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X-terra S-shaft Modded For The Equinox

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I know there's a long and old thread discussing this topic and other Equinox ergonomics but I decided not to bury this post there.  In the last few months I've had some minor issues with the elbow on my swing arm ("tennis elbow" according to my doctor) but worse, recently I've been having wrist pain on the same arm.  I don't know if the latter is related to detecting but it reminded me of the above linked discussion (and others) about S- vs. straight-shafts.  I don't know if the mod I now describe is new.  (After 2 years in the users' hands I would have thought not, but don't recall it on this site, anyway.)  Here's a picture of the almost finished garage mod:


In a nutshell, I've replaced the two lower sections of the Equinox shaft with the two lower sections of the Minelab X-Terra shaft.  Now I'll start at the bottom and work my way up, describing the differences.

Coil to shaft attachment:  Surprisingly (because it seems like Minelab changes dimensions, etc. on every new detector) the gap between the ears is almost a perfect fit.  It seems to be slightly looser with this mod, but that may be simply due to wear on the gaskets.  I measured the shaft's widths and they are very close, possibly about 0.005 inches (~0.1 mm) different.  Different gaskets or just a metal or plastic shim could tighten things up, but for now I'm not going to do that.  Next is the screw/bolt and nut.  The X-Terra had a nominal 1/4 inch diamter bolt while the Eqx is larger, (I think it's 8 mm, slightly larger than the SAE 5/16 inch).  Again, until I find out otherwise I'm not going to be concerned about this as the smaller bolt goes through both parts just fine.

Lower shaft section composition:  The Eqx has a carbon fiber lower shaft section whereas the X-Terra has an aluminum shaft with a plastic extension/insert for the coil attachment section.  I did a quick test-garden check and the mod didn't appear to give any deterioration in performance.   5 in. deep penny and 6 in. deep US nickel, in moderately mineralized soil, I could turn gain down to 5 and still (barely) hear both in Park 1, recovery speed = 5, Iron Bias F2 = 5.  Again, at this point good enough for me.

Middle shaft section:  This is the S-section.  The smaller diameter of this part is why you can't use the Equinox's lower section -- its diameter is too large to mate with the X-Terra S-section.


Middle shaft section (X-Terra) to upper shaft section (Equinox) mating:  This is where things get a bit more complicated.  The O.D. of the X-Terra shafts is right at 3/4 (0.75) inch whereas the Equinox is ~0.78 in.  This 0.03 (~3/4 mm) difference is not acceptable as is.  I used 0.0015 in thick copper tape to build up the X-Terra shaft.  The tape's adhesive adds some thickness as well.  I needed 15 inch length of tape for a complete wrap to make up the difference.  (Note:  I'm going to add another equivalent wrap above the alignment pin as well, but as of now -- shown in the photo -- I only have the one wrap.)  Next, note that the X-Terra has two alignment pins compared to the single one for the Equinox.  Turns out they are 90 degrees out-of-phase.  In addition, the pin size (and thus hole diameter required) is different, this time slightly larger on the X-Terra.  I'm going to drill two opposing holes in the upper Equinox shaft.  Again it appears that the X-Terra was made to SAE dimensions and a 1/4 inch hole is the right size.  To make sure I don't get more hole than I need, and to avoid the sloppy 'triangular' hole that standard jobber drill bits tend to make in thin sheet metal, I've ordered a 1/4 inch reamer from Amazon for the job.

Weight difference:  The X-Terra lower sections and the attachement bolts & nuts are 80 g. (~2 2/3 oz. or ~0.2 lb) heavier than the equivalent Equinox pieces.  I assume this is due at least in part to the carbon fiber composition but the tubing (and other pieces) may also be contributing.

Potential concerns:  I start by pointing out that I'm not a beach/water hunter.  Apparently the drag, etc. in that form of detecting puts more mechanical stress on the connections and parts in general.  In particular, drilling two more holes for the alignment pins in the upper section shaft (which unfortunately are located right at the same location as the already present hole) will result in a weakening of the shaft there.   I don't think that will be an issue for me, but water hunters (who apparently prefer straight shafts anyway) could be scared away from this mod.  I suppose one might be able to buy a replacement upper section from Minelab....  Those holes are the only thing that keeps this mod from being purely 100% reversible and assuming they don't result in future breakage, I have the best of both worlds.  (Of course it helps to have an X-Terra sitting around collecting dust!)

