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RE: [TCML] General Questions About a Pig PoweredCoil (andanIntroduction)



Hi Phil -
 
I can remove the tailstock if I need to. At 200 lbs, it's not something that one does on a whim ;-). I do have a steady rest that should be able to incoporate up to 10" diameter. With that on the end of the lathe, I gain about another 18" so my 30" bed becomes 48". With the clever "extender" on the tool post, I could probably wind up to 60" without much trouble...
 
Tom

________________________________

From: tesla-bounces@xxxxxxxxxx on behalf of Phil Tuck (hvtesla)
Sent: Wed 3/24/2010 9:00 PM
To: 'Tesla Coil Mailing List'
Subject: RE: [TCML] General Questions About a Pig PoweredCoil (andanIntroduction)



Tom,

You wrote>>



" However (embarrassingly) the longest lathe I own is only 30 inches. In
fact, I've somehow collected three 16 by 30 American Pacemaker lathes.
Absolutely fantastic machines - some of the best ever made ... but also very
"stubby" (despite being only 30" between centers, these bad boys whey 7200
lbs a piece). I can squeeze about 32" but that is about all I've got - if I
really had to, I could wind the first portion on the lathe and then
<shudder> do the last several turns by hand."



You can solve this if you are able to remove the tailstock on your
particular type of lathe  (looking on the web I think your lathe will allow
this). You can then wind virtually any length - within reason, and even use
the saddle feed to guide the wire on.



See second photo from the bottom entitled "The coil was longer than the
lathe" at http://www.hvtesla.com/secondary.html



Phil



-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of Thomas Schmit
Sent: 24 March 2010 15:48
To: Tesla Coil Mailing List
Subject: RE: [TCML] General Questions About a Pig Powered Coil
(andanIntroduction)



Thanks for the welcome!



The "pig" is a 15 KVA unit; the primary (my secondary) voltage is listed as
7200/14400 and the secondary (my primary) is listed as 120/220. I will be
running it on 120 because I'd like to make this coil "portable" for some
demonstrations (this is one reason for the variac). I do not believe these
locations have 220 volt access, so I must be content with 120.



The variac consists of three units stacked in one. I was thinking I could
use one of the variacs as an inductive choke (i.e. "ballast") for my pole
pig by wiring the primary in series (and leaving the adjustable tap
unconnected) with the pig. I'm not sure whether this will provide enough of
a choke, however. I could wire two of them in series or, if that is still
insufficient, I can probably dig up a surplus choke from the cloud chamber.
Like I said, this variac is rated for an almost absurd current, IIRC so I
think it should work well, even if I run at 120 volts and 30 amps.



I don't want to shoot myself in the foot before even starting, so if the
general consensus 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 somehow collected three 16 by 30 American Pacemaker lathes.
Absolutely fantastic machines - some of the best ever made ... but also very
"stubby" (despite being only 30" between centers, these bad boys whey 7200
lbs a piece). I can squeeze about 32" but that is about all I've got - if I
really had to, I could wind the first portion on the lathe and then
<shudder> do the last several turns by hand.



I've got a big role of surplus 23 awg magnet wire, so I'd surely like to use
it instead of buying heavier gauge wire.



Now I've read that the length of the secondary conductor should be roughly
1/4 of the resonant frequency wavelength. I've not really though about why
this should be the case - I understand the necessity of matching resonant
frequencies between the two LC circuits but this requirement regarding the
length of the conductor was not immediately obvious to me.



Once I get a design set for the secondary coil, I can calculate the needed
capacitance and sizes of the other components readily. I just need to "fix"
some of these parameters - there are too many variables floating around! :-)




I guess the final question is regarding capacitors. Does anyone know of a
good source for surplus or otherwise cheap capacitors for a MMC setup? I've
got a bundle of ultra-low esr, low loss high pass capacitors for microwave
experiments. The only trouble is they are 0.0047 microfarad and have an
impractically low voltage rating...



Thanks everyone!



~Tom S.



________________________________



From: tesla-bounces@xxxxxxxxxx on behalf of David Rieben

Sent: Wed 3/24/2010 2:01 PM

To: Tesla Coil Mailing List

Subject: Re: [TCML] General Questions About a Pig Powered Coil
(andanIntroduction)







Hi Tom,



Welcome to the hobby. From reading your post

and from the mention of your "real job" pedigree,

it sounds like you should already be adequately

informed on the basic concept of operation ;^)

I guess the only thing that puzzles me is why you

would want to limit the size of your proposed

secondary coil to 8" x 25", considering that you

have a massive variac assemby and a pole pig. I'm

assuming that your pig is of the typical coiler's

size choice range of 10 or 15 kVA and 14,400

volts? I mean it seems like you would be severe-

ly limiting the potential of your power supply to

"choke" it back to a 120 volt, 30 amp service

and "only" be shooting for 6 ft. discharges. And

trust me, if you are like 99% of the rest of us

coilers, those 6 foot discharges will be very im-

pressive at first light but you will soon grow bored

and want BIGGER sparks, especially when you al-

ready have a very adequate power supply to readily

accomplish that. And you certainly have the power

supply hardware already in tow for easily making

sparks 3X that, assuming that you obtain and/or

build the rest of the coil system components to spec.

Then again, you may be space challenged for storage

and/or operation of a giant Tesal coil, too - kind of

where I'm at with my current coil system.

http://www.flickr.com/photos/33464569@N05/3765877471/

http://www.flickr.com/photos/33464569@N05/3118469520/



Anyway, the you should normally aim for a secondary

coil aspect ratio (length vs diameter) in the 3:1 to the

5:1 range and a topload toroid with a major diameter

about equal to the secondary coil length and a minor

diameter about equal to the diameter of the secondary

coil. SO if you secondary coil is 8x25, that would also

be a good appr. size dimension to aim for with your

topload.



Good luck with your project,

David Rieben



----- Original Message -----

From: "Thomas Schmit" <Thomas.Schmit@xxxxxxx>

To: <tesla@xxxxxxxxxx>

Sent: Tuesday, March 23, 2010 5:59 PM

Subject: [TCML] General Questions About a Pig Powered Coil (and

anIntroduction)





Hi Everybody,



I've never used a mailing list like this before, so you will have to

excuse any faux pa regarding the use of said list. For a quick bit of

background, I am a machinist and high energy physicist and it seemed

time that I build a Tesla coil. (No self-respecting physicist can

neglect to build one ;-) ).



I have a 3 phase variac (used for a cloud chamber, originally - its

good to 100 amps and 600 VAC RMS), a single phase pole pig, an old

mil-spec 30 KVDC 5 ma supply, several neon light transformers, etc.

That being said, I'm new to the home-brew high voltage game. It is

considerably different than working for a lab where dropping $10,000

on a power supply is trump change :-D and I could use all the help I

can get!



What I am concerned about now is the design of my coil. I am building

with a 6' spark in mind - that should pretty well max out a 110 volt

supply (the pole pig will be fed through one of the variacs hooked

into 110 volt mains through a 30 amp breaker). I'm looking at a

secondary coil with about 1000 turns of 23 AWG wire, which works out

to a length of only about 25". I am concerned about strikes hitting

the primary coil from the discharge terminal on the secondary.



 I guess I was just hoping I could get some input on the secondary

design. I'm thinking an 8" diameter PVC form - I will clean, bake and

shellac it before winding my coil. Size/length/diameter of wire/number

of turns - these are all variables that I'm not to sure about. I know

what inductance I want to hit, but I can get there several different

ways and I figure you all have already done the hard work for me ...

:-)



 Tom Schmit

>



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