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Re: First light
From: Thomas McGahee[SMTP:tom_mcgahee-at-sigmais-dot-com]
Sent: Friday, January 09, 1998 7:12 AM
To: Tesla List
Cc: LINEMAN23K-at-aol-dot-com
Subject: Re: First light
>
> From: LINEMAN23K[SMTP:LINEMAN23K-at-aol-dot-com]
> Sent: Thursday, January 08, 1998 7:24 PM
> To: tesla-at-pupman-dot-com
> Subject: First light
>
> I have been researching TC's for about a year now but have finally finished
> building my first Tesla coil. I am getting 49" streamers with seldom strikes
> at 52". I would like to thank everyone on the list for their contributions.
> Although I have posted the list but a few times, I have always gotten
answers.
> The majority of my questions were answered from other posts and the search
> feature on the archives (Thanks Chip, good idea).
>
> What I would like to know is, how does my coil stack up against other coils
> with the same input power? Here are my coil's specs:
>
> Power supply: 2 15KV-at-60mA NST's
> no variac
Get a variac! Your whole system will last longer with it!!
Without a variac you are runnung full power all the time...
This is particularly bad when you are trying to tune the coil.
>
> Filter network: Saftey gap, grounded center electrode
> 2 15KVDC doorknob caps in series to ground (each leg)
> 1 3.5" toroid 25 turns #14 in series with
> 1 aircore inductor 2"o.d.x6" PVC wound with #28 magnet
> wire and a 50W 3K ohm resistor (each leg).
> 1 25A line filter (before NST's)
>
> Spark gap: RQ type in parrallel with HV bushings
> 11 electrodes 0.75x6"spaced 0.025" in 6" PVC (capped
> and slits
> cut for air flow).
> 1 Vacuum cleaner motor
I suggest that you have some way to control the vacuum supplied by the
vacuum motor. One method is to use a cheap low power variac. This
is the method I use most of the time. The other method is to have an
adjustable "hole" that you can use to adjust air flow.
I have found that running at about 85% produces the best results for me.
Too much vacuum will actually reduce your output spark considerably.
You have to adjust for best spark.
>
> Caps: 4 Rolled 0.011uF (2 series sets of 2, in parrallel)
> 3 20mil sheets 16"x96" of LDPE
> Al roofing flashing 12"x 91"
> Transformer oil (Texaco)
> Kraft paper between each
>
> Primary: 17 turns 0.25" copper tubing spaced 0.25"
> 15 degree bank
>
> Secondary: 8.5"o.d. (dried and sealed in and out)
> 34" winding length #20 magnet wire 1000 turns
> sealed
>
> Top load: Toroid 4"x20" crafted from styro. and Al tape (looks
> nice)
>
> Misc.: #6 sol. copper hookup wire for tank ckt.
> 0.05" wide brass strips for cap connections
(hobby
> store)
> #14 HV wire for tap lead (neon sign shop)
>
> I am tapped at ~14 turns on primary for best spark. I know I need more caps
> and a larger wire for my tap lead but if someone sees something else I should
> do to improve my coil, please let me know.
>
> Thanks again
> Rusty Duncan
>
Rusty,
I interspersed a few comments into the above. Yes, you need a bit more
capacitance. TESLAC recommends .015 mfd, and you could probably go as high
as .022 (which is double what you are currently using).
Looks like you have built a very nice Tesla coil. This is an excellent
first coil. Many of us remember building first coils that only had a few
inches of output spark. This Tesla list has made it possible for new
coilers to build truly impressive first Tesla coils. Thanks for sharing
your first design with us... and I hope we will be hearing more from
you in the future.
Fr. Tom McGahee