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I know there's a long and old thread discussing this topic and other Equinox ergonomics but I decided not to bury this post there.  In the last few months I've had some minor issues with the elbow on

I agree Tom. I think what GB is saying is we do not see a need for a counterweight with either rod running the 6” coil. Nor I for the 11” coil on the straight shaft for just the reason you mention. Ju

Steve, the weight is an axle socket that weighs about a pound. I can probably get away with a little less at the end of shaft as the coil “floated” a little too much there as compared to the same sock

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I used the CTX for over 4 years but pain in my shoulder and tennis elbow had me thinking the Deus would have to make a comeback but I was never happy with that squeaky thing so when Minelab announced a new light weight detector I ordered one before I knew what it was.

more than happy with the equinox but I still found my shoulder unable to bear more than a couple of hours. Bought the proswing 45 harness and now I can swing all day

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GB_Amateur --

Nice job, on the mod!  

I would like to note that this (your arm and wrist pain) is almost definitely due to the nose-heaviness of the Equinox.  You have to use your wrist/arm to "counteract" the force of gravity pulling down on your coil, since there is no weight on the "other end" (butt end) of the shaft to assist you.  So, you end up doing all the work with your wrist and arm, fighting gravity in order to keep the coil "floating" above the ground.  Hence, fatigue/pain often results.

My way of addressing it, is to add counterweighting.  The proper amount of counterweight allows you to use gravity as an ally -- your hand and wrist are freed up to simply act as a "balancing point" or "fulcrum," as opposed to those muscles having to exert all that force to counter the effect of gravity on the coil.  The counterweight, acting in opposition to the coil weight, helps to "lift" the coil end of the shaft, meaning your hand/wrist/arm don't have to do all the work -- you use gravity as your "ally," instead of letting it be your "enemy."

The "s-bend" shaft will change which muscles you are using to keep the coil floating, and for some folks, using different muscles, helps.  In some cases though, it's still not a solution, as an S-bend shaft doesn't solve the underlying issue -- which is that the Equinox has all of its weight on the "coil end," and none at the "butt end," and therefore YOU have to counteract the force of gravity acting on the coil, using your wrist/arm/shoulder muscles.  It sounds like in your case, changing the muscles being used to counter the weight of the coil when using the S-shaft, has brought relief.  The muscles you are now using, are apparently more capable of applying the needed forces, and thus are not negatively affected (as were the muscles being used when you were running the straight shaft).  So, it sounds like you have creatively arrived at a solution that works for you -- which is of course the objective!  Well done; very nice job, on the mod! 


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3 hours ago, steveg said:

t sounds like in your case, changing the muscles being used to counter the weight of the coil when using the S-shaft, has brought relief.

Thanks, Steve.

Actually I haven't been able to use this modded detector.  The ground is semi-frozen in most of my hunting sites.  I still have to drill & ream the two holes (with one motion since they are on opposite sides of the tube/shaft) which I'll do Sunday when I'm at my friend's house for the Super Bowl.  (He has a drill press; I don't.)  Monday is supposed to be nice weather so I may go out and hope to find thawed ground.  Seems that thicker grass works as an insulator, although too thick and it keeps your coil too far away from the ground, or I end up pressing the coil hard into the grass which exacerbates the elbow & wrist problem!

But thanks to your suggestions I'll play around with adding counterweight.  Naively it seems counter-productive which is why I haven't tried it yet.  But as usual I need to be reminded that balance trumps weight.  Thanks, again.



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GB_Amateur --

I totally hear you, on the thick grass exacerbating the issue.  No doubt about that.  As I understand it, "tennis elbow" results from grip pressure, and obviously, just the machine being nose-heavy means you are gripping it tighter, as you fight to keep the coil "floating" above the ground (whereas, a fully balanced unit can be gripped with just your thumb and index finger -- it's amazing)!  But, the grip pressure issue is exacerbated EVEN MORESO, when you are fighting through thick grass; you will be gripping tighter as you try and force the coil through the grass -- and thus that "tennis elbow" issue can become irritated even more.

