Re: New to list, a few questions

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

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Sean,

At 02:14 PM 7/29/2001 -0400, you wrote: 
>  Hello all,
> 
>I am about to construct my first coil but I am so new to this that I decided 
>to unsubscribe to this list shortly after I subscribed since I figured I 
>wouldn't understand what was being discussed.  Evidently unsubscribing 
>didn't work, so here I am.  I guess I'll stay on the list.

Sometimes the unsubscribe thing does not seem to work.  Anyone can always
write to me or Chip directly to be removed from the list.  But glad you
stayed :-))

> 
>I've been reading and researching as much as possible on the Internet about 
>TC's so I'd have a decent understanding about them before I dove in and 
>built one.   I have forgotten 90% of all the basic electronics I learned 13 
>years ago as a bio-med equipment repairman in the Army so I'm needing a good 
>basic electronics refresher course.  Anyone know of a free or cheap tutorial 
>program available?  My main weakness is the topic of capacitance, pretty 
>important here!

There is a great site that is some kind of on-line training thing for the Navy.

http://www.tpub-dot-com/neets/

> 
>What I lack in electrical knowledge I make up for in mechanical design 
>knowledge so I shouldn't have any trouble with the hardware aspect of 
>coiling.  I have a 9" metal lathe and a medium size milling machine in my 
>garage plus an excellent CAD program on my computer so I can machine any 
>custom parts I need.  I also live in the greater Orlando, Florida area and 
>we have a surplus store here to die for called Skycraft.  They have 
>everything electronic and mechanical there and I do mean everything....but 
>they were sold out of neon sign transformers!  That's something I still have 
>to find.
> 
>Now, a few questions: 
> 
>1) Is there any physical limitation to a rotary spark gap if the mechanical 
>aspects of it were theoretically unlimited?

Aside from the mechanics, you have to make the rotor and electrodes with
enough distance between the conductors so that arcing will not occur from
the high voltages where you don't want it.  The following picture shows
that the electrodes are well insulated from the motor shaft and the
terminals are all plastic and have a good distance between them.

http://hot-streamer-dot-com/TeslaCoils/MyCoils/SmallCoil/small_gap1.jpg

> 
>I have a brushless D.C. motor ( approx. .5 HP) that produces 5,300 RPM per 
>volt. It is from Germany and used for R/C airplanes.
>It can safely handle a 9.6 volt 2400 mah power supply which means it spins 
>at 50,880 RPM with no load.    Even geared down 4 to one for torque this 
>could possibly spin the rotary spark gap at over 12,000 RPM.   I'm confident 
>I could machine a spark disc that would not fly apart at this speed.   If I 
>had to I could even built an engine powered rotary spark gap device using a 
>1 HP R/C car engine.  Output of the car engine is 34,000 RPM with laod 
>applied.  It would be noisy but boy would it rev up.


You may want to consider a synchronous rotary gap that spins at a measly
1800 RPM :-)  These gaps have four terminals and will fire at 120 BPS
matching the AC line frequency.  They are made from typical 1/4HP 1725 RPM
AC motors.  Higher speeds will not be synchronous and you will probably
need a very powerful source of high voltage like a 10kW pole pig
transformer to get any advantage from a high speed gap.

> 
>2) What effect does a higher frequency spark gap produce?   What is the 
>highest resonant frequency anyone has ever heard of anyone producing with a 
>Tesla coil?

The resonant frequency is the natural frequency the primary coil and
capacitor and the secondary coil and top load oscillate at.  That runs
about 50,000 to 1,000,000 Hz and is independent of the spark gap firing rate.

Spark gaps are often built at 1800RPM (four electrodes) or 3600RPM (two
electrodes) to fire at 120 BPS.  Faster gaps can really fire fast.  I have
a gap form D.C. Cox that can do 1000BPS but some have even gone to 2000BPS.
 It sounds like you have the ability to build them even faster :-)  Maybe
some folks that have more experience with high speed gaps will have more
advice than I do.  There are plans to convert an standard AC motor to
synchronous operation at:

http://hot-streamer-dot-com/TeslaCoils/Misc/syncmot.zip

You will not need to study the poor man's tips much below other than for
laughs since you have cool tools and such :-))

http://hot-streamer-dot-com/TeslaCoils/Misc/sync_motor.txt

> 
>3)  I hope I'm not a heretic among heretics when I say that I am getting 
>into this field to explore possible levitation effects on matter.

Cool!  Note that Tesla coils create high voltage alternating current rather
than DC current.  Much electrostatic stuff requires DC, but it depends on
what you are up to.

> 
>4)  Has anyone on this list ever experimented with mixing different forms of 
>energy
>such as operating TC's in the vicinity of Van de Graaf machines,  running 
>multiple TC's in close proximity with different frequency spark gaps, 
>playing with lasers or microwaves in the vicinity of TC's?   

Others may have info here.  Be careful that if the TC arcs to the other
devices that it will not ruin them.  I think Bill Wysock arced a TC to a
big multi kilo Joule high voltage pulse cap once and did a lot of
electrical damage in the nearby area.  Sort of like a lighting bolt.  I
think many of the areas you talk of are reasonably unexplored.  Lasers
(high power) and microwaves may be useful in guiding arcs...

> 
>5)  Has anyone ever designed a rotating Tesla coil?  What would happen (if 
>anything) if the unit spun around the secondary coil axis at a high rpm?   A 
>rotary spark gap could be designed to be co-axial for this configuration.  
>Or....would anything interesting happen if the TC unit remained stationary 
>but the grounding point were disc mounted and spun around the secondary coil 
>with a rotary contact?  Would a sheath of discharge surround the toroid?

"I" can't think of much advantage of spinning the primary, but having a
spinning secondary might be really cool!  People have had motor driving
discharge terminals that sort of spin the discharge point on top of the coil. 

> 
>I have the plans for BTC-5 from Information Unlimited but that baby is a 
>monster so I ordered the plans for BTC-4 and will make the it my first coil 
>project.  I'll build the BTC-5 next year.

Neat!  The BTC-4 type of coil is just right.  "We" will probably have
differing opinions from the plans on how to build it but the idea is
basically sound.  Don't spend too much money on capacitors or anything
until checking here since a number of new lower cost solution like MMC caps
are now available.  Also be careful to use safety gaps and perhaps a modern
filter circuit to protect the NST.

http://hot-streamer-dot-com/TeslaCoils/Misc/NSTFilt.jpg

Don't be surprised if we all have differing opinions on coil construction
other than what the plans say.  :-))  There are folks here that know a lot
and some ideas about how to go about coil construction have changed in that
last few years.  But the plans you have are a good basic guide.

> 
>Thanks for any constructive replies.

Sounds like your off to a great start!  Here are a few links you may find
useful, if not now, later as you are getting into it.

http://home.earthlink-dot-net/~electronxlc/
http://www.richieburnett.co.uk/tesla.shtml
http://hot-streamer-dot-com/TeslaCoils/MMCInfo/mmcinfo.htm
http://hot-streamer-dot-com/TeslaCoils/MyPapers/modact/modact.html

Cheers,

	Terry

> 
>Sean
>