Re: AW: [TCML] Coil pic w/ SRSG

[Gary Lau <glau1024@xxxxxxxxx>]

You're right (obviously!) - yours IS tungsten carbide.  FWIW, gap electrodes
are usually made out of welding rod - pure tungsten.  I'm not sure how
tungsten carbide compares resistance-wise, but it will surely be more
difficult to cut!  Performance-wise, it's not likely to matter
significantly.

Terry Blake's original propeller gap just had the tungsten rod press-fit
into a hole through the polyethylene arbor.  This was actually very snug and
unlikely to move in operation, but I took it one step further and split the
arbor and used two screws to clamp the rod (visible in my photos).  I have
no worries of the rod moving.

On my propeller gap, the motor shaft has a flat, and I have a setscrew in
the Delrin arbor (kinda visible in 3rd photo from top on
http://www.laushaus.com/tesla/sync_gap.htm) that lands on the flat so it
can't rotate.  So, it's important that the motor be able to rotate in its
cradle for a rough phase setting.  Yes, the phase would be likely to get
messed up quickly if friction was the only thing fastening the arbor to the
shaft.

Regards, Gary Lau
MA, USA



On Mon, Jul 5, 2010 at 10:52 PM, Joe Mastroianni <joe@xxxxxxxxxxxxxx> wrote:

> There's a copper disk on the back of the 4" garolite disk.  It's the stuff
> they use for roof flashing.  Not so stiff.  Can be cut with snips, but makes
> a messy circle.
> I was able to cut it at one point with a fly cutter on my drill press.
> For some reason I did it once, and it never worked again.  Tends to bind
> with the bit.
>
> I'm using collars on both sides of the tungsten rod.   I got the tungsten
> from McMaster Carr.  It's sold as tungsten carbide rod.  # 8788A158.
>
> I've actually got all the stuff for a propeller gap but I keep having this
> nightmare vision of one of those 7" tungsten rods flying loose.  Also, I'm
> wondering how to secure the white plastic to the motor.  Seems too "soft" a
> connection if you don't machine it right.  I mean, you're not using a set
> screw with that, right?  What keeps it from coming loose an screwing up your
> dwell setting?
>
> I will try the dremel on the tungsten.
>
> Well, I disconnected the fan, lowered the strike ring - good results.   I
> also tried stacking toroids - I still have my 12x3, and it put it below my
> 18x4.5 just to see what would happen.  But just laying one on top of the
> other didn't seem to do too much...
>
> I was able to cut the garolite sheets I got, finally.   Got a Jasper circle
> cutter, as was suggested here on TCML.  Got a spiral bit for my router and
> used it in "plunge cut" mode.
>
> Well, generally I hate spiral cutters.  I have a rotozip and I avoid using
> it on home improvement projects - it just tends to spew wood/gypsum/paper
> all over kingdom come.  The kerf from the blade is quite wide and all that
> material gets flung outward toward the operator.
>
> The Jasper + spiral cut is basically a rotozip on a jig.  Then making
> another jig to hold down the garolite plate and setting the Jasper Pin in
> the center - I was able to get it to work.  I'm covered in Garolite dust.
>  Used a mask - but mask or no mask, it gets all over and you're breathing it
> no matter what.  And with the Jasper template you need to account for the
> kerf from the bit.  I set mine to make a 7" circle and it came out 6 5/8
> (you get the kerf on both sides of the circle - so the diameter is reduced
> by the bit width x2)  Wish I had thought of that before I cut through a 12"
> square sheet of G10.  Alas.
>
> But I'm going to start on the "production" SRSG.  Thinking to do a design
> like the ones on John's website, where each of the rotating tungsten
> electrodes shorts out the HV supply on both sides - so there's no current
> flowing through the rotating disk itself.
>
> CHeers,
> Joe
>
>
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