Keeper Bars I was asked.

[David Schwab]

Everything is crushable, given sufficient force. The end of a bobbin is perhaps 3/16 wide by 5/16 high, for an area of 0.0586 square inches; this is carrying a force of 1320 pounds, or 22,528 pounds per square inch. This exceeds the compressive yield strength of any bobbin plastic, so the plastic will simply flow slightly until the stress is relieved.

OK, but wind a few bobbins that look like this:



They are hollow in the middle, not at all like a humbucker bobbin, and not at all like a Strat bobbin. You can easily deform them by squeezing them as the wall thickness is pretty thin, but they don't warp when wound. Since they are made like an I beam, so they are hard to deform in the long direction. So the flanges on the bobbin work like a torsion box.

Humbucker bobbins have the added core.

[Joe Gwinn]

OK, but wind a few bobbins that look like this:

[ATTACH=CONFIG]16509[/ATTACH]

They are hollow in the middle, not at all like a humbucker bobbin, and not at all like a Strat bobbin. You can easily deform them by squeezing them as the wall thickness is pretty thin, but they don't warp when wound. Since they are made like an I beam, so they are hard to deform in the long direction. So the flanges on the bobbin work like a torsion box.

These are even easier to crush a bit - the sides can bulge out a bit. Unless the rectangular core is installed with a big press, there will be enough slop between bobbin and core that the load is largely taken by the bobbin.

Humbucker bobbins have the added core.

Think of two coil springs in series, one very stiff (low compression for a given force), the other say a hundredth as stiff (one hundred times the compression for the same level of force). When you compress the two-spring stack, the stiffer spring will not visibly change length, but it is nonetheless getting shorter.

The measure of stiffness of a material is Young's Modulus: Young's modulus - Wikipedia, the free encyclopedia. Larger values mean stiffer materials.

Values for selected materials: Iron and steel: 29 *10^6 psi; Copper and its alloys: 17*10^6 psi; and ABS resin: 0.4*10^6 psi.

Note that the bobbin cross section is a fraction of the copper cross section in a typical pickup coil, and of course the modulus of ABS is a fraction of that of copper. A quick example assuming 6000 turns of single-build #42 wire on a bobbin with channel 3/16" high (perpendicular to the core) by 5/16" wide (along the core) with 0.020" thick walls and 60% fill (ratio of area of insulated wire to winding window area) yields a copper/resin area ratio of about 4.3:1. So, ratio of elasticities will be about (4.3*17)/(0.4)= 183 to 1. This will be hard to directly measure in a pickup bobbin.

[FunkyKikuchiyo]

I think there has to be something else at play besides crushing bobbins - I've had a weird relaxation of the coil on stuff that I KNOW wasn't being crushed. I can say this because it was wound directly onto steel. I don't see how I could've been winding tight enough to deform solid steel at 1/16" thick. It is quite possible that my flanges (that is, top and bottom flatwork) shifted a bit under the pressure, or that wire stretching happened over time instead of immediately as it lay on the bobbin during winding. I know many times when we tie something tightly - yarn, rope, tape, nylon guitar strings (steel strings don't stretch as much as people think) - and come back to it it has changed tension just by stretching over time and it wasn't all immediate. That seems plausible for copper wire, but I really can't say.

David - isn't someone selling little machines to vibrate the top of an acoustic and "wake it up" for a steep price? Sounds like a Stew Mac thing. The aging process is one thing, but spruce tops go dorment and need playing time to come back around. It'll kinda drive you nuts if you rely on natural volume from an acoustic, especially on a classical.

[David Schwab]

I think there has to be something else at play besides crushing bobbins - I've had a weird relaxation of the coil on stuff that I KNOW wasn't being crushed. I can say this because it was wound directly onto steel. I don't see how I could've been winding tight enough to deform solid steel at 1/16" thick. It is quite possible that my flanges (that is, top and bottom flatwork) shifted a bit under the pressure, or that wire stretching happened over time instead of immediately as it lay on the bobbin during winding. I know many times when we tie something tightly - yarn, rope, tape, nylon guitar strings (steel strings don't stretch as much as people think) - and come back to it it has changed tension just by stretching over time and it wasn't all immediate. That seems plausible for copper wire, but I really can't say.

