36" Pompeii Build in the desert

[UtahBeehiver]

No one will ever see the chip by the arch. But this brings up a good point, do you best work, staggers, cuts on the back half of the dome, this is what can be seen when the oven is complete. Make your adjustment or "chips" towards the front end of the dome.

I believe General Tool includes a disc with the program when you buy the Anglelizer, it is just not available for free anymore on the website. If this is not the case, let me know and can run the calcs for ya.

Free float the arch base.

[jim lofaro]

Pretty on the back side; got it.

Starting to think about the inner arch (see photos). I was wondering how to taper the brick. I ran thru these calculations:

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Poster: ColonelCorn76
Join Date: Mar 2005
Location: Simsbury, CT USA
Posts: 97
29jul05

Arch cut calculations

Okay folks, here's the latest installment in "brick oven building...advanced"

Here's how to calculate the dimensions of the bricks (voussoirs) that make up a semi-circle arch ("axe arch").

The dimensions you need to have are:
Arch span - inside distance across the base of the arch i.e. the doorway opening
Brick height - height of each brick (e.g. 4.5" for a standard firebrick on its side)
Brick width - assume taper will go from brick's upper corners downward (called the "extrados") for a 1/2 of a standard 9" brick this would be 4.5"
Joint width - width of the mortar joint you'll be using typically 3/8 or 1/2"

We'll find:
Number - number of voussoirs rounded up to the next odd # to provide for a key brick
Taper width - width of brick at bottom of taper (called the "intrados")

We also need to calculate these on the way:
Max circumference - the measurement you'd get by laying a tape measure around the outside of the arch when built
Min circumference - the measurement you'd get by laying a tape measure around the inside of the arch when built

Step 1:
Calculate the Max circumference = Pi * (Arch span + brick height)
ex: 3.1428 * (16 + 4.5) = 3.1428 * (20.5) = 64.4274"

Step 2:
Calculate the number of voussoirs in the arch = Max circumference / (brick width + joint width)
ex: 64.4274 / (4.5 + .5) = 12.885 -- assumes 1/2" mortar joint

Step 3:
Round up to next larger odd number = 13

So, for a 2 1/4" x 4 1/2" x 9" firebrick split in half with the 4 1/2" x 4 1/2" face being used to create the tapered brick, we'll need 13 arch bricks or voussoirs.

Next we calculate the width of the lower part of the taper:

Step 4:
Calculate the Minimum circumference = Pi *Arch span
ex: 3.1428*16= 50.2848 this gives us the maximum amount of room we have around the bottom of the arch

Step 5:
Calculate the total width of the joints = Number of bricks * joint width
ex: 13 * 1/2 = 6.5 this gives us how much of the bottom arch will be used by the mortar joints because we make even mortar joints top to bottom

Step 6:
Taking the total distance around the bottom of the arch less the mortar joints & dividing by the number of bricks we have will give us how wide those bricks have to be on the bottom
or
Calculate the taper width = Minimum circumference - total joint width all divided by the number of bricks
ex: (50.2848 - 6.5)/13 = 3.368
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From this post:

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https://community.fornobravo.com/for...apering-bricks
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Results showed 2.2 inches intrados. I cut out some paper bricks and placed them around a cutout of the inner arch opening. The angle appears to be reduced but not as neat as I have seen on some builds. Can I extend a string from the center line on the cooking floor under the front of the inner arch up to the outer edge of the arch brick to get the taper angles (see photos)? Seems like the angles change on each brick or at least the position of the deep and shallow angles. Some of Russells photos show an inner arch template with one angle shallower than the other (I believe??). Will all be revealed once I get the Angleizier?

Any advice would be appreciated.

[UtahBeehiver]

We are talking two different type of tapers. First is the one you have already figure out which is the axe arch. The second is what is called a tapered inner arch for mating the dome to the inside of the inner arch. The anglelizer software will not help you here. The tapered inner arch angles are determined by using you IT. I have attached a picture of axe arch similar to you which shows how the IT helps you mark these angles.The top dead center brick on the arch will be the longest one. As you can see from the picture each brick each way of TDC is slightly different. Doing a tapered inner arch is a hard concept to visualize but well worth the effort.

