Indispensable tool issue - i'm flummoxed!

[alexi82]

Re: Indispensable tool issue - i'm flummoxed!

was thinking about that earlier too...

ive got a 20 inch wide and 12 1/2 inch opening planned...that is 12 1/2 inch at the top of an arch.

ive marked out where the opening will be, and where the offset will be for the door jam. to be honest i was going to build up two courses to the opening bricks, build the arch, and then keep going. If i have the opening in the right spot in relation to the dome shape, it should just build around and fit nicely?

[wotavidone]

Re: Indispensable tool issue - i'm flummoxed!

G'day
You now appear to have to IT in place and operational.
Next brain teaser is make a mock up of entrance (cardboard cut out will do) and use you IT to find out where your dome meets the entrance.
A 42 in high dome nominal entrance is 12 1/2 in high 20 in wide.
I'm not bringing this up to tease you. You may as well be prepared now.
These guys are better than me at this point, they're your brains trust and will get you through the dreaded transition.
Regards Dave

Dave raises a very good point. Referring again to the picture of my last build, that IT was indeed used to check that the brick would meet the arch at the top.
I put the swivel point at the centre spot I had decided on (arch was already built) and put a half brick in the IT and made sure that the brick sat on the bevel/chamfer without the bottom edge hanging below the cut edge of the arch bricks.
The brick hung down just a tad, so I moved the centre point forward about a half inch, so the brick was in the right place. Then the IT was used from that position to start the bottom course of the brick in the right place.
It's all about looking at the oven in plan view and ensuring the arch is set back far enough in the circle that everything mates up.
I'd drawn it out on paper to scale with a compass and a square, but it doesn't hurt to check.


Edit:
However, if you want to build the arch as you go, that will work too. If you look at the chamfer I put on the arch bricks in that oven, you'll see they are all the same, I just measured 50mm from the corners and cut a triangle off.
They don't have to be. If you are building along and realise that the dome bricks are going to hang off a bit, the back of the arch chould be a bit lower, just measure say, 35 mm from the corners and cut the chamfer a bit bigger as you go, so you have a full flat surface to meet with your dome bricks.

I wish I was there, it's a lot easier to demonstrate than it is to describe in words.

[alexi82]

Re: Indispensable tool issue - i'm flummoxed!

Yea i can appreciate that it is easier to demonstrate!

I get what you are saying. The idea is you don't want any brick hanging below the eyeline of the arch...so it isn't necessarily a structural issue but an aesthetic one?

Most people seem to say build the arch first so that is what i'll do. i'll lay the first course and the arch...

I am happy with my IT but i should have said that was just a mock up. I want to have something a little more sturdy than a screw into a bit of timber as my pivot point. I'm off to bunnings this morning so going to grab a couple small things. I have some threaded rod at home already so will get a few bits and get the welder out.

from what i have read, casters are good pivot points...?

[wotavidone]

Re: Indispensable tool issue - i'm flummoxed!

We were far too tight-arsed to buy castors for pivot points.
But the castors do appear to work well, so why not?

To me the idea is to ensure the whole thickness of the dome meets the arch. I just like the comfort of knowing we have full thickness mortart joints, etc.

Anyway, in the build thread for the oven my mate and I built early January,
take a look at post #22.
I still managed to build in a little bit of "teardrop" , that we had to cutom cut a couple of bricks at the top of the arch, to take out the tear drop in the next course.
It'll all work mate.
You are close neough to start laying bricks.

[alexi82]

Re: Indispensable tool issue - i'm flummoxed!

Haha fair enough. Last time i build a barrel so I guess I'm keen as to use the IT just for something different...and want to get it right but i'm only faffing around because I won't be laying the first course for a few more days yet so all I can do is muck around with that. Gives me time to think!

[Greenman]

Re: Indispensable tool issue - i'm flummoxed!

The beauty of the castor is that there is no engineering required, just drill the appropriate size hole in the castor wheel and screw the threaded rod into that. Dead easy and cheap as chips.

[alexi82]

Re: Indispensable tool issue - i'm flummoxed!

I now know what you guys were talking about re arch and dome transition. I've used the IT to figure out arch position.

Glad I did. I was probably 2-3 inches out from where it should be.

Might look into tapering some of the bricks for the arch... Seems to transition better in the pics I've seen?