dmun's 36" geodesic oven

[christo]

The brick thickness on this oven should allow for faster heat up times than most of the ovens I've seen that use 1/2 bricks to make the dome. An obvious result of this - it takes fewer total bricks to make the dome.

A couple questions:

Will you use mortar between the pieces or coat the outer layer?

How thick do you intend to make the cladding? I was thinking that a dry fit with cladding would allow for some movement during final fit.

I'm wondering how you plan to assemble this. Actually having a lot of fun thinking about it. I'm envisioning taking the brick pieces and shaping them in to the hexagons and pentagons by gluing their faces with wall paper paste and heavy paper - the paper and organic paste would burn off in the first firing. I guess that could be done with mortar between the joints as well. If the inner and outer faces were papererd - they would hold their shape easily during handling. (hmm - modular - just like geodesic domes were intended to be - there I go mr. MOTO again)

How will you support the dome over the opening? Looks like you've got a cast entryway in mind.

The add on's to the bricks are not cut at an angle to the other brick. If this joint breaks, with the 6 1/2 degree angle be enough to hold them in?

I guess this is what I was getting to when I asked if you were going to mortar between the triangles - if so the mortar between bricks could errode and allow for some movement.

Never mind, just pulled out my calculator, a 6.5 degree angle is rather significant over 2.5 to 3 inches or so.- Even if the little pieces crumbled or somehow fell out the major brick piece would remain in place. (Moto strikes again) I just like this better and better.

Take care

Chris

[dmun]

Yes, everything will be mortared with Heat-Stop. I want this thing to be so strong you could jump up and down on top of it, not that I would. My vision is a solid unit floating on the fireclay base that would handle linear expansion without cracking. I want a non-mortared joint between the entryway and the decorative front arch, for the same reason

I'm not cladding the outside. I have been thinking for months that you don't need any more thermal mass that is in a modular oven, or 2". It would be different if I was planning to make pizzas all day, but I want this to be a quick and efficient heat oven.

I don't know how I'm handling the top of the entry. I may spring for a couple of refractory lintels if I'm feeling flush, or I may piece an arch together out of all my brick scraps. One thing for sure, there aren't going to be any exposed angle irons over my door.

One final thing about Heat-Stop. It's made for really thin joints, from 1/16 to 1/8 in thickness. My one question was whether it was strong enough to hold the triangles together during the second two angle cuts. I'll know soon.

[Les]

Dmun,

This is a very cool approach (pun intended) - but I don't understand why you would want to wave the insulation. I know if all you want to cook are pies, this would suffice. But down the road, if you wanted to cook a roast or turkey, wouldn't you want to retain the heat? The only downside to cladding your dome is the fact we can't see your awesome tile cutting abilities. Am I missing something?

Les...

[dmun]

Originally Posted by Les

I don't understand why you would want to wave the insulation. I know if all you want to cook are pies, this would suffice. But down the road, if you wanted to cook a roast or turkey, wouldn't you want to retain the heat? The only downside to cladding your dome is the fact we can't see your awesome tile cutting abilities. Am I missing something?

Yes, what I'm not doing is adding a layer of refractory material to the outside of the dome to add mass. Remember that my dome is only 2 1/4 thick, which is thin by pompeii standards. I'm enclosing the dome and insulating as much as possible, I'm even saving the old fiberglass I'm taking out of the internal walls to pile on top of the vermiculite. I'm also considering using a layer of foam below the main slab, just to keep things toasty.

I'm a great believer in insulation, not excess thermal mass.

[CanuckJim]

Somebody, a poet no doubt, said "necessity is the mother of invention." In this case, though, it's innovation is the motherload of invention. This is very fine work, very new stuff and done with artistry and artisanship. Well done, dmun, keep it up, patent it and retire rich and respected. The poet, by the way, was Alexander Pope. Shelley wrote a sarcastic poem about monuments that includes the line "look on my works, ye mighty, and despair." Here, the reverse is true.

Jim

[dmun]

Today I cut the brick triangles that make up my geodesic dome. First:



These are the wooden jigs for marking the shapes of the triangles.

Here is another modification to the saw:



You will notice that I've screwed a piece of plywood on top of my angle jigs. Why? The bricks overlap the cut line, and the angle wouldn't be right if they hit the table on the other side of the cut line.

My concern was that the refractory cement wouldn't be strong enough to stand up to sawing. Not a problem. One day after gluing on the triangles, they were strong enough to saw, and even held the two parts of the shard together:

[dmun]

Here are the cut triangles:



On the left are the "5" triangles, and on the right, the "6" triangles. You will notice how I'm using some brick triangle scraps to prop up the triangles into their correct allignment.

Here's a close-up view of the pentagon:



and the hexagon:



Note how the add-on triangles form a minature form of the polygon in the center. As the engineers say, it's not a fault, it's a feature.

I can, without strain, pick up six of the big triangles. This has given me the idea of pre-assembling the shapes, leaving fewer joints to clean up inside the oven, and perhaps reducing the need for internal supports.

[armac]

Hi,

A first post from a wannabe oven builder.

I came across some interesting software aimed at woodworkers that looks as if it might be the thing for designing geodesic ovens. Here's the link: www.ligno3d.com

I downloaded the trial version, haven't spent much time with it yet, but it appears that it may be very useful to design an oven structure to meet size and volume requirements. At about $100 US, it's not a trivial cost, but if it allows the creation of a specific geometry for a specific purpose, it might be worth it.

Looks like Dmun has opened a really interesting door.

[dmun]

I looked at Ligno's page. A hundred bucks is nothing in the CAD world, particularly for one that offers DXF (design exchange format - the autoCAD translation format) and 3d modeling. The real cost of CAD is the time it takes to learn how to use it.

[james]

David,

If you look at the Forno Bravo Artigiano oven, it has a thin refractory mortar coating that helps give the dome a little more structural integrity. We've shipped the Artigiano all over the world, and have never had any damage to the dome (touch wood). As you say, you can jump up and down on it.

I don't think that the extra 1/4"-1/2" of mass will slow heat up discernably, and it will help "set" the dome. Heck, the Artigiano oven has four handles and you pick it up and set it in place. You could use a more traditional refractory mortar (Refrax or Heat Stop II), or make a refractory mortar from calcium aluminate, sand, lime and fireclay, for that layer.

Also, how much of a mortar joint did you allocate in the cad drawing? 1/16? I am guessing that joint will add up over time.

I definitely think this oven should end up in Architectural Digest.
James