dmun's 36" geodesic oven part II

[HeyJim]

Re: dmun's 36" geodesic oven part II

Um, the geodesic oven is really thin, and therefore brittle. I wouldn't even think about it for a mobile oven. I predict it would vibrate apart on the first ride. Any sort of mobile oven is best with a Modular Refractory Oven Do a forum search for "mobile ovens" for much discussion on this topic.

Hmmmm, the one I saw wasn't very thick, but was a refractory oven. And it wasn't modular. But I'll look at the threads about it when I return from camping this weekend.

[3G_]

Re: dmun's 36" geodesic oven part II

I was wondering if anyone has used large format clay paver to create the pentagons and hexagons to buil an oven. Large format pavers are coming out in 400x400x50mm and i though you may bre able to cut the entire pentagon out of one??

[dmun]

Re: dmun's 36" geodesic oven part II

In the US, all our paver slabs are portland concrete based, and that wouldn't do at all. If it were actual brick material it might work, but there would be a LOT of waste.

At the end of my cutting i came up with an almost-no-waste method of making the triangles:

http://www.fornobravo.com/forum/8/dm....html#post4104

[3G_]

Re: dmun's 36" geodesic oven part II

Most common are concrete but you can get solid clay pavers. The waste doesnt worry me too much if the design can be achieved. I has a look at the geodesic link but couldnt get me head around it. Will spend a bit more time on it.

[ThisOldGarageNJ]

Re: dmun's 36" geodesic oven part II

dmun,
How hard was it for you to get building permits for this project ? Did they require formal plans ? Just curious because Ive never seen an oven and fireplace together and wondered how the building dept. felt.
Mark

[dmun]

Re: dmun's 36" geodesic oven part II

At the time I built the oven, and since it was attached to a workshop instead of the house proper, I decided to do without permiting, figuring that sometimes it was better to ask forgiveness than to ask permission. I really wouldn't recommend this. It could raise problems with insurance, with resale, and of course there are significant problems, delays, and fines if you get caught and they issue a stop work order.

As far as what would be required, a simple drawing may suffice. It depends entirely on your local building inspector, who is a law unto him/her self. They may require plans drawn up by an architect or structural engineer. You should emphasize that it's a masonry fireplace, which falls well within the experience of local inspectors.

[ThisOldGarageNJ]

Re: dmun's 36" geodesic oven part II

wow,, you like living dangerously.. I have dealt with many building inspectors and they make a scorned woman look like a boquet of roses. In a nearby town they made them take the whole 2nd. floor off an office because it was 6" over the planned height. Keep low, fly under the radar. Good Luck

Mark

[ThisOldGarageNJ]

Re: dmun's 36" geodesic oven part II

Hi DMUN,
Have you closed up everything for the rain ?? How about a progress report and some more pics ??

Cheers
Mark

[rblanchette]

Re: dmun's 36" geodesic oven part II

Wow, amazing project you've managed Dmun. I found this thread searching for ways of creating a form for a geodesic oven made with castable refactory. I'm looking at making a geodesic mold and then pouring a castable to whatever thickness will work the best. If you could have made yours thicker then the 2.5" that you did, what would you recommend? Much thanks for the 2 great threads!!!

Rob

[dmun]

Re: dmun's 36" geodesic oven part II

Thanks for the kind words. I'm not a fan of concrete ovens, I just don't like the way the stuff looks, but that's personal preference. You could certainly cast those segments, and in fact one of our members did.

If I built another oven, it would be thicker, and I'd use the more conventional pompeii construction. The advantages I imagined that would come from a thinner oven, mostly quicker heat up, didn't materialize. Also, a thicker wall oven is MUCH stronger. Remember, it's a moving object: Every time you heat it up, it expands, and vice versa.

[rblanchette]

Re: dmun's 36" geodesic oven part II

Any kind words you receive are small in comparison to the amazing job you did, and documented for all of us to learn from, if not aspire to.

So I should forget about castable and go with the firebrick? The first place local that I found firebricks had the 9x4.5x1.25 bricks for $6 each, which is why I started thinking about castable. Found a cheaper supplier yesterday for bricks, but no line on castable so bricks it may just have to be.

[dmun]

Re: dmun's 36" geodesic oven part II

The one and a quarter inch thick bricks are called "splits" and around here they are the same price as the full sized ones. They are mostly used for lining wood stove fireboxes.

Firebricks are still a buck and change on this side of the border. You may want to mount an expedition to Buffalo if our Northern neighbors are charging six. Even if they hit you with import duty (which they shouldn't, nafta and all) you'd still be ahead.

[Dourdd]

Re: dmun's 36" geodesic oven part II

Dmum, why d'ya think heat up time isn't quicker with thin bricks? Theoretically, it should be....

[btflorida]

Re: dmun's 36" geodesic oven part II

Dmum

You mention that if you had to do it again you would go with a traditional pompeii design. Besides the heat up time you mentioned that it would be stronger. What is your concern about the strength? You haven't mentioned any problems with yours about any strenthe issues.

How does yours stack up to heat retention? Is there any problems with that?

I am in the planning stages and space is a concern. One option I was looking at was doing a pompeii design but stacking the bricks on their sides rather than on the flat. It seems that the sides would then be the same thickenss as the floor.

The only negative I see is less heat retention and any strength issues you mention. I only plan on doing a few pizzas followed by a loaf or two of bread for the family.

Thanks for any input.

bt

[dmun]

Re: dmun's 36" geodesic oven part II

What I did was very fussy and time consuming, and I had the same cracking issues as everyone else. I just don't think the fussing cutting of the geodesic patterns is beneficial. As far as strength is concerned, My oven has been in use for three seasons and I don't see any deterioration aside from the initial cracking.

My issues with dome strength is a greater understanding of dome and arch dynamics from this page:

Auroville Earth Institute, training courses, workshops on Vaults, Arches, Domes(VAD), stabilized rammed earth walls, compressed earth blocks, vaulted structures, compressed stabilised earth blocks, rammed earth.

A thicker dome can contain the ideal catenary shape within it's dimensions: thinner domes can't as shown in this illustration:



If you're going to lay your bricks up sideways you have to come up with some way for them to fit together, even if you don't go the geodesic route. The gaps between bricks will be an order of magnitude larger than if you lay them up sideways.

Like you, I had limited space. I had decided to fit the whole thing into a five foot square, and chose a conventional brick cladding, so I was squeezed to begin with. In retrospect I would have met the same space concerns by trimming the lower courses of brick where the circle intersected with the rectangle, but laying the oven up in the usual manner, with the four inch thick dome everywhere but in the three spaces where it butted against the side walls.

As concerns heat up time, and heat retention, I don't see any real difference between my thin oven and the ordinary pompeii. I suspect that during heat-up and pizza cooking, the inner part of the dome is what heats up.

Good luck with your project.