Re: Atomic Laboratories 71869 Tesla Coil

["Tesla list" <tesla@xxxxxxxxxx>]

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.