RE: Inner tubes

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

Original poster: "Aric" <a-at-somedogs-dot-com> 

The second item down on this page might be useful to those wanting to fill
various forms with expanding foam.  The final volume should be more
predictable than with the aerosol foams, and since it is a two-part product,
probably needs little or no atmospheric moisture to cure.

http://www.fibreglast-dot-com/showproducts-category-category-22.html

Aric

Original poster: "Lau, Gary" <gary.lau-at-hp-dot-com>

Close.  I tried filling a corrugated aluminum duct toroid with the
"Great Stuff" polyurethane foam in a can, from Home Depot.  The stuff
cures by reacting to water or water vapor, so I added a few spoonfuls of
water inside the toroid.  The greatest problem is that you're guessing
with no feedback whatsoever as to when to stop adding the foam.  It
expands very slowly, so even if one had X-ray vision, it would be
difficult to know when to stop.  With the duct toroid, the consequence
to over-filling is that it burst the seam where the two ends of the duct
were joined (several HOURS after filling).  Perhaps with an inner tube
it would just keep on expanding, symmetrically.  Or perhaps there's no
way to prevent gasses separating from the foam and causing unpredictable
voids?

The machined toroid came out beautifully, but filling an inner tube
would have been much cheaper.  Who wants to be a hero and find out?

Gary Lau
MA, USA