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ebrown123 mikelevy's article
Feb 2, 2020 at 17:57
Feb 2, 2020
Trust's Prototype 213mm-Travel Electric Dirtbike Fork
Clickbait title - there's no electrics in that fork at all.
ebrown123 pinkbikeaudience's article
Jan 29, 2020 at 14:33
Jan 29, 2020
Round 1 Voting Closed: 2019 Photo of the Year
I agree. It would be much better if everyone was able to vote for their top choices and the bottom half of the photos are dropped after each round instead of these brackets. There were some brackets where I liked both and other brackets where I didn't think either were special.
ebrown123 lornny's article
Dec 20, 2019 at 5:20
Dec 20, 2019
Video: Whistler Party Laps with Carson Storch, Kurt Sorge, Vanderham & More - Weekend Slayer Episode 6
We attempted to replicate the failure through numerous test scenarios and during these tests we were unable to crack the chainstay. Here's the video of our testing.
ebrown123 mikekazimer's article
Dec 17, 2019 at 6:40
Dec 17, 2019
Field Test: 2020 Rocky Mountain Slayer Carbon 90 - The One That Broke
@acdownhill: It's totally ok to argue points. That's what the comments are for. And it's a group effort so technicians contribute as much as engineers. And hey, I might just be a dentist who plays engineer on the internet... I can also be wrong. It may have been an over-torqued axle but I think it is much more likely that it is a design or manufacturing flaw in the new chainstay. Only Rocky can say for sure. And I've already pointed out that if they don't actually say anything after looking at if for over six weeks, any design changes will speak for them. At first, I didn't have an opinion either way, whether it was the axle or the frame. Like everyone here I was looking at the pictures and trying to figure it out. That's when I described the method for checking the faces of the failed parts for smooth and sharp faces as it might have suggested or ruled out which it was and wishing the pictures were higher resolution. I would agree that the axle most likely failed in tension. The problem is I couldn't tell from the photo but as many have pointed out, the way a thru-axle sits in a frame it makes shear failure very unlikely. Then the question is, even if we all agree the axle failed in tension, did that tension come from over torquing or from the frame spreading as the chainstay failed first? In my second post I started to lean towards the frame going first from the shape of the failure and that is when I noticed that the crack the chainstay failed along runs up to the that new bearing rib. I also didn't see the chainstay failure as catastrophic, as from the side photo the metal looks bent and worked as opposed to shattered into a few bits. I think this supports a crack that worked itself bigger over some cycles. I also thought that if the axle was cracking first, say from an over-torque, there would be signs. As the crack was working through the axle from the threads weakening it, the riders would feel rear wheel play as if the axle or hub was just loose and none reported that feeling in the bike before it let go. Another point is that the mechanics were pulling the axle in and out often to change the tires. If the threads were starting to go, the threads would start to deform and the mechanic might either see this or feel it as the axle would be harder to start to engage at the threads when they replaced the axle each time. Last, if the threads had started to crack and fail, the mechanic wouldn't be able to get the required torque on the axle with a torque wrench anymore without the axle breaking then. I feel all of this supports a sudden axle failure over it failing from a crack from cycling. So this brought me back to thinking the frame went first. Then the next question is why? Rocky has made thousands of bikes with chainstay pivots and thousands of other bikes have been down A-Line. What was different? Was this double bearing and rib design new or the same as in other Rockys? I didn't know so that's when I flipped through the service manuals to see if this was a new design or already used in other Rocky models. It appears to be a new design. When trying to determine cause of failure, a new element, like the chainstay, is usually more likely than an older proven element, like a thru-axle. In terms of quality control being a factor, it is much easier to maintain and test strength on something simple like an axle compared to a chainstay. It is common practice and inexpensive to test a handful of bolts to failure from each batch to make sure they meet spec compared to testing a handful of chainstays from each batch in the same way. Likewise, I imagine axle manufacturers have tested failure from over-torquing in the process of specifying the proper torque to use. It would pretty easy to build a jig with a wheel in it, over torque an thru-axle to different levels and drop weights on the edge of the wheel to see how much over torque it takes to compromise the thru axle when the wheel is side loaded. Even the staff at pinkbike could manage this one for an article so I suspect manufacturers already have. If it was the chainstay that went first, it might be the new design of the bearing seat with the rib causing unanticipated stresses or it might be the quality control of manufacturing this new design. The design may be fine but it could be a bad batch of chainstays that were being made differently for the first time. And to be fair, it could be something else entirely. Like I said I'm not necessarily right at all. I've just tried to put my best idea forward based on the info and experience I have. If I was Rocky I'd be working very hard to try and duplicate the failure and see what I could rule out and what I needed to focus on.
