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Ongoing Equinox Coil Ear Breakage Issue


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I was wondering what you folks think about the coil ear breakage issue that continues to plague Minelab with coils for the Equinox.  I have several friends who have had the ears break on the 15" coil and have seen other users suffer this same problem with the stock coil.  This past Sunday I had the opportunity to use the 15" coil at the beach and I loved it.  However, the coil ear problem has me a bit leery.  Even the aftermarket coil stiffeners don't seem to help and for all I know they may actually contribute to the problem.  From what I have seen breakage occurs in two spots:  1.  The top of the "loop" where the coil nut and bolt are attached and 2. At the base.  I also wonder if since these ears are thin that coil bolt over or under-tightening could be the culprit,

It seems that there is a defect in this coil ear design that Minelab should be addressing either by an exchange program with a redesigned  coil or an extension of the warranty on the coil.

Thoughts?

 

Bill (S. CA)

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4 minutes ago, Bill (S. CA) said:

I was wondering what you folks think about the coil ear breakage issue that continues to plague Minelab with coils for the Equinox.

Coil support epoxied to the coil and ears. Then added 3/16" epoxied supports to each side of the coil.  Never to break again! 

 

  

coil 2.jpg

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As an engineer, I've given this some thought and closely examined my coil. And saw the cracks, saw them get bigger, then one ear broke. Mine broke at the bottom, seemingly the most common failure mode.

I think the problem is this:
The teardrop rubber washers should protrude above the clevis recess they sit in, this includes when the bolt is tightened. This is the problem. The washers get squashed until the coil ears touch the clevis, plastic on plastic. This does two things: it allows the coil ears to bend inwards more than they were designed for, and it allows wear of the plastic when the coil angle is adjusted, such as when it's packed away flat. Abrasive dirt can also get into this exposed area, worsening the wear. This plastic wear then allows the coil bolt to be tightened further, bending the ears in even more. Repeat this, and the ears get grooves worn in them, the clevis gets narrower. I recommend you take a look at your own coil ears inner faces. If there's a circular wear groove, you're heading for problems.

The 'solution' I have tried is to insert thin plastic shims behind the rubber washers, to space them out 'fatter' , so the coil ears tighten on the washer, not the clevis body, and they don't get bent inwards so much. Shim plastic is readily salvagable from packaging, household items. Thicknesses around 0.2 mm ( 8 thou ) seem a good starting point, use the same thickness under both washers. Scissors and a sharp craft knife will be enough to cut them out. Use the rubber washers as a template.

---------

The second failure I've seen is cracks running from the ear hole out to the edge, often in multiple places. This is caused by improper moulding. The 8mm hole is moulded into the ear, so the liquid plastic has to flow around some 'pin' in the mould, and then join up solidly on the other side. This creates a weak point, when cooling plastic doesn't fully merge.
ML should consider moulding the ears without holes, then drill the hole afterwards as a seperate process. Ideally the hole should be reamed, to give a clean bore that will be resistant to crack formation.

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The solution to ears cracking at the bottom is probably to have taller ears, so the flexing caused by bolt-tightening doesn't cause stress concentration in one small zone. Larger ears would let more/all of the rubber teardrop washer be compressed, instead of just the 'round' part. The tip of the teardrop is further away from the pivot point ( the bolt hole) so it's friction contribution would help resist 'coil-flop' better than the current arrangement.

EarShim7478.jpg

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"So that means the Detect-ED things likely work, as they're there fixing the exact problem you describe"
It certainly looks like that's one part of their solution. I've not seen them in the flesh, of course, so they may be softer ( or harder ) rubber blends, with different friction levels. If less force from the bolt is needed, to achieve the same resistance to clevis movement, that could be useful.

"Coil ears don’t break... people break coil ears. Seems like nearly all the breakage reports are from surf users."

Few people detect surf here in the UK. It's mostly inland, though crop stubble and grass can create a coil side-load. Most people report the ear(s) broke when not in use, the EQX was taken from storage/ a carrying bag etc and it was found broken when the machine was assembled. That was how mine failed. Simply putting the ears under strain continuously for months is enough to cause failure.

