[TCML] General Questions About a Pig Powered
Thomas.Schmit at cern.ch
Wed Mar 24 11:56:08 MST 2010
That's a bit of relief. I'm familiar with 1/4 wave resonators in superconducting RF cavities and even 1/4 wave resonators as a high-q filter but I just couldn't see the application, besides the similar behavior between a tuned LC circuit and 1/4 wave resonator wrt filtering capabilities. Maybe I'll work this problem out formally if I get a chance ...
David - Keep in mind that my definition of "portable" is probably not the same as most people's. I'm used to moving my metal working machinery around; the smallest of which is a 24" Avey drill press. Yeah, I know - you're probably thinking, "oh, a drill press isn't very heavy" but this one weighs 1200 lbs :-D
Thanks again for all the pointers. I appreciate all the help I can get!
From: tesla-bounces at pupman.com on behalf of mddeming at aol.com
Sent: Wed 3/24/2010 7:15 PM
To: tesla at pupman.com
Subject: Re: [TCML] General Questions About a Pig Powered Coil(andanIntroduction)
The quarter wave requirement is a total MYTH! It has been shown time and again, in the archives here and elsewhere, both mathematically and by physical measurement that it is a MYTH. Only a few diehard "Holy Defenders of the Luminiferous Aether" still cling to this hogwash.
A TC behaves with some of the characteristics of a 1/4 wave resonator, wrt voltge and current distribution, but this is tied to the L and C values, h/d ratio, topload size, and only indirectly to wire length. It is almost unfortunate that a moderate size coil of average proportions CAN be made with a length of wire that turns out to be approximately 1/4 wavelength long. This is what keeps the "True Believers" ever faithful.
From: Thomas Schmit <Thomas.Schmit at cern.ch>
To: Tesla Coil Mailing List <tesla at pupman.com>
Sent: Wed, Mar 24, 2010 11:47 am
Subject: RE: [TCML] General Questions About a Pig Powered Coil (andanIntroduction)
Thanks for the welcome!
he "pig" is a 15 KVA unit; the primary (my secondary) voltage is listed as
200/14400 and the secondary (my primary) is listed as 120/220. I will be
unning it on 120 because I'd like to make this coil "portable" for some
emonstrations (this is one reason for the variac). I do not believe these
ocations have 220 volt access, so I must be content with 120.
he variac consists of three units stacked in one. I was thinking I could use
ne of the variacs as an inductive choke (i.e. "ballast") for my pole pig by
iring the primary in series (and leaving the adjustable tap unconnected) with
he pig. I'm not sure whether this will provide enough of a choke, however. I
ould wire two of them in series or, if that is still insufficient, I can
robably dig up a surplus choke from the cloud chamber. Like I said, this variac
s rated for an almost absurd current, IIRC so I think it should work well, even
f I run at 120 volts and 30 amps.
don't want to shoot myself in the foot before even starting, so if the general
onsensus is to make a bigger secondary, a bigger secondary I will make! However
embarrassingly) the longest lathe I own is only 30 inches. In fact, I've
omehow collected three 16 by 30 American Pacemaker lathes. Absolutely fantastic
achines - some of the best ever made ... but also very "stubby" (despite being
nly 30" between centers, these bad boys whey 7200 lbs a piece). I can squeeze
bout 32" but that is about all I've got - if I really had to, I could wind the
irst portion on the lathe and then <shudder> do the last several turns by hand.
've got a big role of surplus 23 awg magnet wire, so I'd surely like to use it
nstead of buying heavier gauge wire.
ow I've read that the length of the secondary conductor should be roughly 1/4
f the resonant frequency wavelength. I've not really though about why this
hould be the case - I understand the necessity of matching resonant frequencies
etween the two LC circuits but this requirement regarding the length of the
onductor was not immediately obvious to me.
nce I get a design set for the secondary coil, I can calculate the needed
apacitance and sizes of the other components readily. I just need to "fix" some
f these parameters - there are too many variables floating around! :-)
guess the final question is regarding capacitors. Does anyone know of a good
ource for surplus or otherwise cheap capacitors for a MMC setup? I've got a
undle of ultra-low esr, low loss high pass capacitors for microwave
xperiments. The only trouble is they are 0.0047 microfarad and have an
mpractically low voltage rating...
From: tesla-bounces at pupman.com on behalf of David Rieben
ent: Wed 3/24/2010 2:01 PM
o: Tesla Coil Mailing List
ubject: Re: [TCML] General Questions About a Pig Powered Coil
Welcome to the hobby. From reading your post
nd from the mention of your "real job" pedigree,
t sounds like you should already be adequately
nformed on the basic concept of operation ;^)
guess the only thing that puzzles me is why you
ould want to limit the size of your proposed
econdary coil to 8" x 25", considering that you
ave a massive variac assemby and a pole pig. I'm
ssuming that your pig is of the typical coiler's
ize choice range of 10 or 15 kVA and 14,400
olts? I mean it seems like you would be severe-
y limiting the potential of your power supply to
choke" it back to a 120 volt, 30 amp service
nd "only" be shooting for 6 ft. discharges. And
rust me, if you are like 99% of the rest of us
oilers, those 6 foot discharges will be very im-
ressive at first light but you will soon grow bored
nd want BIGGER sparks, especially when you al-
eady have a very adequate power supply to readily
ccomplish that. And you certainly have the power
upply hardware already in tow for easily making
parks 3X that, assuming that you obtain and/or
uild the rest of the coil system components to spec.
hen again, you may be space challenged for storage
nd/or operation of a giant Tesal coil, too - kind of
here I'm at with my current coil system.
Anyway, the you should normally aim for a secondary
oil aspect ratio (length vs diameter) in the 3:1 to the
:1 range and a topload toroid with a major diameter
bout equal to the secondary coil length and a minor
iameter about equal to the diameter of the secondary
oil. SO if you secondary coil is 8x25, that would also
e a good appr. size dimension to aim for with your
Good luck with your project,
----- Original Message -----
rom: "Thomas Schmit" <Thomas.Schmit at cern.ch>
o: <tesla at pupman.com>
ent: Tuesday, March 23, 2010 5:59 PM
ubject: [TCML] General Questions About a Pig Powered Coil (and
I've never used a mailing list like this before, so you will have to
xcuse any faux pa regarding the use of said list. For a quick bit of
ackground, I am a machinist and high energy physicist and it seemed
ime that I build a Tesla coil. (No self-respecting physicist can
eglect to build one ;-) ).
I have a 3 phase variac (used for a cloud chamber, originally - its
ood to 100 amps and 600 VAC RMS), a single phase pole pig, an old
il-spec 30 KVDC 5 ma supply, several neon light transformers, etc.
hat being said, I'm new to the home-brew high voltage game. It is
onsiderably different than working for a lab where dropping $10,000
n a power supply is trump change :-D and I could use all the help I
What I am concerned about now is the design of my coil. I am building
ith a 6' spark in mind - that should pretty well max out a 110 volt
upply (the pole pig will be fed through one of the variacs hooked
nto 110 volt mains through a 30 amp breaker). I'm looking at a
econdary coil with about 1000 turns of 23 AWG wire, which works out
o a length of only about 25". I am concerned about strikes hitting
he primary coil from the discharge terminal on the secondary.
I guess I was just hoping I could get some input on the secondary
esign. I'm thinking an 8" diameter PVC form - I will clean, bake and
hellac it before winding my coil. Size/length/diameter of wire/number
f turns - these are all variables that I'm not to sure about. I know
hat inductance I want to hit, but I can get there several different
ays and I figure you all have already done the hard work for me ...
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