dome shape?

[logman]

Re: dome shape?

Thanks David,
I am considering the stainless needles, and I have seen cooking spray mentioned (Pam) as well for a release oil. Are you getting the warm weather as well? From what I saw on tv, you might not need a fire for a pizza right now.

[david s]

Re: dome shape?

Very hot and humid here (we live in the tropics), but we have just returned from Perth in Western Australia where, while it was just as hot, it was quite a dry heat so much more bearable.

[mikku]

Re: dome shape?

Hello all--I am a newbie to this community.
Just came across this thread while researching how to build an oven. I just finished casting a two piece dome using the trapezium shape. Same as a lot of people--feel more comfortable working with wood than with mortar and bricks.
Made both inner and outer mold forms from 2x10 materials. Began by laying out a 16 sided base --750mm diameter, then used the rules from that calculator site for angles etc. Long story short...takes a lot of time to fit all the pieces (glueing and screwing them together) but it came out fine. Tried to maintain an 80mm dome thickness. Inner 1/2 dome is 750mm outer is 910mm.
After completing the mold shapes, sanded and urethane varnished the surfaces. Prior to pouring the castable used Crisco vegetable shortening to lube the forms. ACG company sells castable refractory in my area through a specialty masonry supplier--each dome 1/2 took 100kg . Made a third mold that is an extension of the door area and base for the chimney--another 50kg.

Did the pour yesterday--starting at around 1PM and finished about an hour later. Thinking about waiting until tomorrow to open the mold, worry that the pieces will still be brittle. A lot of the other threads say you have to do a couple of ovens before you get the one you like-- that is the reason for taking all the time making the molds...I think the size is right but all the rest is up in the air.

It is sure nice to see all the information posted on this site.. don't have to feel like a pioneer!

[PsychDoc]

Re: dome shape?

Mikku,

First, welcome.
Second, PICTURES!
Third, if you start another thread you will get more interested feedback

[mikku]

Re: dome shape?

Hello PsychDoc,
Thanks, I need to figure out PICTURES
The new thread is coming--Just spent 1/2 hour typing a reply and lost it somewhere.
New thread will be "CASTABLE DOME IN TOCHIGI-JAPAN", coming soon!

[david s]

Re: dome shape?

If you take to long typing your reply it times out and you lose the lot. Very annoying. Try to keep yor replies shorter.

[brickie in oz]

Re: dome shape?

Or......type it in Notepad and copy-paste.

[mikku]

Re: dome shape?

Hello Al "Brickie in oz" and david s!
This is first for many things--
will try to keep things short. Today I stripped the molds --surprise the parts look fine. But heavy to shuffle around.
Spend a lot of time cleaning the forms and putting them back together so they do not spring too far out of shape. Should have used more shortening for release agent.

[mikku]

Re: dome shape?

#2 short reply..
Next time will probably use the motor oil/kerosene mixture but to put these forms to bed...I greased them up with regular automotive grease--at least it won't dry up too much and keep the forms in good shape.

Also picked up some angle iron to surround the structural base with. The regular temperatures make cement work outdoors not ideal---so will be making the base etc indoors and bring it outside only to do the firing to make the refractory set up. Then back indoors for insulation work and the rest....

[mikku]

Re: dome shape?

#3 short reply
I have no firm plan for what the oven will look like when completed--just winging it. Can imagine a lot of different things but will choose something that is a challenge and fun. When I figure out the pictures thing...you will be able to see my creation with castable....probably a thing of beauty only in its' creators' eye. I have 20/20 hindsight vision--tomorrow I will think of what should have been done first...but today is OK. Anyway my working space is cleaned up again time for happy hour and to check out some flicks.
Mikku- finlander in Tochigi

[mikku]

Re: dome shape?

Hello logman,
A little about my dome design. Made the dome pieces off a pattern layed out on a piece of plywood and built successive levels up---using calculator from that trapezium calculator...the mold is the same profile as it is when completed and it is filled from the top of the dome...in your case you will have a hole above your styrofoam ball. When I stripped the forms, there was a huge difference between the finish on the inside compared to the outside. Inside was smooth and glassy--outside had the air pockets and other marks from water that gets absorbed on the set.

[mikku]

Re: dome shape?

#2 logman--
I think that is just how this stuff looks---using non-metal forms and when you have to be careful with the vibrating. Too much and you make the aggregate settle out and too little lots of pock marks. My form is really heavy duty --1 1/2" 2x10 stock cut into the trapazoid shapes...it did not budge when the soupy stuff went in. With 3/4 and not a lot of outside bracing--might blow out. I thought of making another box around my entire form and filling it with sand when making the pour...after set...just scoup the majority of the sand out and finish up with a shop vac. Then absolutely no worry about a blow out and the only issue would be how much to vibrate to get a good casting. these are just my thoughts rattling around my brain... good luck with your casting!

[logman]

Re: dome shape?

Mikku,
thanks for the encouragement! I got my styrofoam dome over the christmas holdiays and cut a bunch of pieces for the outer trapezoid to surround it. Then i ran into a great deal on a quantity of medium duty tapered full firebricks. I'm thinking about a hybrid approach now....Ugh. The foam form is at least helpful to see what the 2 sizes of tapered brick would look like. I can't do alot as we still have snow in the ground, so i'm mocking up on a piece of plywood in the basement.