dmun's 36" geodesic oven

[dmun]

dome test assembly

Tonight since I'm getting close to putting up the dome, I did as much dry assembly as I dared without a very good armature.



The first two rows pretty much support themselves. I used a stick to hold up the first hexagon, thinking that the others would lean against that. Uh, no. I managed to get three hexagons up without endangering the structure too much.



Here's a top view:



and another one.

This side view shows that the pieces don't fit together like legos. The pieces are slightly out of flat, which effects their fit.



What did I learn?

I need a better armature, to support the center of each piece. The slight variance in the flatness of the bottom which showed up as 5/16 of an inch at the center of each half hexagon in the drawing is in reality almost half an inch.

If I use a full height (4") soldier course as drawn, I'll end up with a 20 inch high dome, and indeed that's what I drew. I now know that it shouldn't be any higher than half the dome diameter, so I'll have to cut those bricks in half. Just as well, as it looks like I'll have to zig zag the support layer to get things to fit together.

It looks like the outside diameter of the oven fits, which I was worried about, since the rumford throat ended up a little bigger and a little further toward the oven than planned.

[dmun]

Heat Stop 50

Heat Stop 50 is a dry pre-mixed refractory mortar. It's a brand name, and I suspect that the stuff that James sells is a similar product. I've only ever used Heat Stop, and the reason is that it's just great. It mixes easily with just a bit of water to a peanut butter consistancy, spreads like a dream, and sticks firebricks together strongly, and with a water resistant bond.

Here's the link.

I get mine from Progressive Brick in northern NJ, who also sells red firebrick and the superior clay rumford throats. It's fifty bucks for fifty pounds, and this expense is part of why I used the cut-every-brick geodesic plan.

The good news is that with all of my oven pre-assembly, and putting together the rumford firebox and throat, I've used only about half of one bag. The secret is to keep your joints tight - 1/16 to 1/8 inch is plenty for a strong bond.

[redbricknick]

Refratorecipe.

Kind sir. I covet the consistency of your refractory mortar. Pray tell, how did you make such fine mud?

[dmun]

My back, my neck,

and a broken blister from the five minutes I forgot to wear gloves. Yikes.

I plan to support the row of blocks with a re-inforced concrete header for supporting the masonry chimney. The new lintel should take all the weight, and keep the existing bricks intact.

Plan B on the window opening is to fill it with glass block. The wavy texture will complement the "rustic" blocks, and let some more light into the workshop.
Did you know that glass blocks are ten bucks apiece? Off to eBay.

[CanuckJim]

Hammering

Dmun,

A bit late to the fray, but you might have been able to salvage more of the old blocks by renting a large Hilti or Bosche hammer drill, with a suitably sized bit. Then, you could have drilled out the mortar and pushed the blocks out, or at least as many as you needed. Although your line of block appears to be holding, I suggest that you put in some sort of header, like a flat piece of iron to span the gap, just to be on the safe side. You could drill out the mortar on each side and remortar it in place.

Work like this is just great for the back, ain't it.

Jim

[maver]

This looks ridiculously good. You actually used a sledge to knock through that concrete block? You've really got me thinking that I should make a Rumford with a form for my outside fireplace just like yours, although I don't think I have the precision or patience - I'm going to look into buying a throat rather than doing the BIA.

Now you get to put the dome together - it'll be as easy as legos, vero?

[dmun]

slab forms

I filled the cavities on the inside that weren't filled with insulating concrete with used fiberglass insulation, with the combustible paper backing peeled off. I closed the top of these holes with pieces of slate.



The form on the inside was braced against the framing on the sides, and against a workbench leg in the front.



After pouring and floating the slab, it was pretty wet on top. I placed the insulation board, Insblock 19, from Kraemer Gunnite (thanks guys) in Southern Jersey, directly on top of the wet concrete to adhere it.



So there it was, a weekend of hard work, and a couple of jobs that I had frankly been dreading.

[dmun]

rebar problems

I burried the rebar in concrete filled block holes on the inside, and in the filled brick piers on the outside. My plan was to use the bend-with-pipe method of tying the slab to the base.





The rebar bent fine, but only to about ten degrees off horizontal. Hammering wasn't effective to get them flatter.



I finally tied them down with another piece of rebar, connected to threaded loops to tie them to the concrete form. This tended to lift the form, so I put a concrete block on it temporarily until the first couple of loads of concrete put some weight on it.

[dmun]

wall busting

It was my hope to save enough old rusticated blocks to patch the window opening.



Here's what I ended up with, one badly battered whole block and a lot of crumbs. Those blocks are about twice as heavy as the modern ones. No wonder they are hard to bust up.



An inside view.



New sonotubes are alligned with the old ones using building paper. This is to prepare for filling the brick piers with concrete, and casting the slab.

[dmun]

wall busting

The building that I'm putting the oven/fireplace into was built as a cinder block garage in the twenties of the last century.


An exploratory bashing the previous week showed that this would be no picnic. Even with a sledgehammer, it comes off chip by chip.



After a day of less than fun hammering, I got a big hole in the side of the building. The good news is that the overhead row of blocks didn't collapse despite an old settling crack, that runs the entire height of the wall.

[CAM]

Wow again

I don't know where it should fit in, but it definitely fits in and I look forward to seeing and encourage the posting of many more pictures with commentary.
If I ever finish building my house I will start my oven and agree that seeing the work and ideas of others is invaluable. Keep it up DMUN.

[maver]

more than an oven

I think the argument to sticky your work and break up your thread would be to make it easier to find e.g. the Rumford portion of your work and because you have done some things with technique that are very well documented and demonstrated with photos - there's a lot in your brickwork pictures that can help other oven builders (all this before even beginning dome construction - I can hardly wait to see that).

On the flip side, it would be a chore to divide your thread - we can rely on the search feature of the forum. I would say just keep doing what you are doing. I appreciate seeing your work. I wish I had 1/4 your planning and patience with the project.

[dmun]

Geodesic oven thread?

I've sometimes felt bad about monopolizing the pompeii thread, particularly when it steps on the postings of someone who's building an actual pompeii.

There might be a place for a "Geodesic oven" category, but until there's more than one, (and I remind you, there isn't even one yet) that might be premature.

I'll defer to James in all this.

[CanuckJim]

Subfolder

Jengineer,

I agree wholeheartedly that a subfolder for Dmun's most amazing, complex, perfect, geometric, historical project would be very worthwhile. It could, perhaps, be titled The Brick Saw Primer. Dmun, your work is superior.

Jim

[jengineer]

Master Craftsman?

I don't know about the rest of you but I think this thread needs to be hit with a sticky or a new subfolder needs to made for the ramblings of DMUN so that they are easy to find and reference.

I am really enjoying this tangent on the building of dual project. It is amazing what a bit of AR, pushing the envelope, perfectionism along with some tools and patience can achieve.