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I have a custom 12" coil (7/8" wide). Can anybody point me toward a good cover? Note I have

found many covers online but very little in the 12" range.

I am posting a pix of my new PI detector. I bought this in kit form and initial testing looks good.

I am in the process of designing a large coil (4' diameter range) to drag behind my ATV.

Thanks for any help and good hunting.


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Hi Sundownr,

Can you provide a link to more information on the PI kit. I've been looking into getting a PI machine and building a coil sled also, however, the cost of a used Minelab has been prohibitive for me in this economy. Also, any info/tips on how to build a coil sled would be appreciated too. ;)


Dale R.

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Hi Sundowner,

It looks like you built the Chemelec metal detector. Since I am not familiar on the exact coil you built it is hard to try to recommend a coil "cover". Did you try looking on Bill Hay's parts list of coil housings? He may have one that might work.

Here is a link to Bill's housings he makes.


If there is not a housing that will work, you may have to simply find something that might work.

As a last resort, you may try contacting another guy who is making his own coil housings. Here is his site.



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Hi Dale,

There are several projects out there that can be built. Information on many of those projects can be found on the Geotech forum. Here is a link to the forum. Just drop down to the project list and read up on some of them.


You might want to read more from this forum since a lot of people have built various PI detectors that are not on the project list. Also, there is a for sale forum at the Geotech site where you might find a working unit that someone wants to sell.

Personally, my preference is the Hammerhead project. It seems to work well and should work for your basic project.

One final note, the TDI or almost any Eric Foster PI can be used for what you want to do since it is quite easy to build a working coil for them.

Keep in mind that most meteorites found are stony types and a large coil will have a difficult time detecting them. The large coil is mainly used for finding very large deep iron meteorites.


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How about Rhino bed liner or equal? I have used this stuff on VLF coils and it works great!

I have heard that any insulative material on a PI coil will reduce sensitivity. I heard somewhere to only use silk tape to keep the coil covers on and not black electrical tape, as the black tape will affect the performance.

What say ye? Will spray on bed liner or tool dip reduce sensitivity on a P.I. coil?

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Hi Bob,

I personally have not tried the bed liner spray material on any of my coils but I will when I get time. In fact, I have a quart can of the Dupli-Color bed coating that I hope to try soon. Keep in mind I use Eric Foster designed PI's. I won't comment on what might cause problems with ML detectors, so I will let others comment on using this type of coating on coils used on ML machines.

Now, I don't expect to run into any problems using the liner material on any of my coils. Generally, the key to whether any coating will have an impact on the detectors I use is whether the coating is conductive or not. If it isn't conductive, it is highly unlikely it will cause any problems.

I have also heard the tale about not using black electrical tape on coils to hold the cover on. To be honest, when testing a new designed coil, I will often hold the coil halves together using this type of tape and so far, I haven't experienced any negative effects nor do I expect to experience any problems. One should also realize common black electrical tape is used to insulate wiring so it can't be conductive and work properly. Most of this tape is rated at 600V or greater, so the rating is higher than any voltage used on most PI designs. As such, I can see no reason it should have any negative effects.

Now, for those unfamiliar with all the different types of electrical tape available, there is a special high voltage tape that is conductive and as such, if it is used it may have an effect, especially if too much is used. This tape is used on high voltage connections at times to eliminate corona problems. However, this type of tape is nothing like what is normally purchased in most stores. Also, one can readily measure the low resistance of this tape with a simple meter.

So, if you are using this type of truck bed coating on coils now and are not experiencing problems, I wouldn't worry. Simply check the coating with an ohmmeter to be sure though. If you get no reading, then it should be fine.

One thing else I will mention is I read somewhere that a person used JB weld to patch a coil. Some of this type of epoxy contains conductive metallic particles. I personally wouldn't use that type of epoxy on coils. I would use another type of epoxy or patch a coil using the more common method of using a slurry of the same material the housing is made of. This will give a better seal that actually bonds such that it becomes part of the original housing. Most coil housings are made of ABS plastic. Dissolving small pieces of ABS plastic in MEK or acetone will create a slurry or paste that can be used to fix about anything wrong with a coil housing including gluing a coil ear back on.

This ABS slurry is what is normally used to seal the halves of most coil housing in use today.


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My apologies for not answering sooner and thanks for the comments.

Yes... this is a chemelec kit located at ===> http://www3.telus.ne...Metal/Metal.htm

Gary, the design engineer, is knowledgeable and easy to deal with. Note it does take some electronic experience to build this kit.

Here is a pix of a coil I bought from Gary... he winds good coils. II will sell this one at cost ($35.00). as I decided to build my own coils.

flat radial coil

nom od = 12 inches id = 10.3 inches

26 turn #20.5 awg

inductance 415.7 uh

dc ohms = .888

Q = 2.82 @ 1 khz

free air resonance = 1.67 mhz

interwire capacitance = 20.9 pf

Have a great day.


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