Q: How light is too light?
Moderator: robbosmans
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I'd be really curious to have looked at the failure surface right after it happened. I wonder to what degree there was a flaw in the manufacturing rather than design.
it's actually possible to come to the conclusion even before realising it makes no sense at all
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tymon_tm
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tymon_tm
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IMO it’s a design weakness. The single alloy cog on the SRAM Red cassette interfaces directly with the freehub driver splines. The single-piece dome that makes up the rest of the cassette has its own interface as well. No matter what cog you’re in, it is directly driving the hub.
The two alloy cogs on the Rotor UNO cassette are riveted onto the steel dome and don’t have their own splined interfaces. This means all your pedaling torque is transferred through the rivets.
Ooooh, that's an interesting engineering choice. The basic Shimano freewheels are now just a stack of riveted cogs driving one of the smaller cogs. So I guess it's not an absurd method, but it sure does demand properly sized and sufficient numbers of rivets.
it's actually possible to come to the conclusion even before realising it makes no sense at all
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tymon_tm
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tymon_tm
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- Posts: 12456
- Joined: Mon Jul 24, 2017 12:02 pm
Dura-Ace cassettes had carrier/rivet failures with alarming frequency actually. For some this would manifest as a squeak...for others the carriers would just self-destruct. There was even a silent update to the design that added additional rivets.
See this BR post: https://bikerumor.com/2014/06/06/shiman ... -creaking/
IMO the SRAM XG-1190 has the best overall design from a strength-to-weight standpoint. My only problem with it is the shape of the teeth on the smaller cogs making things a bit noisier.
See this BR post: https://bikerumor.com/2014/06/06/shiman ... -creaking/
IMO the SRAM XG-1190 has the best overall design from a strength-to-weight standpoint. My only problem with it is the shape of the teeth on the smaller cogs making things a bit noisier.
I just read Shimano's response to the re-design of the DA cassette. Too funny. Japanese's way of doing business is to never admit fault. DA's cassette problem is well documented and yet they refuse to take blame. I find the following line quite funny...yeah, a creak is not a noise, lol.
Nick Murdick Shimano Lead Technical Instructor wrote: ↑Sat May 05, 2018 11:28 pmOf course, if the joint between the carrier and the cog starts to fail it will make noise but that’s different from a creak.
Ah to be fair that's not what he said though, is it? It's basic set theory - every creak is a noise but not every noise is a creak.
But yeah they do have a habit of sending out silent redesigns without publically stating there was ever a problem.
But yeah they do have a habit of sending out silent redesigns without publically stating there was ever a problem.
Just out of curiosity, do you have a picture of the failure?
Correct. The steel between two cogs sheared. Looking at it now in two pieces, that area is very, very thin - and frankly a stupid design. I think the steel cage needs to be thicker OR the rear of the cage should actually interface with the splines. As it is, only the front of the cassette actually engages on the splines and the rear floats - leaving the burden of strength completely on the steel cage. Which, obviously, is folly.
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