Re: Raised secondary problems

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jeremy Scott by way of Terry Fritz <teslalist-at-qwest-dot-net>" <supertux1-at-yahoo-dot-com>


Sounds more like a tuning problem, most likely related
to your choice of topload. (I'm not sure
a bicycle rim has enough surface area. Try a fat
mag wheel rim from a performance auto shop :) )

Coupling K factors of .1 to .2 usually work well,
and I can't see a few inches dramatically throwing the
coupling out of that range.

Try putting the primary at the same level as the
secondary's first bottom turn. If there is arcing
between the two, start removing inner turns from
the primary until it stops. There should be at
least an inch or so between the first primary turn and
base of the coil. (For a medium power tesla coil)
You'll also want to try and patch up any damage
that previous arcs might have created.

After that, start experienting with a larger
topload and adjust the primary tap.

http://www.classictesla-dot-com has a great
calculator that can predict what your
results might be.




--- Tesla list <tesla-at-pupman-dot-com> wrote:
 > Original poster: "Jolyon Vater Cox by way of Terry
 > Fritz <teslalist-at-qwest-dot-net>"
 > <jolyon-at-vatercox.freeserve.co.uk>
 >
 > I have conducted some experiments using the primary
 > shown in
 >
 > http://hot-streamer-dot-com/temp/P001800.jpg
 >
 > to drive
 > a secondary of 880t of 32SWG enamelled copper wire
 > wound on a  2.9" dia
 > former; the primary being grounded at the centre and
 > tapped at the sixth
 > turn for best match.
 >
 > Here are my findings:-
 >
 > When the base of secondary is approximately 1 1/2"
 > below the primary
 > 6" or so long sparks can be drawn from the TC to a
 > pointed electrode when a
 > 16 1/5" dia, 1 1/4 rim bicycle wheel is used for a
 > topload.
 >
 > When the secondary is raised with respect to the
 > primary (so that it is 1
 > 1/2" ABOVE the primary) the spark length falls
 > considerably -it is pitiful-
 > and it is not possible to compensate for this by
 > increasing the number of
 > turns to the tapping point on the primary.
 >
 > However, when the primary is raised with regard to
 > the secondary by only 1"
 > or less arcing occurs between the base of the
 > primary and the secondary
 > winding?
 >
 >
 > The experiment has conducted twice and the same
 > things happened.
 >
 > Is this a matter of under- and over- coupling?  My
 > intention was to support
 > the secondary on a platform 1 1/2" inches above the
 > secondary
 > but my experience suggests this is not possible
 > without severely reducing
 > the spark length.
 >
 >
 > Is there a way of getting 6" or so sparks with the
 > secondary raised above
 > the primary in the manner described
 > e.g. by increasing the number of secondary turns
 > -possibly by using finer
 > wire like 40SWG
 > or by using a larger tank capacitor -I am currently
 > using 22nF and would
 > rather not have to build anything larger than this!
 >
 > Or is the whole idea of raising the secondary a bad
 > idea that should be
 > abandoned in favour of the present arrangement?
 > Jolyon
 >
 >
 >


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