Thoughts on this oven build...

[almondsurf]

Re: Thoughts on this oven build...

David s: thanks for your reply. I am now researching the Melt Extract Stainless Steel Fibers. Do you have experience with these? This might sound silly, but I wonder if they would poke you while working with the mix, after all, most surgical needles are made with similar material. Are they pliable? Most likely I will be using polypropylene fibers, but as you said, they don't add strength.
Do you guys think it would be better to cast the oven in parts (for the refractory portion) then put it together (like this one)? I wondered if that would help with the heat expansion issue.

[david s]

Re: Thoughts on this oven build...

David s: thanks for your reply. I am now researching the Melt Extract Stainless Steel Fibers. Do you have experience with these? This might sound silly, but I wonder if they would poke you while working with the mix, after all, most surgical needles are made with similar material. Are they pliable? Most likely I will be using polypropylene fibers, but as you said, they don't add strength.
Do you guys think it would be better to cast the oven in parts (for the refractory portion) then put it together (like this one)? I wondered if that would help with the heat expansion issue.

Yes, I have lots of experience with melt extract fibres. I mix about three batches of castable a week and add them to it. They call them needles for a reason. I often get stuck which can be a bit painful, but rarely bad enough to draw blood. You learn to handle the mix carefully. They are not pliable, being stainless they are stronger and stiffer than mild steel.

Making a mould for a multi piece casting is more trouble than it is worth for a one off casting IMO. A simple sand castle covered in strips of wet newspaper and the castable trowelled over it is quick and easy. Any minor cracking won't hurt as the dome is a self supporting structure all held together with the stainless needles anyway.

[almondsurf]

Re: Thoughts on this oven build...

Sooo, my friend got back to me and told me he can get me bags of the Calcium Aluminate Cement for $18 per 90 lb bag. Thats a lot less than the $30+ for the fire clay I have priced out.
Does anyone know a recipe using the CAC to make the my dome mold?

[v12spirit]

Re: Thoughts on this oven build...

Yes, I have lots of experience with melt extract SS fibres.

What is the maximum length and the maximum thickness of these fibers?
Does using sewing pins or even wood making nails work?
How much of these nails would one add per volume of castable?

[david s]

Re: Thoughts on this oven build...

What is the maximum length and the maximum thickness of these fibers?
Does using sewing pins or even wood making nails work?
How much of these nails would one add per volume of castable?

The SS fibres I use are 25mm long by around 0.5 mm thick. I think this is the standard. Any longer and they would be more difficult to handle in the mix. Steel nails probably too thick and are not stainless so would probably corrode.
Min addition 2% by weight of dry material of the mix. They are not cheap.

[UtahBeehiver]

Re: Thoughts on this oven build...

Being inquisitive, I did a little googling and found this table of amount of SS needles suggested for refractory cement.

[david s]

Re: Thoughts on this oven build...

Being inquisitive, I did a little googling and found this table of amount of SS needles suggested for refractory cement.

Excellent find Russell. I don't understand why there is a drop off in impact resistance over 4% for conventional castable though.

[jeffrorrt]

Re: Thoughts on this oven build...

Amond.. they early brick oven that the Pompeii are patterned after were built by hand....totally by hand, no power tools, fancy saws, or computer aided graphing tools , If you've researched they other method and feel yourself capable of building that style, you too can build a brick oven, especially with the help, accumulated wisdom and guidance found on this forum. YOU CAN DO THIS!!!!
Jeff

[almondsurf]

Re: Thoughts on this oven build...

Jeff...
Thank you for the support! I read through your "my build" link. Looks like your building a whole outdoor kitchen cooking mecca. Looks great.

[UtahBeehiver]

Re: Thoughts on this oven build...

David,

Your guess is a good as mine. My thoughts might me that Chart 1 is only showing increase in impact resistance by adding ss needles relative to each type not comparing to each other and the conventional refractory starting out higher in impact resistance maxes out where as low cement castable has a broader range to move, just a guess. Either way, this chart should help the casting WFOers.

[almondsurf]

Re: Thoughts on this oven build...

So I gather that I should use 4% (per weight) SS Needles for my mix?

I ran across this thread, which has been quite helpful, for anyone else looking to cast their oven:
http://www.fornobravo.com/forum/f44/...ory-20295.html

That thread basically says that Fire Clay is better to use than CAC because CAC needs to reach EXTREMELY high temps to build a correct porcelain bond that will last and act in its true or full refractory purpose. Sounds like the home brew fire clay mix is the way to go for any castable oven. That is what 'michelevit' used for his build. I think I may be adding some more sand to the mix though.

Any thoughts on this?

[david s]

Re: Thoughts on this oven build...

Most of the commercially made modular ovens are cast from CAC castable. but not sintered. ie taken up to 1000 C. They are perfectly suitable and stable for use as a WFO and will probably be still working well for a generation. If you want a cheaper version then try the Homebrew.

[almondsurf]

Re: Thoughts on this oven build...

David: thank you for being so quick to respond. I don't know if it would really be too much cheaper as I can get 90lb bags of CAC for $18.
Have you worked with both CAC and Fire Clay? If you were to pick one (ease of use and longevity) which would you choose?

[cobblerdave]

Re: Thoughts on this oven build...

G'day
I think I would love to know that the "Shoestring" oven is intact
And working, but, there has been no current pics ....? Or any lengthy explanation of condition.
I'd err to the side of caution
Regards dave

[almondsurf]

Re: Thoughts on this oven build...

Hey Dave, It has been a while since my last post... I, like you, have asked michel to post some new pics of his shoestring oven. I hope he gets back to us soon. I am still in process of deciding on the oven style but am heavily leaning towards the castable.

Other thoughts:
I have asked a few people who have worked with CAC what they would reccomend. They said that Fire Clay is just as good as CAC for what I am doing and is MUCH easier to work with (ie. CAC sets up very fast, expecially in my very dry desert climate). They said it's kind of a pain to use when its really dry or hot outside, but Fire clay can just be re-moistened durring the build process.

So IF I cast this oven, I will use the following formula:
1 part cement
8 parts sharp sand
2 parts hydrated lime
1 part fire clay
4% steal fiber
1% polypropylene fibres
And I will be using firebrick for the hearth

I can't wait to get this done but I have to start on my backyard landscaping first. As of right now, we don't have our backyard landscaping in yet since I'm in a new house. I'll follow back up here soon and will post pictures along the way.