australian electronic gold prospecting forum.com

Detector Technology and Electronics and new detectors => Detector Coils => Topic started by: Dontbstme on Monday January 21 2019 06:35:53 AEDT AM



Title: How big would you go on search coils?
Post by: Dontbstme on Monday January 21 2019 06:35:53 AEDT AM
Hey guys.
A question to all crazies.
What is the biggest size coil you would like to have on your PI, VLF or what ever detector you are using?
What will be the maximum weight you would tolerate for your desired huge coil?

Hesitant to comment??? Who knows what the heavens will drop down. If you don't say you want it no one would hear about it and no one would consider making it for you, huh!


Title: Re: How big would you go on search coils?
Post by: Reg Wilson on Monday January 21 2019 10:09:57 AEDT AM
Already using 38" mono on my QED, and it works just fine.


Title: Re: How big would you go on search coils?
Post by: GARY on Monday January 21 2019 14:18:31 AEDT PM
My largest coil is a 25” mono and since I have been including pics with my previous discussions then below is a 9 gram nugget that I detected at Wedderburn with the 25” mono. Was happy with the depth it achieved on this size nugget which was encased in clay at the bottom of the hole.

As far as the maximum weight that I could tolerate then the heaviest coil I have used is a 24”x12” DDPro hitting the scales at 1.565 kgs.

Gary.


Title: Re: How big would you go on search coils?
Post by: Doug on Monday January 21 2019 14:48:08 AEDT PM
  
My largest coil is a 25” mono and since I have been including pics with my previous discussions and still in the mood to do so then below is a 9 gram nugget that I detected at Wedderburn with the 25” mono. Was happy with the depth it achieved on this size nugget which was encased in clay at the bottom of the hole.

As far as the maximum weight that I could tolerate then the heaviest coil I have used is a 24”x12” DDPro hitting the scales at 1.565 kgs.

Gary.


Nice find Gary! ::10 :: ::23::
doug ::419::


Title: Re: How big would you go on search coils?
Post by: Dontbstme on Monday January 21 2019 17:27:51 AEDT PM
  
Already using 38" mono on my QED, and it works just fine.

What is the weight of this coil? Any pics or link to manufacturer/supplier web site?


Title: Re: How big would you go on search coils?
Post by: Dontbstme on Monday January 21 2019 17:35:56 AEDT PM
I got two versions of mono loops for my two box. The lighter version is 465 grams per 30" circular mono coil.
The other version with higher Q is 675 grams per 30" circular mono coil.

I have also build a 41" concentric coil for VLF with weight of only 830 grams and super stable mechanics.

Some time ago it occur to me that PI for gold prospecting could benefit from the use of huge concentric coils as this will allow the depth penetration for the big super deep nuggets, but also the sensitivity to the small ones. Just a thought.


Title: Re: How big would you go on search coils?
Post by: Reg Wilson on Monday January 21 2019 17:53:13 AEDT PM
  
  
Already using 38" mono on my QED, and it works just fine.

What is the weight of this coil? Any pics or link to manufacturer/supplier web site?
This coil was home built by John-Hider Smith, and is not commercially available
There was a photo of this coil posted a few days back by Bugwhiskers.


Title: Re: How big would you go on search coils?
Post by: Dontbstme on Monday January 21 2019 21:04:01 AEDT PM
  
  
  
Already using 38" mono on my QED, and it works just fine.

What is the weight of this coil? Any pics or link to manufacturer/supplier web site?
This coil was home built by John-Hider Smith, and is not commercially available
There was a photo of this coil posted a few days back by Bugwhiskers.
How heavy it is?


Title: Re: How big would you go on search coils?
Post by: Reg Wilson on Monday January 21 2019 22:06:08 AEDT PM
Dontbstme, Struth mate, how does one go about weighing a coil that big? A bit awkward. When I work out a way of weighing it, I shall post it. Let me just say, it is not very heavy, and an old fart like me can swing it without a harness, but a harness may make it a bit easier.


Title: Re: How big would you go on search coils?
Post by: Dontbstme on Monday January 21 2019 23:56:11 AEDT PM
  
Dontbstme, Struth mate, how does one go about weighing a coil that big? A bit awkward. When I work out a way of weighing it, I shall post it. Let me just say, it is not very heavy, and an old fart like me can swing it without a harness, but a harness may make it a bit easier.
Hi Reg. You can check the weight of the coil by using one of these. They sell for only a couple of quid.
Any way wouldn't an old fart like the possibility to swing 3 times lighter coil at the same huge size?
 I am also an old fart, by the way. May be not that old, but fart for sure... ::620::


Title: Re: How big would you go on search coils?
Post by: dasenator777 on Tuesday January 22 2019 00:15:36 AEDT AM
nice nugg there gary what machine were you using, doesnt look like a qed mate  ::10 ::


Title: Re: How big would you go on search coils?
Post by: mylab on Tuesday January 22 2019 02:06:06 AEDT AM
If a 25" mono can detect a 9 gram at 18" approx by that pic than I wonder how deep a 38" mono could detect a large nugget.
Reg has your 38" coil produced your deepest and largest nugget or has some other coil produced that result and at what depth?


