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RE: Remote Tuned Primary (RTP) ideas...

Hi Gary,

	Such an interesting idea!!!

I ran some numbers in E-Tesla5 where I varied the single terminal height
from 4 to 18 inches above the secondary.  Just by varying the height on my
coil's secondary, I could change the frequency over a 7% range.  

18" = 83100 Hz
12" = 87611 Hz
4" = 89153 Hz

7% is kind of a small range but perhaps a little optimization would make
that better.

I have not run the dual terminal thing yet but E-Telsa5 can do dual
terminals with ease.  It is a simple Q-Basic DOS program that one can
modify easily.  It runs under DOS or a windows DOS icon and it will find
the Fo frequency of any physical secondary configuration.  The program is at:

http://users.better-dot-org/tfritz/E-TESLA5.ZIP

The price is just right too ;-)

I am a bit tired to do it right now but your idea is extraordinarily
interesting!!!!!!  Is also has that "nothing can go wrong and very simple"
attribute which makes such things the only way to go.  You really don't
need the center cylinders expanding within each other since the normal
field distribution takes care of that for you.  You can leave the area
between the terminals open as the field plots in E-Tesla5 and Excel should
show.  The gear motor, battery, fiber optic (or whatever) mechanism could
exist very happily between the dual terminals.  Perhaps simple a air
balloon run from an aquarium pump would be the way to go... 

I think you have a truly great idea here!!!  More investigation to be done...

Cheers,

	Terry


At 09:10 AM 10/27/1999 -0400, you wrote:
>Hi Terry:
>
>I have no suggestions for your cap switching idea, but wanted to throw out
>something that's been rolling about in my head, also on the remote-tuning
>theme.
>
>I was thinking about tuning the secondary topload.  Consider two toroids,
>one atop the other, with a metallic cylinder between them.  The cylinder is
>actually two nested cylinders with some sort of inflatable bellows within
>it.  An (insulated) air hose would inflate or deflate the bellows to vary
>the distance between the toroids.  It may also work out if there's an
>overhead beam above the coil that a string and pulley could do the same
>thing.
>
>It's unclear to what degree the topload capacitance would vary by changing
>the toroid spacing.  Certainly not the same latitude as a binary switched
>primary cap, but smoother and perhaps cheaper.
>
>Regards, Gary Lau
>Waltham, MA USA
>
>
>		
>		Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
>
>		Hi All,
>
>			One of my new projects (one of a zillion I have
>planned for the cold
>		months ;-)) is to make a remote primary tuning device.  It
>has two parts:
>
>		The first is a way to adjust gap timing remotely.  This one
>is pretty
>		simple.  Just a DC gear motor attached to a lead screw to
>rotate the motor
>		on my rotary sync gap.  There is a nut on the handle so when
>the screw
>		turns, it turns the handle allowing about 40 degrees of
>movement.  I will
>		run the motor from a 12 volt gel cell battery and control it
>through two
>		fiber optic cables for total safety (I hate having a wire
>hooked from
>		primary stuff to a box I am holding :o) and to eliminate
>RFI.  The fiber
>		optic circuit is cheap and easy (low tech plastic fiber) and
>actually
>		simpler than trying to safely bring out a regular control
>cable to a hand
>		held box.
>
>		The second part is more interesting.  Having thought of many
>"great ideas"
>		and having them all disintegrate for various reasons, I have
>settled on the
>		following:  I will have an "extra" MMC with four stings.
>They will have a
>		value of 0.5, 1.0, 2.0, and 4.0nF (could be other values
>too).  This device
>		will be parallel with the regular primary cap.  By selecting
>the strings in
>		a binary fashion, I can select from 0nF to 7.5nF of
>additional capacitance
>		in 0.5nF steps.  Four fiber optic cables and simple
>circuits, as above,
>		will select the capacitance from a simple binary thumb wheel
>switch.  Piece
>		of cake!  Except for the four actual switching devices.  
>
>		My "pals" at Jennings could sell me vacuum contactors at
>$2000 a piece but
>		that is kind of rough even for me.  I have taken regular
>relays, pulled the
>		covers off, and submerged them in oil.  It works "sorta
>good" but the ~1mm
>		distance between the contacts of most relays is a bit too
>small.  I would
>		probably have to use two in series which is not big deal (or
>series a DPDT
>		relay's contacts - I just thought of that ;-)).  The
>contacts still make
>		good continuity and the oil and surfaces are not
>contaminated to any degree
>		by the switching.  A fairly typical relay (of high quality)
>will handle the
>		voltage and current of just this small additional
>capacitance so that is
>		not a problem either.  I would have to vacuum impregnate the
>relay with oil
>		to get it thoroughly saturated but that is easy.  Soooo... I
>have three
>		great questions for the collective minds of the great Tesla
>list to help me
>		over some hard spots:
>
>		1.	Is mineral oil the best thing to use for insulation?
>Or is there some
>		other substance (like silicone oil) that is really better?
>
>		2.	There is one serious problem I have found.  Most
>small relays have
>		little isolation distance between the switch elements and
>the coil.  An arc
>		to the coil will probably blow up the control electronics
>(fiber optics
>		prevents such a thing from blowing the operator ;-)).  Some
>small "safety
>		relays" have a large distance between the coil and the
>switches that should
>		work good.  They are usually pricey but they have cheap
>cousins.  However,
>		perhaps someone knows of a perfect relay for such a use??
>Big power
>		contactors would be great but they are really too big for
>such a use.
>
>		3.	I would think there would be a cheap high voltage
>oil (or whatever)
>		relay out there somewhere???  Kilovac makes HV reed relays
>(vacuum) but I
>		think they would be over voltage and under current for this.
>Is there a
>		better commercial relay I could get for not too much money
>that would solve
>		the problem straight away???  I would think a small high
>voltage oil relay
>		would be cheap and easy to make commercially???  I have
>thought of putting
>		the relays in a super high vacuum but that seems far too
>hard for me.  The
>		specs are: 30KV isolation and switching, 100kHz, 2 amps RMS,
>and 70 amps
>		peak.  The fiber optic cable isolation allows these specs to
>be abused
>		wildly ;-)
>
>		Any help, ideas, etc. are welcome.  It would really be cool
>to adjust the
>		gap and primary tuning remotely from simple switches.  One
>could really
>		dial in a coil while at full power very easily with such a
>simple
>		arrangement.  It would be the envy of all your friends :-)
>It would really
>		be useful for people that mount coils 40 feet in the air in
>large arenas
>		and find the tuning is not the same as it was on the ground
>;-))  The same
>		controls would probably work with variacs and such too.
>Just needs a
>		little research and development work...
>
>		Cheers,
>
>			Terry - on the bleeding edge of Tesla coil
>technology...
>
>			terrellf-at-uswest-dot-net 
>
>
>
>
>
>
>
>		
>