I also wind some pickups right onto a steel bar with plastic flanges acting as bobbins. Now most of my pickups get encapsulated in epoxy, but the ones in my personal basses aren't, and they haven't changed tone at all since I wound them. And none of my guitar pickups are epoxied either.

So I'm not discounting what others (that means you Dave!) are experiencing, but since it doesn't happen to me, even with PAF style parts, there must be another reason for it. For example, I don't use any bees wax in my wax, and pot them all the way through the coil in paraffin. They are pretty hard when they cool off. So it might be another aspect of technique or manufacture, and not the pickup breaking in from playing it.

Because I can go and find sound clips from the first few minutes of testing a pickup, and then compare them to the pickup which is still in the guitar, and now a year older, and they sound exactly the same.

David - isn't someone selling little machines to vibrate the top of an acoustic and "wake it up" for a steep price? Sounds like a Stew Mac thing. The aging process is one thing, but spruce tops go dorment and need playing time to come back around. It'll kinda drive you nuts if you rely on natural volume from an acoustic, especially on a classical.

Yes, I believe someone is, and I wasn't able to find it. It's also not as heavy duty as the shaker table Rick Turner was using. Hey Rick, where are you?

[Possum]

Boy this subject has been beat to death ;-) Its a number of things going on, not one in my experience. Coil settling. Magnetic saturation or domains settling into new steel thats never been magnetized before. I don't need to record it, I did years ago and it was plain as day, I don't have time to repeat experiments and slow my work down. Coil setting theory doesn't explain why replacing the keeper with a different one or putting different slugs starts the whole process over again. Also it happens with potted coils too, so explain that one.... If you know its gonna happen you don't make quick judgements on whether a pickup sucks or not, give it a couple weeks...

[big_teee]

In regard to the break in, and Settling.
Without Recorded Proof, IMO Just more, Smoke, Mirrors, & Hype!
Besides that, it really Doesn't matter, it is what it is.
B_T

[David Schwab]

I don't need to record it...

You do if you want people to accept what you are saying is real. Otherwise it's subjective.

I've made new pickup prototypes, and hated them, and then came back the next day and liked it. Did the pickup change? No. I know this because I recorded it. What changed was I had a fresh set of ears. If I hadn't recorded it, I might have wondered why it sounded so different.

This phenomenon also happens when you are mixing down a recording. After too many hours you can't get an objective view of the song. You finish for the day thinking it's good, and then you come back the next day to realize it needs a lot more work. Or vice versa.

And then if you are listening to a pickup settle in over the course of a few weeks, your strings are aging, and loosing top end. So you need to test with a fresh set of strings both times.

So there's lots of little variables at work. And maybe the pickups do change under certain conditions. But we can't say that without doing some kind of testing.

[copperheadroads]

Possum's theory is actually plausible
Some of the other claims get pretty touchy...& you have to tread lightly
I got my ass chewed on another forum for stating when winding humbuckers ,that most winders try to lay wire down as even as possible
then i got attacked "scatterwound" is better even in highgain buckers ....WTF

[Possum]

The point about magnets losing strength first couple of days doesn't wash either, because I seldom use full charged magnets, so they are stable when they go in. It is conceivable, though that maybe when the steel is soaking up the magnetism that overall gauss goes down, but I kinda think not. When you put a steel baseplate on a Tele bridge for instance, gauss goes UP at the poles, not down.
There are enough winders who experience this overall effect who have chimed in over time here on the forum, and I wasn't the first one to note this effect either. To "record it to prove it" means I'd have to build a brand new pickup, put it in a guitar, set up the recording gear, etc. etc. I don't have time to prove what I already know unless someone wants to pay for my time and the pickup ;-) I can give you my Paypal ID, I figure its worth about $600 of my time, any takers?

