Aftermarket Carbon Fiber Shaft question

[nagant]

Running smooth so far but will check it out, thanks. Yeah i caught some fibers under my nail, before i deburred the holes. High speed but not to much pressure. Could you tell me what kind of epoxy and how do you thin it? thanks.

 

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[CharlesUpstateNY]

Running smooth so far but will check it out, thanks. Yeah i caught some fibers under my nail, before i deburred the holes. High speed but not to much pressure. Could you tell me what kind of epoxy and how do you thin it? thanks.

My epoxy is already quite thin, but you could super glue, Minwax Polycrylic, anything to soak and secure the loose fibers. Being careful not to dribble it down inside the tube and gum up the works.

Here's the thing about motion detectors, you can position a metal object (or piece of carbon fiber tube) near the coil, even tape a small metal object right on top of the coil and the machine will still appear to be working properly so long as the object does not move relative to the coil. But if you look at the coil on an oscilloscope you will see the object has loaded up and is distorting the receive winding with a signal. Normally the receive winding is a flat line, zero signal.

Max Depth - I said MAX depth, if you are looking for the absolute max depth from a DD coil its helpful to know how a DD coil works. DD coils are balanced, okay what does that even mean. All it means is that if you measure the coil on an oscilloscope there will be ZERO signal on the receive winding, nothing, a flat line.

The transmit winding in the coil is BLASTING out a huge signal that dwarfs any target signal by some magnitude. So why isn't the receive winding detecting that huge signal? Because the coil has been balanced to null that signal out. If the coil is even slightly out of balance though you can actually see the transmit signal being detecting by the receive winding, it no longer a flatline, the coil is out of balance an no longer functions at peak performance.

How do they balance a DD coil? The overlap the two windings down the center of the coil. Turns out in electronics if you overlap the transmit and receive windings just so, precisely, not too much or too little the receive winding will flatline and not detect any of the signal being blasted out by the transmit winding. Just a tiny nudge hair out of balance and the receive winding detects the transmit signal. The farther out of balance the coil is the more transmit signal the receive winding detects.

With a DD coil in perfect balance, the receive winding flatlined, its disturbing this balance, upsetting the balance by moving a conductive target near the coil that produces the target signal. It doesn't take much to disturb this balance, its extremely touchy. At the max depths the machine is capable of this disturbance is barely a warble, just a little wiggle on the receive winding. It may not even move the TID indicator on the machine. It may not even give the faintest of a tone blip except for every other swing or so. You won't know what the target is really, you just know something has disturbed the coil's balance. On a signal that ridiculously weak what I look for is a pattern of behavior over multiple swings. If its not moving the TID indicator but once every 3-4 swings I look to see if when it does, is it landing consistently in the same general TID area. Is the tone NOT iron. This tells me okay, there is a metal target down there, its not iron, I have no clue what it is because I'm at the very limit of what the machine can even detect, but I know for sure there is something down there disturbing the coils balance.

How extreme can get this? The worst ever deep signal I ever dug, a TID that only hit every several swings, that ID'd around nickel, a tone that wasn't even a tone, more like a warble of the threshold, but consistent over several swings. There were 3 of these things about a foot apart all doing the same thing. Incredibly they were three Spanish 8 reales a big huge silver coin almost the size of a silver dollar. I was stunned a large silver coin like that would produce a signal so ridiculously poor as that, with a TID that far off from silver. Nickel really? No there's more, we dug a hole about 2 foot wide and stuck a coil down in the hole then they were screaming silver. We kept digging, and digging, for hours until the incoming tide chased us off and recovered over 40 Spanish 8 reales from that one hole.

When they were replenishing an east coast beach they ran the giant dredge over the top of a 1700's shipwreck and pumped all the coins up onto the beach. As this loose sand began washing back into the ocean during storms these coins would come spilling out. Sometimes only 1 here and there, sometimes several, in this case it dumped a pile of coins out in that one spot. 40 is nothing I have heard some guys have dug over 100 at times.

Here are two 8 reales still encrusted in a chunk of the ship and sea shells.

 

[nagant]

Great information and thank you, what find too! I got 13 inches between top of coil and bottom of C/F tube, on my tesoro's it's 14 and a half inches. Any big interference diff between carbon and aluminum? Gotta be shorter users with it at the collapsed length that would bring the outer tube closer? No biggie cutting 2 inches off, thanks again.

 

[CharlesUpstateNY]

Great information and thank you, what find too! I got 13 inches between top of coil and bottom of C/F tube, on my tesoro's it's 14 and a half inches. Any big interference diff between carbon and aluminum? Gotta be shorter users with it at the collapsed length that would bring the outer tube closer? No biggie cutting 2 inches off, thanks again.

13 inches isn't bad, remove the coil and wave the carbon fiber tube at the coil about 13 inches out and see if it picks it up. Aluminum is a lot more conductive/detectable than carbon fiber.

Here's how sensitive coils are, coils have to be encased in an antistatic shielding else they will false when touched. Even some anti static shielding spray paints (nickel based) are detectable. Typically carbon black shielding paint is used on coils, its conductive enough to get the job done but not so conductive that its detectable.

 

[metalhealth]

13 inches isn't bad, remove the coil and wave the carbon fiber tube at the coil about 13 inches out and see if it picks it up. Aluminum is a lot more conductive/detectable than carbon fiber.

Here's how sensitive coils are, coils have to be encased in an antistatic shielding else they will false when touched. Even some anti static shielding spray paints (nickel based) are detectable. Typically carbon black shielding paint is used on coils, its conductive enough to get the job done but not so conductive that its detectable.

What material would you recommend to use for the lower shaft if not cf or aluminum?

 

[CharlesUpstateNY]

What material would you recommend to use for the lower shaft if not cf or aluminum?

Historically the manufacturers have used fiberglass or plastic.

 

[vferrari]

Anderson uses CF lower with a 4 to 5 inch plastic standoff from the coil attachment point. A little shorter but similar to what you are showing in your shop photo above.

 

[CharlesUpstateNY]

Anderson uses CF lower with a 4 to 5 inch plastic standoff from the coil attachment point. A little shorter but similar to what you are showing in your shop photo above.

Ditto for the Explore SE Pro lower.

 

[nagant]

Mine works fine and actually i needed to go one hole longer when i got out in the real world today. I'd tape everything to a stick before going back to my old unit.