[TheForge] chip shapes and materials

[Demon Buddha]

Bruce Freeman wrote:
> Frosty,
> Your idea on thermally conductive chips is excellent. 
> What we need is small (maybe 3/4" dia) balls of a
> highly refractory and thermally conductive material. 

	Bruce, simultaneous hig refractivity and conductivity are mutually 
exclusive properties by definition.  It's like wanting a surface with 
both high transmissivity and reflectivity at once.

> But since such refractories are inherently not very
> conductive, how about going back to the "rice in
> porcelain" idea.  Take a wooden bead, 1/2" dia.  Wrap
> it in castable refractory about 1/8" thick, making a
> ball about 3/4" dia.  Push a punch though the bead
> hole to clear away the "clay" at that point.  Let it
> set, then fire it - burning out the wooden bead. 

	I'm sure that would work, but what a PITA.
> 
> Voila', a hollow refractory sphere.  Being hollow, it
> would not "store" heat in the thermally inaccessible
> center.  (This is roughly equivalent to having a high
> thermal conductivity.) 

	How do you reason this?  You want it to store heat, but you also want 
it to return heat.  A problem I see with this is that, unlike coke, the 
refractory has no heat source of its own.  The moment you place work 
between the heat source and a chip, it begins to cool.  At one point, 
the work will heat more from one side than from the other.  It would 
work better if you had burners coming at the pile from different 
directions, methinks.  it would seem that such a forge would have some 
problems with excessive scaling.  I came into this thread very late, so 
this may all have been discussed already.

> I'm also intrigued by the idea of using carbon for the
> chip.  Sure it would burn, but probably not very much.

	I don't think it would be at all strong enough.  Go poking 1" stock 
around in a mass of hollow graphite obkects and I think you'll have much 
breakage.

>  Graphite crucibles are practical, and they take much
> more stress than these chips would have to. 

	Thermal stress perhaps, but they don't usually get bounced around that 
much against hard objects.