Re: async rotary control

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

Original poster: "D.C. Cox by way of Terry Fritz <twftesla-at-qwest-dot-net>" <resonance-at-jvlnet-dot-com>


Also, many of them have the diode bridge built inside near the brush end so
you can just feed them AC from a small variac or or solid state quadrac
circuit.  We use 1 hp units of some of our larger Van de Graaffs with 28 in
wide roller pulleys.

Dr. Resonance




----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Monday, August 26, 2002 5:20 PM
Subject: Re: async rotary control


> Original poster: "marc metlicka by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <mystuffs-at-orwell-dot-net>
>
> Mark,
> While not exactly an answer, I would like to tell all coilers about
> those treadmills that are sometimes tossed out for the garbage men. Most
> of them have a 0-9000rpm 3/4 hp dc motor (with very nice hub) in them
> along with a very nice, simple, robust speed control drive on them!
> I have two that are garbage salvaged.
>  Also, i have one that uses a 1 hp ac single phase motor that uses a
> Salisbury type speed control unit. this is basically the same variable
> width pulley arrangement that snowmobiles use, as you turn the speed
> knob the cable opens one pulley allowing the belt to run deeper in the
> groove (or at a lower ratio) this in turn forces the opposite pulley to
> ride the belt higher (or at a higher ratio).
> Both these styles are very handy gadgets for the shop so next time you
> see an old treadmill along the road side, or at a yard sale, CHECK INTO
> IT! No one will be disappointed.
> Take care,
> Marc M.
>
> Tesla list wrote:
> >
> > Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<A123X-at-aol-dot-com>
> >
> > I have an async rotary made from a 12000rpm angle grinder. Even with
only 2
> > electrodes in the disk it's 400rpm and I wanted to try varying it's
speed to
> > something lower. I was going to use a dimmer switch but when I turn down
the
> > dimmer it actually sounds like it speeds up and also vibrates more. Any
ideas
> > of why that happens? Also I was wondering if a cheap variable
transformer
> > could be made by winding one or two layers of magnet wire on a normal EI
core
> > then sanding the windings on one side and making a device with brushes
on it
> > to slide across the sanded side to vary the voltage? I really don't feel
like
> > buying another variac to control the rotary but I have a nice core and
some
> > thick magnet wire to use and I couldn't think of any reason why a variac
> > needs a O core except so that it allows for the use of a rotating
contactor.
> >
> > Mark
>