughly the top of the dome I had in mind
http://www.thirddegreehardware.com/collections/all/products/the-forgehaus

this is more of the hearth (below dome, sides down, obviously not round)

http://www.millarswoodovens.com/wood-ovens/product/view/1/1

I think this has more of the overall dimensions but with taller sides

http://uuni.net/products/uuni-pizza-oven


Offline biggrigg

  • Registered User
  • Posts: 12
Re: Oven dimensions / ratios
« Reply #1 on: October 11, 2013, 01:39:09 PM »
Here's a rough sketch of what I was thinking.  Hopefully not too hard to read.

http://i.imgur.com/ZRTNygK.jpg

Offline misterschu

  • Registered User
  • Posts: 200
Re: Oven dimensions / ratios
« Reply #2 on: October 11, 2013, 03:37:45 PM »
A 24" outer diameter circular oven is too small.  I built my oven on a 26" grill and it is simply too small.  I am satisfied with it for being used in the backyard of my rented apartment and as a proof of concept for my building technique.  However, the problems stems from the pizza sitting too close to the fire, requiring almost constant turning.  Fine because I'm not a commercial operation and only one pie can fit at a time regardless.  Further, size constraints mean that you have a smaller fire than ideal during cooking and smaller pizzas.

A 24x36 tunnel oven would mean you'd be putting the fire in the back of oven making the hidden side of the pizza cook more quickly than the visible side.  Not being able to see it's cooking progress on the fire side would lead to overcooking.   However, I think with careful management and enough experience on it you'd be able to manage fine.

Similar carts exist in 36x48 dimension, which would allow a Circular oven of 36" outer diameter, which is a much more common and useful size.  Or allow a 36x48 tunnel oven.

There's also the possibility of having on offset oven door on the long side of the cart, allowing the fire to be left or right of the pizza, rather than behind, for either of these dimensions.  I'm unsure about fire/heat/convection in this case, though I believe there's a post somewhere about a mortarless oven than experimented with an offset door.

In terms of dome height:  the forno bravo primavera 70 has a 27.5" floor (70 cm) and a 13.5" dome height.  but doing a search should help you learn more about dome height.

Offline biggrigg

  • Registered User
  • Posts: 12
Re: Oven dimensions / ratios
« Reply #3 on: October 11, 2013, 04:16:15 PM »
Thanks for the info.  24 is definitely on small side and would force the fire to the back of the oven.  Long story short, I got the cart 2 years ago when I lived in NYC and that was the widest I could get through my door.  Not the best forwarding thinking but I still going to push forward with the smaller cart.  Basically, I have the cart, insulation, chimney , 1.5" firebricks and custom cut 24x36x1.25 baking stone.   Just need to build the shell.  I wish I had thought this through better, but I will turn lemons into pizza pie.

Glad to hear the 13.5 inch dome height is found on similar sized ovens.  I am hopefully doing a card board mock up this weekend.  Which I plan to post here as well to get further feed back. 
« Last Edit: October 11, 2013, 04:54:09 PM by biggrigg »

Offline bbqchuck

  • Registered User
  • Posts: 381
  • Location: SoCal
Re: Oven dimensions / ratios
« Reply #4 on: October 11, 2013, 05:05:51 PM »
Given your dimensional limitations, have you considered a Blackstone or 2Stone?  I'm pretty sure a Blackstone will be cheaper than building a WFO of any size.

Offline biggrigg

  • Registered User
  • Posts: 12
Re: Oven dimensions / ratios
« Reply #5 on: October 11, 2013, 05:23:08 PM »
I haven't, mostly cause I am stubbornly set on building from scratch.  which in long run might be more $$ but at this point with all my supplies, it'll be cheaper to finish it by hand.  Unless I could get face value for my parts on craigslist, haha.

Offline biggrigg

  • Registered User
  • Posts: 12
Re: Oven dimensions / ratios
« Reply #6 on: October 11, 2013, 05:54:49 PM »
I did quick 'CAD' design in MS Paint of the front/back of the oven.   Outside of the small width, what do people think of the overall ratios?
Anyone cooking on a similar sized barrel oven?


http://i.imgur.com/OYKvzu3.png

Offline thezaman

  • Lifetime Member
  • *
  • Posts: 1908
  • Age: 61
  • Location: ohio
  • I Love Pizza!
    • lorenzos pizza
Re: Oven dimensions / ratios
« Reply #7 on: October 11, 2013, 08:56:09 PM »
 i had the same idea awhile back and used a cart ,but it was big enough to build a primever 70 on it. i used metal housing to keep the weight down and it worked really well. i think i have pictures if you are interested.

