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New Bobbin Design, strong plastic needed


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1/6/2005 5:57 AM
Andrew C. New Bobbin Design, strong plastic needed
Happy New Year Guys,  
 
This thread I guess is relevant to all strat, tele, and other single coils with alnico poles.  
 
I have been mulling over the fact that I still find forbon and phenolic bobbins very fiddly and annoying to make. And who was it who said, time is money?  
 
The two piece design  
The "two piece" design seems to have the advantage that the magnet wire touches, or nearly touches the magnets. That all important for the first few winds seem to make a big difference to the tone. The disadvantage is that is a hassle to get the two pieces of flatwork perfectly straight, the flatwork must be cut and filed etc, and forbon is prone to some warp, and phenolic doesn't hold glue very well. Further, the magnets must be insulated.  
 
The Molded Bobbin Design  
The "molded bobbin" design for means that the bobbin is easy to mount, very reliable dimensionally and required little or no handling, except to check for small molding errors on which the wire may catch - But it seems the magnets are always enclosed in the mold, and the magnet wire doesn't get to within .5 mm of the magnets. From my experiments you can make a good pickup like this, but nothing magical.  
 
Possible Solution  
If a bobbin could be made from a harder plastic, then I think it could be make strong and stable with the magnets still being exposed to the magnet wire. In the five spaces between the six magnets, plastic columns could hold the top plate to the bottom plate (although it would be molded as one piece). Extra care would have to be taken to ensure that warping doesn't occur, as the bobbin would be less mechanically stable. The only drama would be to insulate the magnets with paint, lacquer or tape as discussed in many other thread.  
 
If anyone has managed to read and understand the above, and could recommend a suitable plastic for the molding process that would be strong enough. I have heard that K-resin would be good, but I know so little about plastics it is scary.  
 
If you can't get what I mean try this "Why do molded strat bobbins look like humbucker bobbins topographically, not strat bobbins?"  
 
 
Avoidance of the words "vintage correct" would be appreciated.
 
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1/6/2005 6:12 AM
Sheldon Dingwall

I've not tested bare rods verses taped ones for tone. How much difference does it make if the rods are insulated by .005-.008"? Can you actually hear it?
 
1/6/2005 10:27 AM
Dr. Strangelove
Sheldon Dingwall wrote:
quote:
"I've not tested bare rods verses taped ones for tone. How much difference does it make if the rods are insulated by .005-.008"? Can you actually hear it?"
Yup.    Dimarzio patented using an air gap between magnet and poles on his PAF-style humbuckers.    The patent uses very subjective terms like harshness and warmth, but the intent is clear.  
 
-drh  
--
 
1/6/2005 3:06 PM
Sheldon Dingwall

"Dimarzio patented using an air gap between magnet and poles on his PAF-style humbuckers.    The patent uses very subjective terms like harshness and warmth, but the intent is clear."  
 
That's for humbuckers isn't it? I'm talking insolating the poles from the magnet wire.
 
1/6/2005 5:08 PM
Joe Gwinn

On 1/6/2005 5:27 PM, Dr. Strangelove said:  
quote:
"Dimarzio patented using an air gap between magnet and poles on his PAF-style humbuckers.    The patent uses very subjective terms like harshness and warmth, but the intent is clear."
What's the patent number?  
 
Is the patent still in force? US patents last 20 years from date of filing (not patent approval).  
 
Does any claim talk of the gap, and if so, in what context. Legally, only the claims have any effect; the rest is pretty talk and explanation, and need not be clear. Nor would a magnet-pole gap cover a winding-magnet gap. Claims must be explicit.
 
1/6/2005 7:51 AM
Joe Gwinn

On 1/6/2005 12:57 PM, Andrew C. said:  
[QUOTE]Possible Solution  
If a bobbin could be made from a harder plastic, then I think it could be make strong and stable with the magnets still being exposed to the magnet wire. In the five spaces between the six magnets, plastic columns could hold the top plate to the bottom plate (although it would be molded as one piece). Extra care would have to be taken to ensure that warping doesn't occur, as the bobbin would be less mechanically stable. The only drama would be to insulate the magnets with paint, lacquer or tape as discussed in many other thread. [/QUOTE]There is no reason this wouldn't work, and use of better resins should eliminate the warping issue.  
 
The best transformer and inductor bobbins are made from polyethersulfone (PES), which can be used at high temperatures, and yet can be processed using ordinary injection-moulding equipment.  
 
PES (and all other resins) can be strengthened and stiffened by addition of chopped glass fiber to the plastic. Resins such as PES are more expensive per pound than more common resins, but pickup bobbins aren't all that large.  
 
Click here for info on PES.  
 
This was the first interesing site that came up on a google search for polyethersulfone, but there are many suppliers. And resin families.
 
1/6/2005 9:42 AM
jason lollar

Keep practicing.
 

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