Re: Treenails??

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Mark Fergerson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <mfergerson1-at-home-dot-com>

Tesla list wrote:
> 
> Original poster: "Tuite, Tom by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<TTuite-at-ALLEGROMICRO-dot-com>
> 
> I think also an important thing may be not to use "pointed" screws.  Use
> instead the ones with flat tips.  I can't remeber the exact physics behind
> this, but its the same reason why lightning rods are pointed.  Come to think
> of it, does any one recall the physics behind that (I think it can still be
> considered quasi-on-topic :) ).
> 
> T. Tuite

  Hi all;

  Absolutely there's a good physical reason not to use pointed metal
screws or pointed metallic anything near a TC if you don't want sparks
off the points; it's the same reason you get streamers from your
topload to the nearest pointed, _not necessarily grounded_, object.
The high voltage gradients near a TC will induce large potentials on
the points which will break down the air's insulating quality
producing unplanned sparks. If the screw is buried in wood or plastic
the hazard is lessened, but not eliminated.

  Matt Demming points out that wood isn't a perfect insulator; screws
points too close together can produce an arc _inside the wood_ when
immersed in the near field of a TC. I'd like to mention that
flat-ended screws (machine screws) still have relatively sharp edges
on the threads (also pointy bits on nuts, and lockwashers when used)
which might make for nice arcs in the wrong places too.

  Caveat: "close" and "too close" are relative terms when discussing
TCs. If you haven't seen any problems with a mid-size system, you
probably won't in future (though it may be instructive to saw apart
cabinets being replaced, to look for internal charring).

  It's not just a safety hazard, it's a performance issue too; power
which could be going into the streamers is being wasted breaking down
the air near all them points.

  As for using treenails, common pegs, or whatever to replace screws,
well, we all like to increase our competence at building our own
stuff; craftsmanship is its own reward, no?

  Mark L. Fergerson