Offline shuboyje

  • Registered User
  • Posts: 1133
  • Location: Detroit
Re: Oven dimensions / ratios
« Reply #8 on: October 11, 2013, 10:37:11 PM »
Your design has no thermal mass and no insulation and is already at its maximum size..  You are far from worrying about ratios.
-Jeff

Offline biggrigg

  • Registered User
  • Posts: 12
Re: Oven dimensions / ratios
« Reply #9 on: October 12, 2013, 02:24:55 AM »
Zaman, would love to see photos if you have them handy.


shuboyje, the part of the design I am getting input on is only the internal structure of the oven.  I have actual put a lot of time thinking about creating the maximum thermal inertia (volumetric heat capacity) for the oven.   I am using refractory grade aluminum silicate insulation in combination fire bricks, cordierite stone and steel to create the best possible efficiency while actually keeping mass to a minimum.   The hearth will be about 5 inch thick of insulation board, brick and baking stone.  That part alone should weigh in around 300 pounds.   the whole dome will be covered in an additonal 3 inches of aluminum silicate blanket and a outer steel casing.   That should reflect the heat back into the oven quite nicely.  I know that 5 inch hearth seems thin, but this oven is on the small side,  it'll heat up quick and won't be pushing more than 5 or 6 pies at a time with it.   Don't need residual heat for baking.  So I think I am ok on that side.  The only thing I was concerned about what the dimensions of the interior dome, as I want good air flow to keep the fire hot and relatively soot free but without making me burn a lot of wood to keep temperature.  I haven't seen a lot of octagonal  barrel-esque designs, so not sure if that because they don't burn well or just something different. 
« Last Edit: October 12, 2013, 02:34:28 AM by biggrigg »


Offline shuboyje

  • Registered User
  • Posts: 1133
  • Location: Detroit
Re: Oven dimensions / ratios
« Reply #10 on: October 12, 2013, 09:35:24 AM »
You really want some mass in the dome, even an inch of castable refractory parted over the steel would be a huge improvement. You also want to ditch the baking stone.  The thermal conductivity is way to high for a wood fired oven and will throw the balance off.

I think the shape will be fine. 
-Jeff

Offline TXCraig1

  • Registered User
  • Posts: 12833
  • Location: Houston, TX
Re: Oven dimensions / ratios
« Reply #11 on: October 12, 2013, 11:04:13 AM »
Do your firebricks go inside the metal structure?

Are you going to insulate the walls or only the floor and dome? If you line the walls with 1.5" firebrick and insulate with 3" CF blankets, won't your internal width be <15" ?
Pizza is not bread.

Offline biggrigg

  • Registered User
  • Posts: 12
Re: Oven dimensions / ratios
« Reply #12 on: October 12, 2013, 12:03:10 PM »
What do most people use as cooking surface for their WFO?   Cordierite stone would conduct too much heat?  High potential for burning bottom of pizza before cooking the top?   I mostly got the stone to create a perfectly smooth cooking surface.  Is there a different material I should use?

Thanks.

Craig, the fire brick would only be used on the floor.  everything else would be insulation and steel.  very similar to this http://www.millarswoodovens.com/wood-ovens/product/view/1/1.     it would be off of the 24x36 cooking area, creating muffin top look.  since there ins't too much weight outside of the floor building it out over the footprint of the cart seemed doable. 

Offline TXCraig1

  • Registered User
  • Posts: 12833
  • Location: Houston, TX
Re: Oven dimensions / ratios
« Reply #13 on: October 12, 2013, 12:13:42 PM »
What do most people use as cooking surface for their WFO?   Cordierite stone would conduct too much heat?  High potential for burning bottom of pizza before cooking the top?   I mostly got the stone to create a perfectly smooth cooking surface.  Is there a different material I should use?

This seems to be one of the best options readily available:
http://www.wgpaver.com/wp-content/uploads/2013/05/Product-Data-Buff-Firebrick.pdf
http://www.wgpaver.com/wp-content/uploads/2013/02/Thermal-Conductivity-of-Firebrick.pdf

Having a smooth floor really doesn't matter much. You just don't want big gaps or steps that would snag your peel. If you are careful laying bricks, it will be perfectly fine.
Pizza is not bread.

Online Tscarborough

  • Lifetime Member
  • Global Moderator
  • *
  • Posts: 3477
  • Location: Austin, TX
    • Pizza Anarchy
Re: Oven dimensions / ratios
« Reply #14 on: October 12, 2013, 12:14:59 PM »
Sorry, but it is a poor design all around.  You want a discrete mass, well insulated and isolated.  Round is best, barrel is OK, and lastly would be a square.  Steel does not provide the correct type of mass to store heat.

