Butyrate Bobbins

[JGundry]

Wouldn't you center the screws and slugs? You certainly wouldn't go by the outside two screws or slugs, since the slugs are larger.

If you keep the centers the same there will be no spacing difference, just a difference in hole size. Are you worried about one coil being .013" larger?

That is true Dave. It is a small difference. You would think that the centers would be the same but they are not. I am just using this dimension as an example of how much time we put into getting the dimensions down. For anyone making these the screw bobbin is the trickiest to decide on dimensions for. You basically have to get some vintage baseplates and covers in an optical comparator, get some vintage bobbins and then work out the dimensions for yourself. If you are doing a basic comparison of the spacing of PAF's, our bobbins, Seth Lover bobbins and some of the other butyrate bobbin repros you would think that they are all the same centers. But just because they fit does not meant they are the same centers. Especially when it comes to the screw bobbin.

An original drawing like Dave's is not much use if it has an arc for the top of the bobbin because clearly it is not the final design.

[Possum]

.....

There isn't ONE true PAF bobbin version, you see variation from year to year, I know why but there's only so much I should say in a public forum. I wish I could post those drawings but can't. The criitcal coil former dimensions on the SL pickup are correct for a certain period of time. I'm sure Seymour and friends chose what sounded best to them; thats the beauty of the variations that happened is it gives one an arsenal of tones to choose from. I've tried them all, being a do it yourself guy. The drawings show the coil former being identical in both, the spacing identical, Frank's explanation holds water there. Some of the actual differences compared to the drawings are curious like the small slug core on some. The Byrdland bobbins were cast without the slug holes and were drilled. The most authentic looking PAF bobbins are the Bare knuckles ones, I'll post photos of those later tonite as I have to photograph some beat up PAF bobbins before I rewind them.... and will show those too...

[JGundry]

There isn't ONE true PAF bobbin version, you see variation from year to year, I know why but there's only so much I should say in a public forum. I wish I could post those drawings but can't. The criitcal coil former dimensions on the SL pickup are correct for a certain period of time. I'm sure Seymour and friends chose what sounded best to them; thats the beauty of the variations that happened is it gives one an arsenal of tones to choose from. I've tried them all, being a do it yourself guy. The drawings show the coil former being identical in both, the spacing identical, Frank's explanation holds water there. Some of the actual differences compared to the drawings are curious like the small slug core on some. The Byrdland bobbins were cast without the slug holes and were drilled. The most authentic looking PAF bobbins are the Bare knuckles ones, I'll post photos of those later tonite as I have to photograph some beat up PAF bobbins before I rewind them.... and will show those too...

Hey Dave if you want to start a thread in which you do A/B comparisons of PAF and other butyrate bobbins please do so. If you want to turn this thread into that frankly I think it is in poor taste.

A thread in which you tell or don't tell all of the important details of PAF bobbins and who makes the best repro, might or might not be useful to somebody like you who does not make PAF bobbins but would like to make them.

I posted photos of the bobbins Belwar and I did so people would know it is within reach. I also wanted to give as many specifics as I could which might be helpful as it relates to actually executing getting them done. Belwar and I were very lucky to get this same info sharing from people who already did this. I'm sure Belwar and I would also happily share information with people as generous with it as Sam Lee Guy.

I think Frankfalbo's comments kind of opened this thread up to A/B comparisons but really I don't want to turn it into that. If you want to do a bobbin shootout let Belwar and I know and we might send you a pair and you can include the bobbins you use also..

[David Schwab]

That is true Dave. It is a small difference. You would think that the centers would be the same but they are not.

I think frankfalbo hit that nail on the head. The stud bobbin shrunk more.

[Possum]

...

I'd be interested to know what values you chose, so yeah send a sample set. I decided not to post the BK bobbins, I wasn't intending a shoot out just to show what others did versus photos of the real deal. Maybe I will do another thread as I have the SL bobbins in naked form as well. For specs, I tried all the ones I've found in the real deal examples and the extreme versions at either end I didn't like much and had problems with what you find in early Patents, probably because there is no real equivalent of vintage wire made now, I'm going to do a thread on that too as some of what I was told and had analyzed was exactly opposite of what I thought was true. Vintage wire is noticably darker in many ways and for various reasons, fascinating stuff. No equivalent has been made since those days.

There is a "sweet" spot set of specs that has the best of both extremes that I use for my PAF's and I don't use the same specs for bridge as I do for neck position. My current set has everything in it tuned for position, but all using authentic PAF specs, and never have varied outside any of those formulas with the VL sets.

