Constructing Pickups (coils, etc) without bobbins.

[peskywinnets]

I'm actually tinkering on with sustainer coils - but thought I'd try to tap into the collective wisdom here! (this should give you a basic idea of the stuff I'm making...ignore the big blobs of hot glue & double sided tape etc - it's just a proto I was testing!)

)

(that coil is actually not bobbinless - it has a lower bobbin edge/surface & was using method 4 outlined below)

I touched upon bobbinless coils in an unrelated thread ( http://music-electronics-forum.com/t15045/ )

& David K gave me some good info...

http://music-electronics-forum.com/t15045/#post120527

Extract ..

"there is no need for a bobbin at all if you don't mind encapsulating the driver/pickup in an epoxy matrix using mold/mould.
You'll need face plates that are very shiny and coated with a mold release agent of some sort. Stick your core between the plates, wind the full 6mm (1/4") width and then squirt the windings with CA glue to hold them together."


However, I'm (still) struggling here to get a successful method for making neat coils/pickups without bobbin edges! (don't ask why I want to make coils without bobbin edges - that's another story!). The concept is easy, but the practise seems rather hard!

Here's what I've tried...

Method 1 - Place two temporary bobbin edgeS/plates up against a bobbin core. Wind the coil....once finished, apply CA (Superglue) to the windings - then remove plates (capilary effect to hold sufficient windings together to allow removal of the bobbin edge plates & then dipping the whole coil in wax to solidify the remaining windings) . Problem: Side plates are glued to the wire too! (due to the aformentioned capillary effect) It therefore needs a lot of force to prise the edges off, resulting in the coil coming out like an accordian!

Method 2 - Place two temporary bobbin edge plates up against a bobbin core. Wind the coil....applying epoxy as I wind - then again, remove plates. Problem: Same problem - Side plates are glued to the wire too!

Method 3 - As above but with cling film wrapped around the bobbin edge plates. Problem: Bobbin Side plates can be removed with care, but cling film sticks to the epoxy on the windings. Fugly.

Method 4 - Change the way the plates are held wrt core (previously the plates were only held temporarily in place while attached on the winder)...but this method, keeps the whole 'bobbin together even after winding. So once winding is finished, the whole bobbin is removed (ie bobbin edges, core with windings) & the lot droppped into molten wax - remove from molten wax...once wax has cooled a little, unbolt the edge plates from the core. Problem wax doesn't permeate through the whole windings, meaning the win dings will vibrate - not good. (I guess this could be improved by using a vacuum?). That said, this is the most successful to date.

It should be said, that with all those attempts, the temporary bobbin edge plates' 'inner surface' were as glossy as can be (I was using freshly cut glossy acrylic - only peeling the protection film off immediately to constructing the temporary bobbin).

Any other ideas?

(by the way, if you're interested in what A Sustainer is/does - here's a very short video clip of me testing the proto photographed above - http://www.tinyurl.com/y9kuoee )

[Dave Kerr]

Did you try coating the acrylic with anything? Maybe something as simple as butchers wax?

[tedmich]

PTFE or FEP side plates....or PTFE or FEP film over side plates or PTFE mold release spray on side plates before CA


all at Mcmaster Carr

[David King]

Teflon (acetal) or cheaper LDPE plates would have been better than acrylic. Wax paper works sometime. Brass or steel shim stock can be heated with blow torch to pop off the glue. Thin fish paper could be left in place.
Acrylic is a very glue-able plastic. Car wax or silicon spray etc make OK release agents. (Just keep the silicone off EVERYTHING else in your shop or you will curse me everyday.)

The one in the photo looks really good BTW. Where are you getting those little slugs from?

[peskywinnets]

Wow...three quick replies....thanks guys.

No, to date, I've not tried any form of release agent (I googled "What doesn't stick to Epoxy!" - and came away from that session thinking there's nothing that Epoxy won't stick too!).

The reason I was using acrylic, is because I have sh1tloads of it to hand - and it's really shiny/glossy (which I'd thought was a 'win' when it came to unstickiness!)

I've never even heard of LDPE plates (& alas, I'm a Brit so access to Stu Mac isn't as cheap/feasible as being on your side of the pond) ...off to Google it & see if I can establish a local source.

