Re: Cutting torroidal cores

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

Original poster: "Finn Hammer by way of Terry Fritz <teslalist-at-qwest-dot-net>" <f-h-at-c.dk>

Ben, all

I cut 2 Staco 25 amp variacs recently to get a variable choke for
ballasting, and they turned out to become very noisy during operation.
The core strips are not glued together, so when they are cut, the flux
repelling causes the ends to open up like a paint brush, and vibrate at
the break rate frequency.

I intend to drill a couple of holes trough the laminations, and mount a
brass bar inside (with threaded holes) and outside (with clearance
holes) to compress the `lams together.


     Please view in a fixed-width font such as
                     Courier.




                        \             \
                         |             \
                          |             |
                          |             |
                       +--+|             |+--+ <-----clearance hole brass
bar
                       |  |+-------------+|  +--+
                       +--+---------------+--+--+
                       |  |               |  |  |<----bolts
      Threaded brass   +--+---------------+--+--+
      bar       --- -->|  |+-------------+|  +--+
                       +--+|             |+--+
                          |              |
                                        |
                         |              |
                        /              /
                       /              /



The cutting was done with a bi.metal hacksaw, and it took about a 1/2
hour of sweaty effort on each to get trough.


Cheers, Finn Hammer

Tesla list skriver:
 >
 > Original poster: "Ben McMillen by way of Terry Fritz 
<teslalist-at-qwest-dot-net>" <spoonman534-at-yahoo-dot-com>
 >
 > Hi all,
 >    Does anyone have any suggestions on how I might go about
 > cutting a 1/2" wide slot in a torridal core? (the kind that
 > you find in variacs) I need to cut a slot all the way
 > through to make a "c" core so that a metal disc can pass
 > between the poles. The cores are made from soft iron strap
 > that's been coiled. They've also got plastic formers around
 > the inside and outside. I've heard mention that they tend
 > to come apart when cut... Is there any way to prevent this?
 > I've got access to a really good machine shop..
 >
 > Thanks for any help!
 >
 > Coiling In Pittsburgh
 > Ben McMillen