Re: filling toroids

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

Original poster: "Richard Modistach" <hambone-at-dodo-dot-com.au> 

there are two part foam emulsions that can be bought,
with all sorts of densities and creaming times.
the creaming time is the time from when the foam is mixed
to the time it starts to expand.
the expansion time is the time from the start of expansion
to the time of finishing expansion.
the rated density is the density of the expanded foam in a free space.
the density can be increased by expanding the foam in a confined space.
different types of foam apply different pressures when confined.
the number of different types of two part foam emulsions is enormas.
the two part foams of course do not require air to set.
a tube would require evacuation before insertion of the cream to
eliminate air spaces.
with a bit of experimentation, done properly, two part foams and
inner tubes should produce some exellent toroids.

regards
richard
aus

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, January 08, 2004 6:49 PM
Subject: filling toroids


 > 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
 >
 >
 >