Big Boys Hobbies

Equinox 15 inch ear stiffener problems

Lostandfound

Lostandfound

Full Member
Joined
Oct 22, 2009
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Location
Durham Ct
Has anybody tried using the ear stiffeners for a 15” inch equinox coil. I have tried one for the 15 inch coil and the stiffeners cracked after about 25 hours of use. Anyone else have this problem. They were made using a 3-D printer in and they’re just too fragile.
 
Depends on what they are printed in. For instance pla is weaker than petg or abs. The type of plastic makes a difference, if I had to guess I would say yours were pla if they were bought as it is cheaper but is the weakest plastic type. Was it a opaque color or translucent? Petg is usually translucent. Abs is opaque but is hard to print and most rarely use it as it is prone to shrinkage and warping.
 
beachrumbum said:
Depends on what they are printed in. For instance pla is weaker than petg or abs. The type of plastic makes a difference, if I had to guess I would say yours were pla if they were bought as it is cheaper but is the weakest plastic type. Was it a opaque color or translucent? Petg is usually translucent. Abs is opaque but is hard to print and most rarely use it as it is prone to shrinkage and warping.
Click to expand...

It seems like the orientation of an object when printing would create possible strong/weak points. I'm not an engineer, but it seems like the worst possible ways to print it would be sitting flat (the same way it sits when installed) or on one side. I think the strongest approach would be to print it on its nose or rear so the layers extend from the base up through the ears. If that makes sense.
 
ToySoldier said:
It seems like the orientation of an object when printing would create possible strong/weak points. I'm not an engineer, but it seems like the worst possible ways to print it would be sitting flat (the same way it sits when installed) or on one side. I think the strongest approach would be to print it on its nose or rear so the layers extend from the base up through the ears. If that makes sense.
Click to expand...

It makes perfect sense, this would be the best case scenario to print on its side so the layers absorb the stress instead of delaminating, often times prints are just oriented so they will print easily. Ie. With the flattest portion towards the bed surface. Otherwise support structures are needed and then have to be removed and could cause their own issues. Of course there is more to it such as temperature the part is being printed at and material quality which effect how well the layers bond. As far as absorbing water, if the part is printed in 100% infill, it should be solid if done correctly. When printing parts one can choose to use a lattice as the fill instead of solid, so the part would have a solid shell around a lattice. this helps save plastic and reduce print time. Mine was printed in 100% infill and of petg and has held up well for some time.
 
beachrumbum said:
Depends on what they are printed in. For instance pla is weaker than petg or abs. The type of plastic makes a difference, if I had to guess I would say yours were pla if they were bought as it is cheaper but is the weakest plastic type. Was it a opaque color or translucent? Petg is usually translucent. Abs is opaque but is hard to print and most rarely use it as it is prone to shrinkage and warping.
Click to expand...

I have to disagree. PLA is stronger (ultimate strength) than PETG. It also deforms less before it breaks, which is very important here, trying to prevent the coil's ears from breaking. PETG is more impact resistant, though, more "rubbery" if you will, and can handle higher temperatures, which makes it better for some applications.

Both absorb water, PETG is worse, but how that affects useful life, if at all, I couldn't say. I'd be interested to hear more anecdotal reports of which plastic holds up better in freshwater or seawater...

Print infill percent (how hollow the interior of the part is) directly affects strength, and print orientation are also very important. The direction of lamination (Z axis) is considerably weaker than the X or Y directions, in shear or tension. So yeah, Toysoldier nailed it, if printed with the base flat on the bed, with the "ears" upright, would make for weaker ears more likely to snap off.

And yeah, beachrumbum is right, print temperature and bed temperature can both contribute to stronger prints, as well as layer height and/or linewidth/layer height ratio, and a host of other factors, too.

And of course, the design of the stiffener is a big deal, too. I make mine so they grip the base of the coil for extra stability, and with beefy fillets holding the stiffener's ears to its base. Printed solid, and printed "nose-up" for the best ear strength.

Lostandfound, what kind of stiffener did you have that broke?

