Sprockets

Not sure but it looks like the chain might have been to tight when the suspension was fully compressed.
I've seen this before and me and my friends all thought that was the cause of the failure. Hope this helps.

Your sprocket bolts were loose. The bolts stretch ever so slightly over time, and if there is any movement at all, the hub will self destruct. I had this happen to me years ago. I had my bolts loctited, so they felt tight. To prevent this from ever happening again, 1) check the tightness of your sprocket bolts before every ride, and 2) never loctite sprocket bolts.

Yeah that is definitely the aftermath of loose sprocket bolts my friend! I've seen it happen quite a few times. That should always be part of your pre ride check list to check before every ride!

The Tusk thread is the one you're referring to in your OP.

http://www.vitalmx.com/forums/Moto-Related,20/Tusk-Wheels-Issues,1295756

http://www.vitalmx.com/forums/Moto-Related,20/Vortex-Sprockets,1310512

Where is Peelout when you need him most?

I take it all the stuff from this is long gone?

From those pictures i would be looking at the outer ring as the possible start point, all the areas of Ally in the hub are clean so that shows a sudden failure as a result of the initial failure.

Understanding the material process and manufacture of the outer ring is key, i have seen gear failures in the radius at the bottom of the tooth due to errors in the manufacturing process. However, assuming that the process is the same, is not an assumption i would make.

I've used several Renthal Twingring sprockets for a total of way over 100 hours without fault. It's not the same brand but the same design.

Ok, so you have a guy who knows what he is looking for, the sections that missing is where i would have looked.

If it failed how im thinking, it would have gone at the end at 12 O'clock in the first picture, and peeled around the diameter under load, until it got to the next bit at 10 o clock , all ' intuatively'

We have these sprockets on 2 of our bikes, and i never heard of an issue, Obviously a stone could have set off the chain of events, but if it enough to do this, i would have expected the chain to break.

If the outer ring is case hardened, then it could go one of two ways, insufficient depth, or too much, Too much may cause brittleness, or possibly crack on cooling, but i would think that this would be visible elsewhere as micro cracking.

They dont guess this stuff, but mistakes do happen.

This video gives an idea of the forces involved, although it is a different type of motorcycle. Fast forward to 1 min mark.

Close this thread BEFORE PeelOut sees it!

There will be NO MERCY when he gets here.

Guys. Rick is a long time D23 A rider that knows how to properly maintain a mx bike. He is of the Amatuzio family that owns amsoil. Dude is legit and can rip on a bike. Glad to hear you walked away from that one Rick!

Is it possible for cast aluminum to fatigue? Any metallurgists in this forum?

I had a sidewinder do this to me years ago. They played me good seemed like they were going to cover it and had me send the sprocket back. Never heard back and couldn't get a penny from them. I stick to AFAM now. Pay more now instead of a lot later.

Had this happen on a 125 a few years ago. Had a similar design pro taper sprocket. We decided that a rock had gotten between the chain and sprocket at the same time as bottoming the suspension. I would imagine this is the same thing you had happen

I'm sure every now and then we as buyers do get a faulty product. It could have started from the day it was made and just went bad , at the wrong time. Those sprockets have to be tough as hell. Because they get put under an extreme amount of force. Rick , I would chalk it up to a fluke honestly. I have been using the twin ring sprockets for the past 5 years or so ( about 10-12 of them ) and have never had one fail. BUT.....with that being said , having two types of metal pressed together with joiner pins ( or what ever we call those things? )....I would think may have a higher chance of failing than a 1 piece sprocket. Seems like most my entire riding group uses these sprockets though , and I haven't seen one fail yet. Let us know if you find something else out.

Yes . anything can fatigue.

Anything can fatigue, but fatigue leaves a trace, that Rick's guy at Amsoil would be able to spot.

Whilst i am not a metallurgist, i have conducted plenty of post mortems of failed parts, both machined and fabricated , with the help of my local lab, using micro analysis .

if you can wade through this, it will give an idea of what kind of thing can cause failure.

https://www.afsinc.org/files/images/CPedia.pdf