Re: filling toroids

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "John Richardson" <jprich-at-up-dot-net> 


Hi Mark,

Try not to laugh at this, as I was hoping to keep it to myself until I had
produced a useable product.  Also keep in mind that we have done what
everyone said was impossible to keep our heavy equipment running, so what is
far-fetched to everyone else is doesn't seem so unrealistic to myself.  (If
a machinist ever saw me sandpapering and filing scuffed pistons, he'd
choke!)


That said here goes:  I too am not happy with the looks of duct toroids,
etc, and have been stewing for a while on how to make a better product.  I
was going to wait till summer to try this, due to lack of indoor space, and
regardless of how it may be flamed, I'm going to anyway.  Start by building
a box that is slightly larger than your proposed toroid size.  In the direct
center, fasten a rod that stands higher than the top level of the box.  This
box is now filled with sand that is going to be wetted down and compacted
well.  From the upright in the center of this compacted sand box, attach a
pre-fabricated "compass", and on the end of this compass will be attached a
plywood or sheet metal form that is exactly half of your desired toroind
shape.  Keep turning your compass and scraping and removing sand until there
is a a form that is half a toroid in the box.  Give the mold a spray with
Pam or similar, and fill to level with plaster.  On top of this, place a
piece of old paneling, etc. that has some old bolts or whatever anchored in
a position that they will sink into the plaster when placed on top of your
box.

 > Original poster: Mark Broker <mbroker-at-thegeekgroup-dot-org>
 >
 > So we have learned through experience that pretty much every attempt to
 > fill a toroid with expanding foam has resulted in an unusable
 > mess....  Have people tried other substances?  For instance I was thinking
 > that the typical aluminum drier duct toroid is most susceptible to denting
 > of the ridges along the rim of the major diameter.  Perhaps partially
 > filling the toroid with a thinner 2-part epoxy (cures via chemical reacion
 > - not air) and spinning it fairly slowly until it cures would make for a
 > much more dent-resistant toroid?
 >
 > I was planning to try that this weekend but was hoping someone had already
 > tried it.  I don't suppose anyone has found an easy way to smooth the
bumps
 > of aluminum drier ducting that doesn't require several layers of
fiberglass
 > and countless hours of sanding?  The masking tape still leaves a pretty
 > bumpy surface.
 >
 > Thanks,
 >
 > Mark Broker
 > Chief Engineer, The Geek Group
 >
 >