Entry arch to dome transition

[guiriguiri]

I came across a stream about how to figure out the angles that are cut into the interior face of the arch bricks, yet I am still struggling with how these angles are found. I am pasting the most helpful post I found to date but I still can't decipher what is actually happening, here is the post...

I finished off my second course and incorporated the first of my tapered arch bricks. Got about 1/3 of course 3 before I ran out of mortar and daylight. The joint thickness on the arch bricks is a little thicker than I wanted so will have to keep an eye on that. Ran into a little confidence crisis on cutting the back angles on my arch bricks, but UtahBeehiver has been helping me through the visualization and I think I am on the right track. That is one of the great things about this forum - knowledgeable people that are willing to help. Having someone to talk things through seems to really stimulate the thinking process. I had to put my marker back in the IT and trace the outline of inner and outer surface of the dome on my arch bricks. I saw this in UtahBeehiver picture gallery, but needed a little help understanding how it all fit together. I clamped a brick in the IT and brought it up next to my TDC arch brick, aligned it with the inner and outer marks, and established the angle needed for the brick to seat. I have no idea whether it will be a full width brick or a sliver when I incorporate the last course into my arch, but I have a good feel on how it will sit. I will use those marks I made on the balance of the arch bricks to cut them to shape as I build up.

or just anyone who can define this process for me. I am really struggling with this one.

[JRPizza]

I don't know if these pictures will help, but here is what I think you are describing, the first is my TDC brick with a "dome" brick held next to it. The diagonal line to the left shows the inner surface of the dome, and the diagonal line on the far right was drawn by mistake The angle of the brick is set by aligning the top edge with a line on top of the TDC brick representing the oven outside surface (pic 2). Then I cut the angle on top of the TDC brick so the dome brick would be tight on the inside and allow a mortar joint to the rear as shown in the last picture. Does this make sense?

[guiriguiri]

JRpizza, I think so. the angle cut into the arch bricks is reflective of the angle set by a brick on the IT. we had success drawing out the TDC angle with this process but as we moved down the arch it seemed as though too much of the arch brick was being removed (we haven't cut the bricks yet.). now i wish i would of taken a picture of it but basically there wouldn't of been a complete flat face on the front of the arch which I haven't seen in any builds and just doesn't seem right.

A better question on my part would be are all the bricks cut to match the angle transcribed into the TDC brick or does the angle change as you move down the arch?

We were holding bricks to the left of the TDC brick in place and trying to mark them in a similar manner and this led to problems.

Another question would be how do the first five or so rows of dome bricks meet the arch bricks, how were those angles found?

I appreciate your help, and yes the photos help! I came across those photos and the corresponding explanation which is the only reason we made it as far as we did.

[UtahBeehiver]

Each brick right or left of the top dead center brick are slightly different and not symmetrical. The diagonal angle of the arch is determined by the angle of the center line of you IT (rod) not the bracket. All courses are determined the same way. The TDC brick will be the brick that requires to be the longest one and the others get shorter as you move down the arch. You do nee to start with a FULL brick not HALF bricks or you do not have enough material to work with.

[JRPizza]

What I did, sort of by accident, is use pretty much the same angles on all the bricks as the TDC brick. Not for the first few rows till I figured out I didn't want to carve into them too much as you point out and you are making custom cuts on the adjoining bricks anyway. You can see in the picture how I angled the side of the bricks to mate with the arch bricks. Look at a few other builds - others might have tackled this differently, but I think this is a good way to go. Even though I used same/similar angles, the bricks do get shorter as UtahBeehiver points out. The intersection of the dome OD moves slightly forward as you get closer to the bottom rows.

[guiriguiri]

UtahBeehiver I am sure this is just my lack of capability to visualize these things but I don't understand how using the rod of the IT gets the angles to cut into the arch bricks. What is the reference point on the arch brick that you are using to "snap" a line on with the rod of the IT tool.

JRPizza you mentioned the line to the left being the inner surface of the dome did you cut that as well, and again I am sorry but the brick you are placing on the TDC to draw the angle what are you aligning on that brick with regards to the TDC? the bottom edge of the dome brick with the top edge of the TDC is what it looks like from picture 2 but I just want to be sure.

Sorry for all the questions I just want a firm understanding of what I am doing before diving into the transition, maybe that is my mistake.

[guiriguiri]

JRPizza never mind I finally put it together... I am a little slow

[UtahBeehiver]

The rod on the IT is (if the IT is built correctly) where the pivot point of the center of the floor at ground zero of the dome. The center of the rod with the brick bracket makes the brick face perpendicular to the dome. If you use the top or bottom portion of the bracket on the other end then the angle is not perpendicular relative to the floor center. Does it make a difference on a single course? Not significantly but it can be cumulative over several courses.

I think DeeJayOh did a CAD drawing somewhere that shows the effect of not using the center of the IT as your core baseline.

[JRPizza]

JRPizza never mind I finally put it together... I am a little slow

No problem - I asked so many questions when I was starting my build I thought Russell and Joe would start to ignore me. Fortunately they (mostly) and others on the forum "held my hand" and helped me wrap my brain around the process. Feel free to ask all the questions you want!