RE: Atomic Laboratories 71869 Tesla Coil

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Peter Birk" <birk@xxxxxxx>

I think you are right on.  Just like the car the school has for Drivers Ed -
its a reliable low performance model made to stand up to abuse.  I would be
happy to work on their car but I don't think they'd appreciate it if I
brought it back with a super charged 500 hp engine and a Hurst manual
transmission.

Raising the coil did virtually eliminate the primary to secondary sparking
but did not inprove performance.  Widening the spark gap seemed to help but
I think I cooked an expensive mica capacitor making it too wide.  Right now
its working better than ever so I think I will call it fixed before I cook
another capacitor.

Thanks

Pete

-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Saturday, November 04, 2006 7:47 PM
To: tesla@xxxxxxxxxx
Subject: Re: Atomic Laboratories 71869 Tesla Coil


Original poster: Mddeming@xxxxxxx

In a message dated 11/4/06 2:59:29 P.M. Eastern Standard Time,
tesla@xxxxxxxxxx writes:
Original poster: "Peter Birk" <birk@xxxxxxx>

Fired up the coil after the changes suggested.  Works better but still can
only draw about a 8 - 10 inch spark.  No more sparks from the case.  Noticed
a lot of sparking between the primary and secondary despite the quarter inch
thick plastic tube and the rubbery primary casing.  Its much worse if the
spark gap is widened over about 1/8 inch.  The primary coil is centered 4
inches from the bottom of the secondary.  I wonder if raising the secondary
to bring the primary closer to the bottom will help this. Here's what it
looks like:
http://hot-streamer.com/temp/PeterBirk/IMG_0134_7_9_1.JPG
http://hot-streamer.com/temp/PeterBirk/IMG_0136_5_9_1.JPG

Stan I appreciate your comments.  This list is dedicated to coilers turning
out technically and aesthetically elegant machines.  I impose on your time
and patience because I need expertise not available elsewhere.  This coil is
old but solidly built by a reputable company - CENCO.  It survived 30 years
of use in a public school - I call that proof of design.  If I can get it
going another 10 years several thousand students will see it and perhaps a
few will be inspired.

Hi Peter,

     You are right, it is a rock-solid design, but it is a rock-solid
"family sedan", not a rock-solid "formula race car". Evidently,
CENCO's aim was high reliability and high repeatability to illustrate
the principle rather than maximizing spark length.

     Yes, raising the secondary a little at a time may really help
with the sparking problem. Another improvement might be adding a
cooling fan in the corner near the spark gap.
Since there is no safety gap, I would recommend limiting the gap
setting to 1 mm/3 kV of tranny output.

   On a more radical note, you could try lopping off about 1/3 of the
secondary and adding a 3X10 Al-duct torroid over the ball. This may
be more changes than you want to make to the vintage design, as tall
and skinny was an assumed good design 30-50 years ago.

   CENCO was interested in a device that would work right out of the
box and work every time. How efficiently was never a question. Ten
inches may be within design specs.

Matt D.