FINALLY!!! - Start Of Building My Oven

[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 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

[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

[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

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

[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.

[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

[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

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

[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.

[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

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 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

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

Hi Guys
As I started to type out this reply 1 day ago, an unforeseen interruption stopped me in my tracks. Sometimes, things like these happen for unforeseen reasons and in this particular case, the reason is as follows. Since completing my reading exercise yesterday of the manual for building a Pompeii Oven by James, I had some time to contemplate and think more clearly on how to approach this project. Initially my plan was to follow James instructions step by step with a few variations.

As you all know, this oven will be built on a movable trolley. With that, comes 3 variations in the step by step instructions. 1 is there will be no real foundation as the oven with not be on a permanent platform. Number 2 is the stand like the foundation will not be on a permanent concrete block by rather a stand fabricated from steel on wheels. The third variation is castable sections of the oven for stability and to avoid it falling apart.

The next variation I will mention only occurred to me during the time I had to contemplate as mentioned above. According to James, he advises that the small difference in cost and overall labour in building a 42? oven compared to a 36? oven is a small price to pay taking into consideration the effort and work that goes into building an oven. I planned on taking James?s advice and build a 42? oven. I calculated the size of the stand I would require and this came in at around 1.6 X 2 Meters. This would result in a considerably large trolley that will be needed and the thought of moving around such a large trolley with an oven on it will be difficult. After much thought, I decided that this will not be the most practical way.
So back to the Drawing Board for me.

I ask the community to for their comments and advise. From the look of things, I will most probably end up going for a 36? oven or maybe even a little smaller.

Just a few questions regarding a smaller oven.
How many 12? Pizza?s can I cook in a 36? oven?
In terms of overall performance of the oven, like heat retention, wood consumption, bake quality, etc, how would if fair against an oven of larger capacity?
In terms of ease of use like loading/unloading of pies, and taking into consideration the smaller oven opening and cooking floor space, how would it be compare to an oven of larger capacity

I look forward to hearing from you guys.
Regards
OM