Re: Metal Rotor = Isolated Motor?

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

Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-qwest-dot-net>" <bert.hickman-at-aquila-dot-net>

Jason,

Some of the prior comments from other list members may be due to an
incomplete understanding of your gap's configuration. 

It sounds as though you have a pair of stationary electrodes, and one of
them is connected to ground? Or are you running the tank circuit current
through the motor's bearings? Are you running the gap motor from an
isolation transformer? If not, then your motor winding is indeed referenced
to mains ground (at least from a high voltage standpoint). 

I won't give you any static about putting your finger on the middle of the
aluminum rotor while testing it with a MOT since you already knew it was
dangerous... I'm just curious why you'd consider risking your life testing
a theory this way. To paraphrase the adage about mushroom hunters: There
are old coilers... there are bold coilers, but there are very few old, bold
coilers.

Please play safely - your future pig won't give you any second chances...

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-net
Web Site: http://www.teslamania-dot-com

Tesla list wrote:
> 
> Original poster: "Jason Johnson by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <hvjjohnson13-at-hotmail-dot-com>
> 
> I see these few posts about my RSG, and I know that there will be more to
> come, but I thought I'd throw in my $0.03141592...
> 
> I do realize that my motor is not isolated from the tank circuit, and that
> it may be possible for HV transients to get back into the motor, but, I
> don't really think that the HV "wants" to get into my motor, for three
> reasons. 1. My motor case and windings are not grounded, they just "float"
> relative to ground etc 2. There is a grounded piece of Al tape that almost
> brushes against the Al rotor, allowing most of the HV transients a safe
> place to go (every once in a while I see the tiniest little blue spark
> between these two, not even enough current to make a mark on the Al tape).
> 3. Everytime there is a presentation, all the energy should just go through
> the tank circuit, and once the rotor moves enough distance, both sparks
> should extinguish at the same time. Before I even put the grounded Al tape
> there I hooked the gap up to a 2000 volt MOT w/o a capacitor in the circuit,
> and let it fire, and PUT MY FINGER on the middle of the Al rotor, and got no
> shock whatsoever, and I was barefoot on a concrete floor (don't give me any
> crap about this, I KNOW it was dangerous). I would be willing to bet a cheap
> DMM that there is very, very little voltage on the shaft of the motor during
> operation.
> 
> The bearings on the motor are also quite fine, as the rotor spins very
> freely, and it still takes almost a whole minute or thereabouts to spin down
> from 3450 rpm, just as it did the first time I ran it (which there was no HV
> present the first time I ran it). There really is no problem with RF
> interference in the house, it has actually gotten better than when I used a
> static gap. I also asked the list a while ago about using an Al rotor
> directly on the motor shaft, and I got some crap about how fast my motor
> would fry :-) HA! Actually it was one comment that I got about how it would
> not work at all that inspired me to do it anyway.
> 
> I have not quite reached an hour of total run time w/ this gap, and I have
> not seen a single problem yet. I really don't think that my 4800 volts at
> ~300mA is much of a problem, but I don't know how it would cope with a
> higher voltage (I'll find out as soon as I get my pig :-). Maybe I just got
> lucky, and maybe someday my luck will run out and my gap will die, but if it
> does then I will eat my words in front of 800+ people on the list.
> 
> Jason Johnson
> 
> ----- Original Message -----
> From: "Tesla list" <tesla-at-pupman-dot-com>
> To: <tesla-at-pupman-dot-com>
> Sent: Sunday, June 24, 2001 12:50 PM
> Subject: Re: Metal Rotor = Isolated Motor?
> 
> > Original poster: "Nebojsa Kovacevic by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <morfeus-at-EUnet.yu>
> >
> > 73
> > Hmmm... Suppose that the wall outlet electricity doesn`t "consume" this
> new
> > current that passes through the body of the motor.  The motor is grounded
> as
> > well as the coil you are using(not directly-but through the complicated
> line
> > of the electric lines that goes through your house-this makes the things
> > getting much worse than you would ever expect), and the connections of
> these
> > two lines are very near to one another(not as like they are hundreds of
> > miles away), and that could couse the trouble of pulling the fire out of
> you
> > system. If the motor by some accident isnt`t grounded - bum!
> > Maybe, somehow, it could work with 4kV, depends on the amperage, but that
> is
> > not what my experiences tell. I would not try this with my 15kV/190mA -
> > thank you.
> >
> > Regards,
> > Nele!   72/73
> > -----Original Message-----
> > From: Tesla list <tesla-at-pupman-dot-com>
> > To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
> > Date: Sunday, June 24, 2001 4:17 AM
> > Subject: Metal Rotor = Isolated Motor?
> >
> >
> > >Original poster: "Gregory Hunter by way of Terry Fritz
> > <twftesla-at-qwest-dot-net>" <ghunter31014-at-yahoo-dot-com>
> > >
> > >Dear List,
> > >
> > >After corresponding a bit with Jason Johnson regarding
> > >his MOT coil with RSG, I have a question:  If one uses
> > >a metal rotor on an RSG, is isolation of the motor (or
> > >the rotor) required?  I'm asking because I assumed
> > >isolation was neccessary, but Jason tells me his RSG
> > >motor isn't isolated. Why doesn't the 4KVAC instantly
> > >fry his RSG motor?
> > >
> > >Regards,
> > >
> > >Greg
> > >http://hot-streamer-dot-com/greg
> > >
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> >
> >