Coil Winding Experimenting Board!

[Charles (Upstate NY)]

Here's my new experimenting board for winding concentric coils, supports coils 7 to 13 inches OD. About 640 holes in all.



Here's the homeshop cnc mill doing its thing.


Here's a wider shot.

[Gary]

Re: Coil Winding Experimenting Board!

So, Lets see a coil wound on this jig.

[william]

Re: Coil Winding Experimenting Board!

Great looking setup Charles. William

[Charles (Upstate NY)]

Re: Coil Winding Experimenting Board!

Soon, I was going to wind one tonight but...the coins and relics were calling and I went out detecting instead. I fed the skeeters while I was at it, they are horrible this year.

I'm going to try making one of these coplaner coils I read about on this site, here's the link to Dave Emery's article.



Click Here

[Charles (Upstate NY)]

Thanks William

Its getting there.

[Beachcomber]

Looking Good Charles!!!!

n/t

[Charles (Upstate NY)]

Here's a pic of a 13 inch concentric wound on the jig

I talked to Dave Emery today who gave me some additional tips on building his concentric coplaner coil design. Inductance/resistance is nicely within factory specs, tomorrow she goes on the scope.

[Gary]

Re: Here's a pic of a 13 inch concentric wound on the jig

One thing I have noticed on most Commerical Concentric coils is they are Layer Wound, Not Scramble wound like yours.

I wonder how much of a difference this might have on the final results in actual detecting?

Take care.........Gary

[Charles (Upstate NY )]

Layered verses bunched together winding, can you engineer types weigh in on this?

For TX my factory coils are neatly wound though RX at least on the factory coils I have is usually just flopped in there.

I think there can be an advantage of flopping RX, I lost a measurable amount of inductance on this test coil by tightly binding RX with zip ties.

Is it worth the effort of layering TX? I don't know, I read that a coil is most efficient when wound neatly layered as you say in a square or rectangular fashion with the windings aligned vertically. But a while back someone on geotech did some testing and found no measureable difference between layered verses bunched together. It could be that factory coils, being machine wound, would just be more work to wind in a bunched together fashion. lol

I built a 14x18 (18 inches wide) double D coil last year in the bunched style and it beat the factory 15 inch coil in depth. Maybe the neatly layered coil windings are more important in things like a telsa coil than a metal detector coil I don't know, I do know a bunch together coil works just fine.

Hey all those crissed crossed field lines are better for finding coins on edge!!! Hows that for a sales pitch in the true spirit of metal detecting ads.

[Dave Emery]

Re: Layered verses bunched together winding, can you engineer types weigh in on this?

Most factory coils use copper wire with a special insulation. They pass a high electric current through the coil which causes the insulation to melt together. This makes for a very rigid coil. As anyone who has ever made a balanced coil will tell you, all you need to have is one floppy turn and you will hear it as the coil is bumped around!!! The main reason that factory coils are wound neatly is to take advantage of this kind of insulation although coil winding machines will always make a nicer looking coil. While it is true that a neater coil will produce a coil with a higher quality factor or "Q" a high Q coil is not required for a balanced searchcoil.

[Reg]

Re: More about bondable wire

Hi Dave,

There are different types of bondable wire available, but I have found it difficult to buy them in small quantities.

Some manufacturers of coils use a special wire made with a specific bondable outer coating that dissolves or partially disolves in alcohol. So, passing the wire over an alcohol saturated sponge while winding the coil, activates the coating sufficiently that the windings will adhere to each other. The windings are then heated or baked to further bond them to each other.

Places such as Wiretron (www.wiretron.com) carry this type of wire, as do several others. This is what Wiretron has to say about the special wire. "Bondable magnet wire is the combination of conventional film insulated magnet wire with the addition of a thermoplastic adhesive coating. The main advantage in manufacturing is the ability to construct free-standing coils (coils without bobbins). The adhesive coatings are designed to be activated by heat (such as when baking in an oven) or solvents. Sometimes a combination of heat & solvent works best depending upon the specific application."

Reg

[Dave Emery]

Re: More about bondable wire

Reg,

The bondable wire sounds like great stuff. Still, for a single searchcoil it is not too tough to simply cover the sucker with epoxy. Most of us will never be winding enough coils to justify the extra cost of the bondable wire. With this said, let's here from someone who knows where we can pick some up!!! Dave. * * *

[Chris]

Re: More about bondable wire

Hi,

I saw once a professional coilwinding mashine on an exibition. This mashine produced "free standing" air coils without a bobin. During winding the mashine "glued" the layers with a hot airgun together. After winding there was no further work step to do. No heating, etc....

Chris

[Carl-NC]

Re: More about bondable wire

I think I've seen the same coil-winding gadget Reg has seen .

One reason that manufactured coils look more "layered" is that they use sandwiched forms that produce neater windings.

Now, since I've recently purchased some large spools of magnet wire off eBay (about 50 pounds worth!), how can I apply an adhesive during the winding operation? Or, maybe the more appropriate question is, what would be a good adhesive to apply? Any ideas?

--Carl

[Carl-NC]

Re: Coil Winding Experimenting Board!

Charles, what's the coolant?