Butyrate Bobbins

[JGundry]

Here is a quick photo of the first pickup with the Butyrate bobbins Belwar and I had done. They took FOREVER to get done but I am glad we did it. Belwar made up Solidworks drawing from original parts he and I had. And I found a plastic molder just outside of Kalamazoo to do the work. I have spent at least 20 hours going to his shop for test runs etc. I still have to head to Kalamazoo to check the final run when we do it. These bobbins are from the last test run. We need to run them with a little higher temperature to get rid of the flow lines. But the flow lines on this batch actually match a Pat# paf I have.

This pickup has slugs I had custom made from the correct vintage allow. I had two batches of slugs made on two different Brown and Sharpe screw machines. These slugs were done on a 00-G Brown and Sharpe. I just placed an order Monday for USA made baseplates and once that is done every part will be USA made!

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. There seems to be a bit more dynamics also. I think the plastic is part of it but the slugs are fractionally smaller in diameter with the Butyrate as per vintage specs and the coil former sizes are a fair amount different with the Butyrate as per vintage specs. There are some other vintage details that are not in the All Parts bobbins that we did with the Butyrate bobins that I think effect tone. I don't think you can chalk it all up to the plastic but these do sound noticeably different in a good way. I think some part of the tone has to do with the softer plastic since these are unpotted.

[Possum]

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Looks great, but the tone differences between a PAF coil design and AllParts bobbin coil design are night and day because they don't make the same type coils. Dimensions are radically different. You can't make a true PAF replica on StewMac/AllParts bobbins. I call those "Korean tone buckers" and pretty much abandoned those years ago because they all sound the same to me. Good job, congratulations. Where's the creme version?

[JGundry]

Thanks Dave.

The dimensions do make a difference for sure. You get a fatter shorter coil. The distance from the wire to the screws and slugs is different also. The screw and slug spacing is not the same on both bobbins. For some reason almost everyone has missed this detail in the Butyrate repro bobbins I have seen.

I'll take a picture of the cream. I just wound only back ones today.


The original All Parts bobbins are Japanese not Korean.

[Possum]

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Actually there isn't one set of dimensions, I've found 3 radically different versions so far, and know why they changed, but none of them are the same as from the land of whale killers (go Sea Shepherd!!!)

[kevinT]

They look nice. I have to commend you and Matt for taking on this endeavor. Putting in a lot of time, energy, and cash to get these done....not to mention all the stress that goes along with doing something like this to ensure that the molder includes all the details. The good thing is is that it will pay off and be very gratifying when they're done.

[belwar]

Well I have to say that Jon did the lions share of the work particularly near the end - He's close to the molder so it worked out well for us. Jon and I work well together, and it probably wont be our last project together.

[theboss]

Looks great Jon!

[JGundry]

Thanks.

I think finding the right molder is pretty important. The guy that did these for us also restores muscle cars as a hobby and he totally understood the importance of all the details that functionally make no difference but you would want if you are doing Butyrate bobbins. We did the circle in the square hole twice and the molder id not put up a fuss. The main down side of getting most parts like this done is it takes a long time to get a quote, get the material, make a change, get a test part.....

[belwar]

Oh course it didnt help that he got the flu, the bubonic plauge, his car wouldn't start, his grandma died, and his dog ate his homework either.. Ok so only two are true.

so whats next jon?

[JGundry]

Oh course it didnt help that he got the flu, the bubonic plauge, his car wouldn't start, his grandma died, and his dog ate his homework either.. Ok so only two are true.

so whats next jon?

You forgot he threw his back out too.

I'm heading down to Kalamazoo Tuesday to run all of them. Fingers crossed.

[belwar]

What year PAF bobbins did you model these on?

Several different specimens were measured ranging from 1958-1960 (I think we looked at 10+ bobbins). When drawing, my reference was a 59. Beyond minor shrinkage differences they were uniform.


There were alot of difficult decisions we had to make including - do we factor in 50 years of shrinkage, or do we make it as it was?

[Possum]

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I don't think they shrank over the years much at all, you are forgetting that injection plastics shrink right out of the mold, you have to account for that when specifying what material you are using and oversize the mold by that amount. I tried to find out what shrinkage for butyrate is, I think its around 1%, but it also depends on proper pressurizing and correct temperature. You can clearly see in the core where shrinkage happened at manufacture by the large dimples, and also dimples on the top in some, more in later years...

[JGundry]

The shrink is factored in during the tooling of the mold. The place doing the tooling applies that shrink factor for a particular material to your original drawing. They would have done the same in the 50's. The pressure or how much they "pack" the plastic in is part of the tweaking that any molder does after the mold is made. Packing the material in more will increase the overall dimension in length by about .004" on this part. Not much at all. The raw material comes with the temp and shrink specs.. Apparently Butyrate has a fairly wide working temperature range. there is actually a fair amount of fine tuning that has to be done once the mold is in the machine. That is what I'm going to the molder on Tuesday for. I want to make sure everything is dialed in ad approve it before a bunch of expensive Butyrate is shot through the machine.

The variation in sink on the top of the bobbins and the coil former is just due to different runs of the same part at different times. My molder even pointed this out to me how the sink can be tweaked a bit. The original molder might not have had the same settings for every run. Gibson might have even brought the mold to different injection molders to get the best price.

Unrelated I brought this molder a 50's P-90 bobbin and the took a lighter to it to smell it. He said it is Styrene. You guys may have know that but evidently a trained nose can identify plastic by the smell it makes when it burns.

[Sam Lee Guy]

Ahhh! Beauty-Rate bobbin!

Just like Venice in Summertime - velly beautiful - velly smelly.

[Possum]

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There is too wide a variation in bobbin cores to be shrinkage or different batches. I wonder why butyrate is so expensive, maybe because its not so common anymore? Its a smell I remember as a kid, I think alot of toys were made out of that stuff, I love the smell of butyrate in the morning, ok gotta go toke on some styrene...suuuuuuuuuuuuck