[JGundry]

I think frankfalbo hit that nail on the head. The stud bobbin shrunk more.

It is easy to tell the slug bobbin did not shrink more. Measurements of the brass mounting screw holes confirm it. If anything the screw bobbins actually have pressure inward that would encourage more shrinking of the screw bobbin compared to the slug. The extreme left and right pole screws on a PAF are often tilted inward because the baseplate or keeper bar spacing is a little wider than the bobbin spacing.

[Possum]

...

There's something else everyone has missed so far, the slug holes are wider at the top than the bottom and the drawings show this too.

[EFK]

"The extreme left and right pole screws on a PAF are often tilted inward because the baseplate or keeper bar spacing is a little wider than the bobbin spacing."

To serve dual duty w/ P90's as well?

[JGundry]

There's something else everyone has missed so far, the slug holes are wider at the top than the bottom and the drawings show this too.

No. The way the mold is constructed the pins and other parts have a draft built in that so the part can be ejected from the mold. There is a taper on the slugs so the top is just a little wider than the bottom for all the holes. The center three holes are often a tighter fit because of the amount of plastic packed into the center creates more shrink as it cools. This creates the sink and also make the center holes a little tighter fit.

[frankfalbo]

I think Frankfalbo's comments kind of opened this thread up to A/B comparisons but really I don't want to turn it into that.

That was never my intention, rather I was trying to defend your screw/slug width variance, when occam's razor suggests the design intent for equal center-to-center dimensions. Call it tolerance, variance, etc. Maybe blame it on shrink, inaccurate mold work, but Seth didn't say "now for the slug bobbin, I want to pull the string spacing inward by a gnat's eyelash". The little brass screw holes can't migrate inward either because of the holes in the baseplate, same as the screw poles in the adjustable bobbin.

Butyrate migrates over time. The only proof any of us need for that is to look at vintage LP mounting rings. They look like they were made of molasses, all warped and melty looking. If you apply tension or pressure to butyrate it will migrate.

Let me be clear: In case it didn't come off right, I compliment you on your new bobbin. Regardless of minor differences, we can all agree that something like this is far better for P.A.F. type of work than "Asian-made factory" bobbins, yes? My advice is we go back to complimenting the bobbin and quit worrying about how it differs from any one particular example of a 60 year old plastic part. I've got news for you. By now they're all different.

[belwar]

Well put my friend.

[JGundry]

Thanks Frank. I appreciate the spirit of the post.

Whether it is shrink variation or variation between mold cavities or a combination the difference is very small. I have two PAF slug bobbins on my desk one from cavity 3 and one from cavity 4 and you can't even force the slug alignment to match up.They both have the same internal former height so should be of the same era. Whether it is a difference in tooling between cavities, shrink over time or a combination of both is an open question.

Dave. I would be interested to know what the pole screw spacing called out on your drawing is? I'm curious to see how that number compares to the baseplate optical comparator readings I got.

[David Schwab]

The little brass screw holes can't migrate inward either because of the holes in the baseplate, same as the screw poles in the adjustable bobbin.

Right, they stayed where they were, because they are anchored, and the rest of the bobbin shrunk slightly.

Probably if you found an old bobbin that was never attached to a baseplate, it would have shrunk uniformly.

It's like old celluloid pickguards. The screw holes stay where they are and the rest ripples between them.

[David Schwab]

This pickup does sound different than the same pickup wound with the same wire spools, on the same machines but with All Parts bobbins. And yes it does sound better IMO. The differences are the Butyrate bobbin pickup has a more pleasing high end and midrange than the on Butyrate pickup.

Since you compared it to an AllParts bobbin with different dimensions, you can't say the material is causing the difference in tone.

For a real test, have some bobbins made with your dies with some other plastic, like ABS, and then do a comparison wind.

They look very good either way.

[Possum]

....

Dave, I made that point earlier on as well. AllParts and StewMac bobbins are a unique design that have nothing to do with PAF's. Also as I pointed out there isn't enough difference in the dielectric rating of ABS and CAB to cause change in tone either, and there really isn't a huge amount of contact with all the windings to make a difference unless the coil was vacuum potted into the coil plastic. It is conceivable that acoustic density could make some change but if I bounce a butyrate PAF bobbin and what I use off a table they are hitting nearly the same note. Duncan makes no claims of any kind for their little buty's for good reason. All they are is the right coil design and have way more "cool" factor. ClownLuthier and I are working away on ours, we'll see how far we get. Its not going to change anything in the pickups I have been making for the last 3-4 years except they'll smell funny