I could add another four slots in the form for a total of eight. You
wouldn't need to use them all on smaller coils, and if you used them all
on larger coils it would be easy to just turn over whichever strips you
didn't want to leave in, such that their slots faced the form.
It would also be possible for someone to put a spacer (almost anything
would work) under a turn as the coil was wound so it would stick out to
make it easier to make a tap on close wound coils.
73,
Dave AB7E
On 1/18/2023 8:59 PM, W7TMT - Patrick wrote:
Dave,
Very cool implementation with the 3D printer. I've wound several sets of coils
for shorten dipoles supported on pairs of telescoping fiberglass windsock
poles. I used the similar, but less sophisticated technique described by AD5X
here:
http://www.ad5x.com/images/Articles/CoilRevB.pdf
From my experience with larger diameter coils, you may want to provide notches in
the form to allow installing extra temporary support pieces that are used during the
winding but then not glued onto the coil. I found that on the 3.5" diameter
coils I wound for my 40M dipole that the larger diameter resulted in very noticeable
flat spots in the windings between the four main supports. Adding the temporary
supports between, and then just not gluing them resulted in a nice round coil.
Flats may not affect the inductance, I don't know. But the rounder units just
looked better to my eye.
73,
Patrick, W7TMT
-----Original Message-----
From: TowerTalk <towertalk-bounces@contesting.com> On Behalf Of David Gilbert
Sent: Wednesday, January 18, 2023 19:31
To: towertalk@contesting.com
Subject: Re: [TowerTalk] DIY Air Wound Coils
This should definitely be feasible. My example was really basic ...
just a cylindrical hole with a rectangular slot on top of it that only infringes on about 40% of the
cylindrical hole. The remaining 10% provided the "snap". A better approach to avoid
glue would be a tighter fit with a ramped entry. If the grips were freestanding and not slots that
should work well. Maybe I'll play with it and update the files.
And although I used four bars, I think two might be sufficient based upon the
coils I've built with #14 wire.
73,
Dave AB7E
On 1/18/2023 6:15 PM, Brian Beezley wrote:
"My final choice was slotted acrylic bars for strength, water and UV
resistance, and ease of solvent gluing the wires in place."
Grant, after seeing several neat coil form designs in the style of Air
Dux, I've been wondering if a precisely shaped groove might hold the
wire reliably without glue. I imagine it snapping into place with a
satisfying sound. I suppose this would work well only for a single
wire gauge.
Brian
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