Re: [TCML] Safety Gap Construction

[Jim Lux <jimlux@xxxxxxxxxxxxx>]

-----Original Message-----
>From: "Nicholas J. Goble" <ngoble@xxxxxxx>
>Sent: Jun 13, 2008 3:23 PM
>To: tesla@xxxxxxxxxx
>Subject: [TCML] Safety Gap Construction
>
>How do I construct a safety gap?  From what I see, it's just three 
>brass balls.  The middle one is grounded and the end two are connected 
>to the transformer wires.  Please correct me if I'm wrong.

That's right.


>
>I only have two questions:
>
>1) Where can I buy brass balls? I've looked on the internet, but I just 
>can't find any.  Or maybe I don't need brass balls at all.  Is there 
>some other way I can construct a safety gap?


They don't need to be brass balls.  A loop of solid AWG12 copper wire will work (think lollipop shaped).  Anything that is adjustable, bigger than a needle point, and reasonably stable will do.

This isn't going to be firing a lot, so you don't need huge thermal mass or cooling.  Tiny points erode and have erratic firing voltage, so that's why a loop of wire works fairly well.  Carriage Bolt heads also work.

If you want brass balls (leaving aside humorous puns and asides) a good source for small rounded electrodes is the "drawer pull" section at the hardware store. make sure they're actually solid metal, and not plated plastic.  You can also get spherical doorknobs.  And, in the lamp department, there are often "finials" in useful shapes, already tapped on the bottom for attachment with a bolt.  Same for curtain rods.  Brass beds and coat stands also have metal spheres.

For slightly larger sizes, you can look at spherical floats used for water or liquid level valves (like in your toilet tank).  McMaster Carr carries them in sizes up to 12".  They're copper or other metals, and unpolished.

>
>2) How can I determine the spacing of the balls? Is there any formul
>to calculate the gaps, or should I just guess?

Disconnect the coil from the transformer.

Set the safety gap width so that it just doesn't fire when power is applied to the transformer.


>
>Thanks again.
>
>Nicholas Goble
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