I machined 2 primaries with my 5'X x 16'Y x 1'Z cnc router. I mounted the spokes to a round base. I
have a couple 4' x 8' sheets of Styrofoam on the table. I routed out a circle to fit the base of the primary, screwed it down then routed the spokes flat true to the router then used a ball router bit to cut the spiral with the horizontal center of the bit just about a 1/16" or so below the top of the spokes, that way you can tap down the tubing and it will hold in place. I used a 3/8" ball for Sparkymatic's primary and just a ball end strait bit for the 18" coil primary which is either 1/2" or 5/8" I can't remember right off hand but the tubing fits pretty snug. I used 3/4" pvc sign board. For Sparky I glued strips of pvc to some mdf with formica veneer and the 18" is all pvc.
________________________________
From: t-burns14 <t-burns14@xxxxxxxxxxx>
To: tesla@xxxxxxxxxx
Sent: Monday, March 3, 2014 1:35 PM
Subject: Re: [TCML] Base
Okay I like the idea of using spokes. This is my first coil so I'm learning how to build and run it as I no through each phase. I use Teslamap for calculations, by half the time I don't know what it's calculating. I'm in AP Physics at my high school and that is helping tremendously as I now know what capacitance, resistance and inductance are as well as how voltage and current relate to these things. So I know that tuning the primary is in reference to the resonant frequency of the primary coil. Does anyone know of a circuit diagram for a Tesla Coil to help me understand? Also, does the resonant frequency of the primary need to match the secondary or just be a harmonic of it?
Sent from my Galaxy S®III
-------- Original message --------
From: tesla-request@xxxxxxxxxx
Date:03/03/2014 2:00 PM (GMT-05:00)
To: tesla@xxxxxxxxxx
Subject: Tesla Digest, Vol 77, Issue 3
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Today's Topics:
1. Base (t-burns14)
2. Re: Base (Jim Lux)
3. Re: Base (Bert Hickman)
4. PT's for possible sale sold! (David Rieben)
5. Re: First notch quenching? (Steve Ward)
----------------------------------------------------------------------
Message: 1
Date: Sun, 2 Mar 2014 14:42:10 -0500
From: t-burns14 <t-burns14@xxxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: [TCML] Base
Message-ID: <COL401-EAS34C3F566A16006DA0ED787EB8C0@xxxxxxx>
Content-Type: text/plain; charset="utf-8"
I have an opportunity to use a CNC milled piece for my base, as seen in one of the Geek Group videos. The milled a spiral into the piece of plastic and then just hammered the tubing into the spiral cutout. I'm wondering what material would be good for that. They might have been using High Density Polyethylene, because I remember them saying it was food grade and polyethylene is used for cutting boards. Any insight?
Thanks
Sent from my Galaxy S?III
------------------------------
Message: 2
Date: Sun, 02 Mar 2014 12:08:31 -0800
From: Jim Lux <jimlux@xxxxxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: Re: [TCML] Base
Message-ID: <53138FBF.9050402@xxxxxxxxxxxxx>
Content-Type: text/plain; charset=UTF-8; format=flowed
On 3/2/14 11:42 AM, t-burns14 wrote:
> I have an opportunity to use a CNC milled piece for my base, as seen
> in one of the Geek Group videos. The milled a spiral into the piece
> of plastic and then just hammered the tubing into the spiral cutout.
> I'm wondering what material would be good for that. They might have
> been using High Density Polyethylene, because I remember them saying
> it was food grade and polyethylene is used for cutting boards. Any
> insight? Thanks
>
It probably *was* a HDPE cutting board, unless they happened to have a
source for HDPE scrap. Otherwise, you're buying a 4x8 foot sheet of the
plastic.
HDPE cutting boards are readily available in a variety of useful sizes,
and are cheap. There are also polycarbonate cutting boards.
------------------------------
Message: 3
Date: Sun, 02 Mar 2014 14:25:32 -0600
From: Bert Hickman <bert@xxxxxxxxxxxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Subject: Re: [TCML] Base
Message-ID: <531393BC.80401@xxxxxxxxxxxxxxxxxxxxx>
Content-Type: text/plain; charset=UTF-8; format=flowed
You're correct. High Density Polyethylene (HDPE) or Ultra High Molecular
Weight (UHMW) polyethylene are both good choices. Both materials are
strong, easy to machine, are excellent electrical insulators, they don't
easily carbonize/track, are readily available, and are relatively
inexpensive.
