FINALLY!!! - Start Of Building My Oven

[david s]

Re: FINALLY!!! - Start Of Building My Oven

If you increase the diameter by 20% you increase the dome volume by 99% with a subsequent increase in fuel consumption,weight, building time etc. Most folk cook one pizza at a time because it's the waiting for people to spread out the dough and do the toppings that takes the time not the cooking. If you manage the oven well you can do multiple pizzas in a small oven too. Mine is 21" and wil fit three 9" pizzas if I take out all the coals and maintain a fire on the side.I cooked 70 of these pizzas in one night (refiring the oven once)

[Oven_Man]

Re: FINALLY!!! - Start Of Building My Oven

David S: Before I begin my response, I must first use this opportunity to thank you for all the advice so far, as you have been most helpful. I hope to hear much more from you as I progress.
Now to my response. If my understanding is correct and by means of example, if the dome weight of a 22? Oven is 80KG and one increases the oven size to say 27?, this will significantly set the dome weight at a whopping 160KG. If that is correct, then there?s much more to think about in terms of mobility as the increased oven weight could really impinge on the ability of my trolley to move the oven around.

I have a few questions regarding a smaller oven.
Is there any specified area of the oven that the fire needs to cover, like a percentage of the oven size?
Does the fire need to be placed in a specific section of the oven e.g. back or side?
In terms of the width and height of the oven opening, is it more difficult to Load/Unload pies from an oven that is small in size? The reason I ask this is because I know that the width and height of the oven opening is calculated based on the size of the oven in its entirety.

Look forward to hearing from you.
Thanks
Regards
OM

[david s]

Re: FINALLY!!! - Start Of Building My Oven

Oven man,
Firstly my mobile oven weighs around 170 Kgs, but my permanent oven which is the same size weighs 250 Kgs. I reduced the weight by making the walls a little thinner, using aereated concrete for the base, making the outer shell as thin as possible and making the outer arch in lightweight concrete. It needs to be fairly light because I roll it on and off the trailer frequently.I think 250Kg would be too much for both me and my trailer.
The fire in all ovens usually fills the whole dome and the coals cover the entire floor regardless of size. Smaller oven, smaller fire.
Usually when cooking pizzas a fire is maintained on the side.
Height of oven opening should be 63% of internal height.Width is personal preference and I don't think it matters all that much.
Smaller ovens are much easier to load because you don't have to reach in so far. my pizza shovel has a 500mm handle and I use it for fire tending and is one handed.
A smaller oven has the disadvantage of having its opening a bigger percentage of the oven wall area which must increase heat loss when open

[Oven_Man]

Re: FINALLY!!! - Start Of Building My Oven

David, did lessening of the thickness of your mobile oven and other modifications to lessen the weight, impact on the bake quality compared to your permanent oven?

The fire in all ovens usually fills the whole dome and the coals cover the entire floor regardless of size. Smaller oven, smaller fire.

Sorry for the dumb question to follow, but could you elaborate a little on what you meant in the statement above with regards to the fire covering the entire dome? Do you mean the fire should be large enough to reach the dome physically?

Also you mention the term coal. Is this reffering to charcoal or wood?

I believe there is this little metal type of a stand that sits inside of the oven on the dome whereby the wood is lit ontop of this stand. Have you heard of this before and is it efficient?


Thanks again for your assistance.
I really appreciate it
Regards
OM

[david s]

Re: FINALLY!!! - Start Of Building My Oven

No, the slightly thinner walls seem to make little difference in performance, they both seem to work the same.
After about 45 mins I try to get the whole dome filled with flame. The flames swirl around inside, it's really cool (hot).
When the flame has all gone from the burning wood you are left with coals.
I think forno bravo sell the fire grate thing.Folk seem to think it works ok.

[david s]

Re: FINALLY!!! - Start Of Building My Oven

Although my mobile oven walls are thinner, it has slightly more insulation so I guess the two alterations kind of cancel each other out.

[Oven_Man]

Re: FINALLY!!! - Start Of Building My Oven

A dome engulfed in a flame sounds hot, err, I mean cool.
From the 42? oven I initially planned on building, to a 36? oven which seemed the most viable option to now a 26-30? oven which seems most practical. Thanks to you Dave, I?m actually glad I didn?t rush into things and be impulsive in starting to build an oven of large capacity as that would be a sitting duck due to its weight.

Now that I more or less know which direction I will be taking, I will do some prep work in terms of drawing the oven on paper and then create a list of materials required.

If you don?t mind me asking, what is the thickness of your hearth, dome, ceramic blanket and ceramic boards?

I guess adding more insulation resolves the problem of heat loss due to thinner walls and thinner hearth.

Thanks and seasonal greetings.

