Re: Variable capacitor for tinkering with

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Hollmike-at-aol-dot-com>

Hi all, 
  The topic of a variable cap seems to have gotten some interest, so I thought
I'd share and idea with you.    I have 'invented' a variable cap that might be
of interest.  I am not sure just how much variablilty it would have yet,
because I have not yet made one to test out.  I think I will this week and will
let you know if it is worth trying.  Sorry for a such a long post, but I hope a
few people will find it interesting. 
   The original variable cap my idea is based on is simply two lengths of pvc
pipe of different diameters.  In this original cap the idea is to have both
pipes covered with aluminum foil.  I believe the larger pipe should be sealed
on one end to prevent arcing between the plates.  To alter the capacitance, one
would simply vary the distance the inner pipe is inserted into the outer one. 
Of course the inner pipe doesn't necessarily need to be made from pvc and maybe
a cardboard tube would be of a more convenient diameter to fit more snugly
inside the outer tube.   It was a long time ago that I read about this cap, so
I cannot remember who published the idea.  It may have been posted on Bill
Beatty's site, but I would hate to incorrectly credit anyone with the idea. 
Perhaps others have seen this and can tell us. 
   My 'invention' is similar, and has the disadvantage of only having about
half the maximum capacitance as the variable cap described above for the same
size cylinders.  It uses the concentric cylider idea, but rather than altering
the capacitance by changing how far the inner cylinder is inserted, I had the
idea that a number of equally spaced strips of foil could be glued along the
length of the cylinders(all connected together at one end).  The capacitance
would be altered by simply rotating the one of the cylinders with respect to
the other one. 
    As I said, I have not tested this idea and don't know how well it would
work, but thought I'd toss it out to you and see what you think about it.  Does
it seem practical?  I won't know until trying it, I guess.  Both variable caps
that I described seem simple enough to construct. 
     My original intention for this cap design was conceived when reading about
scalar waves and I was wondering how a generator could be made(If this is even
possible?).  I had the idea I could charge such a capacitor with a HVDC source
and place a long string of HV diodes on the HV lead.  Then I would spin the
inner cylinder(since it would be grounded should not have to worry about frying
the motor).  This would, in effect, create a time varying capacitor.   Since
the voltage would change as the square of the change of capacitance, it would
effective(hopefully anyway) create a rapidly changing voltage
source(alternating weill dispaced from ground), but one that would not have
minimal current, assuming no corona losses.   I don't even know if there is any
practical uses for scalar waves, so I haven't tried the idea yet, but I still
wish to make such a variable capacitor, so I will this week - just for fun.
&nb!
sp; 
    The most interesting aspect of this design(for the so called scalar wave
generator-  if such a concept is real)  is that as the capacitance goes towards
zero, how high would the voltage go?  I a sure some kind of arc over or corona
losses would occur, but if properly insulated, I think one could achieve
thousands volts above the input voltage at the minimum capacitance.  Of course
placing a toroid on the outer cylinder would help limit this as the total
capacitance would never go to zero when the plates are not aligned. 
     I cannot say that this "time varying capacitor" would work or that scalar
waves can be generated or would even be useful.  This was all really just a
thought experiment.  I hope that  either of the variable capacitors described
might be of interest or use to someone on the list and that is the reason for
the post. 
  Cheers, 
Mike