Winding heavy gauge (#36) wire

[Mark Hammer]

So, with the long weekend and all, thought I'd finally take a stab at winding a low-impedance pickup for my bass. I made a coilform out of some plastic I had and used some hex screws for slugs (7 in all, for 4 strings), with some over-sized ceramic magnets underneath. I used #36 wire, and stuffed as much as I could get on the coilform, ending up with what I think was somewhere between 1500 and 2000 turns, and a DCR of around 550 ohms. Haven't installed it yet, but my usual "test" of tapping the blade of my utility knife on the polepieces gets me a signal of around 20-50mv; something that would yield a clean output that would not overdrive an amp (and maybe even tolerate a little preamping along the way).

What perplexes me, though, is the VERY spongy quality of the physical coil. I'm used to getting a little sponginess around the middle of the "long stretch", when winding guitar pickups with #41-43, which I can usually tame with a little wax potting to help pack it in. But this does not respond well to embedding wax in it. It flares out at the middle enough that the risk of microphonics seem high to me.

So, you'll pardon the pun but I'm trying to wrap my head around the physics of it, and figure out what I could do to make a tighter coil when using wire this thick. For example, is the shape of the ends of coilform critical? Do they need to be wider or rounder or something to allow for appropriate tension to be achieved?

I doing it slowly the recipe?

Was my mistake attempting to make a single coil for all 4 strings instead of a split 2+2 thing?

Should I just pour on the wax and let that solve things?

How do people achieve nice tight coils with wire this thick?

[madialex]

i'm gonna say you are going to have to wind this super slow. that way the thicker wire has more time to lay on the bobbin flat.

[big_teee]

So, with the long weekend and all, thought I'd finally take a stab at winding a low-impedance pickup for my bass. I made a coilform out of some plastic I had and used some hex screws for slugs (7 in all, for 4 strings), with some over-sized ceramic magnets underneath. I used #36 wire, and stuffed as much as I could get on the coilform, ending up with what I think was somewhere between 1500 and 2000 turns, and a DCR of around 550 ohms. Haven't installed it yet, but my usual "test" of tapping the blade of my utility knife on the polepieces gets me a signal of around 20-50mv; something that would yield a clean output that would not overdrive an amp (and maybe even tolerate a little preamping along the way).

What perplexes me, though, is the VERY spongy quality of the physical coil. I'm used to getting a little sponginess around the middle of the "long stretch", when winding guitar pickups with #41-43, which I can usually tame with a little wax potting to help pack it in. But this does not respond well to embedding wax in it. It flares out at the middle enough that the risk of microphonics seem high to me.

So, you'll pardon the pun but I'm trying to wrap my head around the physics of it, and figure out what I could do to make a tighter coil when using wire this thick. For example, is the shape of the ends of coilform critical? Do they need to be wider or rounder or something to allow for appropriate tension to be achieved?

I doing it slowly the recipe?

Was my mistake attempting to make a single coil for all 4 strings instead of a split 2+2 thing?

Should I just pour on the wax and let that solve things?

How do people achieve nice tight coils with wire this thick?

Is it possible that the coil form is compressing, or collapsing a bit while winding?
I notice this when winding around a metal center versus other materials.
With a maget or metal center to wind around , everything stays nice and tight.
On different plastic bobbins, or forbon type bobbins, you always get some flaring or compression if you wind tightly?
T

[Mark Hammer]

Nah. It's a very robust solid piece of poly carbonate or something similar that I drilled holes into for the slugs. No flaring possible.

[big_teee]

I agree, try real slow winding, and maybe more tension, if flaring is not an issue.
Also when I'm making overwound humbucker P/Us, I stop and push down the wire on the flat sides with an orange stick, or chop stick.
It keeps it on the bobbins better, for real full bobbin situations.
Then Pot the Hell out of them!
Good Luck,
T

[Jim Darr]

Mark,

If you are hand guiding with some scatter, you will get greater air gaps using the thicker wire from the turn-to-turn aspect of the wire crossing over each previous turn. It is more pronounced using heavier gauges even with moderate scatter. This will tend to produce a spongy coil especially towards the middle of the coil even with a lot of winding tension. If you are machine winding, try changing the TPL to more closely match the wire diameter with the coil height. And you can always try winding at a slower speed.

Keep us posted.

[Mark Hammer]

Good point. Since the Allen screws I'm using for slugs can be purchased with different lengths, I think I may try simply making a taller coil form so that more of the windings can be in close proximity to the slugs. That, and slower winding, will hopefully descrease the accumulation of air gaps, given that my winding method makes it very difficult to NOT produce scatter.