Regards
OM

[david s]

Re: FINALLY!!! - Start Of Building My Oven

Hearth thickness 75 mm aerated concrete, it also acts as insulation under the floor.
wall thickness 48 mm
insulation 77 mm vermiculite, no blanket

[david s]

Re: FINALLY!!! - Start Of Building My Oven

[QUOTE=david s;75686]If you increase the diameter by 20% you increase the dome volume by 99% with a subsequent increase in fuel consumption,weight, building time etc.

I ran over the maths a little more carefully and actually a 25% increase in diam. gives you a96% increase in volume of the dome, but if you assume that the wall thickness of the dome remains the same the n it would increase the volume of wall thickness (weight) by 53%) Hope my previous post was not too misleading.

[Oven_Man]

Re: FINALLY!!! - Start Of Building My Oven

Hi David

Thanks for the info though my reply is a bit late. I have been working tirelessly with Cad Artists to try and sketch the oven. I am trying cover every detail.

The dimensions I wish to use are as follows.

Oven Interior (Cooking Floor) - Width 28". Depth 28"
Oven Exterior (Dome) - Width 34". Depth 34". (This means the wall thickness of the dome will be 3")
Insulation - Width 4" Ceramic Blanket. Depth 4" Ceramic Blanket. I may add an inch of vermiculite insulating concrete.
Oven Landing - +- 2 Inches

Based upon the above I would require and stand with the following dimensions.

38 Inches Width X 40 Inches Depth

What's you thoughts?

With regards to the interior dome height, is there any calculation I should use. I'm thinking of going as low at 13 Inches above the cooking floor. The dome will not sit on the cooking floor but around it. If my cooking floor bricks are 2 Inches thick, I will have to make my dome height 15 inches so it caters for the 2 inches thick cooking floor.
Secondly, my understand of the dome height is that it should be for e.g 13" above the exact center of the cooking floor. Is there any rule with regard to the curve of the dome whereby maybe the cooking height should be equal from the centre, throghout the dome.

Thanks and regards

[david s]

Re: FINALLY!!! - Start Of Building My Oven

Your plan sounds ok. I think 4" blanket is overkill, but you can't overdo the insulation. The form is usually a hemisphere and that is the best combustion chamber and also the best at re radiating the heat evenly although departure from the ideal will still work ok. Check out Joey Valderains oven. You can calculate the weight if you work out the volume of the hemisphere shell plus the floor, insulating slab, supporting slab, insulation, outer shell, flue entry, flue and door. It all adds up.

[Oven_Man]

Re: FINALLY!!! - Start Of Building My Oven

4" is overkill but I thought I would increase the insulation and decrease the wall thickness, basically cancelling each other out.

I've looked a Joey's oven and I'm gonna start reading through his thread from Page 1 as he is along the same lines as I want to be. Unfortunately I can't view any of his pictures. For some reason they are being blocked but once I sort out my PC, I will view them

I have attached a rough sketch of the proposed shape of the dome I wish to use on my oven. Do you think I'm in the right direction?

Thanks
Regard
OM

[Oven_Man]

Re: FINALLY!!! - Start Of Building My Oven

Hi David.

I dont know why, but I just have this 6th sense that's telling me to question the curve of my dome in my design. I am about finished with the sketch of my dome and will start making my mould which will then inturn lead to my cast.

I have attached a picture with the curve highlighted in red. Please advise on whether you think I have done it correctly or should I make any ammendments. I have attached the same picture in a previous post without the red highlights, in case the highlights are blocking some of the view.

I have also found the following website that has some mathematics on a Torispherical Dome, which I know isn't anywhere close to what we building but I thought that the mathematics is quite intersting though its gibbarish to me.
Torispherical Dome -- from Wolfram MathWorld

Really looking forward to hearing from you.

Thanks

[dmun]

Re: FINALLY!!! - Start Of Building My Oven

I don't understand your drawing. The dome looks hemispherical to me, and the red lines don't seem to follow the curve of the dome. Could you clarify what you're asking?

[Oven_Man]

Re: FINALLY!!! - Start Of Building My Oven

Hi Dmun

The sketch I have shown is that which a CAD Designer had designed for me. My request to him was as follows.

" I want a dome that is 14 Inches high at the centre of the dome and 30" in diametre with the dome walls being 3 Inches thick. "

The red lines were not meant to follow the curve of the dome. I just used them as guidelines to point out the original curve of the dome that the CAD artist had designed.

You mentioned that my dome looks hemispherical. After researching a bit on hemispherical domes, it seems that my dome does look that way.

It took me a while to put what I need into words. My description was putrit to say the least but eventually the CAD artist and myself got somewhere. Now that he understands what I require, asking him to modify the dome sligtly wont be a problem.

Would mind guiding me in the right direction as to what sort of dome it should be? I'm sure if I can describe it to him, he should get it right.

Thanks