Link to pix of my prototype and V2. Current (V3) version has even more ear support.
https://metaldetectingforum.com/showthread.php?t=285729
 
The ear stiffener topic has been kicked around a few threads. Yes, the 3d printed ones on ebay that are really basic are no good. Best combo I've used, and still use is:

Double up detect-ed rubber grommets (I think it's 1red and 1 thin black) per side, just so the grommet sticks out a little. Takes the pressure off the upper tab.

Buy an ear stiffener that allows for the zip tie to be installed, like the one in the previous post. This strengthens the coil from all downward pressure.
 
TorqueMaster said:
I have to disagree. PLA is stronger (ultimate strength) than PETG. It also deforms less before it breaks, which is very important here, trying to prevent the coil's ears from breaking. PETG is more impact resistant, though, more "rubbery" if you will, and can handle higher temperatures, which makes it better for some applications.

Both absorb water, PETG is worse, but how that affects useful life, if at all, I couldn't say. I'd be interested to hear more anecdotal reports of which plastic holds up better in freshwater or seawater...

Print infill percent (how hollow the interior of the part is) directly affects strength, and print orientation are also very important. The direction of lamination (Z axis) is considerably weaker than the X or Y directions, in shear or tension. So yeah, Toysoldier nailed it, if printed with the base flat on the bed, with the "ears" upright, would make for weaker ears more likely to snap off.

And yeah, beachrumbum is right, print temperature and bed temperature can both contribute to stronger prints, as well as layer height and/or linewidth/layer height ratio, and a host of other factors, too.

And of course, the design of the stiffener is a big deal, too. I make mine so they grip the base of the coil for extra stability, and with beefy fillets holding the stiffener's ears to its base. Printed solid, and printed "nose-up" for the best ear strength.

Lostandfound, what kind of stiffener did you have that broke?

Link to pix of my prototype and V2. Current (V3) version has even more ear support.
https://metaldetectingforum.com/showthread.php?t=285729
Click to expand...

I have to disagree as well, you can see in various testing that petg is just a better filament for this application. Here is a few such test from a reputable source. This is also hotly debated on the net so info may vary from source to source. As you mentioned pla is brittle and is effected by shock much more easily than other plastic types, so even if the tensile strength is there it still shatters if this makes sense.

https://3dprinterly.com/pla-vs-abs-vs-petg-vs-nylon/

https://www.matterhackers.com/news/filament-strength-testing

https://www.eclipson-airplanes.com/plavspetg

Not to mention that pla degrades due to uv rays and is classed as biodegradable. From personal experience I will stick with petg or better yet nylon when I need strength. Not to take away from the fact that we both have valid arguments and reasoning. One thing here is evident though and that is a lot of factors must be considered. Maybe minelab should pick this up since their choice of plastic was poor?...
 
Last edited:
beachrumbum said:
I have to disagree as well, you can see in various testing that petg is just a better filament for this application. Here is a few such test from a reputable source. This is also hotly debated on the net so info may vary from source to source. As you mentioned pla is brittle and is effected by shock much more easily than other plastic types, so even if the tensile strength is there it still shatters if this makes sense.

https://3dprinterly.com/pla-vs-abs-vs-petg-vs-nylon/

https://www.matterhackers.com/news/filament-strength-testing

https://www.eclipson-airplanes.com/plavspetg

Not to mention that pla degrades due to uv rays and is classed as biodegradable. From personal experience I will stick with petg or better yet nylon when I need strength. Not to take away from the fact that we both have valid arguments and reasoning. One thing here is evident though and that is a lot of factors must be considered. Maybe minelab should pick this up since their choice of plastic was poor?...
Click to expand...

It looks like we have different views on what's best to protect the ears. I don't disagree -- PETG is a great material for lots of real world applications. Even this one. Its also the semantics of the word "strength." One of your links shows PLA has higher tensile strength than PETG , one avoids saying it, but should have, and the third never tested pure tension. PLA is roughly 33% "stronger." That said, a thicker design of PETG can be equivalent in strength to PLA and benefit from it's other properties as well. If the design is "over-engineered" in PLA it'll should be fine in PETG.