ebrown123 mikekazimer's article
Dec 16, 2019 at 13:03
Dec 16, 2019
Field Test: 2020 Rocky Mountain Slayer Carbon 90 - The One That Broke
@mdhorner: The truth could be uglier. Rocky may not have even tested the new double bearing rear pivot with that new bearing seat rib. They previously stated that the Wade Simmons Pipedream project was the test mule for the this Slayer and they made the Pipedream with the rear end and single bearing chainstay pivots from the 2018 Altitude. Someone at Rocky may have decided that since they were taking an already proven and tested rear end and just making it beefier by adding a second bearing that it didn't require any testing even though it was a new design. It might not be the rib that I've pointed out. It might be something more subtle like the new position of the axle closer to and higher above the pivot than previous models puts the chainstay in more tension at the beginning of the stroke than before or worse, cycles the chainstay between tension and compression, where it didn't before. Might have been an oversight, might have been cost related, might have been in a rush to market. Only Rocky can say. If a lawyer for Luca, Pinkbike, or worse, another injured rider comes calling, I hope Rocky has all of its development and testing well documented. The frame failed over six weeks ago. That's a lot of time for Rocky to figure out what happened, yet based on their statement for this article they don't seem to know yet which I find more troubling than the failure itself. Or they may already be in PR damage and liability control mode. The giveaway will be any design changes they make in that pivot going forward.
ebrown123 mikekazimer's article
Dec 16, 2019 at 10:11
Dec 16, 2019
Field Test: 2020 Rocky Mountain Slayer Carbon 90 - The One That Broke
One further Addendum: I went through the various Rocky service manuals I have to see why this hasn't happened before. The 2020 Slayer appears to be the first model to ever have two bearings separated by a machined rib in the chainstay pivot location. Even the Maiden and the powerplay models only use a single bearing in that location. On paper, I can see why two bearings would seem stiffer and stronger than one. But on paper, the stress risers from that machined ridge and pressed bearings may not have shown up. Even in a frame fatigue testing rig, if there wasn't a lateral load being cycled it might not appear either. Cycling frames up and down isn't the same as real world cycling of frames side to side.
ebrown123 mikekazimer's article
Dec 16, 2019 at 9:29
Dec 16, 2019
Field Test: 2020 Rocky Mountain Slayer Carbon 90 - The One That Broke
Addendum to my own post: Looking at the failed chainstay pivot closer, I'm leaning towards crack propagation starting there, and more specifically at the stress riser caused by that inside machined ridge that the bearings seat on as it has a sharp transition. You can see the crack starting there and angling outward on the chainstay. Because the pivot is completely visually obscured by the seatstay pivot once the bike is assembled it would be hard to see the crack starting in the chainstay. The crack may have also started on the inside of bearing seat at the ridge and worked towards the outside of the chainstay, making it harder still to diagnose. Also if the chainstay had failed catastrophically in one shot, it's hard not to believe that the chainstay pivot bolt there wouldn't have been a weaker link and sheared before or with the chainstay itself. I wouldn't be surprised to see Rocky address this with a redesigned chainstay without that machined seat in the centre of the pivot and a different bearing and bolt configuration.
ebrown123 mikekazimer's article
Dec 16, 2019 at 9:07
Dec 16, 2019
Field Test: 2020 Rocky Mountain Slayer Carbon 90 - The One That Broke
I've experienced and investigated these kinds of metal failures below. If pinkbike had shared clear focused close ups of the broken frame and axle it would be pretty easy to see which broke first. On a metal failure you can often seen the whether it was a catastrophic, one cycle failure, or a crack propagation, multiple cycle failure by looking at the metal faces at the break. If the broken faces are sharp and crisp it is likely catastrophic. If part of the faces are smoother and then transition to sharp and crisp it is more likely that a crack started at the smooth end, those sharp surfaces rubbed against each other over more cycles, becoming smooth, while the piece continued to weaken as the crack grew. Then the rest of the break occurs suddenly in the weakened part and results in sharp faces for that last region of the crack. So if the frame is showing part smooth, then sharp faces at the break, it likely cracked first, rubbed while the crack grew and then failed once the crack was big enough to cause the part to weaken to sudden failure, taking the axle with it. If the frame is showing all sharp faces at the break, then likely the axle failed first and the frame failed catastrophically next.
ebrown123 jamessmurthwaite's article
Oct 8, 2019 at 7:15
Oct 8, 2019
The EWS Announces an eMTB Race Series for 2020
The EWS is just moving to claim the space before the UCI or FIM says it's the official body for electric motorcycle racing.
ebrown123 danielsapp's article
Sep 9, 2019 at 15:01
Sep 9, 2019
4 New eMTBs (Plus New eMTB Tech) - Eurobike 2019
@WAKIdesigns: So as our resident Swede, are you are saying you want the Husky Extreme Cross EXC 10? Most of their frames look like they have some kind of modular motor mount so you could potentially mount any motor brand you wanted with a different adapter or even none at all when you leave the battery at home. It's like a Billy bookcase on wheels
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