Offline biggrigg

  • Registered User
  • Posts: 12
Re: Oven dimensions / ratios
« Reply #15 on: October 12, 2013, 12:53:51 PM »
Tscarborough, any resources you could point me to, to help me understand the fundamentals of oven shape?  I would like to understand why round is best.  Perhaps there are ways of creating similar heat currents in different shapes?  Also, when you say discrete mass do you just mean well insulated or something more to that?
« Last Edit: October 12, 2013, 12:58:19 PM by biggrigg »

Online Tscarborough

  • Lifetime Member
  • Global Moderator
  • *
  • Posts: 3477
  • Location: Austin, TX
    • Pizza Anarchy
Re: Oven dimensions / ratios
« Reply #16 on: October 12, 2013, 06:05:55 PM »
I mean a mass that is appropriate to the use of the oven.  If you plan on cooking 2 pizzas, use the steel.  If you plan on 10, you need 2-3 inches of refractory material.  If it is to be used for continuous, or occasional party use, you need 4-5 inches of mass.  By discrete, I mean isolated from the enclosure, and it needs to be insulated by a material other than the thermal mass itself.  Insulating brick do not work for thermal mass, steel does not work for thermal mass, sand is not an insulator, nor is glass, cobb, or tinfoil.

Shape is really preferential, a barrel oven requires more finesse, but you never put the fire in the back, it runs down the side.  A round oven radiates evenly and gives you the most square inches of usable floor space, and it needs to be large enough to allow you to move the pizza around to make for an even bake.

I have a barrel, 22"x36", and I use 4" of coals and fire on the left hand side, leaving me a very narrow area in which to cook.  I have to constantly turn the pizza or it will burn at Neapolitan temps.  I do not normally cook Neapolitan, so it is not an issue, but if that is what you want, you need to go round, low dome and as large as you can afford to heat.

There are other ratios and dimensions that are important, but until you wrap your head around the futility of a steel wood fired pizza oven, they do not matter.

Online Tscarborough

  • Lifetime Member
  • Global Moderator
  • *
  • Posts: 3477
  • Location: Austin, TX
    • Pizza Anarchy
Re: Oven dimensions / ratios
« Reply #17 on: October 12, 2013, 06:11:07 PM »
When I say narrow area, I mean 18", and I normally cook 16" pizzas, so it is really tight.

Offline biggrigg

  • Registered User
  • Posts: 12
Re: Oven dimensions / ratios
« Reply #18 on: October 12, 2013, 10:40:34 PM »
I appreciate the feedback.  I intentionally left out a lot details of the oven itself, which obviously left open for interpretation and scrutiny, mainly because I didn't want to type a novel.  I'm not good with words.   I'm good with ideas and concepts.   I don't think anyone here gets what I am truly doing so I tried to isolate the part of the oven that I wanted to get feedback on.    I know I am not building a replica of a Stefano Ferrara oven.   Anthony Mangieri is not slinging pies in my oven.  I am but one man, wanting to cook for my self.  I am interesting in learning real facts of ovens, preferably first hand and if failure is part of my learning experience so be it.  Everyone has an opinion about how things should be, and I respect that you came to understand the nature of your oven in a unique set of experiences but your experiences aren't mine.  so they are foreign to me and I don't truly understand.   you say my design is bad and lacks thermal mass etc etc etc.  I haven't even began to explain these things, nor did I really even want to get in such detail.     I would like to hear about specifics of oven shapes and why (preferable with some sort of documentation) that a partial octagonal shape would produce good/bad results;  while circular and spherical shapes would produce such exceptional results.  What is that difference?   Thermal currents?  conduction, convection, radiation.  these are concepts I understand; fundamentals of transfer of heat.  why do I need 2-3 inches of refractory material for 10 pizzas but not one.  What I can do for one, I can repeat for   300.  Just for note, I have mentioned twice now that the whole design features a minimum of 3 inches of refractory grade insulation around the whole oven; steel is but structural for maintenance shape. 

And just for arguments sake, everything contains thermal mass and everything is a insulator.   They just vary in the efficiency and effectiveness to do so.  If something wasn't an insulator then 100% of heat would transfer through it, no resistance.  not true for sand or glass or cobb or tinfoil or air.  Just because something is slick doesn't mean there is no friction. 
« Last Edit: October 12, 2013, 10:55:39 PM by biggrigg »

Offline shuboyje

  • Registered User
  • Posts: 1133
  • Location: Detroit
Re: Oven dimensions / ratios
« Reply #19 on: October 12, 2013, 11:50:37 PM »
Are you here to teach or learn?  You come asking questions, but when you didn't like the response you began teaching.  Not a very good way to get advice.  Use the search function, you will find your answers quicker then you will get them in this thread with the tone you have now taken with people trying to help you.
-Jeff