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Re: 1st Motorized Spark Gap!
Tesla List wrote:
>
> >From jgore-at-cyberramp-dot-netThu Oct 17 21:24:49 1996
> Date: Thu, 17 Oct 1996 03:11:39 +0000
> From: jgore-at-cyberramp-dot-net
> To: tesla-at-pupman-dot-com
> Subject: 1st Motorized Spark Gap!
>
> OK, heres the deal:
> This weekend I'm going to finnish my first motorized rotary spark gap.
> I'm using a centrifuge motor controlled by a light dimmer switch (very cheap, very fast).
This may not work - SCR dimmer switches go crazy around Tesla coils
because of the transients. Use a universal motor and a variac.
> I have these dumb questions:
The only dumb question is an unasked one...
>
> 1) I have a computer program RotJit which says a large disk with lots of
> bolts in it would be better than a small disk. What sizes (diameter) are
> most of your spark gaps? Whats the largest diameter I should use? Would
> an 8 or 10 inch diameter disk wobble too much? I have no machine tools,
> so the tolerances won't be exact!
>
A rotary requires a fair degree of precision in construction so that it
doesn't self-destruct (taking a piece of the coilers' hide in the
process!). The rotor must be balanced - the rotor and shaft must be
concentric and the electrodes evenly balanced and located. The center
hole for the shaft must be drilled at preccisely a 90 degree angle
versys the rotor. If this can't be done with your equipment, you'll need
to use the services of a mahine shop. Don't try the "quick and dirty"
route on this - these things pack LOTS of rotational energy which can do
LOTS of damage to life and limb!
> 2) Is there a certain speed-range that most of you find works best? I
> realize that speed probably affects tuning, but what would be considered
> to slow or to fast?
Speed affects dwell and rep rate, but not tuning. Optimal rep rate is
complex, and depends on how rapidly you recharge the cap. Rates of 120 -
720 have been used by coliers with good success. Over this is probably
not necessary.
>
> 3) Has anyone thought about magnatizing the bolts on the plastic disk
> along with the stationary bolts so as to help quench the spark? Did /
> could it work?
Right idea, but it would take much stronger magnetic fields. Small
rare-earth magnets can provide the strength. The conductive arc is
"stretched" into a longer curve by the field, making it somewhat easier
to quench. Although some on the list have tried this, I haven't heard of
any measurable improvements.
>
> 4) Can the arc from a moterized gap hurt your eyes? I'm only using two
> neon sign transformers at 9KV. I always thought this was just for arc
> welders but I've been told differently and have been very carefull.
Yes. Like a welders arc, it puts out lots of ultraviolet light. Looking
at this for any extended time can give you a painful case "hot sand in
the eyes".
>
> 5) Anyone have any good advice/warnings for a first time motorized gap
> builder ;-)
>
> I have lots of books on how-to, but have only talked to one person
> with practical experiance.
Determine if you actually need a rotary. If you're only going to drive
from neons, a rotary won't improve your performance. - it'll only smoke
the neons! Don't try to go cheap and dirty on a rotary. Build it right,
using the right tools, or have someone build it for you. Make sure you
have adequate protection around the rotor to protect you from rotor
disintegration or electrode failure. Another alternative: buy one from
Ed Wingate. If you're only using neons, build a vacuum or air blast gap
to maximize performance.
Safe coilin' to ya!
-- Bert --