[TheForge] Chip forge

[Bruce Freeman]

Frosty,

I think your ideas on making spheres are good.  Marbles used to be made by cutting marble cubes (yes - marbles actually were made of marble at one time) and rolling these between iron disks with grooves.  The corners of the marble cubes wore off, leaving ... marbles!

This can be done with clay, allowed to dry to the "leather" stage.  Other sphere-cutting procedures are known as well. But perfect spheres wouldn't be needed for a chip forge - just fairly spherical "chips."

Now about surface to volume ration.  Seems to me that cuts both ways.  Once a sphere were up to temperature, it would hold that temperature better than an oddly shaped chip.  Is that better or worse?

But there's a trick used for some years in my industry (chromatography) on the micro scale:  Porous spheres.  These have the shape of spheres, but pores either at the surface or all the way through.  The purpose is specifically to increase surface area.

Now, I'm reminded of some china cups which have translucent patches where (so I've been led to believe) dry rice grains had been encorporated into the clay and later burned out during the firing.  Maybe some such approach could be used for chip-forge speheres.  Take the clay-like (rammable refractory) sphere and roll it in something organic - pearl barley, radish seeds, poppy seeds, or whatever.  THEN fire it - and the organic burns off, leaving semispherical hollows in the surface of the ceramic sphere.  This would represent a significant increase in surface area.

To make a fully porous sphere, mix the organic matter into a castable refractory, let it set, then fire it slowly.  The organic matter would burn out, leaving a fully porous sphere.

The trick here is to make the sphere porous to the desired extent, without making it too fragile.  One way to achieve that would be to combine broken fire brick with the organic matter, then mixing them both in with castable refractory.  Let it set, then fire it.  

I have tried none of these ideas, but get them from my reading about ceramics.

Bruce
NJ

>>> frosty at customcpu.com 3/3/2006 9:04:10 PM >>>
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I've given a couple shapes some thought:

Spheres will make for the least restriction in flame flow but provides the 
least surface area/volume ratio of any shape so heat transfer in and out 
will be minimum. Making spheres will I think be the most hassle as well.

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