Before settling on this design approach, you may want to think about how
you will tap the primary. Most coilers find that they need to adjust
primary inductance for fine tuning. Even changing the size of the
topload will result in a tuning change. Using a series of slotted radial
"spokes" of machined HDPE would provide you with the same degree of
primary support while also permitting easy tapping.
Bert
--
Bert Hickman
Stoneridge Engineering
http://www.capturedlightning.com
***********************************************************************
World's source for "Captured Lightning" Lichtenberg Figure sculptures,
magnetically "shrunken" coins, and scarce/out of print technical books
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t-burns14 wrote:
> I have an opportunity to use a CNC milled piece for my base, as seen
> in one of the Geek Group videos. The milled a spiral into the piece
> of plastic and then just hammered the tubing into the spiral cutout.
> I'm wondering what material would be good for that. They might have
> been using High Density Polyethylene, because I remember them saying
> it was food grade and polyethylene is used for cutting boards. Any
> insight? Thanks
>
>
> Sent from my Galaxy S?III
> _______________________________________________ Tesla mailing list
> Tesla@xxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla
>
------------------------------
Message: 4
Date: Sun, 2 Mar 2014 12:30:29 -0800 (PST)
From: David Rieben <drieben@xxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Subject: [TCML] PT's for possible sale sold!
Message-ID:
<1393792229.61418.YahooMailNeo@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>
Content-Type: text/plain; charset=iso-8859-1
Just wanted to let everyone know that the PTs that I had listed for
sale this past Friday are already sold.
?
Thanks you,
David Rieben
------------------------------
Message: 5
Date: Mon, 3 Mar 2014 02:57:49 -0600
From: Steve Ward <steve.ward@xxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Subject: Re: [TCML] First notch quenching?
Message-ID:
<CAD=yrf=3TM_XSz8tTRyRTMno9sDUHocT+wVSG50UBGnphEYKnw@xxxxxxxxxxxxxx>
Content-Type: text/plain; charset=ISO-8859-1
(snip)
>
> > I do use this technique in my latest DRSSTC drivers (not published
> > anywhere yet). I use it mostly for current limiting, so that instead
> > of terminating the gate drive upon current trip, i simply let the
> > primary "coast" by leaving off 1 half-bridge (the diodes commutate).
> > This allows the primary to ring with only the damping the secondary,
> > and not regen to the DC bus.
> > I very much like the results of having this added control of the
> > bridge.
>
> I think I understand the diode commutating point, but don't you still need
> to reverse the phase of the driven half-bridge?
Nope. You dont want to "invert" the drive voltage, you just want to "zero"
it. Its funny, when i was thinking about how to originally do it, the
first idea was to make both half-bridges switch together (in phase) during
the coasting time. However, if you just leave off the one half-bridge that
needs to get "inverted" the same behavior will happen naturally via the
free-wheeling diodes. This avoids any difficulties in passing the signal
through the gate drive transformer.
> Further, wouldn't you also
> be better off continuing to drive the other half-bridge, to avoid leaving a
> 'high impedance' gate on the low-side of that half-bridge with possible
> attendant Miller effect issues? (I feel quite out of my depth with that
> last
> question.)
>
Its a great point to raise because that exact problem could exist. My
drives use gate drive transformers, and the driver for the transformer
"clamps" the GDT primary to 0V, which serves as a low impedance "short" on
the GDT secondaries (which connect to the gates). So basically the IGBT
gate looks pretty much shorted. Leaving an IGBT gate "open" is a bad idea.
>
> Turning back to the point of the original post (so this is not a complete
> hijack), do I understand the (at least theoretical) approach you would
> recommend for a DRSSTC then to be: (i) As a goal (but subject to component
> limitations), to time the ending of each burst to correspond with the
> 'first
> notch'?
This is great for achieving the best input power to spark length efficiency.
> (ii) To use your 'coasting' technique to implement current
> limiting, but not end-of-burst?
You may not even need this control, but i like it :-).
> (iii) To implement end-of-burst by not
> driving the IGBTs? (Why would that be better than 'coasting'?)
>
Coasting vs Regenerating at the end of burst? Well, thats something that
needs to be tested for each case. For coils that end the drive at a notch,
i would let it regenerate to the DC bus through the diodes (all IGBTs off
at end of burst) to capture what little energy is left. I dont think
coasting would contribute to the sparks in this case, since the secondary
is presumably already at its peak, and will be ramping down at this point
anyway. For coils that are "detuned" to operate without notching, i would
think the coasting would be better to let that stored primary energy get a
chance to make its way through the secondary to the sparks.
Steve
> MBD
>
> _______________________________________________
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> Tesla@xxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
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