RE: [TCML] Could this be a breakout point?

["Lau, Gary" <Gary.Lau@xxxxxx>]

My toroid is fastened to my secondary with a length of 1/4-20 threaded rod and a wingnut.  The end of the rod sticks out above the top of the central disk by a good 1-2", (probably more, not sure) but because it is within the toroid's minor diameter, there is no corona.

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of Quarkster
> Sent: Sunday, September 07, 2008 11:15 PM
> To: Tesla Coil Mailing List
> Subject: RE: [TCML] Could this be a breakout point?
>
> Steve -
>
> I think you may have a problem with corona from the "points and edges" on the
> nuts you are using to secure the wiring. Instead of the top nut you could use a
> tapped brass ball to increase the radius of curvature, but the increased overall
> height of the ball could also cause corona problems. Its not clear from your photo
> how much shielding this stud will receive from the toroid. In my experience, even a
> small projection from the last few turns at the top of the secondary will generate
> significant corona, even if the toroid is just a few inches above the bump in the wire
>
> I share your concern about the vulnerability of the last turn of the secondary, and
> how it is connected to the topload. My solution is a bit complicated, but it
> completely isolates the secondary wire from any possibility of damage where it
> connects to the topload. Also, it (almost) completely eliminates the possibility of
> arcing inside the secondary coilform.
>
> First, I install a sealed plastic baffle inside the secondary, about 3" below the last
> turn of wire at the top. This baffle is sealed in place with a large bead of electronic-
> grade RTV silicone sealant on both sides so it is completely air-tight. The baffle has
> a short ceramic standoff insulator mounted in the center, secured with a nylon
> screw. I run the last turn of the secondary through the wall of the coilform, and
> secure it to the top of the standoff with a small soldered-on ring terminal.
>
> Then, I install a second, thicker plastic baffle (or top plate) flush with the end of the
> coilform, secured with multiple screws coming in through the side of the coilform. If
> you are using standard PVC pipe, this can simply be a PVC pipe cap (although I
> think an internal baffle looks better). In the center of this plate is a length of 1/2",
> 3/8" or 1/2" diameter threaded metal rod ("all-thread"), secured with nuts and
> washers on both sides of the top plate.The all-thread is long enough to position the
> topload at the desired height. I use a short piece of small diameter wire to connect
> the top of the standoff insulator to the bottom of the all-thread. The all-thread is
> what supports the topload, and the small piece of small-gage wire inside the
> coilform mechanically isolates the actual secondary windings from any mechanical
> stresses that might be "accidentally" applied to the topload.
>
> It may sound like overkill, but I had an experience long ago where I broke off the
> wire at the very top of the secondary, and because the secondary had been
> meticulously epoxy-coated I could not "unwind" a few turns at the top of the
> secondary to get enough wire to make a new connection to the topload.
>
> So, now all my secondaries are epoxy coated, have a sealed internal baffle, and
> have the actual secondary windings mechanically isolated from their connection to
> the topload. Having learned "the hard way" about internal arcing and broken
> secondary wiring, I make sure that I won't experience these types of failures a
> second time.
>
> Regards,
> Herr Zapp
>
>
>
> --- On Sun, 9/7/08, Stephen J. Hobley <shobley@xxxxxxxxxx> wrote:
>
> From: Stephen J. Hobley <shobley@xxxxxxxxxx>
> Subject: RE: [TCML] Could this be a breakout point?
> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
> Date: Sunday, September 7, 2008, 12:06 PM
>
> My goal has been to terminate the coil wire on the cylinder.
>
> The solution you describe is what I have now, and I'm concerned about
> the fragility of the coil wire.
>
> Steve
>
> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of bartb
> Sent: Sunday, September 07, 2008 2:01 PM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] Could this be a breakout point?
>
> Hi Steve,
>
> It may be a problem. You'll of course have to try it to find out. It is
> best to cap the top and use the top cap for the toroid connection.  I
> personally would not feel comfortable with this connection. It may run
> ok at first, but at some point something will cause it to breakdown
> (humidity, tuning, coupling, etc..). I recommend you consider this a
> temporary solution and begin looking around for a more permanent top cap
>
> connection. It's not that difficult to make a top cap. It would be nice
> if we could find a ready-made cap, but sometimes that's not possible, so
>
> we must then fabricate something. It's at that point we start taking
> these shortcuts which can end up a hasty and poor decision. But top caps
>
> can be made from many materials (even wood if necessary).
>
> Take care,
> Bart
>
>
>
> Stephen J. Hobley wrote:
> > I made some changes to the secondary today - creating a connection
> > terminal for the toroid.
> >
> > http://www.stephenhobley.com/breakout.jpg
> >
> > But does this look like it might be creating an unwanted breakout
> point?
> >
> > Steve

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