[jim lofaro]

Thanks again Russell. I am taking the inner arch process a cut at a time, saving the inner/outer dome radius cuts for later. Thanks for the short cut.

Note to self-inner/outer dome radius cuts:

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https://community.fornobravo.com/for...e-i-done-wrong
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The procedure used for the initial side tapers was:

• Using a string on the paper model cut the paper bricks at the angles prescribed by the string from the bottom center position to the outer corners of the brick.
• Measure the length of the thinner (downward) brick face.
• Average the lengths (44mm).
• Select the paper brick with the average length.
• Cut a wooden jig using the paper brick.
• Mark the brick to be cut and cut using a 10 inch wet saw.
• Trim with a hand grinder using a diamond blade.

One down, 9 to go.

JLo...

[jim lofaro]

Is it considered best practices to cut a small chamfer on the outside of the inner arch where the vent would be located?

[UtahBeehiver]

Any reduction of flow restriction is good. I seen this done a few times. Consider a S shape vent like JR's build. If I were building another oven I would do something like it for minimal flow restriction

[jim lofaro]

Do not thing i have the skill set to do the S-shaped vent like JR but it is early yet. starting to think about how to insulate the inner arch from the vent area. any builds i should read?

[UtahBeehiver]

I personally like the "L" shape vent bricks for insulating from the dome. Look at Gulf's build. Based on what I am seeing with your axe arch, the skill set is there to do a S shape chimney.

[jim lofaro]

Thanks again Russell (and also to Gulf). Let me ponder this a bit.

Note to self- Notched vent brick:

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https://get.google.com/albumarchive/...CPP5z4nqgsGFNg

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[jim lofaro]

The quest continues:

Tapered the sides of the brick that will be used for the inner arch (see photos). See any problems? The TDC block is a bit thin.

Starting to think about the inner arch angles. Let me do my home work:

https://community.fornobravo.com/for...ome-transition

[Gulf]

I did notch my brick but, with only a 1"X1" notch for the heat break. Many others afterward did more of the "L shape". The small notch leaves more of a reveal but it does not weaken the brick as much imo. Also, disregard my entry's foot print. It was done that way to accommodate a very heavy all masonry chimney/flue. The below pic, (though not to scale but, with the same notch), is more inline with what many have done.

[jim lofaro]

Thanks Gulf. Added the 1*3 inch stainless floor break. Stuffed the ss with insulating board and put it on a 1.5 inch thick insulation board (see photos).

[deejayoh]

Looks like you have laid the floor break flat. Interesting, I think most have put the stainless in with the narrow edge up. What's your thinking there?

[jim lofaro]

Not sure i have any thinking here. Just assumed the narrow edge was down.

https://plus.google.com/photos/10287...94477744845506

https://plus.google.com/photos/10287...94486927219890

[jim lofaro]

here is my IT (see attached). Note I labelled what i have thinking is the Axis of Rotation. Additionally the center line of the is brick is also the center line of the IT rod. Any problems anyone can see with the IT?

JR states:

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Having the arm pivot point closest to the floors surface and axis of rotation at the centerpoint is the best way to make a perfect hemispherical dome. That is what I was trying to achieve, although I think all of the other variations will produce an oven that works. The forum owners had this picture which puts the axis of rotation at the floor but it is off center, so the dome will be a little wider than twice it's height, unless you make adjustments. Having the tool centered in the middle but above the floor (like with a caster) will make a dome that is taller than half it's radius. I was inspired by both Gulf's build (Mississippi 44") and also by jcg31, where it looked to me like they were going for optimum placement of both axis of rotation and location of pivot point. My pivot point is actually about 1/2 inch above the center of the dome, and at course 5 I did two rotations to shorten my arm by 1/7 of an inch (my threaded rod has pitch of 14 TPI). I'll do the same probably twice more and end up with almost a perfect 19.5 high dome. I really like the symmetry or a 39 inch oven - my door opening is also 19.5. and outer dome is at 48 inches, which fits my sheets of insulation perfectly

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Is it a problem if i do not make adjustments to my IT as i go up?