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DD COILS ON THE WAY

A

Anonymous

Guest
Hi All,
11in DD coils are now in production for the Goldquest SS v2. Here are three all balanced up and awaiting potting. They will be headed across the pond to Mr Bill, early next week.
The coils run easily at 10uS delay, are fully shielded with independant shields, use a cable whose braid is not detected by the coil and are waterproofed for submersion.
The low ground noise obtained with the DD configuration will enable the Goldquest to perform in the more iron mineralised areas; helped, if need be, by the double filter and variable SAT control.
Eric.
 
Hi Charles,
No, I buy them in. I used to have a vac form machine, but I don't have room for it now. I prefer to outsource mechanical parts as much as possible.
Eric.
 
Hi Eric,
To find the mechanical parts like coil shell and handles for a metal detector is the biggest problem. Can you tell us where you can buy the coil shells and the handles? Is the DD coil shell from Hayes Electronics? Another question to your posted picture. Why is the coil on the right side different in assembling than to the other two (the overlapping of the D-coils)? Has it a reason?
Chris
 
Hi Chris,
As a manufacturer, I have special arrangements with a number of suppliers for mechanical parts, both off the shelf and custom made. Some of the stock parts have to be modified in house to suit my detectors, so my suppliers list has to remain confidential to some degree.
If you rotate the right hand coil through 180 degrees, then it is correct <img src="/metal/html/smile.gif" border=0 width=15 height=15 alt=":)"> , but then the connections are on the opposite side <img src="/metal/html/frown.gif" border=0 width=15 height=15 alt=":("> . It doesn't matter which coil underlaps or overlaps, as all is symmetrical, or nearly so. One designer was going to try winding a pair of DD coils like Chinese rings; one interlocking the other. This would swap the overlap on one end of the coil assembly. Would there be any detectable difference <img src="/metal/html/confused.gif" border=0 width=15 height=22 alt=":?">
Eric.
 
Hi Eric,
thanks for your reply. I can understand that your supplier list is confidential. No problem. I was looking for a nice handle like the professional one. The "DIY" handle I made (see picture) is from a 3/4 inch PVC water pipe. The PVC pipe is to flexible. If you swing the coil the search head is shaking to much. Maybe I'll find a better "DIY" solution.
Has anyone a better "DIY" solution for a handle? Please post your pictures.
Chris
 
Hi Chris,
Looks nice. I tried pvc pipe some years ago, but you need to find a thick wall (high pressure) variety to be rigid enough. Fibre glass tubing is rigid enough and it is possible to find two diameters that telescope into one another from some suppliers.
Have a look at Whites website under accessories. They do various rods etc.
Eric.
 
Have you tried molding fiberglass? A mold is easy enough to carve and laying the fiberglass is pretty straight forward. There are books about it.
The sovereign elite arm cup is a two piece unit that clamps onto the rod. And so it the SS one from detector pro. That may do it for you too.
bing
 
Hi Chris,
If you made the loop yourself, where did you score the shell?
I get my wife to check for aluminium walking sticks whenever shes in opportunity or second hand shops. She found a real nice one last year, it's a _,--- shape, can't remember how you decribe it, anyway it has a good wrist cuff and sturdy handgrip, I needed to exchange the lower adjustable rod for a fiberglass one. And as you already know, Hays has the lower connectors.
I like the shafts and fittings Eric uses, it would be good to know of a consistent source of mechanical components. I must check out Whites too.
Cheers
Kev.
 
Here are two DD coils ready to go. The one on the right shows the final resin finish on the underside. This is protected by the removable cover, shown at the top. The complete coil, with cover attached, is shown topside up on the left.
Eric.
 
a spray in foam "space invading" compound that most hardware stores sell.
I have also used light wood dowling like balsa or oregon pine to stiffen the shaft. Works quite well without too much extra wieight.
Hard Nosed
 
I purchased some lightweight fiberglass tubing from this place, its not carbon fiber but its quite rigid and much lighter than pvc.
Like Eric said take note of the OD on the fiberglass tubing and ID on your aluminum upper shaft to match, though note the sizes include a +- tollerance so give yourself a little wiggle room.
 
Eric,
What product do you use to pot your coils? If you dont want to give the exact product, something suitable. Thanks,Joe
 
any coil I have seen is epoxy by Eric, these seem to have the same half shell covering and poured epoxy with flat surface finish on bottom.
 
Hi Joe and Don,
Yes, I use epoxy, but it is done in two stages. First is a specially formulated lightweight resin which fills about 3/4 of the shell. When this has cured, a hard wearing, denser resin is the final fill. The result is a strong waterproof coil which is also lightweight for its size. The resins are also selected so that they are not too brittle, to minimise the danger of cracks developing if accidentally dropped or hit on a rock while swinging.
There is more to making a good coil than is apparent from the external appearance <img src="/metal/html/glasses.gif" border=0 width=15 height=15 alt=":geek:">
Eric.
 
I just placed an order with the company below for their El Cast TS-100 Black, I'm going to give this a try.
There are hundreds of epoxy products out there, a good place to start looking is for black box type epoxy, the stuff developed for the DOD to encase their electronics from prying eyes.
Properties I consider important are low shrinkage, high shore D hardness, low viscosity, lower weight per fluid ounce, pot life, and cure time.
On a side note, think twice at least before doing business with www.epoxy.com.
 
To make a coil that looks as nice and performs as well or better than a factory coil is a whole bunch of work. If I had stuck to golf instead of messing around with custom coils I'd be on tour by now given the effort. <img src="/metal/html/biggrin.gif" border=0 width=15 height=15 alt=":D">
 
Eric,
I am looking at your DD coils at public libary.
The out side shield appears to have about a 1"
gap where coils over lap.Does the independent
shield around each turn have a gap at each turn or
does braid run the length of coil.
Frank.
 
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