36" Pompeii Build in the desert

[jim lofaro]

Been thinking about the brick angle/bevel jig (see photos). Stole the design from Russel et. al. Anything else to consider in the jig design?

I labelled the plate, stop, and lever. Not sure if these are the right terms but… Seems like the side angle is determined by elevating (pivoting) the top plate and the bevel by moving the lever. Sound about right?

Russel mentioned in post #90 that “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.” I am not sure what that would look like in real life. Do I cut an inch in from the inner portion? 2 inches? Any photos out there of these limited cuts?

[deejayoh]

With that thick of a base, you may lose some of your ability to cut through some of the sharper angled bricks - I know that issue doesn't come up as much with this design - but something to think about. you could gain 1/2 or so of additional headroom by using plywood or steel for your base.

[jim lofaro]

Thanks Deejayoh. BTW, grand job on the dome calculator. It has forced me into a relearning event for radians, trig functions, etc.

Metal jigs certainly have an appeal. Let me try a few cuts with this apparatus. Maybe then take the jig to a new level.

I have a bit of an overbite (2-3 mm) at a few locations between my soldier course and the first chain (see photo). Is this a problem? What is the best way to correct this out-of-round problem?

[UtahBeehiver]

Adjust your IT to gradually move back to round.

[deejayoh]

Can you post a picture of your IT? I suspect the issue might be that it's not hitting at the center of the brick

[jim lofaro]

So looks like I got it wrong. The tilt is the angle of the plate while the side angle is the angle of the lever:
TILT = the angle of the plate = Column NTexas's template
SIDE ANGLE = the angle of the lever = Column O

See previous post #93 for what I call Plate and Lever and photos for the dome calculator spreadsheet input and output.

Also trying to figure out how to create a template for my dome bricks like Texas (https://community.fornobravo.com/for...jigs-and-forms) (see photo). Looks like the inner bottom and outer bottom calculations are in the spreadsheet but I do not know how to calculate the Top calculations (inner Top and outer Top). Any help would be greatly appreciated.

[UtahBeehiver]

I did my build before DJ put together his great spreadsheet. I used the following table as benchmark for cutting the bevels and tapers. As I mention before, only cut 5-6 bricks at a time and dry fit to see if you need to make adjustments. In Tex's manual calculations, it you look at the description in his post he is using the new bottom radius of the new course and the top radius of the existing course. You just have to get in there and experiment, there is no one size fits all process that works for every build. Don't get to caught up in over thinking it.

[JRPizza]

Jim, it looks like you have decided to both bevel and taper your bricks? That is more work than necessary to have a pristine looking dome interior, but like Russell says there is no one size fits all solution. I also used DJ's spread sheet when I cut my bevel angles and it got me very close. Between my beveling setup being not too precise, my ability to set the angle exactly, and some minor geometry differences (I don't think my oven height, radius, etc matched the spreadsheet exactly), I used the spread sheet as a guide to set my angles. When starting a row, I just beveled two bricks (one left and one right) and placed them in position to see if there were any adjustments needed (any exposed inverted vee). If there was I just raised/lowered my "jig" and kissed the beveled edges with the saw to correct,then cut the rest of the row with the adjusted setup.
Another quick trick - if you are going to try to eliminate having your vertical joints align, you will make the bricks progressively narrower as you build up. Since my cuts were not exactly matching the spread sheet, I figured out that the width of the base of the bricks in a row should be cut the width of the top of the bricks on the row below. If you do this and start placing the bricks opposite your opening and work towards the front you will have all evenly spaced joints. It took me a while to figure this out which is why I ended up with a few mismatched bricks on my lower courses. There is a point near the top where the bricks starting getting pretty narrow where you can go to double the width of the tops below and reduce the amounts of cuts. You can see this if you check out some build pics.

[jim lofaro]

So I compared the bottom inner numbers used in the DFW build with my numbers from the dome calculator and found for the first four chains there were only minor differences. I used the Top numbers from the DFW build and the Bottom numbers from the calculator to create a paper template for the first chain (see photo). Transferred the template to a brick and adjusted the dome brick jig to match the template lines. Cut and placed the brick. Eureka; or at least I see no space to speak of. Not bad; 8 days to cut 3 brick.

[UtahBeehiver]

Although still a dry stack, be careful of the joint bond. Right now one course one brick over joint of soldier joint. You may need to adjust a width to avoid vertical bond joints.

[jim lofaro]

Mortared the first row in using the DFW brick template method to set the jig up. My major take away from this exercise is that I have absolutely no faith in my wooden jig configuration. Think I will attempt to build a metal jig and compare that to the DFW brick template for the second row.

[jim lofaro]

Well looks like 3 days of rain are scheduled here. Unheard of. Gives me an opportunity to catch up on reading/writing.

Deejayoh; I woe u a picture of my IT. After the rains.

JR in post #98 are you suggesting I could get a tight fit with just the bevel cut (2-20 degree measurements for my build)? Also u mention a quick trick of using the inner top measurement of the previous row as the as the inner bottom measurement of the next row (see sketch)? Do I have this right? Sort of the equivalent to one man’s ceiling is another man’s floor; dimensionally speaking of course.

Completed the metal bevel/side angle jig. Metal workers of America have nothing to fear from me. Also cut out a brick template for the second chain using the same method as I used for chain 1 (Post #99).

[JRPizza]

Yes, you can make your interior totally tight, or as tight as possible, only using bevel. Lots of builders have done this, and several that used the taper have said they would bevel only on their next build. I expanded on this in the post linked below (click on the #42).
Also, yes, "one man’s ceiling is another man’s floor; dimensionally speaking of course". The amount of bevel gets more pronounced as you progress up the dome, making the bases progressively smaller (at least until you can go double wide) will help you keep all your bond lines at visually optimum spacing. I don't know how structurally important this is, as I developed a crack that went right through a brick, but it was what I did trying to copy some of the craftsmen (craftspeople?) on the forum. You start out getting two dome bricks per full brick, then as the dome bricks get smaller you will get to three, then eventually four course bricks per full brick. That is when you can double the thickness and go back to two bricks per full one. Does this make sense? If you don't care about vertical bond lines, you can certainly build an oven with less cuts and waste.

[jim lofaro]

Actually the 2, 3, 4 and back to 2 dome bricks/brick does make sense.

[jim lofaro]

Completed the second chain and made initial contact with the inner arch. Used the floor/ceiling method described by JR and the angle from the spreadsheet. Observed that using the bevel only creates angles on the sides of the dome brick. More at the bleedin’ obvious than anything else but it was news to me.

Set the angle of the jig using wood blocks cut to the height of:
Opposite = adjacent * tangent(@)
Such that for course 2:
Opp = 800 * tangent (3.3 degrees) = 11.5 mm
Where 800 is the width in mm of the bottom jig plate.

Not sure if this is proper but appears to work for chain 2 and 3.

Starting on chain 3 that will be the first major intersection of dome and inner arch. I will be on the lookout for the DD.