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RE: spark gap design

Terry,
The way I would try to center the copper tubing would be to fill each piece
with epoxy or some robust filler.  Once cured it could then be gently
chucked in a 3 jaw chuck on a lathe.  Then with the lathe running the 1/4"
drill is applied to it.  Should be fairly centered.  In case the drill
drifts slightly, go in only half way and then turn your piece around in the
chuck and meet the first hole from the other end.

Russ Thornton
CSR 2040, 
Building 989, Rm.  A1-N20
Phone: (407) 494-6430 
Email: thorntor-at-rc.pafb.af.mil


> ----------
> From: 	Tesla List[SMTP:tesla-at-pupman-dot-com]
> Sent: 	Saturday, August 22, 1998 5:19 PM
> To: 	'Tesla List'
> Subject: 	spark gap design
> 
> 
> 
> ----------
> From:  terryf-at-verinet-dot-com [SMTP:terryf-at-verinet-dot-com]
> Sent:  Saturday, August 22, 1998 2:06 PM
> To:  tesla-at-pupman-dot-com
> Subject:  Re: spark gap design
> 
> Hi Jim,
> 
>         Cleaning the gaps in my 60 x 4 mil gap is easy.  I get a 4 mil
> ribbon of metal and just force it down through the gap sections.  The
> epoxy
> is strong enough to take the stress.  The metal ribbon pushes out the
> "stuff" that builds up.  I have been able to force out some pretty nasty
> melted blobs and stuff with little trouble.  If you really want to clean
> it
> well, a fine 400 grit wet dry sand paper ribbon will just barely slide
> into
> to gaps and you can pull it back and forth the clean the sections.  You
> will need some air in a can or something to blow the dust out.  It is very
> important to use lots of strong epoxy on the sections to be able to clean
> the sections in this rough way.  Of course, gluing a section bake in place
> is no great challenge.
>         I have noticed that the black oxide that builds up does hurt
> quenching some but after a point really doesn't seem to do much harm.  The
> real killer is to push very high currents through the sections and allow
> the sections to over heat.  This allows the copper to melt and then you
> get
> melted copper bits shorting the sections.  Fan cooling does a lot to
> prevent this.  If the sections could be plated with a high melting point
> material it would help much.  Perhaps someone knows of a simple way to do
> this.  Perhaps having the sections chrome plated would be worthwhile??
>         I have been trying to think of a way to have the sections rotating
> during operation.  This can be done, but I was trying to find a way that
> wouldn't require any high tolerance machining and such.  The part I am
> stuck on is how to center a 1/4 rod in the pipe sections.  It would have
> to
> be very accurately centered.  Other than precision machining, I can't
> think
> of a way to do it.  Mounting and rotating the shafts would not be
> difficult
> once I had the sections on steel shafts.  I can get bronze bearings that
> would work but that is expensive and not everyone would be able to find
> them.  I definitely want to keep it cheap and simple. A small low-speed
> motor turning a axle with rubber band drive belts to each section could
> provide a simple, cheap, and low tolerance drive system.  Preferably, the
> sections would be insulated from the shafts.  The best I have come up with
> so far is to wrap shipping tape around the shafts until it reaches the
> inner diameter of the pipe.  A long difficult process at best.  Fans and
> such blowing on the assembly should provide very good cooling.  I will
> probably go the 3/4 in copper pipe with somewhat wider sspacing for such a
> design.
> 
> Any thoughts, hints, or ideas are welcome.
> 
>         Terry Fritz
>         terryf-at-verinet-dot-com
> 
> 
> 
> 
> At 11:16 PM 8/20/98 -0500, you wrote:
> >
> >----------
> >From:  Dsurfr-at-aol-dot-com [SMTP:Dsurfr-at-aol-dot-com]
> >Sent:  Thursday, August 20, 1998 4:50 PM
> >To:  tesla-at-pupman-dot-com
> >Subject:  spark gap design
> >
> >Hi All: I finished cutting the copper pipe for an RQ sparkgap I plan to
> >assemble this weekend. In my impatience to see the improvement I placed
> the
> >segments in a row (ala Terry F's gap) on a piece of plexi, holding them
> in
> >place with double faced tape. Gap was .03, ten gaps total. Even without
> re-
> >tuning the improvement was obvious & I recommend anyone still using bolts
> for
> >a static gap should switch immediately. My question is as follows: I
> noticed
> >that there was some "carbonization"? building up on the pipe segments
> after
> >only a few short runs. How often do you have to clean the gaps, how hard
> is
> >this to do & does sanding or whatever widen your gap each time causing
> you to
> >regap? If so it would seem that Bert Pool's gap design (where the pipes
> are
> >laid on fiberglass rods allowing them to be rotated or easily removed for
> >cleaning) would be far superior. Thanks,  Jim
> >
> >
> >
> 
> 
>