Re: 3/4 wavelength secondaries
Tesla List wrote:
> > Subject: re: 3/4 wavelength secondaries
> >From hullr-at-whitlock-dot-comWed Jul 24 21:43:11 1996
> Date: Wed, 24 Jul 1996 11:16:33 -0700
> From: Richard Hull <hullr-at-whitlock-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: 3/4 wavelength secondaries
> Tesla List wrote:
> > >From sgreiner-at-wwnet-dot-comTue Jul 23 21:59:58 1996
> > Date: Tue, 23 Jul 1996 21:32:37 -0700
> > From: Skip Greiner <sgreiner-at-wwnet-dot-com>
> > To: tesla list <tesla-at-pupman-dot-com>
> > Subject: re: 3/4 wavelength secondaries
> > Thanks to Richard Hull, Robert W. Stevens, and John H. Couture for their
> > answers to my query re the subject.
> > I have snipped all of the above responses since they virtually reiterate
> > the same ideas, ie., it should be possible to wind a 3/4 wave coil and
> > make it resonate somewhere near its 3/4 wave frequency, taking into
> > account its cself, etc.
> > Richard, I want to do this if its possible. I understand it "should break
> > out 1/3 of the way up the coil. If it is a standing wave, maybe it won't.
> > John, I have my own home-brewed program to design coils. It does
> > approximately what you suggest as far as satisfying the numerous
> > applicable equations. It uses Wheeler and various other accepted
> > equations for L, wavelength and frequency.
> > Robert, I have a coil in which the wire length is "fairly" close to the
> > 1/4 wave resonant frequency. This coil will put out discharges exceeding
> > 36" from a 4.5" insulator on top with only a 1/4-20 screw for the top
> > terminal. there is also a great amount of corona from the top several
> > turns of the secondary. Driving power is a 15kv 120ma neon.
> > Why did I bring this all up?
> > I have tried to design and wind both 1/4 and 3/4 wave coils to be run
> > with none or very little terminal capacitance with the idea that given
> > the same energy delivered to the terminal capacitance, and using the
> > energy equal to 1/2 cv^2...then decreasing the terminal cap should lead
> > to increasing the voltage. Although its been a couple of years since I
> > read Tesla's CSN, I believe he thought he was winding 1/4 wave coils and,
> > if memory serves, he used very small terminal caps. I understand about
> > corona and the fact that a toroid should build up the energy before
> > breakout, but is that really how a TC works? I should not be able to get
> > 36" discharges from a 1/4-20 bolt if that assumption is true.
> > snip
> > I would certainly appreciate any comments to this and I would especially
> > like to hear from anyone who has built a 1/4 or 3/4 wave coil that comes
> > in close to the correct frequency.
> > Thanks for listening
> > Skip,
> Your math is correct on the given energy, higher voltage for smaller C
> bit. However, this math is thwarted by the reality of the matter in the
> real world.
> Let us say we have a fixed energy input. Now, let us say that we have
> 50% more voltage available with no toroid, or removal of the load. We
> now use a bolt or very small electrode on the end of our coil. We all
> have seen what happens. A vast shower of sparks, often hundreds, break
> out all over the terminal or bolt in all directions. The air break down
> voltage of a bolt is about 15KV and a small 2" ball, about 60kv. Thus,
> as the Tesla coil's resonant rise builds to millions or billions of volts
> it will break out way before this voltage is achieved or at 15 or 60Kv!!
> The extra energy creates EXTRA SPARKS!! Sparks which dissapate the
> energy incredibly quickly as more and more fingers are added at the
> BREAKOUT VOLTAGE.
> True, given enough power, the ion cloud around even the most miniscule
> terminals will be overcome by the energy. This extra energy will expand
> the spherical ion cloud and the spark length will grow even with a bolt
> only electrode. But, my goodness, we are stupidly making a large ion
> terminal with brute power!! There is absolutely no reason why a 20 foot
> arc can't be made to issue from of a 1/4-20 bolt! But Gee-whiz at what
> power level and at what size of a coil would this happen!! I don't want
> to even imagine it!!!
> A huge toroid or large top C absorbs and stores this energy as it is
> being created by resoant rise. The toroid's size and shape determine the
> voltage of break out, say one million volts. If you make a coil that is
> not capable of generating one million volts, the spark will never occur
> and RF radiation is all you get. But let that 1 million volt mark be
> reached and you will have a single, long, hot ribbon of flame releasing
> all the stored energy in huge singular arcs moving slowly around the
> coil. We have all seen this too. Am I right?!!! If you haven't, then
> you owe it to yourself to try it! You will like it! The spark return
> from a giant toroided system using a given power input will always vastly
> exceed anything from a system with little or no toroid. This is just a
> simple fact of physics and "the doing".
> Tesla used small terminals in Colorado becasue that is all he had. A 36"
> diameter sphere is no small terminal, but compared to his system size and
> power, it was vanishingly small!!
> He learned quickly though from a long and tedoius group of daily
> experiments with an elevated isotropic capacity in Colorado and didn't
> repeat the Colorado "mistake" with Wardencylffe! He planned and
> constructed the largest regular formed terminal load ever created for his
> tower. His voltage would rise forever to incredible levels due to the
> incredible storage capacity of his top terminal.
> Finally, the voltage produced by a Tela coil is a function of the
> resonator coil's inductance and the current injected into the base. The
> top terminal may load this a bit, but the value of the voltage created in
> the system is not determined by the top C at all. I hope this helps this
> thread a bit.
> Richard Hull, TCBOR
You always make some very good points. I mentioned in another post that I do not
understand the physics of a TC. That notwithstanding, I think I have a question which
bears on this whole discussion. The gap fires and a pulse of energy is delivered to the
secondary from Cp. In fact several pulses are delivered since there is oscillation in
the primary circuit. The pulse(s) propagate up the secondary to the terminal capacitance
whatever it may be. The pulse is partially absorbed by the terminal cap and reflected
back down the secondary (?) as an oscillation. The oscillations in the secondary are by
definition AC. How can a pulse of AC charge up the terminal cap (assuming that the first
pulses are not sufficient to cause discharge breakout). If what we are doing is only
charging up the terminal cap with the first positive (or negative) swing of the pulse
train until the toroid reaches breakout voltage, then I can understand your point. But,
if we are somehow actually charging up the terminal cap using successive pulses, then i
am at a loss.
Can you be more definitive? I would appreciate it.