Re: Sync Motor Wanted

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

Original poster: Edward Wingate <ewing7-at-rochester.rr-dot-com> 

Tesla list wrote:
 >
 > Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>
 >
 > Hi Ed,
<snip>
 > That is the problem...  A lot of folks take the rotor to their local
 > shops.  Not sure how economical it would be to make say ten in a row where
 > setup and the logistics are already done.

Just trying to explain what you want and why, to a local shop, can be an
exercise in frustration! Synchronous rotary spark gap is NOT a common
term and can garner some strange looks and comments.

 > >And grinding is NOT the way to do it. Especially if you're talking about
 > >hand grinding. A vertical mill is easier and will remove material more
 > >quickly.
 >
 > I think of it as an art form :o)))  It is easier if one does not have a
 > powerful vertical mill ;-))   The laminated steel is tough to mill right
 > the first time by an amateur (guess how I know this ;-)).

<snip>

OK, you do the art form and I'll opt for ripping off as much metal at a
time as possible. If the chips aren't landing six feet away, the machine
isn't working. :^)

 > >Shim the shaft?
 >
 > Most used motors, and some new ones, tend to have a lot of axial shaft
 > play.  That makes it hard to get electrodes to fly close to each other
 > without crashing, especially at startup and spin down.  So I shim that end
 > play out.  Of course, one has to do it right so it will not bind when the
 > motor heats up and all.  With shimming, one can use an old salvage motor
 > too which vastly reduces the cost.

That's why I've always used and recommended ball bearing motors. No end
play to contend with.

 > >I've been selling complete asynchronous rotaries and separate rotors for
 > >many years now and the reaction from hobbyists on a budget when they ask
 > >for a price on a 7" rotary can be very interesting. Usually there is a
 > >longer than normal silence. I charge $650 for a complete 7" asynchronous
 > >rotary and that doesn't even reflect the true hours of machine and
 > >assembly time involved.
 >
 > Cool!!  Do you sell converted motors alone?

Hold on. I sell ASYNCHRONOUS rotaries.... and "separate rotors" in the
above paragraph means balanced rotary gap rotors complete with tungsten,
not motor rotors.

 > >Too bad motor armature laminations aren't iron, because that would make
 > >the job easier. They are silicon steel and are much harder on tooling
 > >than iron. :^)
 >
 > Yep!!!  ;-))  They can also snag up and the laminations.  Chip can tell you
 > about that :o))  Probably a cobalt cutter job.

Judging from past posts and the above, you seem to have a thing for
cobalt. Cobalt alloy tooling is only marginally better than high speed
and not really worth the cost. I never used cobalt in the Rapid
Prototyping Center where I worked at The Big Yellow Box, it was either
high speed or carbide. On the subject of machining, here's one for you
to ponder. :^) Carbide cutters are the only kind to use on 99.9% of
plastics.

 > > > Ok, I guess I am just a little surprised this cool part of Tesla 
coiling is
 > > > not a "buy off Ebay" (or anywhere else) part!!!
 > >
 > >I guess I'm not, because there's more involved than meets the eye and a
 > >very limited market.
 >
 > I wonder how much people would be willing to pay for just the
 > motor??  Perhaps the price would simply be too high and those that are
 > willing to pay really would want to whole gap anyway...

That's a very good question. TBD.

Ed Wingate RATCB

P.S. In another post about my palm sized coil the transformer voltage
was left out, it's 20 ma/ 2 KV.