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Re: Rotary Spark Gap - Construction Questions
Ross!
Forgive me for wawing my arms again, and suggesting another design than
the time proven one you have already chosen.
I am thinking about the "Model 2000" (I used to call it the "Milennium
Lace" because it was fun one time, but too much self promo now, I
thinks...)
Anyway, this gap was designed to take advantage of the more recent
possibilities that have become available in determining optimum break
timing. This is possible by modelling the coil in Microsim, and this was
pionered by Terry. The 200 BPS instance was explored in debth by Richie.
I scratched the surface running at 300 BPS, and you can see an account
of this work at my homepage, link at bottom.
This gap is not hard to make, and it has the advantage of full
adjustability of the static electrodes, so that you can explore the
thrill of more than 120 BPS operation even on an AC driven coil. You
have the fiberprobe stuff that is indispensable as an aid in setting it
up. As I have written before, this gap has hemispherical ended
electrodes, and this is in my mind the key to it`s success.
I make no claims to this observation, by the way, Bill Wysoc pointed it
out in a mail on Mon, 14 Jun 1999 in a post subjected: Thorated vs Pure
Tungsten
Credit when credit is due.
Unfortunately, I have not been able to verify it`s virtues against other
designs.
Just my 10 cents.
Cheers, Finn Hammer
http://home5.inet.tele.dk/f-hammer/tesla/tesla.htm
Tesla list wrote:
>
> Original poster: "Ross Overstreet" <ross-o-at-mindspring-dot-com>
>
> Hi Gang,
>
> I have a new project on the drawing board. I want to build a 10"x45"
> secondary, PT powered coil that will be operated primarily in DC mode. I
> would also like to run it as an AC coil, but I'm willing to do several hours
> of work to reconfigure (I don't care to do all the initial design work so
> that it will be an easy swap-over. I don't mind having 2 sets of caps, 2
> rsgs, etc).
>
> My main design challenges right now are the rotary spark gaps for a large
> system.
>
> ----ASRG----
> I'm looking for nice speed controlled gap from 0 to about 800 breaks per
> second. I'm half-way basing my desgin Kevin Ottalini's DC coil that does
> well all the way out to 700 bps. After reading lots of TCML archives, it
> appears that the ideal motor for such a task is a 1/2 to 1 HP "Universal
> Motor" that apparently can be run on either AC or DC. Chip mentions that he
> uses one of these on his gap
> http://bhs.broo.k12.wv.us/homepage/chip/details.htm
>
> I don't know anything about this type of motor. Can someone suggest
> sources/costs for such a motor? I will probably wind up using a phenolic LE
> rotor with 3/16" tungsten rod electrodes. Looks like 6000 RPM with 8
> electrodes can get me the 800 bps I desire. Don't worry with sending the
> usual safety alerts - all will be cut on a good mill, statically balanced,
> contained, etc. I can use any advice/links on high speed ASRGs and
> universal motors.
>
> ----SRSG----
> I also plan to build the typical SRSG using a design similar to the ones
> shown in the links below. This design seems to be what many of the
> professionals and big-coil hobbyists have settled on.
>
> (TTR design) http://www.ttr-dot-com/rotary_spark_gap.htm
> (*) http://www.foxtail-dot-com/Teslathon/D1/DSCN0007.JPG
> (*) http://www.foxtail-dot-com/Teslathon/D1/DSCN0006.JPG
> Brian Basura design: http://fp2.hughes-dot-net/brianb/rsg.htm
> (*=TTR design on display SoCal Teslathon 2K, photo by Jody Kravitz)
>
> There is an abundance of info on the web about this type of design, but
> there does seem to be one magical problem - what sort of dwell time works
> out best. (ok, ok, I don't want to start the mechanical dwell not equal to
> electrical dwell argument so from here on out I'll just call it electrode
> overlap) I know that this is power throughput dependant, but maybe we can
> agree on some ballpark figures for coils driven from PTs or small pigs.
> This question comes up after seeing one of my buddies almost attack his SRSG
> with a sledge hammer. The initial design used .375" electrodes all the way
> around. This made the electrode overlap a little over 1000us. The coil
> would barely run. After changing his rotating electrodes to 1/8" and
> offseting the stationary electrodes a little, he got the overlap down around
> 500us. This made a world of difference in his coil! Now Brian's coil is
> one of the hottest 6.5" sec, PT powered coils out there!
>
> Has anyone else stumbled across electrode sizes or overlap times that worked
> really well on this size system? Are there upper/lower limits that should
> be used early in the design stages? I have read that 1/8" stationary
> electrodes don't work too well on 5KVA or above coils due to overheating.
> Unless I'm doing my math wrong, most of the well performing gaps that I
> reverse engineered from the photos on the web all have electrode overlap
> times around 500us. Ideas?
>
> Making arcs in SoCal
> Ross-O
> http://users.better-dot-org/roverstreet/