36" Pompeii Build in the desert

[UtahBeehiver]

https://community.fornobravo.com/for...ctoforno/page4

[jim lofaro]

So back to my paper dolls, if I look at Joe’s sketch in post 55 of this thread I see the IT brick intersecting the upper back corner of the TDC brick. The point of intersection of the IT and TDC bricks is essentially level and also on the same plane as the floor. So my question concerns the orientation of the IT brick with respect to other arch bricks. Is the IT brick level with the floor or level with the back corner of the arch brick (see photos)? Not sure I have my geometric descriptions right so feel free to correct any and all.

[JRPizza]

Jim, I think you are a little over thinking, and I don't understand your images above. Looking at Joe's picture in post #55, he shows the TDC brick and a dome (4.5") brick held in the IT in proximity to the top of the arch. The angle of the top of the TDC brick should be such that the IT held brick is tight to the arch on the inside, and there is a mortar gap on the outside similar to the rest of the bricks in the dome at that height. That was what I shot for. Each row will "mate" with the arch in a unique way, but you just want to sort of match the shape of the dome on the inside. I did a lot of custom cuts and tried to show them. Here is a shot of one of the lower row bricks intersecting the arch. See how I angled the brick to the right to sort of lay over the arch? I built up my arch as I went as that helped me visualize and eventually mate the arch and the dome together.

[Gulf]

Jim,

I am sorry about confusing you with my drawing in post #56. Forget about the orientation of the brick to the floor. The only things that you should be concerned with when cutting the inner arch is the slope and the distances from the center of the dome at the floor. I would like you to step back for a minute and think about the way some of the first domes were shaped. They would take a string and tie it to the anchor point at the center of the floor. A knot was tied at the exact distance of the ID of the dome. That was one of the original ITs. Though not perfect, it had the slope and the distance from the center for placing each brick.

Now, take a string or cord that does not have a lot of stretch in it. Tie it to the anchor point at the center of your floor. Tie a knot at approximately 18.5" for the ID and another for the OD at 23". When the string is pulled taught, every thing you need is there. The slope, the inner radius, and the outer radius can then be transferred to both sides of each arch brick. You can see in the below pic that the string will not reflect the off set of the brick as it is sitting in the IT, but it is close enough for "government work" . I still advise using the IT to do this, but hopefully, the string will help explain how the IT is being used.

Now apply this to these other posts in your thread as well as what JR has above.

https://community.fornobravo.com/for...763#post402763

https://community.fornobravo.com/for...599#post402599

https://community.fornobravo.com/for...756#post402756

I hope this post doesn't muddy up the water even further.

[jim lofaro]

Thanks for the guidance guys. Looks like I will have a few methods to check and recheck the inner arch angles prior to making the cuts. My goal is to gain some basic understanding of applied geometry with this build even if everyone on this forum has to suffer a bit.

So I have gone back to finishing the soldier course and mortaring 2 of the vertical supports for the arch (see photos). My thought here is to get a more realistic view of the arch pillars prior to marking the arch bricks. Any flaw in that logic? I will end up with ~0.5 inch gap on each side where the dome meets the arch pillars. OK just to mortar that gap in? Any thoughts on mortaring the soldier course to the dome pillars at this point?

Also thinking about a redo of my IT. I like the idea of being able to mount different heads to the IT.

[UtahBeehiver]

See if this helps Taper Arch Help.pdf

[jim lofaro]

The quest continues. Reworked the IT using a castor, ½ inch rectangle tubing, and 3/8 inch threaded rod. It essentially reduced the number of moving parts compared to the original IT.

I marked the inner (18 ½ inches) and outer (23 inches) dome radii using the IT (see photos). Cut a string and knotted it at 18 ½ and 23 inches running the knotted string from the base of the IT to the outer arch mark. The results of the two methods appeared to be similar giving me confidence in using the IT method for marking and cutting the inner arch angles.

In the mean time I mortared the remainder of the soldiers and the 3 pillars for the inner arch. Dry fit the inner arch with the pillars. Had to recut some of the pillar brick to account for the mortar thickness and dry stacked the arch yet again. Mortared the two 3/8 inch gaps between inner arch pillars and dome yesterday and will check it today.

The plan today now that the pillars are in place is to mark the inner/outer angles of the dome bricks using the IT. The proposed method will be:

• Place the inner arch bricks flush with the vent side inner arch.
• Place a brick in the IT (IT-brick)
• Line up the bottom of the IT-brick with the inner and outer radii marks of the TDC brick
• Mark the slope and the location of the inner radius cuts.The inner radius angle is normal to the slope at the point where the IT-brick contacts the face of the IT (18 ½ inches).
• Using the TDC angle mark the near side of the two adjacent inner arch bricks.
• Mark the far side of the adjacent bricks by lining up the bottom of the IT-brick with the inner and outer radii marks using the far side inner/outer lines.
• Repeat the process of making the near side angle using the previously marked bricks and the IT-brick for the far side angle.

Let me know if I missed anything or just flat got it wrong.

[jim lofaro]

Forgot the photos.

[UtahBeehiver]

Looks like you figured it out . I am assuming your inner dome radius is 18.5" all the way around the dome. If not, it is not a big deal other than you will need to bring back to round as you go up. That is why an adjustable IT is so important.

[jim lofaro]

Here is a question: Can the arch bricks be considered symmetric on either side of the TDC brick? The thinking is I could mark and cut all the bricks say to right of the TDC brick and transcribe those cuts to the left side bricks. Or is it better to mark and cut each individual arch brick?

[Gulf]

They should be symmetrical. However, there is only one mark left to scribe. If you can use the IT to scribe the inner radius underneath the arch, you will have every reference point that you need already marked on each arch brick imo.

[UtahBeehiver]

The right side will not transcribe directly to left side, they are mirror images. Looking from the inside of the dome, the left side of the bricks on the left side of the arch angles downward. On the right side of the right side of the arch this side angles downward. You are only talking 10 bricks, take you time and cut each one it will be worth the effort, once cut you can't go back you already spent a lot of time tapering the arch a little more time won't matter.

[UtahBeehiver]

Again, here is an example, the angles are more pronounce on this build but the concept applies to your build

[jim lofaro]

As usual many thanks to u’all for the guidance. Well I did not read Russell’s post until yesterday and had tried the ‘symmetry’ method which did not work for me. Angles from the right side bricks for the outer dome started to pull away from the outer dome radius line by ½ inch or so. Recut the left side arch brick at the outer dome radius to the tip of the inner dome radius and that looks better to me (see photo). Any other cuts I need to make on the arch? My plan is to build the arch as I go just in case there will need to be refinement cuts as the dome is built.

Starting to think about taper/side angles of dome brick using Deejayoh’s dome calculator spreadsheet and the jigs offered by Texas (https://community.fornobravo.com/for...-forms?t=21566). Any thoughts?

[UtahBeehiver]

Much better, if you build arch as you go, just keep the arch bricks ahead of the dome bricks. Watch out for mortar joint creep (they seem to grow wider) since you have a very small key stone and not much to work with if you need to reduce width.

The spread sheet gets you in the ball park, I would only cut a 5-6 bricks at a time (not the full course all at once), see how they fit and align. You really only need to cut the inner portion of the taper/bevel not the whole side of the brick for a tight inner fit. Let mortar be you friend. Also do the best work on the back half of the dome and make adjustments towards the front half of the dome. No one can see the oops there once the dome is done.