Re: Cap break down voltages / Rotary Question

        Re: Cap break down voltages / Rotary Question
        Wed, 9 Apr 1997 11:00:12 -0700
        "DR.RESONANCE" <DR.RESONANCE-at-next-wave-dot-net>
        "Tesla List" <tesla-at-pupman-dot-com>

To: Julian

It's possible that a small lateral movement of the motor shaft within
bearings could have cause the damage.  Disk might move sideways and hit
your stationary electrodes.  

Unless you are running a system with coupling exceeing 0.25 you should
need less than 3600 RPM for optimum performance.  Sometimes less than
works even better than high speed for a large coil system.

The arcs striking the ceiling might be attaching themselves to some
wiring.  Be careful in this area --- shut your coil down late at night &
to bed --- wake up and discover the spark inside the wall started a
fire.  Then watch the insurance company try to weasel out of it due to
nonstandard use of a home or some other fine print. 

Just a thought.


> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-poodle.pupman-dot-com
> Subject: Re: Cap break down voltages / Rotary Question
> Date: Monday,April 07,1997 4:50 PM
> Subject: 
>             Re: Cap break down voltages / Rotary Question
>        Date: 
>             Tue, 04 Mar 1997 04:16:18 -0800
>        From: 
>             julian <julian-at-glosilk.demon.co.uk>
> Organization: 
>             GlowSilk Computer Services Ltd.
>          To: 
>             tesla-at-pupman-dot-com
>  References: 
>             1
> Thanks Ed Sonderman, Richard Hull for your advise.  Home made caps at
> 10KV RMS are about right.
> Running a pole pig without balast.
> Well this is not exactly true, The pole pig is connected via a 100m
> extension leed and the wire resistance provides some balasting (5 ohms).
> My pole pig is 5KVA at 11KV.
> When running the coil I run my rotary spark gap at high speed which
> gives very smooth running.  At lower speeds I can feel the kick back
> from the pole pig as vibrations in the variac.
> I use an 8A variac protected with 13A fast blow fuses. These fuses blow
> if smooth running is not achieved.
> This weekend I took Eds advise and built a larger toroid.   I had some
> stainless steel flu duct that was being dumped at a nearby building
> site.   There was sufficient to make a 24" toroid.   Adding this to my
> 10" x 36" meter coil, I needed extra primary capacitance.
> So with the primary tapped at turn 9 and 0.05uF the spark length
> increased from 36" to 40" possibly more as the garage size is now
> limiting spark length.   Arcs keep striking the ceiling and tripping the
> house lights.
> To give me more head room I then used my 7" x 21" coil with the same
> toroid almost with the same tune point I measured 45" arcs.   I then ran
> the coil on full power, no increase in spark length due to near by
> objects, but the sparks are very bright, and I am sure would go further
> given the room.
> During this run the spark gap took a hit.  For some odd reason the
> strike caused the electrodes on the rotary spark gap to colide, and self
> destruction followed.
> I would like to ask the list if the gap design I have is any good.  
> Basically I have a high speed motor (10,000 rpm) and a rotor disk made
> from fiber glass PCB copper clad board.   Two electrodes are mounted on
> the disk which are electrically connected by the copper covering.  
> These electrodes pass two stationary electrodes with a clearance of
> about 0.5mm.   I find that when the gap is running at operating speed
> the 6" disk streches and the 0.5mm gap closes almost to the point of
> collision.
> I calculate that with 1/4" electrodes the dwell time:
> velocity of electrodes is
>    6*3.14*10000/60 = 3140 inches per second
> dwell time is
>    0.25/3140 = 79uS
> Flaming round problems don't seem to be a problem.  (No visable signs)
> The remaining rotor disk following the failure has lost an electrode. 
> The electrode which is 1/8" diameter has ripped a grove from the point
> it was mounted to the outer edge of the disk.  Is it possible that I am
> running the motor to the point of failure of fiber glass?
> Comments Welcome
> Julian Green