Laminated Core

[Chris Turner]

So, I'm thinking of trying my hand at making a laminated core from layers of sheet metal.

What would suffice as a good material for electrically isolating the layers? Would plain old double-sided Scotch tape work, or maybe some sort of thin PVC-based tape?

[Joe Gwinn]

So, I'm thinking of trying my hand at making a laminated core from layers of sheet metal.

What would suffice as a good material for electrically isolating the layers? Would plain old double-sided Scotch tape work, or maybe some sort of thin PVC-based tape?

The voltage between laminations is of order a millivolt. Anything mechanically strong enough will work, even a layer of varnish obtained by dipping the laminations and allowing them to dry before assembly.

Mylar film and epoxy is one option, as is onionskin paper and epoxy. The laminations must be completely degreased for the epoxy to stick.

Be sure to deburr the edges of the laminations, so you won't get accidental current loops.

[David King]

Once you glued the lams together you are all done with cutting, grinding drilling etc.
I'd try some thin transfer tape. I love the stuff from Sellotape/scapa in CH but I can't find it in the States. It's Scapa 4456. Thinner than 3M.
Dick Blick sells something similar i'm sure:
Double-Coated Tapes - BLICK art materials

[ken]

If you're making a prototype, how about simple mylar packaging tape? Once you put tape on both sides of the lams, just glue them together.

ken

[Chris Turner]

If you're making a prototype, how about simple mylar packaging tape? Once you put tape on both sides of the lams, just glue them together.

ken

Yeah, it's just for a prototype at this point. I'll probably just use double-sided Scotch tape for now.

[David Schwab]

I've used double sided tape, and also paper and super glue.

[Mark Hammer]

Some Asian-made guitars, such as some Univoxes, would use humbuckers where one or both coils looked like a sort of "staple" coil from the top, but was two soft iron (?) slugs butted up against each other, looking like a pair of "combs", such as you'd see along the outside of a Jaguar pickup. Of course, there would be a ceramic magnet linking those slugs and another that might have adjustable screws in it.

Would you consider this a "laminated" core or does lamination have to involve more than two blade-like pieces?

[big_teee]

So what is the benefit of a laminated core?
Is it something you can hear, or very mynute?

[Chris Turner]

So what is the benefit of a laminated core?
Is it something you can hear, or very mynute?

It reduces eddy currents, therefore you can get more highs from the same size core (compared to a solid core)

[Joe Gwinn]

It reduces eddy currents, therefore you can get more highs from the same size core (compared to a solid core)

Exactly. Vary the effect by varying the lamination thickness. Power transformer laminations are in the range 0.010" to 0.014".

Metal Shim Stock | MSCDirect.com

[fieldwrangler]

Are we suggesting laminating parallel to the long or short dimension of the pole bar (as viewed from above) for optimum effect?

[Mike Sulzer]

Are we suggesting laminating parallel to the long or short dimension of the pole bar (as viewed from above) for optimum effect?

Probably long; it is easier. Short would give smaller loops for the same thickness, and so less eddy currents.

[fieldwrangler]

In fact, this is what I've often thought about laminated cores; if you really wanted to minimize eddy currents you'd hafts face up to the proverbial "inconvenient truth" about making lots of little strips.

[Mike Sulzer]

In fact, this is what I've often thought about laminated cores; if you really wanted to minimize eddy currents you'd hafts face up to the proverbial "inconvenient truth" about making lots of little strips.

I do not see the need for a laminated core. If you want no eddy currents, but need a sufficiently high permeability material to carry the permanent field to the strings, use ferrite.

[Joe Gwinn]

I do not see the need for a laminated core. If you want no eddy currents, but need a sufficiently high permeability material to carry the permanent field to the strings, use ferrite.

The issue is to get the desired amount of eddy current loading, to get a desired sound.