PETG wins in impact resistance no question. It's fair to say PETG is overall way "tougher" than PLA.

I'm viewing the ear breaking situation like this: constant stress from a too tight bolt and/or poor ear to shaft fit, plus a lot of back-and-forth stresses work hardening the ears, and with occasional harder knocks. I think many (most?) are breaking from day-to-day use, not some catastrophic impact. I'm looking at this like we need titanium spars in a jet fighters wings -- strong, immobile. Reduce movement of the coil ears as much as possible. For the same amount of material, I think PLA does that better.

Are the coils outdoors enough for UV to be a factor? I've had PLA house numbers on a black mailbox for over a year, no *visible* signs of degradation... It's been said these stiffeners "wear out" over time, I'm curious what they were made of and how long/what conditions wore them out.

AFAIK, no one is sacrificing their coil ears to see what exactly makes them break, so we do the best we can to preserve them. Yes, for sure Minelab should have used a different material, or more of it.

REAL_RAT_FINK mentioned the thin spacers - between the shaft and coil ears - to keep the ears straighter when the bolt is tightened down. I think that's a great idea.

For any given design of a stiffener, the better solution, in my opinion, is the stiffer material. PLA. If long outdoor exposure makes PLA degrade faster than PETG that's certainly a factor. If the design is already "beefy" then PETG will do a fine job as well. I'll print in either one with a clear conscience. And yeah, nylon would be great, but it requires more investment in the printer and consumables, and possibly air filtration...
 
Some intriguing statements from you guys who know alot more than me regarding the materials ,3D printing , etc. When I broke the ear (1) not both , on my 15" coil it was at the beach. Medium hard sand with NO stiffener. But it was at a downward angle and I believe my bolt was over tightened. I did this because I don't like a floppy coil. In and out of water , contours of the beach , etc. So....my question is ; what do you guys think about a COIL STABILIZER ? Such as what whites offers on their PI beach machines. I've used these for years. Couldn't these take some pressure off the Nox coil ears ? Maybe that's why my DF ears have never broke and I lean on it , bang it up , etc.
 
TorqueMaster said:
It looks like we have different views on what's best to protect the ears. I don't disagree -- PETG is a great material for lots of real world applications. Even this one. Its also the semantics of the word "strength." One of your links shows PLA has higher tensile strength than PETG , one avoids saying it, but should have, and the third never tested pure tension. PLA is roughly 33% "stronger." That said, a thicker design of PETG can be equivalent in strength to PLA and benefit from it's other properties as well. If the design is "over-engineered" in PLA it'll should be fine in PETG.

PETG wins in impact resistance no question. It's fair to say PETG is overall way "tougher" than PLA.

I'm viewing the ear breaking situation like this: constant stress from a too tight bolt and/or poor ear to shaft fit, plus a lot of back-and-forth stresses work hardening the ears, and with occasional harder knocks. I think many (most?) are breaking from day-to-day use, not some catastrophic impact. I'm looking at this like we need titanium spars in a jet fighters wings -- strong, immobile. Reduce movement of the coil ears as much as possible. For the same amount of material, I think PLA does that better.

Are the coils outdoors enough for UV to be a factor? I've had PLA house numbers on a black mailbox for over a year, no *visible* signs of degradation... It's been said these stiffeners "wear out" over time, I'm curious what they were made of and how long/what conditions wore them out.

AFAIK, no one is sacrificing their coil ears to see what exactly makes them break, so we do the best we can to preserve them. Yes, for sure Minelab should have used a different material, or more of it.

REAL_RAT_FINK mentioned the thin spacers - between the shaft and coil ears - to keep the ears straighter when the bolt is tightened down. I think that's a great idea.

For any given design of a stiffener, the better solution, in my opinion, is the stiffer material. PLA. If long outdoor exposure makes PLA degrade faster than PETG that's certainly a factor. If the design is already "beefy" then PETG will do a fine job as well. I'll print in either one with a clear conscience. And yeah, nylon would be great, but it requires more investment in the printer and consumables, and possibly air filtration...
Click to expand...

