To taper or not to taper?

[SCChris]

Thanks Chip, no worries!..

I took the idea from a roman who found the idea in Athens, after it had come from a Phoenician who knew a mesopotamian who stole the idea from someone in the Hindus valley, who took it from.....

Leveraging ideas makes this site and our ovens better and better..

Anyway, I sure wish I'd found a 14" saw, it would have made the cutting slick.

Chris

[Amac]

Chip

Make sure you keep the top slope of the brick pointed and the center of the floor of the oven

I take it the "and" is a typo and should be "at".
One maybe small point is that if you point the top of the brick at the floor then an IT as designed by JCG31 with a 90° angle will not grip the brick correctly. JCGs IT - which I believe is the best - is designed so that a line through the center of the brick points at the centre of the dome. To fit properly you would need to change the angle of the IT to match the angle of the brick with the top shaved off.

David S

However the higher you go the bigger the horizontal spaces will be

I'm pretty sure you have something in mind here but I didn't notice this - and it doesn't sound right - could you clarify what you mean here? Unless you are not making a hemisphere I would have thought the spaces should be the same.

[mrchipster]

Originally Posted by Amac

I take it the "and" is a typo and should be "at".

Sorry about that it is fixed.

Originally Posted by Amac

One maybe small point is that if you point the top of the brick at the floor then an IT as designed by JCG31 with a 90° angle will not grip the brick correctly. JCGs IT - which I believe is the best - is designed so that a line through the center of the brick points at the centre of the dome. To fit properly you would need to change the angle of the IT to match the angle of the brick with the top shaved off.

That is a very good point and I was always fighting with my ID and that is the reason. I should have shaved off the bottoms of the bricks and that would have fixed the minor misalignment.
You are very observant. Great catch.

Chip

[Amac]

I should have shaved off the bottoms of the bricks and that would have fixed the minor misalignment.

That will probably work fine - if the cut is substantial to be really precise the shaft should be repositioned centrally or there might be a small overhanging "lip" inside at each row. Having said all that it is hard to be so precise.

That IT if it is built accurately grips the top of an uncut brick with it's 90° angle. The top of the brick is then pointing over the dome centre - the bottom of the brick under the dome centre and the centre of the brick directly at the dome centre. So the closest point to the dome centre is the middle of the brick. The top and bottom shold be a little further - the hypoteneuse if you like -so they should be the same.

[mrchipster]

I remember doing the math on this and for true precision both the top and bottom of the brick would need to be cut. And I also remember saying to myself ..... Close enough for government work.....

Chip

[GianniFocaccia]

That will probably work fine - if the cut is substantial to be really precise the shaft should be repositioned centrally or there might be a small overhanging "lip" inside at each row. Having said all that it is hard to be so precise.

I ended up tapering the tops and bottoms of each brick in order to maintain a small outside mortar gap. The overhanging lip I couldn't live with so a couple of passes across the edge of the diamond blade took care of that quite easily.

I'm wondering if just using a dome template may be easier than using an IT?

[Amac]

Chip

Close enough for government work....

Jeez Chip - I had a look at your build thread and I see you actually ground the top layers into rounded bricks - some government work that - very impressive.
Gianni

I'm wondering if just using a dome template may be easier than using an IT?

I'd say some hybrid kinda like what Dejayoh is using would be good. I found the IT good - I see Chip used two at once. I wasn't working fast enough to use two. Also I guess the fact that you had a "compressed" dome would have involved readjustments

[david s]

Originally Posted by Amac

Chip




David S


I'm pretty sure you have something in mind here but I didn't notice this - and it doesn't sound right - could you clarify what you mean here? Unless you are not making a hemisphere I would have thought the spaces should be the same.

Amac,
The horizontal spaces between each chain of bricks will be the same, but the spaces between adjascent bricks ( vertical spaces ) will get larger because the radius gets smaller as you get closer to the top.Therfore you have to cutmore angle off the side of each brick.

[GianniFocaccia]

Also I guess the fact that you had a "compressed" dome would have involved readjustments

This is true. After I cut my dome template I didn't have the patience to design and build an adjustable IT so just went without. It was easy to periodically (every 4-5th brick) stand my dome template up to ensure the next brick was keeping the course in-round. After doing this for a course or two, matching each brick face angle flush against the curvature of the template went fairly quickly.

I think an IT works better if one doesn't need to be fussy about each vertical joint and wants to go fast.
John

[Amac]

OK David - that makes more sense - I guess the word "horizontal" threw me