On 11/23/21 8:46 PM, Joshua Thomas wrote:
> Iâ??m not sure where youâ??re buying from, but 8 oz of 28awg magnet wire, 155C
> polyurethane insulation, is a whopping $14.14 straight from Remmington
> Industries. Manufacturer is Elektrisola.
>
> That size was just over the amount I needed to wind my 3.5â?? x 16â?? coil.
>
> If you want the heavy-build wire, thatâ??s $1 more, and you get about 10 ft
> less.
>
> If you want to go all the way up to the 240C polymide insulation, that goes
> up to $38.41â?¦ but no one in any reading Iâ??ve done has ever given any
> indication that is necessary.
>
> Iâ??ve still spent more money on my CDE caps than all the magnet wire I have
> combined.
>
$30/lb is actually fairly expensive for magnet wire. $5-10/lb
(depending on copper prices and insulation) is more common (in 5 lb
spools). However, if you can get small spools, maybe it's not a big
deal - the caps dominate the cost most of the time.
The heavier builds are sometimes nice - they space the turns a bit and
are more rugged.
28 AWG is pretty small. I usually shoot for around 600-800 turns and on
a 2 foot secondary, that's 0.030 inches/turn - AWG 24 in heavy build is
about 0.227", so that works out ok.
Why thicker? It's stronger. Less likely to break. Lower series R
losses. The tradeoff, lower inductance. AWG 28 at 50 TPI for an 18"
long winding is 16 mH, 24AWG at 35 TPI is 8 mH, so the resonant
frequency is higher by 0.707, but one can make one's topload bigger if
the frequency is too high.
I don't know that there's a "best frequency" to operate at - anything in
the "50 kHz to 500 kHz" seems to work - The big determinant of spark
length is power and that's independent of your resonant frequency.