Conductive Carbon Fiber Lower Rods

[Hydan]

Is there a solution or way to solve the problem, or is there anything temporary? We want to benefit from the device to the maximum extent and increase the sensitivity

 

 

 

[Steve Herschbach]

3 hours ago, Hydan said:

Is there a solution or way to solve the problem, or is there anything temporary? We want to benefit from the device to the maximum extent and increase the sensitivity

This is generally only an issue for nugget hunters running the small coil at extreme sensitivity levels. most users will never notice it. Simply knowing about it and minimizing coil movement relative to the rod is a solution. For me it’s an annoyance, not a reason why you can’t use your detector and get good performance out of it.

[HardPack]

I use three different VLF for gold prospecting, the SMF MInelab EQX900, the SMF Nokta Legend and the SF Makro Gold Chaser. Both the SMF VLF MD have carbon fiber lower shafts, the Gold Chaser does not. On hillsides the coil angle in relation to the lower shaft is constantly changed to keep the coil tight to the ground. While scrubbing the ground any coil knock with either the Legend or EQX900 against any object causes the coil to vibrate. This vibration of the coil, think of a rapid pendulum, in relation to a carbon fiber lower shaft yields a signal tone. On highly mineralized ground the TID range is depressed especially for smaller gold. Coil knock tones, hot rocks, cold rocks, bird shot, tacks, small gold tones all fall within this narrow tight TID range. Long story short the old SF Gold Chaser and its non carbon fiber lower shaft wins the day every day except when the PI shows up. I have a Nokta Simplex plastic lower shaft ordered for the Legend, hopefully it fits. I have yet to find a non-carbon fiber replacement shaft for the EQX 900 11/16” (17mm) od x 22” lower shaft. I suspect the EQX 900 lower carbon fiber shaft may explain why the Coiltek Nox 10x6 has to operated at sensitivity settings below 10. Thanks Gerry for connecting the dots.

[steveg]

Hi all.

Looks like lots of posts in this thread got lost, that provided much more of the "back story," but I'll give an update here.

I will be able to offer a non-conductive lower rod, in the near future, for the Minelab Manticore, and Minelab Equinox 700/900.

There are two avenues I am pursuing...

1.  A lower rod made from a 100% Kevlar tube.  Kevlar is non-conductive, and I have spoken with one of my carbon-fiber tube suppliers who has confirmed that they can make a 100% Kevlar tube.  They will be sending me a couple of samples, in a red/black color pattern (that I will attach, below).  I need to ensure that the tubes are "stiff enough" (high-modulus), and strong enough at the necessary diameter/wall thickness, to do a good job.  I am fairly confident that the tube will meet the needs/specs for this application.  

2.  A lower rod where the top half is carbon fiber, but the lowest ~12" would be plastic (Delrin).  The smaller end of the Delrin "adapter," or "extension" would epoxy into the carbon tube.  Meanwhile, the Manticore (or Equinox 700/900) clevis/yoke would be epoxied into the larger end of the "extension."  I will attach a CAD drawing of my design for this plastic "extension."  This would be the "fallback" plan, in the event that the Kevlar tube proves not to be feasible for whatever reason.

Both of these options will require a higher cost than the current Manticore carbon-fiber lower rods I offer.  Kevlar tubes are a good bit more expensive than carbon fiber, though I'm waiting for pricing information from my supplier to see just how much more expensive they are.  Meanwhile, the plastic extensions would also be expensive, since they would not be injection molded, but instead would be CNC-milled individually, from a Delrin plastic "blank," which is an expensive means of production.  So, one consideration is that I will need to see which option -- the Kevlar tube, or the combination carbon-fiber tube plus Delrin "extension" -- is more cost-effective.  I prefer the Kevlar alternative, if possible, even if a bit more expensive overall, as it would be a much lighter solution (perhaps lighter even than carbon fiber, as I understand it).

I will attach pictures of the plastic extension I have designed, and the Kevlar color pattern I'm planning to start with (though it could be changed to another color).

Thanks all.

Steve

[Hydan]

What is the expected cost in the future?

 

[steveg]

Hydan,

I won't know about pricing, until I get price quotes back from my suppliers on the cost of the Kevlar tubes, and the cost of the plastic extension (assuming I end up having to go that route, instead of the Kevlar tube option).  

Current cost of a carbon lower rod for the Manticore is $75 plus shipping.  I will keep the price as low as I reasonably can, depending upon the cost of the materials.  

Thanks!

Steve

[RobNC]

I'm wondering WHY carbon fiber on these rods is conductive. I just tested my Legend and can confirm it is indeed sparking off with a pointer like others have mentioned.

The bigger concern is how much extra noise is that introducing to the equation? I know the coil wires are covered and supposedly shielded but one can't help but think that conductive carbon fiber is just drawing in all kinds of crap in the environment like a big antenna. Gee this puts a whole new spin on why a lot of new detectors are seemingly more susceptible to EMI and RFI. Never would have thought the carbon shafts were conductive. Thanks for pointing this out.

[steveg]

Rob --

Carbon shafts are NOT "acting like antennas" and causing "EMI interference."  Please read the portion of the thread where I shared the information from Tom Dankowski...

Newer detectors are more susceptible to EMI in some cases, but NOT due to the carbon-fiber shafts.  It is due to the fact that the newer machines are designed to be high-sensitivity, "hot" units, and as such -- with manufactureres trying to push these machines to their maximum limits in terms of detecting deep targets, and small targets -- susceptibility it EMI is a side effect of the highly sensitive modern detector designs.  

Unless a coil is "in motion" relative to the shaft, or vice versa (which is not usually the case), the carbon shaft is not detected by the detector.  Meanwhile, the effect of the (stationary, relative to the coil) carbon-fiber lower rod on the electromagnetic field surrounding the coil is minimal, and the effects on detecting an in-ground target negligible at most, i.e. essentially a non-issue, per the engineers who do the design and testing.

This thread is primarily discussing a VERY SPECIFIC effect during target recovery of very small gold, where a coil -- bent flat against the shaft, and is being bumped/moved by running a handful of dirt on top of the coil -- can momentarily "report" on the presence of the carbon fiber as the coil is slightly in motion relative to the shaft, while the coil is being moved/bumped.  Beyond that, all of the available evidence/testing suggests that carbon-fiber is NOT detrimental to detector performance on in-ground targets.    

Steve

[phrunt]

You can transmit electricity through carbon fibre.

It makes a good radio antenna too, so it receives a signal well.  I should do a video how good some carbon tube works as an antenna for FM radio.