36" Pompeii Build in the desert

[UtahBeehiver]

Well, that was me that put the ss widthwise and I believe it is similar to Gianna Focacia's heat break. I can't remember why but it work out that way.

[UtahBeehiver]

With the pivot point off the floor you will have to make some tapered arch length adjustments since as you move vertical the ID of the oven at the base will increase as you move up. I think you know that you will need to use a whole brick, not a half brick to make the tapered inner arch.

[jim lofaro]

Any thoughts on notching the outer surface of the inner arch like shown in the attached (shanxk8 build i believe)? I was thinking in terms of insulating the inner arch from the vent arch.

[jim lofaro]

Looks like i screwed up somewhere. The inner arch appears to be to far inside the dome (see photo). Maybe i should have added a few more soldier brick before jumping to the inner arch??

[JRPizza]

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

Jim, your dome will be higher than the radius at the bottom by the height of the pivot off the floor. I believe lots of ovens have been made this way. I tried to get as hemispherical as possible, as I did not want to try to build a low dome oven but didn't want it to be any higher than necessary either. No data on effects of a higher dome, just didn't want to do it.
I also see you think you might not have placed your arch forward enough. Did you do a layout first? I discussed arch placement a bit in my thread after learning from Russell and Gulf. I have seen folks build a little extension on their oven with a very forward arch (SableSprings) but not sure you want to have one that is too far inward. Is it too late for you to correct?
Do you know what the distance is from the center line to the front part of the arch? I could probably do a quick check for you using my cad program.

[david s]

Jim, your dome will be higher than the radius at the bottom by the height of the pivot off the floor. I believe lots of ovens have been made this way. I tried to get as hemispherical as possible, as I did not want to try to build a low dome oven but didn't want it to be any higher than necessary either. No data on effects of a higher dome, just didn't want to do it.
I also see you think you might not have placed your arch forward enough. Did you do a layout first? I discussed arch placement a bit in my thread after learning from Russell and Gulf. I have seen folks build a little extension on their oven with a very forward arch (SableSprings) but not sure you want to have one that is too far inward. Is it too late for you to correct?
Do you know what the distance is from the center line to the front part of the arch? I could probably do a quick check for you using my cad program.

Or you can do a quick scale drawing like this with the three dimensions indicated as well as drawing the thickness of the dome wall and arch. I think you'll be ok as there is usually way more room than it appears because the dome slopes back away from the arch as it gets higher. Most builders end up with an entry far deeper than is necessary and a shallow entry is way easier to work when cooking.

[jim lofaro]

Thanks JR.

About the only layout I did was pencil and paper plus many dry builds. I believe it is correctable by adding another soldier on each side of the dome and move the arch forward (see photo). I will need to extend the floor out but one lives and learns. The original distance from the center line to the back of the arch is 10 ½ inches and 15 inches to the front of the arch. The configuration in the current photo puts the back of the arch at 15 ¼ inches and 19 ¾ inches to the front of the inner arch.

[jim lofaro]

OK, put pencil to graph paper and came up with an entry arch located 12 ¼ inches from the dome center (see attached). When she warms up a bit I will be doing a bit of dry stacking.

[JRPizza]

Nice sketch! I looked at a layout I did for a 36" hemispherical oven, with a 12.25 inch opening, and had the front of the arch at 22.5, so you certainly are in the ballpark with your new dimensions. Your sketch does not exactly match your build as the angle that is drawn intersecting the TDC brick should originate a distance above the floor equal to the height of your pivot, but that is probably all in the noise. There is a bit of wiggle room in moving the arch in and out and still maintaining a round shape. You can move the arch inward till there is barely any projection at the top (which I have seen) or maximize the projection to get plenty of ledge to build your vent off of. I kind of split the difference on mine.

[Gulf]

So, it is a 37" oven. I agree with JR, you are in the ballpark. Using your 12" opening height, I came up with the below numbers.
I've got to clean those dry erase marks off of the freezer before swmbo gets home .

[jim lofaro]

Great idea using a dry erase board. Nice reference to SWMBO. I have only heard the term used on Rumpole of the Bailey.

So u'alls thought is that I could move the arch front out to 22 inches from the center of the dome and it would still work? That would be grand as it would increase the dome usable surface area (should have built a bigger one). Attached is a picture of the inner arch at 17 ½ inches from the front of the arch to the center of the dome.

Next question; how do I use the IT to set the outer and inner dome radii as shown in post #33 of this thread?

[UtahBeehiver]

The IT should already be set for the inner radius of the dome, ie 39" ID oven should be 19.5" radius. The outside radius is the half brick dimension, ie 9" brick = 4.5". The slope of the top angle equal is the same as the centerline of the IT rod. You may have to make some inner radius length adjustments since the IT pivot point is not exactly at the floor elevation. This is common. Remember that each brick each way of top dead center are different.

[JRPizza]

This is what I did for a "reality check" of my model. I placed the outside edge of my arch form where I wanted the face of the arch to be. This gave me something to index the bricks to as I built the arch. I placed a brick flush to represent TDC, then put a dome (half) brick in my IT and traced where the inside of the dome would be. Ignore the mark on the right it was a mistake. This will show you if the form is in the right place and give you an idea of how to angle the arch bricks.

[jim lofaro]

Thanks all. Having a bit of a confidence crisis after missing such a major component as inner arch placement. Back to dry stacking and going over calculations. Watch this space.

[jim lofaro]

Moved the front of the inner arch 22 inches from dome center. Will need to add ~4 more brick to the soldier course. Moved the thermal break and did some creative cuts on the floor. Will end up losing more than half of the landing but figure on adding a small shelf around the outside of the hearth (aka Russell).