Re: Test Cap, dry/oil
From: Peter Electric[SMTP:elekessy-at-macquarie.matra-dot-com.au]
Reply To: elekessy-at-macquarie.matra-dot-com.au
Sent: Friday, December 05, 1997 5:49 AM
To: Tesla List
Subject: Re: Test Cap, dry/oil
Fellow Capacitor builders:
I have had an idea about this for some time that seems to have been born
out by Gary's experiment. If you have an air space cap, it will have a
lot of air between the plates causing a fair bit of looseness between
plates. When you measure its capacitance with a small applied voltage,
the plates will be at a certain spacing and you will get a certain
reading. At a higher applied voltage you will get a higher reading as
electrostatic attraction will cause the plates to be closer together.
Under normal TC operating conditions, this cap will have a small range
of capacitance value rather than a single value and should have a less
sharply defined tune point on the primary. This may be the cause of the
cap heating and lack of energy in the sparks that Gary describes. Adding
oil on the other hand will do a lot to "stiffen up" the cap. This may
also be why commercial caps seem to perform slightly better than our
home made jobs. It might be worth doing some experiments with flat plate
caps held very tightly in metal frames.
What do you think?
Tesla List wrote:
> From: gweaver[SMTP:gweaver-at-earthlink-dot-net]
> Sent: Thursday, November 27, 1997 10:16 PM
> To: Tesla List
> Subject: Test Cap, dry/oil
> I made a test capacitor. Metal plates are 5" x 12" aluminum foil. 6
> of 6" x 13" poly .006 mil. I put a #24 copper wire on each metal
> plate and
> rolled up the cap. Wrapped it with 2 turns of masking tape to hold it
> The finished cap measures about 1.125" dia x 6" long. It measures
> uf. on my meter.
> I connected the dry cap to a 6K 20 ma furnace ignition transformer and
> tiny TC. The output sparks are 3" but not very hot. After 2 minutes
> of run
> time the cap started getting warm. I placed the cap in a small
> and poured oil over it. The TC sparks are still 3" long but the
> sparks are now much hotter.
> I have been thinking about making a dry poly rolled cap for a small
> desk top TC and did this test to see the results of a dry cap on the
> The oil makes a big inprovement in the discharge sparks. The
> sparks did not get any longer but the power output appears to be about
> double. Much thicker and hotter sparks.
> Gary Weaver