[TheForge] Another hollow sphere idea

[Bruce Freeman]

Keep us posted on your progress.  I'd be working on a chip forge too, if I had the time...

Here's the reason I think that heat transfer from the chips may prove less important than from the flames:

I work with chromatography, which often involves heating a "column" (think "tube"), either empty or packed, to aid in the motions of chemical compounds down the column.  Formerly, the common wisdom was that you got the column up to temperature and that was that.  When you injected a cooler material (the sample) it was assumed that it was heated by the hot tube and/or packing.

Then someone did the math.  Pretty simple, really, but if you don't ask the question, you don't get the answer.

It turns out that the heat for warming the sample comes from the fluid entering the column, NOT from the tube or packing.   By analogy, I strongly suspect that the chips in a chip forge act as little more than support for the steel being heated and as INSULATION against cooling.  I have not proven this, nor do I intend to any time soon.  I toss it out as food for thought.

If this is the case, then we want "chips" that are easy to work around, that don't impede the flames, and that don't take forever to heat up.  Preferably they should be penetrated by the flames (i.e., should be hollow).

Bruce
NJ


>>> frosty at customcpu.com 3/17/2006 4:47:38 PM >>>
This sounds workable, maybe even easy, definitely worth a try.

Heating the metal is largely transfer from the chips to the steel but the 
burning gas will be carrying part of the load as well. So, if this works 
easily enough then it'll be a matter to determine how thick to make the 
shell.

If I have time this weekend I'm going to try ramming up a test forge. I'll 
be using a fire clay, sand, cement refractory for the tests. Once I get a 
workable unit I'll use a high end refractory, either alumina or high 
phosphate rammable. (I already have about 60lbs of the high phosphate 
rammable)

For the tests I'll make the rounded off cubes for chips and again use a high 
end refractory once I get a working shape/size/etc.

I'll also make a small quantity of barrel and life saver shapes starting 
with 3/4" x 3/4" and tweeking from there.

Don't know how far I'll get this weekend, we have a vet clinic and a number 
of critters to take, a wood stove to install and a barn to clean. I might 
not get farther than the forms but I have everything on hand so who knows.

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

Meadow Lakes, AK.

http://www.artmetalradio.com/ 

From: "Bruce Freeman" <FREEMAB at pt.fdah.com>



I just caught up with the postings.

I liked the idea of slip-casting hollow spheres, but agree it would be very 
slow.

How about a modification to my wooden bead idea:

String wooden beads or styrofoam spheres (~1/2" dia) on a 1/4" dowel.  Dip 
the dowel in a castable refractory and let it set.  (Repeat if necessary, 
but preferably have a mix of the appropriate viscosity to do it in one dip.) 
Fire "slow" to dry the refractory, then to full heat to fuse it.  By this 
time the dowel will have burned off, so work over an appropriate material so 
the whole mess doesn't fuse together.  This should work fairly quickly, once 
the bugs are worked out.

And to clarify WHY hollow spheres may be desirable:
1) Spheres won't pack tightly - hence burning gases will pass through 
easily, AND it should be easy to insert the object to be heated.
2) Spheres are relatively strong, so won't easily crush.
3) Being hollow and perforated, the hot gases will (to some extent) pass 
through them.
4) Being relatively (?) thin shells, there is no issue of heat "from the 
center" taking long to get to the surface.

The presumption here is that we want the burning gases to do the heating, 
and not to be heating using heat stored in the chips.

Bruce
NJ



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