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RE: [TCML] Insulating the primary coil

A Dremel works great on cutting Plexiglass or whatever trade name your part
of the world uses  (Perspex, Plazcryl, Acrylex, Acrylite, Acrylplast,
Altuglas, Polycast, Oroglass) using a reamer tool bit. 

Also if you have a Belt sander or Linisher its easy to make a simple crude
lathe up to get a good finish to the edges as I have done here:-

(This disc was originally for a Wimshurst machine)


-----Original Message-----
From: bartb [mailto:bartb@xxxxxxxxxxxxxxxx] 
Sent: 02 October 2008 02:02
To: Tesla Coil Mailing List
Subject: Re: [TCML] Insulating the primary coil

Place a Plexiglas disc on top of the primary and don't use a ring. I've 
however only done that on one coil. But even with a Plexiglas disc on 
top of the primary and overhanging the outer rim, strikes can still find 
their way to it or the wire attaching to the primary (right through any 
wire insulation). I don't get any strikes through the Plexiglas. If you 
have a coil that has enough power to get down to the primary but not 
quite enough to get to the floor, it's real easy to hit the primary often.

BTW Steve, cutting a circle out of Plexiglas is easy. I use an aluminum 
flat bar (about 1/4" thick by 1"wide and maybe 14" long). I drilled a 
hole in one end for a shoulder bolt. This end mounts in a hole in the 
center of the Plexiglas which the bar pivots at. Along the opposite end 
of the bar I drill a 1/4" hole at the radius of the circle I want, then 
pounded in a scribe. The scribe is actually a punch for removing bolts 
when the head was broken off (forgot the name of this, but it has 4 
sides which end in a point). I put this "scribe" to a bench grinder and 
sharpened the end to a very sharp point. Anyway, I then simply scribe a 
channel into the Plexiglas at the radius desired (both sides of the 
Plexiglas). It then is easy to snap off the excess around the circle. I 
know they probably have tools for this, but it's easy enough to make 
your own. Works great. The largest circle I've cut is about 24" and the 
smallest is about 5". Obviously for a primary disc, cut the outer circle 
then an inner circle about 1/2" larger diameter than the secondary 
diameter so you can slide it down the secondary and let it rest on the 

Take care,

Stephen J. Hobley wrote:
> What is the current wisdom on insulating the primary coil? 
> Does this help to reduce strikes on the primary? 
> Or is it much better to leave the coil exposed and add a strike rail?
> Thanks,
> Steve

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