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RE: Foam-core Toroids

When we were still based in Grand Rapids we watched the construction crews 
bring in smi-trailers of giant styrofoam blocks used in some type of fill 
application. They used over 50 blocks in a size of about 10'X10'X30'. They 
buried them in sand and filled in concrete around and over them, then a 
layer of asphalt on top. The blocks were of VERY high density and quite 
strong. I'm sure if you contacted some of the larger construction companies 
they would know of these.

>Original poster: "sundog" <sundog-at-timeship-dot-net>
>Hi all, Gary,
>   I dunno if you'll be able to find it, nor how it'll cost, but for a 
>styrafoam" toroid of immense porportions, you may try hitting a dock
>supply/manufacturing.  Where I used to live by Old Lake Hickory, TN, you
>could get a block of the good high-density stuff (no idea of the real name)
>at either the boatyards (shaped into a form for small hulls/parts and
>fibelglassed over) or a dock supply, as they were used a lot for the 
>Given the EPA's dislike for the stuff, you may have a hard time finding it
>now.  Hit up fiberglass shops, and find out where they buy their foam and
>for how much.  I believe you can get it in 2" thick sheets, or maybe the 
>'ole 5'x5'x3' blocks I got in TN. unfortunately, it's been quite a few 
>since then
>                                                               Sundog
>-----Original Message-----
>From: Tesla list [mailto:tesla-at-pupman-dot-com]
>Sent: Sunday, September 10, 2000 1:44 PM
>To: tesla-at-pupman-dot-com
>Subject: Foam-core Toroids
>Original poster: "Lau, Gary" <Gary.Lau-at-compaq-dot-com>
>While there is nothing that looks as nice as a professionally spun toroid,
>consider the agony you would feel if and when it fell off the top of your
>coil and became permanently dented.  I think most of us that have made
>toroids out of corrugated aluminum duct have eventually had them dented 
>these sorts of mishaps.
>I recently tried an experiment to improve upon the durability of home-made
>toroids.  I attempted to fill my 6" x 22" Al duct toroid with a 
>foam.  This stuff cures to a fairly rigid high density material.  The stuff
>I used is called "Great Stuff", at Home Depot, for $3.97 a 12 oz can (not 
>be confused with a latex-based product also sold there).
>I drained two cans of the stuff and it appears that another 1-2 cans are
>still needed to completely fill it.  I would recommend that anyone
>attempting this have more cans than necessary on hand so that it can be
>filled in one operation, rather than on successive days, with a portion of
>the filling hardened, then filling more.  I was initially concerned that 
>foam wouldn't cure being in an air-tight container.  The can said that to
>ensure curing in enclosed spaces, to sprinkle some water, so I squirted a
>couple oz. of water into the toroid prior to foam injection.  It turns out
>that there is no problem with the foam curing, it hardened just fine.
>The resulting foam core toroid is now more dent-resistant than a non-filled
>one, but the density of the Great Stuff foam is still less than what I 
>like it to be to render the toroid totally dent-proof.
>What I would REALLY like to find is a vendor who can supply a nice smooth
>styrofoam toroid, ready for me to cover with aluminum tape.  I think the
>density and light weight of this construction would make it very resistant
>to denting, and hopefully such a foam toroid could be bought for far less
>than a spun metal toroid.
>I'm interested only in sizes larger than my 6" x 22" so life preserver 
>don't help.  Any thoughts on whether such a styrofoam core could be
>custom-made for a nominal fee?
>Regards, Gary Lau
>Waltham, MA USA

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