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Oh and one more thing…the 1/2" X 1/2" square of AL weighs 0.5 grain and the 1/4" X 1/4" square of AL weighs 0.125 grain so there is more AL mass in the 0.7 grain Al slug than the other two.
Dan
Dan
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Re Post #223, yes more like real world test results, thanks.Comment
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Filling out the Racetrack Coil profile.
Chance PI Racetrack Coil Build Details
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To continue from where I left off with photo of the coil wound on its Lexan form in posts 215 & 216 of this thread:
Now it is time to fill out the coil profile using 3/8" polyethylene 'Backer Rod' and some 1/8" thick polyethylene sheet. These materials must be trimmed to shape and a razor blade works great. For the rod I made a special tool from a piece of 3/8" ID steel tube. A series of 4 steps each about 1/2" long were cut into the side of the tube at depths equal to 1/2, 5/8, 3/4, & 7/8 of the thickness of the 3/8" backer rod. These steps are used as a cutting guide for the razor blade to remove a consistent amount of material while creating a flat surface on the rod. See photos below.
The tool usage is pretty self explanatory from the photos.
The first step in filling out the profile is to attach 4 pieces of trimmed Rod with super glue to the parallel insides of the coil form. I trimmed the rod 1/8" thicker than the winding thickness on one side of the coil. See photo below.
The photo shows all 4 pieces glued to the form. More later on filling out the inner and outer perimeters.
DanComment
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It's been a bit longer than I thought it would take to put out this next sequence of filling out the profile of the racetrack coil using polyethylene backer rod and 1/8" thick PE foam sheet. The attached pictures show the details of the process. The intent is to protect the windings from crushing and to provide structure for the adhesive cloth tape over wrap. Paper hospital tape is used to hold the foam pieces in place where there was not enough free space on the coil form for super glue attachment. Then paper tape was wound around the foam profile bundle at about 1 1/2" spacing to keep it in position.
Dan
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looks like a lot of work, wowComment
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More work than a bunch wound coil for sure but the result is a very fast, self shielding coil with very low capacitance and high sensitivity. Since there is no separate shield layer all that fuss and work is eliminated. In my opinion a great coil is at least 50% of a detectors performance and I think it is worth the extra effort. In the end it really is not as difficult to do as it seems.
Regards,
Dan
Next posting will be the cloth tape over wrap in preparation for the fiberglass armor coating!Comment
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The pictures attached are of the cloth hospital tape overwrap. It is important that the tape tension does not distort the profile. This tape layer is to provide a barrier to resin getting to the windings. The tape is applied with about a 50% overlap.
Ready for fiberglass!
DanComment
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i have some juggling rings here from which i cut some coils body for basket coil
2-4€ one piece, but you have not to cut it in shape
one of them is a glow in the dark ringComment
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Will this frame work OK?
I cut this frame for a basket weave coil as described throughout this thread. It's 8" diameter. It's 5/8" wide and .090" thick Lexan. I scaled it from the template drawing also on this thread. I'm afraid it might be too narrow causing the wires to be too parallel after weaving. I hate to start over but I will if I have to. Any input would be appreciated.Comment
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It is narrower than I am doing on my coils. As outlined in my posts of this thread my coil forms are 1" to 1.050". This width is desirable because as you point out the wires are not as parallel as with the original Russian design that they were constrained by trying to fit it into an existing housing. Also they used magnet wire and this all leads to higher capacitance and a slower coil. All this said, I'd wind your form with 24 awg 600 volt PTFE (teflon) insulated stranded wire and see how it performs for you. The loss in speed may be insignificant if you are not trying to sample below 10us in search of very small gold nuggets of about 5 grain size.
Regards,
DanComment
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--------------------Originally posted by baum7154 View Post
I'd like to clarify, if it is not already apparent to all, that even though this thread is titled 'Chance PI Coil' that these coils, weather round or 'racetrack' are just fast mono coils and are useful on any PI detector and should be a significant improvement over traditional 'bunch wound' coils at very short sample delays for searching out small gold etc.
DanComment
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Thanks again Dan!
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Juggling Ring
Thats a good idea B1Comment
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---------------------------------------Originally posted by grandpastar View Post
How deep are your slots in the coil form?Comment
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5/16".Comment
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