Arch to Dome Transition

[SuperT]

I am really nervous about the next few courses of brick. I am at a loss for how to connect the chains to the arch. To make the arch, I took the half bricks and cut them in half to make this so in essence, the arch you see in the pic below consists of 2.25" x 4.5" bricks laid horizontally against the form. Not understanding the physics behind this I am really nervous about the weight of the chains coming above the arch and what will they have to hold on to? I just can't imagine that arch holding any weight. Should I take it down and start with angle iron...its just I really like the look.

Any expertise would be greatly appreciated.

Tony

[Hendo]

Re: Arch to Dome Transition

Tony,

I'm nearly at that stage too, and recommend you have a look at the thread at http://www.fornobravo.com/forum/f8/c....html#post9764 - there are some good suggestions on this topic.

Balty Knowles used longer dome bricks to meet up with the arch, and some Dutch dude used longer arch bricks (there is a URL listed, but the English translation doesn't seem to work any longer). Both methods seem to achieve a similar result.

Or you could develop a 'teardrop' shape at the front of your dome to enable your dome bricks to meet up with the arch.

Perhaps some more experienced builders could weigh in here.

Good luck,
Paul.

[Dutchoven]

Re: Arch to Dome Transition

My concern with this arch is with the thrust from the bricks in the dome. When you are laying the brick on the thinner side called "shiners" in an arch the arch has to be very well designed and set because the line of thrust has to stay in the middle third of the bricks. in the case of a 2.5 in thickness you have .8 of an inch to play with. You might consider mitering the doorway bricks to match the angel of the bricks in the bottom couple of courses and continue on the same miter and you will have an angled siet of arch brick to transition the dome rings onto. Some masons even double the miter on the higher bricks in the doorway arch to smooth the exit of gases from the oven, in that case the bricks will have somewhat of a point. I know it is hard to describe in words but, your arch will be more stable if you lay the bricks on the wider 4.5 inch side.
I will see if I can take some pictures for you to give a better idea of what I mean.
Best
Dutch

[dmun]

Re: Arch to Dome Transition

I second Dutchoven's suggestion that the bricks laid on their narrow side means it's a little too weak. You don't have a side view, but I suspect the bricks don't go back very far, and remember that the oven curves in strongly at that point. You might consider re-doing your arch with a hollow form that you can leave in place until the dome is completed, and laying an arch with deeper bricks, laid on edge rather than face.

Remind us again, what mortar are you using?

My personal preference: I don't like angle irons. I think the huge difference in expansion between brick and iron makes that a weaker choice than even an indifferently built arch. That said, there are lots of successful ovens with angle irons.

[SuperT]

Re: Arch to Dome Transition

So TEAM FORNO

After reviewing Balty's as well as the German page I couldn't read, I thought, what if I take the water saw or my angle grinder and using a whole brick on edge, fit it onto the arch bricks where the chains join and then have the other side sloped on the angle of the next chain. Kind of a hybrid of Balty's and German Dude...It might not be the prettiest, but that part will be covered anyways?

See my diagram...am I on the right track?

Tony

[maver]

Re: Arch to Dome Transition

I think that would work if this doesn't push the arch too far into the oven - you may need to do less than full length bricks in the middle with full length on the sides due to the curve of the dome away from the arch. If you stagger the joints rather than placing it directly over the first chain of arch bricks it should be stronger. Your idea saves you having to rebuild the arch, but that's extra cutting. I think building an arch is more challenging though. You will be able to see the seam on the underside of the arch - it will look like a double arch, but you don't have to tell anyone why it's there and can instead just tell them that a single arch did not pose the required degree of difficulty.

Marc

[SuperT]

Re: Arch to Dome Transition

I like that :-) extra difficulty; as if I needed any...I drew out the principle but like you said, I'll have to cut to fit to make sure the dome curve is maintained in the middle as opposed to the sides and did plan to stagger them. I'll let you guys know how it turns out.

Thanks
Tony