Surf pi coil building

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Louis Kriedemann

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Surf pi coil building

  • on: June 22, 2014, 11:27 AM
For those who are building their own detectors and coils
Earlier in the week I started building a different type of coil for my pi called a flat spider coil. It is a timeous job and took a couple of days until such time that it can be handled.
The coil winder almost took as long to make as the coil ;D
it has an inner diameter of 22cm and outer of 23.5cm. I used 0.40 enameled wire. 23 turns. 280uH
these coil are known to have the lowest 'Q' (interwinding capacitance) of all coils and for that reason I gave it a try
Did a bit of comparative testing in the workshop this morning with my 10 inch round and the 9 inch spider.
Although these test dont mean too much right now I cant wait to built a housing for the spider and test it in the real world against the same coil on wet beach
                                                10"      spider
50c coin                                    20cm     22cm
3" nail                                       24          29
5mm 9ct ring                             21          25
2mm 18ct ring                           22          23
2mm silver ring                         21           22
5mm silver chain                       18          19
8mm 9ct ring                             24          26

the tests were all run with sensitivity at 5/10. at a higher sensitivity the depth would increase slightly

Paul van Heerden

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Re: Surf pi coil building

  • on: June 22, 2014, 05:35 PM
That is an interesting looking coil luuk. How did you make those spirals?
Paul

Louis Kriedemann

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Re: Surf pi coil building

  • on: June 22, 2014, 06:43 PM
Its quite a process to make the winder. (photo attached)
wood roundel with the circumference measured out(odd number only) and drilled 6mm holes all round, used 6mm wood dowels cut in sections to insert into each hole. used drinking straws cut up to fit over each dowel.
the coil is then wound, over/under repeatedly to the correct amount of turns.
when complete the coil get several coats of shellac over a couple of days to bind the windings.
then the dowels are removed and the coil is very carefully slid off the winder, more shellac and once dry and stable the straws are removed

Paul van Heerden

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  • Detecting Noob
  • Posts: 3104
  • Detector: Garrett ATPro, Cscope CS4PI
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Re: Surf pi coil building

  • on: June 22, 2014, 08:35 PM
Is shellac like nail polish?
Paul

Louis Kriedemann

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  • Posts: 583
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  • Detector: surf pi, Fisher CZ20, fisher f75 and Barracuda pi
  • Location: Vredenburg

Re: Surf pi coil building

  • on: June 23, 2014, 08:17 AM
Is shellac like nail polish?

shellac is a type of varnish. mostly used in the old days but you can still get it at some hardware stores
You can use anything as long as it will not damage the enamelling on the wire

Metal Detecting Forums South Africa

Re: Surf pi coil building
« Reply #4 on: June 23, 2014, 08:17 AM »