Is this a senisble way to 'flatten' and arch?

[Puy de Dome]

Long story short... was going to build a barrel shaped oven, then after reading stuff here I decided to build a domed oven - the Pompeii one.

Anyway, so I ring my nearest supplier - 100 miles away and am told that they sell firebricks to create a dome.

So I get there...

Uh uh, what is a dome to the supplier is a barrel to me... see this pic:



These bricks are shaped to create an arch...

BIG question: can I widen this arch, SAFELY, by inserting another ordinary brick in between?

See this pic:



I would use a former anyway to build this, but now I am back to building a barrel shaped oven, for better or worse, but it's a fair bit narrower than it would have been if it was a normal dome.

What would you do? Put up with the reduced width (still got the length), or try to widen the arch?

Would it work? Please help.

PdD

[dmun]

Re: Is this a senisble way to 'flatten' and arch?

Guessing from your picture, 16 taper bricks form a 20 inch internal arch, is this correct? (see enclosed sketch)

What are the dimensions of your full size and thin bricks?

What is the target size of your dome?

[Puy de Dome]

Re: Is this a senisble way to 'flatten' and arch?

Yes, the internal measurement is a fraction over 20".

The full size bricks are:
4.5" x 3" x 9"

The thin ones are:
4.5" x 1" x 9"

The wedge shaped bricks are:
3" at the widest point
2" at the thin end
4.5" along the side between these two
9" in length

I have a maximum diameter of 42" to span - anything within that would be cool.

PdD

[dmun]

Re: Is this a senisble way to 'flatten' and arch?

This drawing shows a four inch vertical soldier course, with two rings of taper bricks, followed by a single ring of the three-inchers. It stays pretty close to the semicircular shape, until it gets to the center when all bets are off. Unless you are planning a cut-every-brick perfect fit dome, there's not much advantage in using the taper bricks. I know around here they're a lot more expensive. They would, however, make a great entry arch, as superimposed on the front.

[CajunKnight]

Re: Is this a senisble way to 'flatten' and arch?

Draw out the size and shape you intend for you dome on cardboard or whatever. Lay it on table and lay out bricks. You may have to add straight bricks here and there to get the size and shape you desire. You may have to add a shim to outside face of bricks sometimes, just keep interior brick faces close as possible. It helps to see what you need to do. Now trace the bricks with description of each and keep as a guide.

[Puy de Dome]

Re: Is this a senisble way to 'flatten' and arch?

Thanks both.

So technically, and within the laws of physics/gravity, would the dome stay together?

It appears that using three, say, standard bricks in the centre of the arch is asking for trouble, because they appear t be able to drop down.

Or is it simply the case that the taper bricks either side act in a sideways movement to hold all bricks together?

If so, then this is going to be the way to go to get the width.

PdD

[dvonk]

Re: Is this a senisble way to 'flatten' and arch?

If you are building an arch (not dome) two flat bricks together is not good from my point of view. I wouldn't do that at least.

[Puy de Dome]

Re: Is this a senisble way to 'flatten' and arch?

Dvonk - I'm inclined very much to agree with you on that.

However, I do think that the second image Dmun attached looks promising - two tapered bricks followed by a straight one, then two more tapers etc.

To my mind, this effectively elongates the tapers.

PdD

[dvonk]

Re: Is this a senisble way to 'flatten' and arch?

Yeah.
Most of all I didn't like the image of two flat bricks on the top of arch. But tapered-straight-tapered in any combination should work, I guess.

I even made a couple of semi-taperd bricks - just around the keystone.

[Puy de Dome]

Re: Is this a senisble way to 'flatten' and arch?

Think I'll go for it.

Thanks.

PdD

[Puy de Dome]

Re: Is this a senisble way to 'flatten' and arch?

Well, for better or worse, I went ahead and made a former for the arch.

Wish I hadn't...

Here's the first arch:



As you can see, it's a bit wonky - not helped by my cack-handed jigsaw abilities - the form wasn't so great.

Since that photo I have laid the firt five chains or so by hand with no former, and have decided to pay each chain from here on up y supporting each chain with sticks at the appropriate place. With the grey fire cement, it all feels very secure.

I'll follow this with 1" ceramic blanket, and then two or three inches of vermiculite (do you guys call it 'vermicrete'?). After that will be some more padding until I get to the outer shell which will be brickwork of some kind.

Here's a photo of the oven and stand as of half an hour ago:

[dmun]

Re: Is this a senisble way to 'flatten' and arch?

It appears that using three, say, standard bricks in the centre of the arch is asking for trouble, because they appear t be able to drop down.

Remember that when you get to the top of your dome, it's a group of odd wedges, or whole brick segments in a bunch of mortar. This is particularly true with three inch bricks instead of 2 1/4 inchers as it exaggerates the spreading of the bricks as the circles get smaller.

[Puy de Dome]

Re: Is this a senisble way to 'flatten' and arch?

Well, here it is a couple of days later.

First of all, here's a pic of the sky when I just went outside to take some photos for you:



Nice, eh?

Anyway, here's the business:



Shows a frontal view of things.



More of a close-up of my cack-handed brick laying.



So it comes together pretty much. I'm now expecting to have a squarish-front/chimney piece, with the main oven being covered by insulation and then a covering of some sort - hopefully bricks, but might be some other materials that I find.

[Wlodek]

Re: Is this a senisble way to 'flatten' and arch?

Not sure what's wrong with your brick-laying. This whole layout looks really good!
What is the plan for the roof? Not sure it can be bricks in our climate ...
W.

[Puy de Dome]

Re: Is this a senisble way to 'flatten' and arch?

w-

Roof-wise - I decided on putting on the insulation layers and then getting a plasterer to apply a layer of render/stucco, then paint it.

I did at one point think bricks could look nice, but I have bought two lots of second-hand/unwanted bricks of fleabay, so to apply a third non-matching set on the roof could have looked too patchworky.

Brickwork ain't too bad - a few errors here and there.

PdD