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CONSTRUCTION OF SECONDARY

 * Original msg to: Esondrmn-at-aol-dot-com


 > From: Esondrmn-at-aol-dot-com
 > To: richard.quick-at-slug-dot-org
 > Subject: Construction of secondary

 ES> Richard,

 ES> In reading your discussion with Dan and comments with BTW, 
 ES> I have a question about my soon to be completed secondary.  
 ES> Again, it is 6.0" dia PVC with several coats of polyurethane 
 ES> under and over the #22 magnet wire (approx 950 turns).  I am 
 ES> constructing PVC end caps that are routed so they just sit down 
 ES> in the coil about .25" and are flush with the outside surface of 
 ES> the coil.  I had planned to use PVC glue to cement the end caps 
 ES> in place.  Dan's comment about exploding coils raises a concern 
 ES> here.  

That was my comment. I have had a couple of internal explosions. The 
wire usually holds the sidewalls together, but the end caps blow off, 
the discharge terminal goes flying (good for a dent or two) and the 
unwound ends will splinter. There may be some plastic "shrapnel" from 
the splintered ends depending on the vapor/air mixture and the potency 
of the resulting explosion.

 ES> Am I going to be trapping explosive cement fumes inside the coil 
 ES> form - waiting to be ignited by the first spark? I really want to 
 ES> avoid this!! Thanks, Ed Sonderman

Well if the coil is sealed, and the wire is not allowed inside, spark
can't get to the air/vapor mixture to ignite it. So if the proper
construction guidelines are followed it should not explode regardless
of solvent vapors. However, I do not, and have not, advocated solvent
based adhesives for this purpose for just this reason. I have always
advised the use of two-part epoxy for bedding down the end caps. Good
quality "clear" two-part epoxies with set times of 5 - 30 minutes are
available from most hobby shops and hardware stores. This is the stuff
to use as there are no highly flammable vapors or fumes. Make sure the
surfaces to be cemented are scored or roughed up to allow the epoxy a
good bite. 
 
Richard Quick


... If all else fails... Throw another megavolt across it!
___ Blue Wave/QWK v2.12