Title: Re: How big would you go on search coils?
Post by: Dontbstme on Tuesday January 22 2019 04:14:07 AEDT AM
  
If a 25" mono can detect a 9 gram at 18" approx by that pic than I wonder how deep a 38" mono could detect a large nugget.
Reg has your 38" coil produced your deepest and largest nugget or has some other coil produced that result and at what depth?
The depth I see on the picture is about 8". IMO 18" for 9 grams is out of the question.
The bigger coil would be deeper to the bigger nuggets, but unfortunately not by too much. The increase of depth from 25" coil to 38" will be exactly 17.1% for the same size targets.


Title: Re: How big would you go on search coils?
Post by: GARY on Friday February 1 2019 16:00:00 AEDT PM
  

The bigger coil would be deeper to the bigger nuggets, but unfortunately not by too much.

The increase of depth from 25" coil to 38" will be exactly 17.1% for the same size targets.


Interesting you say that figure of 17.1% and how did you came to that conclusion?

I may have to test if that holds true between an 18” and 25” coil?

Gary.  



Title: Re: How big would you go on search coils?
Post by: Dontbstme on Saturday February 2 2019 05:53:16 AEDT AM
  
  

The bigger coil would be deeper to the bigger nuggets, but unfortunately not by too much.

The increase of depth from 25" coil to 38" will be exactly 17.1% for the same size targets.


Interesting you say that figure of 17.1% and how did you came to that conclusion?

I may have to test if that holds true between an 18” and 25” coil?

Gary.  


It derives from a basic rule of thumb. If you increase the diameter of a coil twice the sensitivity of the system
 will raise by 50%. From there you can predict very close what will happen with different coils providing they are with close enough electric parameters.


Title: Re: How big would you go on search coils?
Post by: GARY on Saturday February 2 2019 10:59:33 AEDT AM
Okay thanks so using that basic rule the increase in depth from my 18" to 25" will be exactly 14% for the same size targets.

And since both coils are of the same series and from manufacturer I would assume they have close enough electric parameters.

Gary.


Title: Re: How big would you go on search coils?
Post by: Dontbstme on Saturday February 2 2019 17:35:20 AEDT PM
  
Okay thanks so using that basic rule the increase in depth from my 18" to 25" will be exactly 14% for the same size targets.

And since both coils are of the same series and from manufacturer I would assume they have close enough electric parameters.

Gary.
Well then, measure them and see what comes out of it.
Those electric parameters you can measure easily with any multimeter that has resistance and inductance range.


Title: Re: How big would you go on search coils?
Post by: Dontbstme on Thursday February 21 2019 21:03:52 AEDT PM
  
Okay thanks so using that basic rule the increase in depth from my 18" to 25" will be exactly 14% for the same size targets.

And since both coils are of the same series and from manufacturer I would assume they have close enough electric parameters.

Gary.
Hi Gary. Have you checked what is the exact increase of depth from 18" to 25" mono.?


Title: Re: How big would you go on search coils?
Post by: GARY on Friday February 22 2019 07:08:23 AEDT AM
  
Hi Gary. Have you checked what is the exact increase of depth from 18" to 25" mono.?

Okay after checking back through my test records then these were the results using the exact same settings on my GPX in FINE GOLD timing.

On a 23-gram gold nugget the 25” mono produced exactly 15% extra increase of depth than the 18” mono.

On a 95-gram gold nugget the 25” mono produced only 6.25% extra increase of depth than the 18” mono.

On a 101-gram gold nugget the 25” mono produced exactly 14.28% extra increase of depth than the 18” mono.

On a 100mm x 50mm x 10mm thick Aluminium Block (98.47% - 99.03% pure) the 25” mono produced exactly 16% extra increase of depth than the 18” mono.

Have yet to test the 25” mono on my 15oz Lead, 30oz copper piece & an Aluminium Drink Can. However if we were to say add the 14% to the results below that I achieved on these targets with an 18” mono then that would show:

18” mono on 15oz Lead - 30” + 14% = 34.2” with the 25” mono.
18” mono on 30oz Copper - 27” + 14% = 30.78” with the 25” mono
18” mono on Aluminium Drink Can – 41” + 14% = 46.74” with the 25” mono.

Gary.


Title: Re: How big would you go on search coils?
Post by: Dontbstme on Friday February 22 2019 16:53:31 AEDT PM
  
  
Hi Gary. Have you checked what is the exact increase of depth from 18" to 25" mono.?


On a 95-gram gold nugget the 25” mono produced only 6.25% extra increase of depth than the 18” mono.



This one is odd! The response to all other targets is very much as expected, but this one? Weird.
It will be interesting to see if by this rule you get to test a 6" mono (roughly 4 times smaller than the 25") what will come out of it. On small targets the differences will be less than double, but on big ones should be about 100%.


Title: Re: How big would you go on search coils?
Post by: GARY on Saturday February 23 2019 09:46:18 AEDT AM
  

This one is odd! The response to all other targets is very much as expected, but this one? Weird.


All that I can put it down to is that particular 95-gram nugget is owned by a friend which is different in that it has a jagged & porous type surface area compared to all other test targets having a solid type surface area.

Gary.