[copperheadroads]

i just read what i posted ....sorry i must have deleted more than i wanted
Merry Christmas Friends

[Possum]

Merry Xmas Tree to you too, I'll probably be working, lol ;-)

[big_teee]

The point about magnets losing strength first couple of days doesn't wash either, because I seldom use full charged magnets, so they are stable when they go in. It is conceivable, though that maybe when the steel is soaking up the magnetism that overall gauss goes down, but I kinda think not. When you put a steel baseplate on a Tele bridge for instance, gauss goes UP at the poles, not down.
There are enough winders who experience this overall effect who have chimed in over time here on the forum, and I wasn't the first one to note this effect either. To "record it to prove it" means I'd have to build a brand new pickup, put it in a guitar, set up the recording gear, etc. etc. I don't have time to prove what I already know unless someone wants to pay for my time and the pickup ;-) I can give you my Paypal ID, I figure its worth about $600 of my time, any takers?

I've got 6 Cents, and that is More than it would be worth to me.
T

[David Schwab]

The point about magnets losing strength first couple of days doesn't wash either, because I seldom use full charged magnets, so they are stable when they go in. It is conceivable, though that maybe when the steel is soaking up the magnetism that overall gauss goes down, but I kinda think not. When you put a steel baseplate on a Tele bridge for instance, gauss goes UP at the poles, not down.

If a magnet is stuck to a keeper, it wont discharge. That's why they call them "keepers!" As you pointed out with the Tele example, if you measure your magnet's strength and then stick it to a piece of steel, and measure it again, you will see that you are getting more pull when on the steel. The inductance has raised. So the steel isn't soaking up the charge.

There are enough winders who experience this overall effect who have chimed in over time here on the forum, and I wasn't the first one to note this effect either.

That still doesn't prove it's actually happening. As I pointed out, it happens in other situations, like when mixing down a recording.

To "record it to prove it" means I'd have to build a brand new pickup, put it in a guitar, set up the recording gear, etc. etc. I don't have time to prove what I already know unless someone wants to pay for my time and the pickup ;-) I can give you my Paypal ID, I figure its worth about $600 of my time, any takers?

Well you are making new pickups, right? I test out pickups all the time, but not for regular orders. So it doesn't seem like you trust your idea is right, does it?

As far as paying you, I can make my own set and record it... oh wait, I've done that already!

Tell you what, the next humbucker I make for guitar, I'll do careful recordings when I wind it, and then at intervals of time afterwards, and post them here.

[copperheadroads]

If a magnet is stuck to a keeper, it wont discharge. That's why they call them "keepers!" As you pointed out with the Tele example, if you measure your magnet's strength and then stick it to a piece of steel, and measure it again, you will see that you are getting more pull when on the steel. The inductance has raised. So the steel isn't soaking up the charge.



That still doesn't prove it's actually happening. As I pointed out, it happens in other situations, like when mixing down a recording.



Well you are making new pickups, right? I test out pickups all the time, but not for regular orders. So it doesn't seem like you trust your idea is right, does it?

As far as paying you, I can make my own set and record it... oh wait, I've done that already!

Tell you what, the next humbucker I make for guitar, I'll do careful recordings when I wind it, and then at intervals of time afterwards, and post them here.

Actually i have noticed just the opposite
when i fully charge a tele bridge pickup with A5 magnets it 1200 gauss +/- & after i put the baseplate on it goes way down

[Possum]

6 cents for probably 12 hours worth of work or more, no thanks ;-) Yes I'm making new pickups, I don't think a customer wants me to hang onto his pickups while I solder and cut the leads to length and record the changes over 3 months then send him a pickup thats all beat up. If you're not experiencing it at all, which I find kind of strange, you're probably using all pre-made parts, still, there should be some level of change that is noticeable. Use your Syscomp, and LCR meter, measure at the same room temperature, rig up some way to take direct readings off the pickup while its still in the guitar. I've had a couple customers who played their new pickups all day or take them directly to all night gigs tell me they experienced them change over the long hours of playing, going from dark and choked feeling to brightening up and loosening up over that time. I don't make my buckers like anyone else and that does have something to do with it. I don't make bass pickups so if you're talking about your bass stuff, I have no idea if you could hear this happen on that instrument. Maybe its because I don't use threaded keeper bars, yuk yuk....