Re: Toroids from Foam

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

Original poster: "sundog by way of Terry Fritz <twftesla-at-qwest-dot-net>" <sundog-at-timeship-dot-net>

Hi Ted,

   James, Dave, and I used a hot wire saw to cut the 16" discs for the 
massive toroid we made for Dave's big coil.  We used some safety wire and a 
variac and a LV battery charger to put a few volts across the wire (doesn't 
take much power at all), and tested it on scrap till we got it up to an 
acceptable cutting temperature.  Too hot and the foam melts a substantial 
distance from the wire as you're cutting it, too cold and it will take 
forever to cut.  You want it hot enough to make a thin, clean cut, and cool 
enough it doesn't melt a big thick line through your work.  Expect a *fast* 
cutting rate with most foams. I've had cheap-o foam cut at 2-3 inches per 
*second*.

   My suggestions -
     Make a jig that resembles a band saw, with a very deep thoat.  Use 
safety wire for the cutting wire (cheap and plentiful).  Secure it at the 
bottom to a loop or eye. Avoid sharp kinks, it gets hotter there.  At the 
top put a spring on the upper arm and attach the wire to the spring.  Make 
sure it's under some tension, because it's gonna stretch when it gets 
hot.  Try some scrap in it till you get the heat setting just right, then 
leave the variac where it is and just unplug it.  Saves the trouble of 
fiddling with the variac.  There is some smell, but it's much easier to 
blow a smell out with a fan than to clean up shreds of foam (which gather a 
charge and friggin stick to *everything* for a week, and often run from the 
broom!)  Just don't ask how I know....

Hope it helps!

Shad G5-1203

At 05:46 PM 9/5/02, you wrote:
>Original poster: "tesla by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
><tesla-at-paradise-dot-net.nz>
>
>Team
>Has anyone used the hot wire cutting technique to avoid the room filled with
>snow effect ?
>Rgds
>Ted L in NZ

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Shad (Sundog)
G-5 #1203
"Ever stop to think, and forget to start again?"
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