Re: Streamer loading effect

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

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi Steve,

Congrats on the detuning success! Some comments below:

Tesla list wrote:

> Original poster: "Steven Ward by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<srward16-at-hotmail-dot-com>
>
> Now the arcs ar so big that its really not noticeable, but what do i
care, the arcs are
> great!
>
> I have a question about efficiency with my coil.  On the classic tesla java
> TC calculator, they say my coil with a rotary gap, could produce a 6 foot
> arc.

The equation used is sqrt(input watts) * 1.7. This is John Freau's original
spark length emprical
equation. JavaTC uses this same original equation at this time. John has
updated the formula a few
times to reflect transformer types, etc. I've chosen to keep the original
equation. My reasoning is
simple. It's a spark length empirical formula and at best a close
guestimate which is based on input
VA measurements and spark length. I wouldn't think to hard on it, your coil
is doing fine. A rotary
may help or may not. It's difficult to identify how well the RQ gap is
performing without a direct
comparison. Gaps definately play a role in spark length. Well, anything
does that allows energy
transfer at decreased losses. I've built several RSG's (some bad, some
good). Performance is in the
workmanship, material, and operation of the RSG, as with anything.

> This makes me wonder about how helpful rotary gaps really are.  Im
> using a somewhat undersized RQ gap, and getting close to the theoretical,
> optimal output for my coil.  Am i missing something here, or is my coil
> quite efficient for the spark gap that i have?  Or would perhaps a RSG boost
> my output beyond 6 feet?

The spark length in JavaTC is thrown into the RSG design area "only"
because there was nowhere else
to logically put it at the time. The formula does not differentiate between
gap types (see John's
equation). It's based completely on wall plug input watts for what John
acheived at the time the
original equation was derived.

>  This 6 foot figure that the calculator gave me is
> somewhat puzzling.  If John F. can get 42" (or 44" now) from a 12/30, why on
> earth would a figure for 6 feet on a 1800w coil make sense for high
> efficiency?  I know larger coils loose efficiency per power.  Oh well, i
> should just be happy with what i have, and what i have is good enough for me
> :)

The last report I saw from John was a comparison of different NST's. There,
John's TT-42 coil
acheived 38" using a Jefferson 12/30 NST running 140V input (uses variac to
step up input voltage).
On his website, John mentions 42" using a "rubust" NST. The term "robust"
indicates the NST is
pulling more than it's rated VA rating. For 42", he was probably delivering
620W or so to the coil.

If you do a search in the List Archives, search for "TT-32 TC results and
specs". This was a post
from John and may help. It includes the TT-42 coil as well.

If we were to model the 38" case in JavaTC, we would enter 140 in the
"Applied Vin" input box. This
changes the output watts to the coil to 490W and is identified as effective
output power. The spark
length then shows 37.6" and very close to 38". It may be helpful to measure
input volts and amps to
verify your actual watts if you haven't done this already.

On a side note, I'm nearing completion on the next version of JavaTC
(v9.2). This new version will
include a static gap section (which can also be used for safety gap
settings) and will help identify
gap setting vs. arc voltage, bps, RQ gaps, etc.. The transformer section
now includes ballast
current input for those who externally limit current. Also new are help
files instead of the simple
text box notes used currently. The help files provide more detailed
explanation and graphical
representation of measurement. I'll post to the list once I complete a few
more details.

Take care,
Bart