Advice Needed: 42" changed to 36"

[paulkjrobbins]

I made some progress. I figure I should post some pictures. I started a new post in the photo album folder to upload to periodically. If you are interested, here you go: https://community.fornobravo.com/for...n-provo-ut-usa

Russel & Mongo, thanks for all your help to get off the ground.

[paulkjrobbins]

I am so glad you caught that Russel! I will lay down 2 1/4" courses so that I can interlock them. I think I will also buttress the bottom course with homebrew going out at a 45. Do you see any problems with this? Thanks again for your help.

[UtahBeehiver]

With a "full" soldier course, the horizontal load from the dome may require buttressing. You may want to look at this and consider a half soldier or a half header since you previously taught physics. A full 9" brick for a tapered inner arch at TDC should be fine. This is one of the most difficult concepts for builders to visualize.

[paulkjrobbins]

That is great advice. Thank you! I'm going to get an early (for me) start and see what I can get done.
Best,
Pau

[mongota]

Pre-construction, without a doubt trying to imagine the geometry of the arch/dome intersection and how to cut the arch bricks was the hardest thing for me to figure out.

Once I started building and I had the footprint laid out on the hearth slab and a stack of bricks in front of me? The reality of it all is that it was ridiculously simple how it all came together.

I do know that a few folks that have built with different dimensions have done a full-scale drawing on kraft paper, or a scaled drawing on graph paper. Does not need to be fancy. I'll attach a horrific drawing, and it's not 100% correct, but the gist is to draw a birds eye view of your inner (36" circle) and outer (40-1/2" circle) dome dimensions. Then locate your arch template. Locate it by having the corners of the template meet the 36" circle of the dome floor.

Then measure what I've shown as dimension "X".

Now draw the side view. Again inner (18" radius half circle) and outer (22-1/2") lines of the dome. Carry the arch template dimensions on to this drawing, but registering it off of "X". You can then draw in a brick sitting on the top of the template and see if the 9" length will hit or intersect the points it needs to hit. With most geometries (mine included) a 9" brick was more than long enough to go from the outside edge of the template to the inside face of the dome.

You can also do this on site, using the IT, swing it around to see if it hits the required points.

I hope this makes sense and I haven't muddled things up more! If I did, it'll be Russell to the rescue.

[paulkjrobbins]

Are you doing an Axe arch or a full semi arch. Mongo's is a full arch and your original drawing is an axe arch. Either case the inside base of the arch intersects the arc of the dome. See pic. Also, you need to start with a full brick to do a tapered inner arch, not a half brick. I have attached a couple of pics to help you visualize. The top dead center brick (TDC) will be the longest brick.

Thanks guys, this helps. I am going to do an axe arch, I didn't know they were called that. I'm not being very clear in my questions. for the TDC brick to be long enough to meet the dome on the inside. The way I am thinking about it, if the inner arch is too wide then a 9" brick won't be go the distance. I am also realizing that mine will be different as well since I switched to a 36", my dome will taper back differently than yours. Maybe I need to use the IT tool to see where the TDC brick will end up and then plan my inner arch accordingly? What I am trying to figure out is the dimension in green below.

I really appreciate it. As you can tell, I am still trying to wrap my mind around this. Almost done cutting out the floor tonight after work. Hope to finish tomorrow and start the soldier course. I ended up putting my floor bricks up on the wide edge so the floor bricks are 4.5" deep. I plan on putting some cardboard in the gap and soldiering bricks up the length so the soldier course is 9" tall (4.5" above the floor). Thanks so much for all your help and advice, this forum really is amazing.

[mongota]

Did Russell's photos explain it? My arch template was aligned as was the one in his photo, with the inside corners of the template sitting right on the circle that makes up the circumference of the oven floor.

[UtahBeehiver]

Are you doing an Axe arch or a full semi arch. Mongo's is a full arch and your original drawing are an axe arch. Either case the inside base of the arch intersects the arc of the dome. See pic. Also, you need to start with a full brick to do a tapered inner arch, not a half brick. I have attached a couple pics to help you visualize. The top dead center brick (TDC) will be the longest brick.

[paulkjrobbins]

Mongo, Thank you for your advice so far, it has been invaluable. I was looking through your build and I had a question about the placement of the inner arch. How far our did you place the arch? It only looks like it has a couple of inches outside of the oven. If you look at the snipit from your album it would be the top of the green outline. I am wondering if there is a sweet spot for the arch because I just realized I need to make sure it is not out too much or I will not have enough brick at the top of the arch to extend in to match the dome. Thanks for your help!

[mongota]

paulkjrobbins

So I think I understand how to do the thermal/expansion break between the inner and outer arch. What I don't understand is that after the inner and outer arch are done, firebrick is laid on top of both to level for the chimney base plate. Doesn't this connect the inner and outer arch thermally and for expansion purposes? I know I am missing something. Has anyone else thought along these lines before? (This is assuming that the arches butt up against the thermal break instead of doing the L-Bricks for the outer arch)

See the attached photos. They might not have loaded in order...however:

One photo that shows the landing tunnel being built should show how I isolated the vent arch from the dome arch. The ends of my tunnel bricks have an "L" shape at the end, so the "L" end of the vent arch brick wraps around and covers the dome arch brick. I used two lengths of ceramic fiber rope between the bricks.

Another photo should show the vent arch completely done. As built, the vent arch is not mortared to the dome arch.

The last photo should show how I made the transition from the top of the tunnel arch to the chimney anchor plate. As built, the landing tunnel still remains isolated from the dome arch.

Hope that makes sense. There are myriad ways to accomplish the same thing. The one I used was the one that made sense to me and that I found easy to understand and execute.

Good luck!!

[NCMan]

It's extremely rare to ever have to replace a floor or even a brick. It may happen once in awhile on commercial ovens, but even then it's rare.

[paulkjrobbins]

So I think I understand how to do the thermal/expansion break between the inner and outer arch. What I don't understand is that after the inner and outer arch are done, firebrick is laid on top of both to level for the chimney base plate. Doesn't this connect the inner and outer arch thermally and for expansion purposes? I know I am missing something. Has anyone else thought along these lines before? (This is assuming that the arches butt up against the thermal break instead of doing the L-Bricks for the outer arch)

[paulkjrobbins]

Hi Everyone,
After building my concrete hearth slab and pouring vericrete and putting FB on it and cutting out a 2 1/4" floor, my wife and I decided to redo almost everything. We are going to go down to a 36" oven which is unfortunate since we just built everything up for a 42". I am thinking of building it at a 45-degree angle off of one of the corners. Since I already cut out my floor for the 42" (2 1/4" thick) I was wondering if I could just put another 2 1/4" layer of firebrick on top of fit and then mortar a 4 1/2" soldier course on top of the lower firebrick since it will stick out. If anyone could give input as to whether this is a bad idea I would really appreciate it. I wonder if it will affect expansion of the dome. It could be nice to only remove the top if the floor ever needs replaced. Attached is anything that you may see off/missing would be greatly appreciated.