Re: Now I'm a real coiler 51cm (over 20 inch) after 1 hour.

Congratulations on first light! My responses are interspersed below.

Tesla List wrote:
> Original Poster: "G.Wilson / B.Petersen" <wilson-at-vossnet.de>
> Hello All
> After all the months of careful tinkering - it works ! 51cm Sparks to a
> grounded metal washing stand (well, several hits). Not bad.
> Here are the specs
> Sec  4 inch with 19 inch winding length AWG 23,5 (0,6mm)
> Toroid - 2 -one metal foil on foam around 2" x 6", the other 4" alu.
> duct about 14" dia -must be about 15pF together.
> Primary inverse conical 20 deg with 0,25 inch copper tubing, spacing 0,3
> inch, 10 turns (about 5,5 tapped at present)
> Cap - "MMC" 3 strings of 14 x 70nF "ERO" MKP caps rated at 1000v  giving
> 0,014uF
> NST 6kV 50mA giving about 15 inch sparks and NST 7,5kV 75mA giving over
> 20 inch.
> RQRSG - 4 gaps total of about 1/8 inch - vacuum cleaner fan cooled.
> Terry Fritz HV Filter ( 4 safety gaps, 4 x 4k7 50W resistors, ceramic
> bypass caps).
> variac, line filters etc.
> I have a lot of questions
> 1) Has anyone got a general text about tuning?

Check out: http://www.velocity-dot-net/~djb/tesla/texts/tuning.txt
Looking at the parameters of your coil, I'd think that you may need to
increase the number of turns a bit at the tapping point to bring it into
tune - probably something more like 7-8 turns.  

> 2) should I add several more strings of caps to get 0,018, 0,023 or
> 0,028uF?

Your 7500 V 75 mA NST will support a tank cap of up to 0.028 uF.
However, you'll need to retune your system... I estimate the primary tap
setting for a 0.028 uF tank cap would be just about where you're tapped
right now - about 5.5 turns. Using a larger tank cap will increase the
"bang" energy each time the gap fires. Since the transformer can deliver
sufficient current to fully recharge the larger cap, this should result
in more energy transfered to your secondary and longer, hotter

> 3) The RQ style gap with only 4 gaps fired somewhat erratically and the
> safety gaps fired regularly. Is this normal or is the system probably
> not tuned?

Your system is not in tune. You may also be a bit over coupled (the
secondary may need to be elevated a bit more versus the primary
winding). This can be a common problem in coils using conical primaries.

> 4) what determines the type of sparks - I prefer the "Lazy" ones that
> seem to take about 0,5 second to reach full length and then to disapper
> - but I often had rather more of a flickering effect.

Mostly the toroid radius of curvature and the main gap breakrate. A
higher, and smooth, breakrate coupled with a toroid that just breaks out
will give you single streamers that visibly "grow" over multiple "bangs"
as you've described. You're erratically firing at present, and this is
preventing consistent retracking of the streamers.

> 5) I want to build a single gap with large brass water fittings - and
> with a vacuum quenchung (vacuum cleaner) or a synchronous rotary spark
> gap - which would be better and where can I find plans for a synchronous
> spark gap.

In order to build a synchronous gap, you'll need to find a synchronous
motor (or modify an induction motor so that it becomes synchronous). One
of the best summaries of induction motor operation and modification for
synchronous operation is by Brent Turner. Brent's information package
can be found by going to Brent's section at the FUNet site:
Some of the files you're looking for are:
motors.txt, motors_1.gif, motors_2.gif, salient1.jpg - salient6.jpg and
salnt 1t.jpg - salnt 6t.jpg. These pictures (and others) are worth
10,000 words and should get yopu started

> I have a lot of other questions - but this will do for now.
> Just what every self respecting mad scientist should have in his cellar.

Safe coilin' to you!

-- Bert --