Chance PI coil...

[baum7154]

After the first layer of fiberglass has cured the whiskers are removed using a Dremel tool and a sanding drum at the lowest speed possible.





Dan

[baum7154]

Attached below is a photo of the first fiberglass layer being applied to the 'racetrack' style of coil. This coil is wound in what is properly known as a '3D Coil' according to some old crystal radio antenna references. For our purposes it also has the advantage of a pretty good degree of self - shielding. For this reason I will refer to this type of coil wind as a '3DSS' weather a circular, elliptical, oval, square or any other shape so long as it is wound in the unique geometry of the coils in this thread. This should eliminate the confusion of calling it a spider coil or a basketweave coil, neither of which exhibit any self shielding.

The attached photo shows the 1 1/2" wide fiberglass mesh strip applied with about a 33% overlap.



Dan

[baum7154]

That's what I thought. One more question. My coil is sealed up and I don't know which wire is from the outer winding. Is there a simple way to identify it now? Guessing is only a 50/50 chance. Thanks in advance Dan.

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You will have to connect the wires to your detector and set it for short sample delay about 8 to 10us and lay your hand on the coil to see if it is detected. Then reverse the leads and see if your hand is detected. There is a significant difference between the two hookups. You want the one that won't see your hand. Make sure to remove any rings on your test hand.

Good Luck

Dan

[grandpastar]

Oops.

That's what I thought. One more question. My coil is sealed up and I don't know which wire is from the outer winding. Is there a simple way to identify it now? Guessing is only a 50/50 chance. Thanks in advance Dan.

[Qiaozhi]

After looking at the instructions for building the MPP, is this coil considered a mono or a balanced?

If you're referring to the Chance PI coil, then it's a mono.

[baum7154]

After looking at the instructions for building the MPP, is this coil considered a mono or a balanced?

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This coil is considered a 'monocoil' having a single winding and technically I believe it's operation is 'unbalanced', having the outermost winding placed at system ground.

Regards,

Dan

[grandpastar]

Maybe a dumb question.

After looking at the instructions for building the MPP, is this coil considered a mono or a balanced?

[grandpastar]

I knew I could count on you Dan! Thanks again.

[baum7154]

I've been under the impression that these coils are made with one continuous length of wire, 60+ feet long. Some of what I have read makes me question this. I don't see any joints in the wire though. Please clarify.

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You are correct that they are one continuous length of wire. I would say that they are more like 72' of wire if you include a twisted pair 3' feed line of the same continuous wire for a 30 turn 8" round coil. The beauty of this design is speed, high sensitivity, no additional shield, and no solder joints in the coil that would otherwise be detected at the most sensitive settings.

Regards,

Dan

[grandpastar]

Just to be clear!

I've been under the impression that these coils are made with one continuous length of wire, 60+ feet long. Some of what I have read makes me question this. I don't see any joints in the wire though. Please clarify.

[baum7154]

Hi Dan
I like your latest coil, Looks well engineered
When time permits shall have a go making that one myself, thanks for sharing
All the best

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Thanks Dave, I have quite a few hours in the design trying to make a coil that has the advantage of a 'blade' type of coil field for quicker area search and good sensitivity to small gold. Will be fiberglassing the coil soon so it will be ready for true 'in the field tests' this summer. Air tests look encouraging but as we all know only putting it to use will tell the true story. That said it does have enough sensitivity to detect a .95 grain gold nugget at about 1" in air using my modified CHANCE PI detector.

Regards,

Dan

[baum7154]

I decided to remake my coil frame to Dan's dimensions after all. I trust Dan's experience and I'd rather recut it now before I go any further. [ATTACH]33018[/ATTACH]

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On my coils with the 8" round or for that matter any 1" wide coil form configuration I've decided that 1/4" of space should be the minimum from the deepest point between the inner slots and the outer slots. This way there is little proximity or parallelism between the first 5 windings and successive windings.

Best of luck!

Dan

[satdaveuk]

Hi Dan
I like your latest coil, Looks well engineered
When time permits shall have a go making that one myself, thanks for sharing
All the best

[grandpastar]

I decided to remake my coil frame to Dan's dimensions after all. I trust Dan's experience and I'd rather recut it now before I go any further.

[baum7154]

5/16".

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5/16" is .312" and 24awg 600 volt PTFE insulated wire has a diameter of .042". With 30 turns of wire around your form there will be 6 wires crossing each other in each of the slots. I was concerned that the slots could hold the depth of 6 wires. So 6 X .042 = .252" and that easily fits in your .312" slots. In fact the slots could handle 7 wires each or 35 turns around the form.

No worries!

Dan