[TheForge] chip shapes and materials

[Jerry Frost]

From: "Demon Buddha" <osan at netlabs.net>


>
>
> 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.
>

That would be my misuse of terminology. How about this, High heat resistance 
and high conductivity? It's what I meant.

>> 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.

Agreed, almost as much a PITA as slip forming a lattice. So how about we 
compromise and slip form hollow spheres? That'd be really simple with a two 
part gang mold. Pour in the slip, swirl it around while the plaster sucks a 
little moisture from the clay, pour out the excess, let it set a bit and 
break the gang mold open. Getting even wall thickness on the spheres would 
be a simple matter of weighing the whole sheebang after you pour the slip 
out. If is't short, pour more in and swirl some more. If it's too over 
weight . . . Oopsie, redo time.

>
> 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.
>

Yes, you want it to store heat but you want it to shed and absorb heat 
quickly too. Given a choice I'll take chips that are highly conductive over 
a high specific heat. Bottom of my desirable list is holding heat. 
Insulating chips are not on my list at all.

>> 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.
>


Good points but clay graphite crucibles are known for being reasonably 
tough. Then again I may be thinking of something else, I've never messed 
with one.

Frosty
-------------------------------
If it ain't forged
it ain't real.
Wrought iron is.
The FrostWorks

Meadow Lakes, AK.

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