And yes, I hear you about the "counter-intuitiveness" of counterweighting.  The knee-jerk reaction is "I bought this machine because it is touted as being super-light; why would I want to turn around and add weight to it?!"  I totally get that.  But, think of it this way.  What if I asked you to carry two 2x4 boards, both four feet long.  One is dry, and weighs 3 pounds, the other is wet, and weighs 4 pounds.  Naturally, to carry either board for any appreciable amount of distance, what you'd tend to do is grab either board right at the center (i.e. where it is BALANCED), and then you'd carry it at your side, parallel to the ground.   As long as you are carrying it at the balance point (which is how you intuitively do it), you could carry either the 3-pound board, OR the four pounder, with little issue.  The extra pound of weight, between the 3-pound and 4-pound board, makes very little difference.  BUT -- try carrying EITHER the 3-pound OR the 4-pound board by holding it a foot from one end (i.e forcing the board to be imbalanced, and "nose-heavy" on one end), and see what happens!  Of course, the "imbalance" of the board thus causes carrying it to be quite a struggle, as one end of the board wants to tilt toward the ground, and you are fighting to keep the end of the board from dragging...

If the S-shaft doesn't fix the issue for you, counterweighting is your solution (or a harness, as Nig the Dig mentioned).


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Thinking about easy counterweight for the Minelab Equinox, I reaized that a paper roll of US clad dimes weighs right at 4 oz (1/4 lb) and fits inside the end of the shaft!  If you want to get the stock plastic endcap fully back on I think you need to use the lowest (farthest from shaft butt) location for the arm cup mounting.

A mnemonic rule of thumb:  US coinage (5 cent, clad 10 cent through half dollar) have very close to the same density as pure copper:  8.96 g/cm^3.  That's about 79% the density of pure lead (11.35 g/cm^3). 

Another one:  Pure tungsten and pure gold have almost identical densities (19.30 g/cm^3 and 19.32 g/cm^3 respectively).   You can buy tungsten weights but they aren't as cheap as lead, etc.


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I tried out my new configuration yesterday for a 3 hour hunt in a local park.  My first impression is that I haven't improved the situation (wrist stress & pain).  I subseqently tried to balance the torque around the grip (the 'fulcrum' as steveg notes) and that is way easier said in theory than done in practice.  Here is an experiment I did (using the S-shaft configuration) which shows how bad the problem is:Equinox_extension.thumb.JPG.62c2a7abed26665f54e992cf63f35dc4.JPG:

I added the (straight) middle section of the Equinox back into the system, but now inserted into the butt end of the detector shaft.  That adds 17.5 inches (44.5 cm) to the length of the shaft!  I then added weight at the tip (far) end, centered over the tightening nut, to see what it would take to balance the detector at the front edge of the control module mount (grip handle / fulcrum).  Result: 22 1/2 oz (640 g or 1.4 lb).  Total detector weight = 4.6 lb (2.1 kg).  I conclude that trying to get the weight (actually torque) balance to occur at the grip/handle is too ambitious of a goal for the Equinox.

One thing I made worse by swapping out the lowest section of the stock Eqx shaft is that, being made of carbon fiber and thus lighter, I added front-end torque when I replaced it with the heavier X-Terra 705 front shaft.  (Weight difference of 0.14 oz = 4.0 g.)  Further, I think the X-terra's lowest shaft extension weight isn't uniformly distrubuted since for it the plastic coil-mounting stem is more substantial than the one on the Eqx lowest shaft section.  However, we're talking ounces or grams (in-oz or cm-g of torque), so without doing a similar balancing act with the Eqx stock configuration I think it's safe to conclude balancing it about the handle mount point is equivalently impractical.

Having said all that, does adding weight to the butt end of the shaft lessen the torque on the human wrist?  Yes.



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GB_Amateur -- glad to see you experimenting!