I’m not going to get long winded here, yes the first link does show petg as having a higher tensile strength but lacking in ability to absorb any flex. I have worked with both materials and real world use has me convinced petg is the superior material. The fact it does have some flex and ability to absorb impact is one reason I would choose it for this application. The part is not providing the support, merely reinforcing it. I’m not easy on my gear and hunt many hours in saltwater. My ear stiffener has seen at least 1,500 hours in the saltwater this year. I downloaded the coil stiffener from thingiverse as there is no need to reinvent the wheel on this one. It has served me well, printed in petg and truth be told I’m bad for using the detector as a crutch in the water and yes, I’ll probably eat those words and my coil will break, had a friend who’s did with the stiffener she bought on eBay on. Anyway, that’s the beauty of 3D printing, one can choose different materials and see how they behave in different applications. One thing I’m sure we can agree on is this is an issue that should not exist if proper field testing were done, how many are breaking the coil ears water hunting? I’m guessing here but could it be 100%?
 
beachrumbum said:
I’m not going to get long winded here, yes the first link does show petg as having a higher tensile strength but lacking in ability to absorb any flex. I have worked with both materials and real world use has me convinced petg is the superior material. The fact it does have some flex and ability to absorb impact is one reason I would choose it for this application. The part is not providing the support, merely reinforcing it. I’m not easy on my gear and hunt many hours in saltwater. My ear stiffener has seen at least 1,500 hours in the saltwater this year. I downloaded the coil stiffener from thingiverse as there is no need to reinvent the wheel on this one. It has served me well, printed in petg and truth be told I’m bad for using the detector as a crutch in the water and yes, I’ll probably eat those words and my coil will break, had a friend who’s did with the stiffener she bought on eBay on. Anyway, that’s the beauty of 3D printing, one can choose different materials and see how they behave in different applications. One thing I’m sure we can agree on is this is an issue that should not exist if proper field testing were done, how many are breaking the coil ears water hunting? I’m guessing here but could it be 100%?
Click to expand...

Who's long winded, lol :p ok guilty as charged.

Ok, surviving 1500 hours in the salt water is hard to ignore. Which thingiverse design did you use?

I read about someone who did primarily field stubble detecting, and found coil ears broken the next time they went to use it. Someone just reported similar here on friendly (not sure where they detected) but that the break was not during use, either.

Obviously can't condone using it as a crutch, awesome it has survived that! Best to design for that abuse -- make the distance between the shaft and the stiffener base almost zero -- transfer the weight to the coil base as much as possible rather than the ears.
 
See guys , that's what THE KOB is talking about ! A coil stabilizer !!! Weight and torque are transferred to the coil and shaft. Not the ears.
 
KOB said:
Some intriguing statements from you guys who know alot more than me regarding the materials ,3D printing , etc. When I broke the ear (1) not both , on my 15" coil it was at the beach. Medium hard sand with NO stiffener. But it was at a downward angle and I believe my bolt was over tightened. I did this because I don't like a floppy coil. In and out of water , contours of the beach , etc. So....my question is ; what do you guys think about a COIL STABILIZER ? Such as what whites offers on their PI beach machines. I've used these for years. Couldn't these take some pressure off the Nox coil ears ? Maybe that's why my DF ears have never broke and I lean on it , bang it up , etc.
Click to expand...

Not familiar so I googled it -- what I'm seeing is a device that keeps the coil from flopping but nothing to transfer weight down the shaft to the coil. It would need a hole and pin through the shaft for that, instead of the ziptie. And be much beefier and symmetrical on both sides of the shaft. The concept could be developed I suppose...
 
TorqueMaster said:
Not familiar so I googled it -- what I'm seeing is a device that keeps the coil from flopping but nothing to transfer weight down the shaft to the coil. It would need a hole and pin through the shaft for that, instead of the ziptie. And be much beefier and symmetrical on both sides of the shaft. The concept could be developed I suppose...
Click to expand...
Not really weight down the shaft per se. But it is attached through the coil bolt and then attaches with a nut /bolt with a plastic clamp around the shaft , securely. I believe the weight is distributed through the bottom 3" of the stabilizer to the coil. But also the bottom of the shaft as well. The whole thing is adjustable for the angle on how you want the coil to "sit". I can send a pic tomorrow if needed. But I think you can still find these at some suppliers. I think it would be a great invention for a Nox. Something a little heavier duty on both sides like you said. Maybe wrap around the shaft or part way ?
 