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Minelab equinox is a fantastic machine the market is pushing for giving hunters all the bells whistles with there new products hopefully minelab keep giving us upgrades with software and addressing probs /you get a lot more bang for your buck these days than just couple of years ago /maybe the treasure is in the hunt and  the journey the tools just keep getting better

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My coil ears broke on a high school soccer field this summer.  I had a coil ear stiffener attached - didn't help at all.  I don't use it anymore.  Replacement coil took about a week - kudos to Ft Bedford Minelab repair depot team.  Both ears broke at the base and the coil just fell off, dangling by the cable.

I spoke with John at Ft Bedford I asked if anyone knew what was causing the problem and how aware Minelab was of the problem.  John said he felt over tightening of the coil bolt appeared to stress the coil ears causing them to break.  He also said Minelab was very much aware of the problem.  The replacement coil came with the washers, coil bolt and coil cover.  I keep the coil bolt looser now - so far, so good.

The 800 is going swimming tomorrow - we'll see how that goes 🤥

Coil ears, drowned control pods and the annoying weak sound pinpointing issue.  Will these problems ever be remedied?

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16 hours ago, PimentoUK said:

As an engineer, I've given this some thought and closely examined my coil. And saw the cracks, saw them get bigger, then one ear broke. Mine broke at the bottom, seemingly the most common failure mode.

I think the problem is this:
The teardrop rubber washers should protrude above the clevis recess they sit in, this includes when the bolt is tightened. This is the problem. The washers get squashed until the coil ears touch the clevis, plastic on plastic. This does two things: it allows the coil ears to bend inwards more than they were designed for, and it allows wear of the plastic when the coil angle is adjusted, such as when it's packed away flat. Abrasive dirt can also get into this exposed area, worsening the wear. This plastic wear then allows the coil bolt to be tightened further, bending the ears in even more. Repeat this, and the ears get grooves worn in them, the clevis gets narrower. I recommend you take a look at your own coil ears inner faces. If there's a circular wear groove, you're heading for problems.

The 'solution' I have tried is to insert thin plastic shims behind the rubber washers, to space them out 'fatter' , so the coil ears tighten on the washer, not the clevis body, and they don't get bent inwards so much. Shim plastic is readily salvagable from packaging, household items. Thicknesses around 0.2 mm ( 8 thou ) seem a good starting point, use the same thickness under both washers. Scissors and a sharp craft knife will be enough to cut them out. Use the rubber washers as a template.

---------

The second failure I've seen is cracks running from the ear hole out to the edge, often in multiple places. This is caused by improper moulding. The 8mm hole is moulded into the ear, so the liquid plastic has to flow around some 'pin' in the mould, and then join up solidly on the other side. This creates a weak point, when cooling plastic doesn't fully merge.
ML should consider moulding the ears without holes, then drill the hole afterwards as a seperate process. Ideally the hole should be reamed, to give a clean bore that will be resistant to crack formation.

----------

The solution to ears cracking at the bottom is probably to have taller ears, so the flexing caused by bolt-tightening doesn't cause stress concentration in one small zone. Larger ears would let more/all of the rubber teardrop washer be compressed, instead of just the 'round' part. The tip of the teardrop is further away from the pivot point ( the bolt hole) so it's friction contribution would help resist 'coil-flop' better than the current arrangement.

Pimento,

Very nice reply to my post.  I was hoping for an engineer's take on this.  Interesting that you address the cause of both types of cracking.  My initial thoughts were that bolt over-tightening was the main culprit.  If in fact, outside of molding defects, the washers are the issue I'm a little surprised that Minelab hasn't made thicker washers for Equinox owners.  Seems to me it would be a very inexpensive solution rather then having to swap out coils at the rate they are. 

I like your shim plastic solution, very nice DIY idea.  Do you feel that the Detect-Ed Coil Savers would do the same thing?

 

Bill (S. CA)

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"Do you feel that the Detect-Ed Coil Savers would do the same thing?"

The coil-savers seem to offer little adjustability, that's likely their weak point. And it only takes a fraction of a millimetre to make the difference. Ed's choice of rubber compounds is good, but fine-tuning of the mechanical aspect is also needed, I think. [ if he has a punch tool made up, it may also be useable for teardrop shim manufacture ]

I'm thinking that if a softer rubber was used, it would give greater friction, but it would also compress more, possibly resulting in the plastic-plastic contact. Perhaps have a half-thickness washer, backed by a non-compressible spacer?
The stock rubbers supplied by ML seem adequate, and resourceful folks can source plastic sheet from a wide variety of places around the home, which is why I thought that was the simplest solution.

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