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Ew83

Damaged swingarm bought off eBay

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Ad: "no gouges or dents."

 

See pics..what do y'all think? Too risky to run it or is it okay? I like slamming my back tire into stuff. As far as I can tell, no cracks. Looks like he ran the chain too slack and it dug into the bottom of the swingarm. That last one might have been a manufacturer stamp of some sort?IMG_20190823_210916.jpegIMG_20190823_210921.jpegIMG_20190823_210814.jpegIMG_20190823_210626.jpegIMG_20190823_210835.jpeg

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Of course I have no x-ray eyes, but from what I can see I'd say you can run it without any risk. I have seen swing arms far worse than yours that worked fine.

Concerning the guy who sold it, well I better shut up.

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Posted (edited)

Lol look at any bike that has been used for enduro and you'll find waaaaay worse than that.  Unless you're making a living jumping 150 ft jumps I would run without question.  If the ad said no marks or gouges I would be a little perturbed but it would depend on what I paid for it. You could always ask for a small refund and see what happens.  If not make sure to leave appropriate feedback.

Edited by PTECH
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Thanks for easing my mind y'all. I was just annoyed that it said no gouges and had 0 close up pics of it. I'll run it.

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Take a look at the term "Stress Riser" or stress concentration. Due to the way that aluminum is sometimes affected by gouges,cuts etc. a stress riser can occur. Think how you create a weak spot along a folded line in a piece of paper and you can understand what a stress riser is.

Here is a quick overview:

How can I reduce my stress concentration?

1: Reducing Stress Concentrations

Avoiding sharp corners and only using rounded corners with maximum radii.

Sanding and polishing surfaces to remove any notches or defects that occur during forming and processing.

Lowering the stiffness of straight load-bearing segments.

Placing notches and threads in low-stress areas.

----------------------------------------------------------------------------------------------------------------------------------

To help reduce the possibility of what is called catastrophic failure,do as much as possible to remove sharp edges around a gouge or cut by carefully rounding with a file or emery cloth.

Google search results for Stress Riser:

https://www.google.com/search?q=Aluminum+stress+riser&rlz=1C1CHMO_enUS580US738&oq=Aluminum+stress+riser&aqs=chrome..69i57j33.8480j0j8&sourceid=chrome&ie=UTF-8

 

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Take a look at the term "Stress Riser" or stress concentration. Due to the way that aluminum is sometimes affected by gouges,cuts etc. a stress riser can occur. Think how you create a weak spot along a folded line in a piece of paper and you can understand what a stress riser is.
Here is a quick overview:
How can I reduce my stress concentration?
1: Reducing Stress Concentrations
Avoiding sharp corners and only using rounded corners with maximum radii.
Sanding and polishing surfaces to remove any notches or defects that occur during forming and processing.
Lowering the stiffness of straight load-bearing segments.
Placing notches and threads in low-stress areas.
----------------------------------------------------------------------------------------------------------------------------------
To help reduce the possibility of what is called catastrophic failure,do as much as possible to remove sharp edges around a gouge or cut by carefully rounding with a file or emery cloth.
Google search results for Stress Riser:
https://www.google.com/search?q=Aluminum+stress+riser&rlz=1C1CHMO_enUS580US738&oq=Aluminum+stress+riser&aqs=chrome..69i57j33.8480j0j8&sourceid=chrome&ie=UTF-8
 
Cool! Yeah I got a structural engineering degree but we never covered that stuff. Interesting.

I'm returning it for a new one for about $150 more. Figured if it fails I want to be to blame not someone else I bought it from

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10 hours ago, Ew83 said:

Cool! Yeah I got a structural engineering degree but we never covered that stuff. Interesting.

I'm returning it for a new one for about $150 more. Figured if it fails I want to be to blame not someone else I bought it from

Then why did you ask?  By far the greatest response was its fine as it is.

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Were there not pics of the item in the ad?  

If you insist on perfection, and interpret that used swingarm as being gouged and dented to the point of being unsafe or unusable, maybe eBay should be dropped as a future parts source.

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The indentations are from the plastic chain guide that wraps around the swingarm. Any swingarm that's been used will have that. Take a dremel to any raised edges on the gouges, clean and grease the bearings up and use it.

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Were there not pics of the item in the ad?  

If you insist on perfection, and interpret that used swingarm as being gouged and dented to the point of being unsafe or unusable, maybe eBay should be dropped as a future parts source.

Yeah the pics did not show the damage and it said no dents and gouges. If there were pics I wouldn't have bought it.

 

I don't know at what point a swingarm fails, but I do know the manuals recommend that any dent or gouge requires the swingarm to be replaced and they recommend against trying to fix it. I know part of that is their prerogative to sell parts but i don't know enough to know what is fine and what isn't.

 

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2 hours ago, Ew83 said:

Yeah the pics did not show the damage and it said no dents and gouges. If there were pics I wouldn't have bought it.

 

I don't know at what point a swingarm fails, but I do know the manuals recommend that any dent or gouge requires the swingarm to be replaced and they recommend against trying to fix it. I know part of that is their prerogative to sell parts but i don't know enough to know what is fine and what isn't.

 

I get where you're coming from and your concern. My response was based on what I'd consider in the pics as purely cosmetic and I stand by that, especially for a part $150 less than new. Fwiw, I always throw in a correction factor for the condition of any used item for sale on eBay. If the seller claims it's a "10", it's probably more like an "8". 

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On 8/25/2019 at 8:09 PM, Ew83 said:

Cool! Yeah I got a structural engineering degree but we never covered that stuff.

I'd be returning my degree if this is a foreign concept, not the swingarm.

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