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dmun 07-02-2006 09:08 AM

dmun's 36" geodesic oven
This post marks the start of the construction of my pompeii inspired oven. There has been a lot of discussion about how the bricks could be cut so that they fit evenly,without mounds of mortar. This usually involves the idea of three dimentional trapezoids, which are different on every level. My idea is to create an oven using the form of a geodesic dome. Anyone who has seen a soccer ball is familiar with the idea:

It's hexagons alternating with pentagons. Geodesic domes are constructed from triangles, and the pentagons are made of five triangles, and the hexagons from six triangles. What size to make the triangles? Here's a handy web-based dome calculator from Desert Domes.

But, but, but, (I hear you say), fire bricks are rectangles and you need triangles, and triangles with 6 1/2 degree tapered edges! This is crazy!

That's it exactly. I am crazy, and I'm not advocating that anyone else do this. If you want a perfect fit oven, buy one of James' modular ovens. As I explained to a friend the other night: You've heard of labor-saving appliances? Well a wood-fired brick oven is a labor-consuming appliance.

dmun 07-02-2006 09:11 AM

CAD stuff
Here's a map of the top of the oven, with the two types of triangles labeled:

Here's a side view in outline:

Here's a look at the two types of triangles, superimposed on the size of a firebrick:

Here's more of a 3D look:
Click for a bigger version of this drawing

That's all for now. There should be some progress pictures this weekend.

dmun 07-02-2006 09:15 AM

Here's a flashback to before the rains
Back before the east coast was under water, I started digging the footings for my oven. Since this will be part of an existing structure, and support a two-story masonry chimney, it needs full footings below the frost line. Here's a picture of the dig:

As soon as the mud puddle at the bottom of my three foot rectangular hole dries out, I'll be back to pouring footings, but in the meantime:

dmun 07-02-2006 09:19 AM

brick triangles
As previously mentioned, my oven will be made from triangles, tapered 6 1/2 degrees on a side. Here's a dimensioned drawing of the triangles:

That side angle? Here's the jig on the diamond saw, for cutting the angle:

Those are aluminum triangles, screwed on from the bottom through the drain holes.

dmun 07-02-2006 09:41 AM

cutting the triangle blanks
The bricks, which are standard grade firebricks, in "red" (really sort of a reddish brown) from Progressive Brick, in Hasbrouck Heights NJ. That's a 45 minute drive from me, but i really like the darker firebrick. They were .70 usd per brick when I bought 150. I also picked up a 50 lb bag of Heat_Stop, for fifty bucks.

The bricks cut with amazing ease. The Chinese saw worked like a champ, blasting through the firebricks quickly, easily and accurately.

I started by cutting the bottom edge angle for every full triangle, and then cutting the pointy tops of the "6" triangles. This left almost enough ends to make the tops of the "5" triangles. I cut one corner off a bottom brick to get the right number.

I then mixed up a little Heat-stop to the consistancy of peanut butter, and spread it on the uncut edge of the triangles. I put them in position, and scraped off the excess. Later today when they dry more, I'll scrub the visible face with water and a brush.

james 07-02-2006 12:42 PM

This is so cool, I'm at a loss for words -- so I will use the highly articulate "wow." We are all going to be engrossed watching your progess and seeing your "dome" come to fruition.

This will be the Swiss Clock of Italian Pizza ovens.

I'm sure you have though of this -- what will the impact of thermal expansion and contraction be on the various pieces and mortars, along with the pull of gravity? I have to imagine that they will move in harmony, and that the geodesic dome will stand forever.

Keep it up!

dmun 07-02-2006 01:36 PM


Originally Posted by james
I'm sure you have though of this -- what will the impact of thermal expansion and contraction be on the various pieces and mortars, along with the pull of gravity? I have to imagine that they will move in harmony, and that the geodesic dome will stand forever.

I think the refractory cement is closely matched to the expansion of the firebrick. A couple of years ago i put a Rumford fireplace into the opening of an old coal grate in my house, using the same materials. I've not had so much as a hairline crack, although it's not subjected to the same extremes of heat.

As for geodesic domes, they are hugely strong. The place that has the dome calculator uses them to make pavilions for things like Burning Man. They are made out of half inch conduit, and you know how flimsy that stuff is. They crimp and bend the ends, and bolt them together, and multiple people can climb on the frame.

DrakeRemoray 07-02-2006 06:31 PM

This is truly amazing. I cannot wait to see some pictures of assembly!!


christo 07-02-2006 07:56 PM

That's what I'm looking for!
Hadn't thought of the geodesic dome when I was trying to calculate brick angles. I figured I would end up with a cut list for each row of bricks.

Going this way makes all those calcs un-necessary.

Nice Job. Can't wait to see it assembled.

Fio 07-02-2006 08:37 PM

Looks pretty neat. Take lots of pictures, I'll bet you can sell your story to Architectural Digest.

I'm amazed.

- Fio

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