Pdx 42" update

[Macrinehart]

Good Tip JRPizza! I will adjust accordingly.


Have cut half way around the back, top cuts.

One thing I noted, because my opening arch is supported by one brick, the arch doesn't make a perfect semi-circle. Instead, there is a taper to the cuts moving from the keystone to the floor. I think this would be easier if it was a half circle without the supporting bricks! But then my opening would be too small. I'm committed now!

[Gulf]

I'm trying very hard to figure out what is going on here. On a hemispherical arch the top dead center brick protrudes further into the dome than the risers? Perhaps it is the viewing angle or the inside diameter cuts are yet to be done?

[Macrinehart]

I am about 90% confident, but let me submit a drawing for reference. Because the center of the arch is elevated above the oven floor, the IR of the oven isn't equadistant from the IR & OR of the opening arch. The same is true for the Oven OR.

In order to mark the OR I started with the keystone and shifted it to so that the IR and OR are alinged with the inside face and upper face of the Keystone. Then I linked up the inside faces of all the bricks in the arch. Finally I used a metal survey tape to mark the ray from the pivot point through the IR and marked the point where the ray intersects the OR of the opening arch.

[UtahBeehiver]

The tapered arch is only partially done. There is no cut back that follows in inner diameter of the dome. This is why the top dead center brick is the longest brick and the shortest ones are at the bottom of the arch. This is what Gulf is talking about.in his post. I also believe, as JR pointed out the arch form is too far in and affecting how the inner arch bricks are being formed.

[Macrinehart]

The tapered arch is only partially done.

That is correct, I am working on finishing the outside cuts first, and if understand your meaning UtahBeehiver the "cut back" are the cuts that are roughly perpendicular to the cuts I've already made.

I am going to reposition the arch support per JR's guidance after I finish the outside cuts so that I can mark the IR of the dome on the underside of the opening arch.

[UtahBeehiver]

The inside bottom of the arch form should be where the ID of the dome and the form intersect. The cut back is the inside arc of the dome and whether its is perpendicular or not depends on the arch shape. I attached pic showing how the IT scribes the inner dome arc,

[Macrinehart]

Today I was able to finish the over and undercuts for the opening arch. I repositioned the arch form per UtahBeehiver's guidance.

I'll note this is not a perfect job, but is it good enough? Some of my overcuts were a little too deep, I think there is 3/16" - 1/4" variance, which you can see in pictures below. I'm thinking this can be resolved with a little extra morter in the problem areas, although that may not be an ideal solution if the morter is too thick?

As always...feedback is welcome. If necessary I can pull out some problem bricks and replace them.

[Gulf]

Ok. It appears that on your top dead center brick that you will have about a 1.5" reveal inside the dome. That is about perfect imo. However, the reveal on your first riser is much wider. Scribe a line on the inside of the arch to make that reveal constant through out. Then scribe an outside diameter on your dome brick. Connect the lines on each side of each brick from those reference points and there you have it. Refer back to my link. It's all there. If you need something on the link explained, I'm here.

[Gulf]

Hopefully this rough mark up will help

[UtahBeehiver]

Gulf's pic pegged the issue perfectly. The blue line should be the ID of the dome and the yellow line should be the OD of the dome as shown in my pic in post 177 and also shown in JR's post 117.

[Gulf]

Here is one included inside the link I previously shared.

EDIT: It may not be clear in the photo. But, the OD scribe mark is on top of this brick. The purple line is the actual tapered cut. The purple line is drawn from the 1.5" reveal to the OD scribe.

[Macrinehart]

Gulf and UtahBeehiver, I think pictures from post 177, 189 and 191 are painting a clear picture. I guess where I'm getting confused is that the undercut that I actually cut in the picture from post 189 follows the ID of my dome. But the overcut I did was intersecting with the undercut at the inside face of my arch brick, which is the error. Also didn't help that I cut those overcuts first. But I think I understand now.

So, when I was positioning my arch form, I set it so that the Keystone has OD and ID intersections almost exactly as Gulf has illustrated on 191. Looking at the post 189 again, I think my undercut doesn't need to change. Instead, I should measure the distance from bottom of the undercut to the top of the undercut on my keystone (about 1.5") and then mark that line on every brick in the arch. That should reproduce the blue line on post 189.

From there I can then mark a 4.5" line on the side of each brick, staring at the blue line and intersecting with the top of the wedge at 4.5", which is the depth of my brick. That will produce the purple line shown on post 191.

Finally the purple lines can be connected on the top of the wedge, yielding the yellow lines from post 189.

Thanks for your patience!

[Gulf]

It sounds like you may have it now. Though I did not quite understand why you would only ".....mark every other brick".
I find it less confusing to completely mark every brick on all for sides before going to the saw.

Also, "Finally the purple lines can be connected on the top of the wedge, yielding the yellow lines from post 189."

It may be just the wording, but that is a little backwards. The Outside diameter scribe (yellow line) from should be established first. Then the tapered cut (purple lines) can then be drawn by connecting the intersections of the Outside Diameter And the 1.5" Reveal

[Macrinehart]

Hehe...did I say "every other"? meant "every".

I think my method for measuring the OD would be a bit inprecise. But I will mark every brick first and then rebuild the arch and check all the measures before I start cutting.

[Gulf]

There are some simple but, precise methods for marking the OD. The link that I shared shows one method. This one was made from a coping saw that I took apart temporarily for the job. There are others. Any offset that will allow you to mark around the corner and attached to the pivot point to gauge the distance from it will work. The staged pic below only shows one brick being marked. However, on this build, the OD and ID for the entire arch was actually marked at one time while it was dry stacked.