36" build in heart of Europe, Czech Republic

[mrotter]

OK, CaSi along with mortar are about to be shipped, will arrive soon. I will cut CaSi to desired shape and that will be it this year, I will probably not risk freezing of the mortar, it seems they recommend stable temperatures higher than 5C. So, continuation in the spring next year I guess.

[UtahBeehiver]

Just don't leave the CaSi outside. It will readily absorb moisture in the air.

[mrotter]

No worries, I will place it somewhere in my garden house, maybe also wrap it in some plastic bag.

[mrotter]

Stuff arrived - some CaSi boards (40+30 mm), managed to get 4 boxes of Fiberfrax insulation (many squared meters) for free (!), 75 kg of refractory mortar (I wrapped those tightly into plastic bags), and fire-resistive rope + fire resistive "mesh" to be applied into underlying layer of dome render.

Also, made first version of IT.

[mrotter]

Now I am thinking about final dimensions of oven footprint. I also decided to make inner diameter of 34", instead of 36" to fit onto my stand which is about 144x169 cm. With ID of 34" I aim to have CaSi underlying circle of diameter 137 cm (85 cm inner, 25 cm bricks, 15 cm insulation, 8 cm perlcrete, 4 cm render).

Height of dome will be around 17", therefore according to FB plans sufficient opening width should be 18" and height 11". Do these dimensions seem about right?

Also, question I am tackling my head with: how do I decide how much forward/backward should be opening pushed inside/outside of the dome circle? So that my opening arch meets relevant oven brick course just fine?

[mrotter]

I mean this shift.

[UtahBeehiver]

The inside of the arch (top left and right corners) need to intersect the ID of the dome. On the IT there are a couple issues you need to be aware off. First, the pivot point is offset from the center as well as the off the floor elevation. This will affect the dome dimensions as you go up in course so you need to make adjustments. Second, this one is critical. The line from the center point on the floor and the "L" bracket "must " intersect the midway point on the brick, IE if the bricks are 50mm thick then the intersection point needs to be at 25mm. the way the L bracket is currently mounted to the wood appears to be too high. Material look good, not sure what the square mesh is going to be used for (under the CaSi?)

[mrotter]

The inside of the arch (top left and right corners) need to intersect the ID of the dome. On the IT there are a couple issues you need to be aware off. First, the pivot point is offset from the center as well as the off the floor elevation. This will affect the dome dimensions as you go up in course so you need to make adjustments. Second, this one is critical. The line from the center point on the floor and the "L" bracket "must " intersect the midway point on the brick, IE if the bricks are 50mm thick then the intersection point needs to be at 25mm. the way the L bracket is currently mounted to the wood appears to be too high. Material look good, not sure what the square mesh is going to be used for (under the CaSi?)

The IT I made has almost no offset from floor elevation (almost exactly level with floor), offset from the center is about 1-2 cm max. Yes, I am perfectly aware that I might shorten IT by small margin to reach perfect shape. I read that somewhere in JR pizza thread I guess.

[mrotter]

"Second, this one is critical. The line from the center point on the floor and the "L" bracket "must " intersect the midway point on the brick, IE if the bricks are 50mm thick then the intersection point needs to be at 25mm. the way the L bracket is currently mounted to the wood appears to be too high."

Please elaborate. I plan to have my IT center mount point a bit "buried" under the floor line. In other words it will not be mounted on the same level as floor bricks - center brick will be temporarily removed and thinner piece of wood (about 2 cm) will be used as mount point for IT - in a way that I will make sure that IT starts first course of dome in a perfectly "level" position. That should enforce almost perfect hemispherical shape by itself, should not it?

[mrotter]

Material look good, not sure what the square mesh is going to be used for (under the CaSi?)

I am not sure how to translate to English - it is "render reinforcement mesh" and it is made specifically for ovens/fireplaces - it is placed and covered by render layer and it ensures that the render (or even perlcrete layer if thin enough) is "flexible" and is able to withstand tensions better - should eliminate any potential cracks if made properly. Works the same way as metal rebar mesh used for concrete slabs.

[UtahBeehiver]

Okay there are three issues to solve. First, vertical offset of the pivot point, this is where you bolted the adjustable wood arm to the metal swivel caster. This will be corrected if as you say lower the bolted point to floor level. Second, the bolted pivot point is not at the center point of the swivel caster but horizontal offset. So at the bottom of the dome say it is 36" diameter, at the top of the dome it will be different (by offset). This can be corrected as you move up in course by your adjustable IT, you just need to be aware of these dimension changes, This comes into play if you do a tapered inner arch. Lastly, from the center point of the swivel (not the bolted part) along the adjustable wood pieces, the line needs to intersect at the halfway point on the brick at the L bracket or you bricks will NOT be perpendicular to the center of the dome, this error is cumulative at each course so it gets worse as you go up and you see the brick faces not matching the previous row.

[mrotter]

Lastly, from the center point of the swivel (not the bolted part) along the adjustable wood pieces, the line needs to intersect at the halfway point on the brick at the L bracket or you bricks will NOT be perpendicular to the center of the dome, this error is cumulative at each course so it gets worse as you go up and you see the brick faces not matching the previous row.

I think I know what you mean. Can you draw a line to show which parts of L and swivel should be lined? My English is not that good, but looking at

https://community.fornobravo.com/fil...photoid=443243

the L bracket should be placed "higher", so the line should lead from center of the brick (bricks are 50 mm, so 25 mm) to the turning point?

[UtahBeehiver]

Okay, try this.

[mrotter]

Perfect, will post adjustments tomorrow.

[mrotter]

The inside of the arch (top left and right corners) need to intersect the ID of the dome. On the IT there are a couple issues you need to be aware off. First, the pivot point is offset from the center as well as the off the floor elevation. This will affect the dome dimensions as you go up in course so you need to make adjustments. Second, this one is critical. The line from the center point on the floor and the "L" bracket "must " intersect the midway point on the brick, IE if the bricks are 50mm thick then the intersection point needs to be at 25mm. the way the L bracket is currently mounted to the wood appears to be too high. Material look good, not sure what the square mesh is going to be used for (under the CaSi?)

Thanks for the picture. I actually made some tests, and subsequently tweaked IT. You are right. If your L is placed too LOW -> subsequent edges of bricks are too far. Of L is placed too high -> subsequent edges of bricks are too close and not sitting properly. I tweaked the tool so that L can be also partially adjusted vertically. I will take that behavior into account when working with inner vent arch. See pictures. THanks for this again.

You say: "The inside of the arch (top left and right corners) need to intersect the ID of the dome." I see. That is the only condition to make sure that arch meets dome "correctly"? I am aware of tapering bricks to get proper shape. Will all bricks in arch have same length? I saw some posts where they are same length, then I saw som comments from you where you mention that TDC brick is the longest brick in arch. I am bit confused. Also, I plan to build arch as I go with courses, it will sit on premade form of course.

Also, measured bricks, they are actually 68 mm thick.