I just don't understand all this ear worry. I never tighten the coil hard on any of my machines. I always leave the coil loose enough that when I go up or down hill the coil basically stays parallel with the ground by itself. It doesn't wobble at all when swinging but very slight ground pressure up or down allows it to move easily to march the contour of the ground. I have been doing this for fifty years and just don't get how coils get overtightened. I mean no squirrel is going to run out and unscrew your coil for you because its not very tight. I have never lost a coil nut ot bolt and especially now these plastic bolts don't unscrew themselves if not tightened down hard.
 
gunsil said:
I just don't understand all this ear worry. I never tighten the coil hard on any of my machines. I always leave the coil loose enough that when I go up or down hill the coil basically stays parallel with the ground by itself. It doesn't wobble at all when swinging but very slight ground pressure up or down allows it to move easily to march the contour of the ground. I have been doing this for fifty years and just don't get how coils get overtightened. I mean no squirrel is going to run out and unscrew your coil for you because its not very tight. I have never lost a coil nut ot bolt and especially now these plastic bolts don't unscrew themselves if not tightened down hard.
Click to expand...

I don't want my coil moving AT ALL. But I am a beach hunter. Sand is different. Lots of falsing bumping the coil. I really don't want to apply slight ground pressure to move it , though I have tried it. It takes time to constantly do that on a beach. And I am a volume hunter. Also there is a very fine line of just skimming the sand. I'm not worried about the drunk squirrel backing out the nut. It ain't coming out. Just a preference is all...
 
TorqueMaster said:
Who's long winded, lol :p ok guilty as charged.

Ok, surviving 1500 hours in the salt water is hard to ignore. Which thingiverse design did you use?

I read about someone who did primarily field stubble detecting, and found coil ears broken the next time they went to use it. Someone just reported similar here on friendly (not sure where they detected) but that the break was not during use, either.

Obviously can't condone using it as a crutch, awesome it has survived that! Best to design for that abuse -- make the distance between the shaft and the stiffener base almost zero -- transfer the weight to the coil base as much as possible rather than the ears.
Click to expand...

To clarify I was not accusing you of being long winded, more so saying I had a lack of time to post. I appreciate your feedback and that is how things get improved, varying opinions and ideas that can be adapted to existing ones.

I went back and looked for the design that I printed, looks like it has since been taken down. I’ll try to post a pic here later if you like. It is a decent design and I still have the files somewhere.

I wonder what the actual percent of breakage is on these things, My arm cuff broke out of the blue one day, just fell apart and I was out the equinox for a week.

Don’t use the detector as a crutch when digging LOL! I’mbad about it but the surf isn’t always pleasant and it helps me stay put.
 
gunsil said:
I just don't understand all this ear worry. I never tighten the coil hard on any of my machines. I always leave the coil loose enough that when I go up or down hill the coil basically stays parallel with the ground by itself. It doesn't wobble at all when swinging but very slight ground pressure up or down allows it to move easily to march the contour of the ground. I have been doing this for fifty years and just don't get how coils get overtightened. I mean no squirrel is going to run out and unscrew your coil for you because its not very tight. I have never lost a coil nut ot bolt and especially now these plastic bolts don't unscrew themselves if not tightened down hard.
Click to expand...

This! I hunt in the water a lot and have never had any issues. I keep mine loose so it moves naturally with the contour of the ground as you state. I am NOT easy on mine at all and I do not understand how people are breaking these.
 
hddeuce03 said:
This! I hunt in the water a lot and have never had any issues. I keep mine loose so it moves naturally with the contour of the ground as you state. I am NOT easy on mine at all and I do not understand how people are breaking these.
Click to expand...

With mine having it loose and moving sand gets in and wares at the plastic making it thin and breaks.
 

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