Re: async rotary control

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

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