Jim's Build for the Common Man

[Tscarborough]

Re: Jim's Build for the Common Man

Unless the material the arch is made of is strong enough in tension you need to. Even a hemispherical arch still has force vectors not in line with the legs.

[oasiscdm]

Re: Jim's Build for the Common Man

Didn't think that was necessary for a hemispheric arch.
Brickie?

[Tscarborough]

Re: Jim's Build for the Common Man

Any arch should be buttressed.

[jimkramer]

Re: Jim's Build for the Common Man

I decided to go with an arch, instead of a straight opening, based on forum feedback. I removed one opening brick from each side, to lower the starting point of the arch, so I could make a steeper arch that makes a 12.5" opening. You guys think I have to buttress it, or is it steep enough?

So now I have to cut arch bricks. Me and a friend stared at it for 20 minutes before calling it a day. It was too confusing to figure out how to determine the angle of the cut on the inside of the oven, that the dome bricks will be resting on. Any tips for how to figure that out? I'll read through a few more threads, so it will be more clear.

[david s]

Re: Jim's Build for the Common Man

Be careful if using insulating firebricks in the entry if in an area where they will be subject to wear and tear. Although they will insulate very well, they are quite soft and brittle and will abrade easily if banged with bits of wood or metal peels.you should be able to arrange it so they are not exposed.

[brickie in oz]

Re: Jim's Build for the Common Man

Beautiful. Your insulating bricks don't bear any weight above them, right?

Just call me Al, no need for beautiful.....

I have insulating fire bricks in the base of the chimney, from memory there is about 600-800kgs sitting on them, so they can take weigh alright.

[jimkramer]

Re: Jim's Build for the Common Man

Brickie-

I just saw your oven pics. Beautiful. Your insulating bricks don't bear any weight above them, right? Whatever spans that opening in my oven will have bricks on top, so I don't think mortaring them straight across will work.

[brickie in oz]

Re: Jim's Build for the Common Man

At this point, I'm not going with a straight opening for time savings. I actually think the straight line will looks better with the lintel, instead of a brick arch. But maybe I'll do an arch for longevity.

I actually went with the flat entry, but being a barrel shape the flames dont exit the oven proper, they go up the internal flue instead.

My flat entry is made entirely of insulating fire brick (no lintel) and just glued into place with refractory bog.

[jimkramer]

Re: Jim's Build for the Common Man

At this point, I'm not going with a straight opening for time savings. I actually think the straight line will looks better with the lintel, instead of a brick arch. But maybe I'll do an arch for longevity.

[cobblerdave]

Re: Jim's Build for the Common Man

Seems like it could be bad, to have red hot iron under the weight of bricks. However, it's in the fb basic plans. I would think that means that other people did it a long time ago, before an arch became more popular. Don't know if those ovens are still standing. Do you think the angle iron could bend or break? The other option would be to span the opening with a cast lintel, but would that be strong enough across a 20" span, since I can't use rebar to reinforce it?

Gudday
My ovens got the steel lintel on the oven entrance and still standing, and I recon will survive a bit longer. Yes I have cracks, no biggies and also rust, not that bad.
Would I build that way again, No. I have built an arch into the outer entrance now and I can tell you they are not that hard to do. And with the help of this lot you will be able to put up an arch ,no worries .
Regards dave

[mrchipster]

Re: Jim's Build for the Common Man

Yes, that part of the oven gets quite hot. All the gasses leaving the oven (and sometimes a fair bit of flame) pass through the top of the flue arch. I would cast, not carve w/refractory.

Sometimes a fair bit of flame.

[jimkramer]

Re: Jim's Build for the Common Man

Seems like it could be bad, to have red hot iron under the weight of bricks. However, it's in the fb basic plans. I would think that means that other people did it a long time ago, before an arch became more popular. Don't know if those ovens are still standing. Do you think the angle iron could bend or break? The other option would be to span the opening with a cast lintel, but would that be strong enough across a 20" span, since I can't use rebar to reinforce it?

[brickie in oz]

Re: Jim's Build for the Common Man

The top of the oven opening will be supported by angle iron

Bad move, steel and fire dont like each other, or more correctly they love each other too much.

[deejayoh]

Re: Jim's Build for the Common Man

Deejayoh, if it's in front of a heat break, you think I'll still have to use refractory? Not sure I can carve and shape that.

Yes, that part of the oven gets quite hot. All the gasses leaving the oven (and sometimes a fair bit of flame) pass through the top of the flue arch. I would cast, not carve w/refractory.

[jimkramer]

Re: Jim's Build for the Common Man

Here's a very rough sketch of the lintel as I see it now. It started out as a way to make it all faster, by making just a straight block to hold up the chimney (round clay flue, or duratech). But now it's turned into something that will take more time and experimentation than an arch, which I'm fine with now, since I really like the idea.

The top of the oven opening will be supported by angle iron, and the lintel will be separate from the dome, in front of a heat break (that I still have to work out.) I'll reinforce the lintel with thin rebar. Not sure how I'll get the curved look yet - by carving a block of setting concrete, or using chicken wire for curved parts. It might not come to as much of a point on either side as in the sketch, but this is roughly the idea - something shaped and curved instead of a straight edged block.

Deejayoh, if it's in front of a heat break, you think I'll still have to use refractory? Not sure I can carve and shape that.