dome shape?

[logman]

Great site! I haven't seen a trapezium dome mentioned, looks nice in that it only has 4 different sizes of bricks. I saw Dmon's geodesic build and thought about the trapezium design and maybe casting the segments. Feedback appreciated!

[logman]

I haven't found any prohibitions about posting links, here is an example about whthe trapezium design:
Trapezium dome design

I assume you would be better off rotating each course so the joints don't line up.

[wotavidone]

I suppose that's pretty much what I did. I intend to find out this weekend whether it will fall down when the fire is going.

http://www.fornobravo.com/forum/atta...e-800x600-.jpg

[wotavidone]

Fascinating website you linked to. I tried out the trapezium dome calculator, and came to pretty much my only objection to the concept - the calculator gives the sizes required for a 16 segment dome, and the biggest dome you could make and still cut the sgements from 9 x 4.5 bricks is a touch under 24 inch diameter.
What is needed is a calculator for a larger number of segments.

[logman]

That was why I paid attention to Dmun's geodesic dome - where he glued up bricks. I saw inn that thread the concept of forming these segments in a mold instead, it seems alot easier to cut the compound angles in wood and put together some forms. I'm thinking you could form two adjacent segments as one piece, so 8 pieces per row. I'm looking around western NY for some reasonable priced castable refractory material.

[nissanneill]

logman,
what you need to decide is whether you want a challenge in ornate oven construction (which only you will see and appreciate) OR build a relatively simple and quick Pompeii which works well.

Neill

[logman]

Hi Neill,
you probably touched on the heart of my question. I am quite proficient in wood, and have a fair amount of concrete work under my belt and I suck at bricks. The idea of making some (easy for me) wood molds and cating refractory segments seems easier than all the brick work. If the refractory is higher cost, I'm hoping not buying an HF saw would offset that. Lots of conjecture on my part at the moment, really only want to build once, so I'm open to hearing lots more input.

Wota, i've only seen the trapezium layed out with 16 sides. somebody with some geometry or CAD background could probably do what you are seeking. I had played with the calculator radius until I go to 9 inch bricks once, but they would have to be glued together like Dmun did with the geodome, so I quickly thought about casting instead...

[deejayoh]

Very interesting concept.

Here's an article that gives a recipe for a "homebrew" castable refractory. It might be of interest to you. the hard part is probably getting the Calcium Aluminate Cement. But I am guessing it's a cheaper way to go than premixed if the cost of refractory mortar is any indicator

Keep us posted!

[logman]

Well, I'm been off thinking and working, and I'm on plan B. I got a 30 inch stryofoam ball (in two halves) from Plasteel and cut all the trapezoids to make a 38+" outer dome shape, so I will have about a 3 inch gap between the forms to pour castable refractory into. I need to wait for spring and make the base before I put it together as I could get it thru the door in the house.
I'm debating a single pour versus just the dome, and a second pour for the front arched doorway and chimney starter.....

[shuboyje]

Are you still planning to form trapezoid "bricks" or are you going to cast over the half sphere? I'm a bit confused.

If you plan to cast trapezoid bricks make sure to get the manufacturers data sheets prior to purchasing. It will contain info about making cold joints which will be pretty critical to your plan. Castable refractory is not brick, and you might need to take this into consideration with your design.