Compounds to retain windings in place on toroid cores

[Jack Smith-6]

A common question concerning inductors wound on toroid cores is whether
a retaining compound should be used to fix the windings in place.

In the case of the cores used in the K2, retaining compounds are not
necessary and should not be used. However, this question still comes up
and there are cases where retaining compounds are necessary, or at least
desirable.

I've added a page to my web site showing how to make Q-Dope and
presenting measurements for similar coils retained with real GC Q-Dope,
my homebrew Q-Dope, beeswax and hot glue.

http://www.cliftonlaboratories.com/coil_coating_compounds.htm

Jack K8ZOA



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[WE0H]

Why not use hot glue on the toroids in the K2? That link shows hot glue
as a very good wire retaining compound. Does anyone have any data that
suggests a K2 would not function to the manufacturer's spec's if hot
glue was used on all the toroids?

--
Mike
WE0H
K2 #6698




Jack S wrote:

> A common question concerning inductors wound on toroid cores is whether
> a retaining compound should be used to fix the windings in place.
>
> In the case of the cores used in the K2, retaining compounds are not
> necessary and should not be used. However, this question still comes up
> and there are cases where retaining compounds are necessary, or at least
> desirable.
>
> I've added a page to my web site showing how to make Q-Dope and
> presenting measurements for similar coils retained with real GC Q-Dope,
> my homebrew Q-Dope, beeswax and hot glue.
>
> http://www.cliftonlaboratories.com/coil_coating_compounds.htm
>
> Jack K8ZOA

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[Jack Smith-6]

Mike:

If it isn't needed--which is is not in the K2--don't use it. My
measurements do not, for example, show the long term effect of retaining
compounds. Nor do they show what happens when the temperature is
increased and some compounds soften. I'm reasonably confident Q-Dope is
stable from working with it over some considerable time, but I don't
have the same confidence factor for the other compounds.

All of the K2 toroids are wound to X number of turns, not to a specific
inductance value. Any shift in the windings from being un-retained are
highly unlikely to change the inductance more than the typical
core-to-core variation. (Ferrites are commonly quoted as +/- 20%
core-to-core variance and powdered iron is more like +/- 10%. Windings
shift after measurement might account for 1 or 2% change.)

Jack K8ZOA


Mike-WE0H wrote:
> Why not use hot glue on the toroids in the K2? That link shows hot glue
> as a very good wire retaining compound. Does anyone have any data that
> suggests a K2 would not function to the manufacturer's spec's if hot
> glue was used on all the toroids?
>
>  
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