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Old 01-12-2020, 01:43 PM   #1
kodama
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Metal wishbone FAILURE

Today I got in the pool with some friends to test out some guns and have some off season fun.

I figured I would shoot my 65 hole gun first as a warm up and check the target and such.
While loading the metal wishbone just broke unexpectedly. I was very surprised and when the band popped off I first thought that the band failed since it is almost two years old and needs replacement.
Instead I noticed the metal wishbone broke in the middle where it hooks on the shark fin.

I have no clue how this could even happen? It has never been bent so I am eliminating metal fatigue. It has never been heated and rapidly cooled causing excessive tension in the metal.

However the gun a Seatec Snake is 6years old and has seen intensive use. Third pair of bands so far. The metal wishbones came standard on the gun and although I have tried dyneema instead I love the site picture and how neat the bands sit so I kept using them.

Any idea how this could happen? You would think that these things last longer.

I have two more pairs made of Titanium made by Sigalsub maybe these will last longer.
The original made by Seatec are just stainless.



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Old 01-12-2020, 01:47 PM   #2
brandon cadalzo
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Re: Metal wishbone FAILURE

Damn! I’m just happy it didn’t happen as you we’re finishing loading the gun! Coulda torn your fingers up something fierce!


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Old 01-12-2020, 02:04 PM   #3
kodama
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Re: Metal wishbone FAILURE

I got lucky since stupid me forget to bring gloves and wasn’t wearing any somehow I only got a minor scratch.
It could have been so much worse...Luckily my buddy had a spare pair of gloves I could use.
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Old 01-12-2020, 02:41 PM   #4
popgun pete
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Re: Metal wishbone FAILURE

Metal fatigue is the cause, as the wishbone loads up on the tab it gets sprung by the load going on and tweaks the metal as it takes up the strain. It happens on all metal wishbones if they are used enough times. That usually only happens if they are re-used as wishbones will outlive the bands. The idea behind articulated wishbones is they are less likely to be sprung, although their main aim is a straight lie of the bands on the gun as they run up to the muzzle.

If you clamp a thin piece of stainless steel rod in a bench vice and then bend it back and forth you will eventually bust it. Aluminium alloy is even worse, it has a short fatigue life, so is not used in wishbones.
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Old 01-12-2020, 03:15 PM   #5
kodama
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Re: Metal wishbone FAILURE

I see, I didn’t look at it that way. Indeed every time you load you apply stress causing it to fail eventually.

I wonder if the wire on these titanium wishbones is stainless or TI? I am sure the larger is completely made of TI.




I may have to consider using a small articulated wishbone without wire like this one. I expect those will last much longer.



I noticed they sell the wires separately as well.
but I am not sure if I want to go that route again.
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Old 01-12-2020, 04:00 PM   #6
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Re: Metal wishbone FAILURE

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Originally Posted by kodama View Post
I see, I didn’t look at it that way. Indeed every time you load you apply stress causing it to fail eventually.

I wonder if the wire on these titanium wishbones is stainless or TI? I am sure the larger is completely made of TI.




I may have to consider using a small articulated wishbone without wire like this one. I expect those will last much longer.



I noticed they sell the wires separately as well.
but I am not sure if I want to go that route again.
second and third one maybe strong but you should be careful it may cause injury to your finger , also beside the fatigue exposed Stainless in seawater will suffer from crevice and pitting corrosion .
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Old 01-12-2020, 04:31 PM   #7
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Re: Metal wishbone FAILURE

After so many band changes just throw them away. Depending on how much you use your gun is a factor as bands conk out even if not used, so a little used gun with the bands always left on the gun may go through more band changes with fewer actual loading cycles. It is the number of loading cycles that kills the wishbones.
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Old 01-12-2020, 05:26 PM   #8
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Re: Metal wishbone FAILURE

The cause was that you're using sharkfin shafts. Those wire wishbones are for notched shafts. Sigal wires are better than Seatec, but if I go with sharkfins, I'll use dyneema.

I've used a Snake for many years and I'm talking from my experience.
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Old 01-12-2020, 05:37 PM   #9
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Re: Metal wishbone FAILURE

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The cause was that you're using sharkfin shafts. Those wire wishbones are for notched shafts. Sigal wires are better than Seatec, but if I go with sharkfins, I'll use dyneema.

I've used a Snake for many years and I'm talking from my experience.
Well he got six years out of them, so not too bad.
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Old 01-13-2020, 02:09 AM   #10
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Re: Metal wishbone FAILURE

You are pretty lucky as metal wishbones can slice you up pretty good even with if you have a thin wet suit on. But metal wishbones really do clear up your site picture as they spread the bands out wide. I think if you are going to use metal wishbones, best is to use them on the last band you pull back. This way if they break there is less chance that they will slice you up ... and trust me ... they can really slice you up and if you are far away from a boat and have severed an artery you might bleed out before you reach the boat. The rate that steel wishbones break depends on how you load the bands and how much they will bend and unbend (metal fatigue). Of course it also depends on how thick the wishbone wire is initially. I received some metal wishbones from Ocean Rhino that seem like it would be impossible to have them break. But on many european bands they use pretty thin wire on their wishbones.

Here is a picture of a cousin of mine that had his arm sliced open with a broken metal wishbone. He was lucky to have someone near him help him to the boat and get emergency treatment. I have heard of others that have been also sliced up by broken metal wishbones but this seems to have become more rare as now almost everyone uses dyneema wishbones.
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Old 01-13-2020, 03:27 AM   #11
kodama
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Re: Metal wishbone FAILURE

That looks pretty damn nasty I hope you’re cousin recovered well! I guess I got really lucky I suppose since I only got minor scratches.


The Ocean Rhino wishbones you are referring to are they articulated wishbones?
I could only find these cable wishbones. Are you using these?


The accident you mentioned did this happen with a wire wishbone or a solid stamped/cut wishbone as in the picture below?



I just really enjoy the clear side picture of articulated wishbones but now I am doubting to continue using them.
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Old 01-13-2020, 04:00 AM   #12
popgun pete
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Re: Metal wishbone FAILURE

Metal cable wishbones can develop meat hooks, so need to be checked periodically.
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Old 01-13-2020, 01:14 PM   #13
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Re: Metal wishbone FAILURE

Yikes. Glad you're okay. I've always been leery about using metal wishbones for this reason and this seems to reinforce that. While not the same thing, I recently fractured my finger when it got caught in one of my bands. It had slipped when I was loading. Shitty mistake on my end, but it would have been tons worse if I had a metal wishbone.
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Old 01-13-2020, 01:28 PM   #14
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Re: Metal wishbone FAILURE

And ALWAYS wear gloves when using metal wishbones.
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Old 01-13-2020, 07:32 PM   #15
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Re: Metal wishbone FAILURE

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Originally Posted by popgun pete View Post
Metal cable wishbones can develop meat hooks, so need to be checked periodically.
Yes, but the steel cable itself is so strong that I have NEVER had one break. As the cable strands break, you seem to have plenty of warning that replacement is due. Solid wire can snap without much warning.

I had an experienced friend that claimed that you could examine the solid wire wishbones with a strong magnifying glass and he said they when tiny cracks became visible, it was time to replace the solid wishbone.
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