[HBR] Coils

[john]

Apart from the issue of tapping a coil, if needed, I've found that winding 
with small gauge insulated wire makes for an easier job, rather than with 
magnet wire. This assuming the coil can tolerate the added turn to turn 
spacing, etc...

John K5MO


At 01:40 PM 12/24/2006, you wrote:
>Darrell wondered:
>>Does anyone have a better method than using strips of Duco cement for
>>attaching coil windings to polystyrene coil forms?
>
>I agree with the comments that Duco's not good.  The original product was 
>cellulose acetate with a solvent appropriate to that.  It didn't work well 
>on polystyrene.
>
>There was a special glue consisting of polystyrene in a solvent that was 
>effective.  Is Q-Dope what I'm thinking of?   Clear Krylon plastic spray 
>is a dilute version of the same thing, though you'd have to be careful to 
>get the right item as Krylon has been 'shelf-spaced' like everything else 
>-- that is, one product has become three or more as manufacturers 
>discovered that the more shelf space their stuff occupied, the more they sold.
>
>With product using a proper solvent you get a different problem: They work 
>well because the solvent does dissolve the base material, so you get a 
>real bond.  BUT in doing so, the solvent causes the base to expand 
>slightly, which can easily lead to cracking or crazing.  I think either 
>the Q-Dope or Krylon would be worth trying, but I would test first on a 
>scrap piece.
>
>Krylon also makes a line of spray can paints that bond to plastics. Those 
>are somewhat different, I believe, and since they're intended for use on 
>plastic might not cause the cracking/crazing problem.
>
>The clear polystyrene-in-solvent products will have NO effect on Q. They 
>are complete non-conductors, and were often used in high voltage 
>applications.  With the paints the issue would be the pigment; my guess 
>would be that they'd be okay too but some study of labels and possibly 
>experimentation would be a good idea.
>
>Use of a complete covering (Krylon ...) will increase the distributed 
>capacitance of the coil significantly but probably not enough to take it 
>out of the range of the trimmer.
>
>Walt Hutchens
>KJ4KV
>
>
>
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