|
|
Post by pasto76 on Dec 16, 2011 12:37:15 GMT -8
I read that forming castable refractory requires a vibrating table. If I mount my bench grinder on my home made welding cart and turn it on, will that count as a vibrating table?
is reinforcing wire ever used in refractory? good/bad?
|
|
|
|
Post by matthewwalker on Dec 16, 2011 15:06:37 GMT -8
I've tried every power tool in my shop for this. The only one that worked well, and it works very well, is a sawzall with the blade removed held firmly against the table.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Dec 16, 2011 16:20:07 GMT -8
An heavy impact drill or electric chisel should work even better.
There are also polycarboxylate based concrete plasticisers to make concrete self compacting.
SCC is a Japanese invention.
|
|
|
|
Post by pasto76 on Dec 16, 2011 19:18:17 GMT -8
I've tried every power tool in my shop for this. The only one that worked well, and it works very well, is a sawzall with the blade removed held firmly against the table. thats a good idea, thanks for the tip. btw how long does this take? |
|
|
|
Post by matthewwalker on Dec 16, 2011 19:57:48 GMT -8
Depends on the mix and the mold, and your expectations. I am using it with a fiberglass mold to make concrete countertop sections. I run it for about 5 minutes and the part comes out like glass. That's a totally different application though, so I'm sure it will be different for you.
|
|
|
|
Post by machinemaker on Dec 16, 2011 20:04:28 GMT -8
I could be full of c--p, but I have been using refractories in industrial uses for a couple decades. The only reason I know to use vibration is to work bubbles out and to help keep the material monolithic. If you are casting a cylinder for a heat raiser lets say that it is 2" thick, you can just take a 1x2 and ram it up and down as you pour the castable into the forms. You can over vibrate castable just like concrete and segrate the components.
kent
|
|
|
|
Post by machinemaker on Dec 16, 2011 20:08:37 GMT -8
Don't use steel reinforcement in refractories. It will expand and contract with heat and crack the refractory.
kent
|
|
|
|
Post by pasto76 on Dec 17, 2011 7:48:25 GMT -8
Don't use steel reinforcement in refractories. It will expand and contract with heat and crack the refractory. kent ah, thanks everyone for the feedback. promise to post pics when I get to building since we all love pics |
|
|
|
Post by pasto76 on Dec 17, 2011 8:03:17 GMT -8
one other question related to materials - Im doing a lot of reading and have a lot of questions and half baked ideas
I just read on permies on an older thread wherein someone says that fireclay is powdered porcelain.
I see toilets for free on craigslist all the time. Feasible to get a toilet or sink and pulverize/mill it into fireclay?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Dec 17, 2011 8:31:35 GMT -8
Fire clay is clay with a high content of alumina.
Kaolin the stuff porcelain is made of is exactly that.
You can break it into small pieces ( <= 5 mm ) and mix it with fresh fire clay to save some
money.
However you can not powder it fine enough( <=2 µm ) that it would regain the properties of clay.
|
|
|
|
Post by machinemaker on Dec 17, 2011 9:16:40 GMT -8
bags of fire clay are so cheap I can't imagine taking the time to try to powder up toilets. Maybe if I had a large ball mill already, but I don't. I don't know where you are located, but look in the yellow pages for refractories, masonary supplies or boiler repairs and see if you can find a supplier for commercial refractories.
kent
|
|
|
|
Post by kwillets on Dec 17, 2011 13:58:20 GMT -8
|
|
|
|
Post by Donkey on Dec 17, 2011 21:16:56 GMT -8
Clay that's fired isn't clay anymore.. It looses it's properties as "clay" and becomes pottery instead.
It IS still great to mix in. Potters call it grog and it helps temper the clay, acts better than sand in the heat of the kiln and all that.
|
|
|
|
Post by josephjcole on Dec 19, 2011 15:22:08 GMT -8
I don't know exactly what you are planning on doing with the clay, but you probably don't want porcelain or kaolin clays for making refractory. Kaolins have a very small particle size which makes them more prone to thermal shock. So although they can withstand very high temperatures they won't do well with the rapid heating/cooling that occurs in a rocket stove.
The pottery supplier should have 50lb bags of powdered fireclay. Hawthorne Bond is a popular one among potters, get it in the largest mesh size they have.
best of luck
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Dec 20, 2011 0:39:02 GMT -8
Clay has by definition a very small particle size, smaller than 2 μm.
The term "fire clay" seems often used to refer to synthetic refractory materials
made from clay minerals by burning and then breaking into smaller particles again.
This synthetic "fire clay" can have particle sizes up to more than thousand times of the original.
Thermal shock has other reasons than very small particle size.
Glass and ceramics are prone to thermal shock because they are not elastic,
have low thermal conductivity, and high thermal expansion coefficients.
Alumina has a thermal conductivity from about 30–40 W/(m·K), which is higher than that
of some alloyed steel.
Ceramics burned from high alumina clay like kaolin have a relatively high thermal conductivity, the more alumina the higher.
The bigger particle sizes of synthetic "fire clay" makes it harder for small cracks to become
big cracks, because the connection at the boundaries becomes weaker with size.
With bigger size cheaper materials can be used.
There the smashed porcelain makes sense.
|
|