Also, would it be better to wait for the epoxy to go completely hard, or just part cured (sufficiently to hold the coil windings in place) wrt removing the edge plates?

[jonson]

one Brit to another. low density polythene, so if you want thin, an industrial extractor bag or thicker, nip round the Co op and get a litre of milk, drink it and cut the bottle up. Our 5 litre plastic liquid containers are ldpe as well.
Scientific have got bondable wire which would be a quick way to go.

[peskywinnets]

one Brit to another. low density polythene, so if you want thin, an industrial extractor bag or thicker, nip round the Co op and get a litre of milk, drink it and cut the bottle up. Our 5 litre plastic liquid containers are ldpe as well.
Scientific have got bondable wire which would be a quick way to go.

Thanks....but your reply prompts more questions - wtf is an industrial extractor bag (you sure you aren't american, as I've never stumbled across one of those before ...lol). I prefer thin to thick....so I would rather try & find one of these 'extractor bags', but I checked Argos & nope...they ain't got any (do you mean those thick heavy duty clear bags as used by cleaning companies etc?)

How/why would a bondable wire be the quick way to go? (I'm wanting something here that doesn't bond!)

[David Schwab]

Wow...three quick replies....thanks guys.

No, to date, I've not tried any form of release agent (I googled "What doesn't stick to Epoxy!" - and came away from that session thinking there's nothing that Epoxy won't stick too!).

No, that's not true! How do you think they mold things in epoxy with rubber molds? They use a release agent.

I'll tell you right now what works and you probably have it at home... Vaseline.

I cover the outsides of my pickup shells with a coating of it before I pour epoxy in them so if I get a spill or smudge, it comes right off.

Butcher's wax will also work.

Do you have that coil on top of a pickup?

[peskywinnets]

Do you have that coil on top of a pickup?

Thanks David!

...no, there's no pickup below the coil - it's all 'self sufficient' so to speak. (my version of a sustainer has 'pole' pieces, which makes the coil look a little like a pickup. The slugs you can see are only 5mm tall - I had to make them myself)

[David Schwab]

Thanks David!

...no there's no pickup below the coil - it's all 'self sufficient' so to speak.

So why do you need it so thin then?

[jonson]

Sorry Pesky I'm down the road in Essex. Didn't realise about the coil, i'm not into those sustainer thingys, so why not an aircoil, thats an easy option. Industrial extractor bag used to collect dust and shavings on the bottom of industrial workshop extractors. A good test is to cut a narrow strip and stretch it and watch what occurs. Plenty of suppliers over here or I 'll cut of a big chunk and stick it in the post to you.

[peskywinnets]

So why do you need it so thin then?

Because it's a surface mount sustainer (ie no routing necessary to fit it) - and there's only about 5mm or 6mm gap between most guitars' strings & the guitar body itself (ie when fretted at the top fret), therefore I have to eliminate stuff that robs me of 'coil height' - & bobbin edges rob me of coil height!

Here's the same proto taken from a different angle....



That said, because it looks a bit crap, I have since made a cover from perspex that fits over it....it now only looks partially crap.

so why not an aircoil, thats an easy option. .

The coil has to have a ferrite core.

A good test is to cut a narrow strip and stretch it and watch what occurs. Plenty of suppliers over here or I 'll cut of a big chunk and stick it in the post to you.

What should it do when stretched? No need to post it (but thanks anyway!) as I'm sure I can track down some - I'll head into work tomorrow with a big pair of scissors!

[jonson]

Still use an aircoil with a ferrite core unless it has to be tight on there. By the way love the name, do you read viz.

[peskywinnets]

I'm clueless about aircoils...I'd taken them to have air core...but now you've just wrong footed me by suggesting slapping a ferrite core in one! I need to Google & then come back to you as if I know what I'm on about.

Re reading Viz...many moons ago...but I'm originally a Geordie & such words are in constant use in my vocabulary!

[Bruce Johnson]

Just for reference, another great product for repelling glue is clear packaging tape, the 2" wide tape for closing up boxes. It's amazingly resistant to glues and epoxies. I lay down strips on fixtures where glue may drip, and on blocks to seal up silicone molds, etc.

You could stick a piece on your bobbin flange and trim it with an Xacto knife. It's like a permanent wax. If it gets chewed up, peel it off and put more on.