Re: Cutting torroidal cores

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

Original poster: "Dr.Resonance by way of Terry Fritz <teslalist-at-qwest-dot-net>" <resonance-at-jvlnet-dot-com>


Use a 1/4 inch stainless steel banding around the ends to prevent them from
opening up.  also, use another 1/4 inch SS band around the entire
circumference --- must be SS or it will heat up red hot and break.

I've cut them and then inserted a spacer of 1/16th inch plastic between the
cut ends and epoxied them shut.  Also the powerful clamping action of the
banding works to make them run smooth and quiet.  If excessive space is
allow they will run very noisy as you report.

Do it this way and no noise at all --- small 60 Hz hum but that's all.

Dr. Resonance




----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, January 19, 2003 9:21 AM
Subject: Re: Cutting torroidal cores


 > 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
 >
 >