A couple of things; at 17.5" long for your "extension," it should not have taken that much weight (22.5 oz.) to "balance."  So, my question is, what do you mean when you said "balance?"  Remember, to "balance" the machine does not mean that you put enough weight in the butt-end until the machine sits "flat" -- i.e. parallel to the ground; instead, you only need enough weight so that the coil "rises" and the butt-end "sinks" enough, such that the machine rests in DETECTING POSITION -- i.e. roughly the angle that you use when you swing the machine (angle meaning the angle between the shaft, and the ground).  And it takes much less weight to achieve "balance" that brings the shaft angle to "detecting angle," than it does to bring the shaft to "parallel to the ground" position.  Using a 17.5" extension, and using DETECTING ANGLE as your goal, it should require quite a bit less than 22.5 ounces (with 11" coil attached)..

I will also note that PERFECT balance (again -- meaning the machine "rests" at "detecting angle") is often not necessary, to achieve substantial improvement in comfort.  Remember, with NO counterweight, your wrist/hand/forearm are doing ALL the work, to keep the coil "floating."  BUT, with every ounce of counterweighting you add, you are REDUCING the amount of force you must apply, using your hand/wrist/arm muscles (i.e. increasing the degree to which you are allowing gravity to ASSIST you).  The number is different for everyone, but many of my customers find substantial relief at 12 oz. to 16 oz. -- and remember, that's with only a 4 1/2" extension.  If you used a 17.5" extension, that 12 oz. to 16 oz. number would be reduced substantially (maybe half?)

Just some thoughts...but I suspect you would need to use a lot less than 22.5 oz. of counterweighting, to feel a substantial improvement in your machine's "swingability."


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1 hour ago, steveg said:

So, my question is, what do you mean when you said "balance?"  Remember, to "balance" the machine does not mean that you put enough weight in the butt-end until the machine sits "flat" -- i.e. parallel to the ground; instead, you only need enough weight so that the coil "rises" and the butt-end "sinks" enough, such that the machine rests in DETECTING POSITION -- i.e. roughly the angle that you use when you swing the machine (angle meaning the angle between the shaft, and the ground).

Yes, I was balancing the shaft in a horizontal position.  Per your suggestion I put the detector at the correct angle for detecting.  It took right at 1 lb or ~450 g. mounted on the end of the 44.5 cm (17.5 in) extension.

FWIW, the difference is much more related to the fulcrum point than the shaft angle.  Previously I was balancing on the back side of the shaft at the lower intersection point of the handle and shaft.  This time I actually put my hand on the handle (normal detecting position) and balanced between the two middle fingers of my hand.

So I reduced the counterweight from 1.4 lb to 1.0 lb and the total weight from 4.6 lb to 4.2 lb.  (Coincidentally isn't this close to the weight of some of the popular White's VLF/IB detectors?)  However, to use this perfect balance with 1.0 lb counterweight, I still need that awkward very long shaft extension....

32 minutes ago, phrunt said:

Geez, you could poke someones eye out with that thing 🙂

Better said in one of my favorite movies! 


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GB_Amateur --

16 oz. sounds much more reasonable, for "complete" balance, at correct "detecting angle," when using such a long extension.  And yes, WHERE on the handle you use as your "balance point" does matter; beneath the handle, on the bottom of the shaft, requires more weight to balance than -- as you found -- at the mid point of the handle.

Finally, if you can find a way to use a shorter extension, but keep that same 16 oz., I'd be curious to hear your thoughts.  Again, that won't give you "PERFECT" balance, but for many of my customers, that's enough weight, in a 4 1/2" long counterweight attached to the butt-end of the shaft, to bring SUBSTANTIAL improvement...

And yes, you talked about the White's machines...I have never used one, but just looking at many of their units, I'd expect them to be much more balanced, and thus more ergonomically correct, than the Equinox, given that the "box" is mounted near the rear/butt-end of the shaft -- thus serving as effective "counterweighting."

The moral of the story is -- "lightweight" is good, but NOT at the expense of proper balance.  As such, given that we are using copper-filled coils, there is thus a limit there as to how light a coil can be made.  And therefore -- assuming proper balance is desired -- that also imposes a limit as to just how lightweight a machine can be (since the weight of that relatively heavy copper-filled coil MUST be "offset" at the opposite end of the shaft, if you wish to achieve a balanced unit).


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