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Re: The Shiny New AM831 Group Buy (A) Thread!
Eddy, can you tell us which checks and eventual retrofit we can do to existing frames to correct (potential) flex problem?Are spare bolts available for purchase?
October 29, 2021, 07:13:20 AM |
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Re: The Shiny New AM831 Group Buy (A) Thread!
It is worth showing the link assembly issues with pictures rather than just words to get the message better across, so I've drawn some (not to scale, dimensions exaggerated, showing the principles). This is the 831 assembly of the upper link to one of the rear triangle eyelets, as far as I could make it out. Grey is the aluminum link, black the carbon triangle, blue the ball bearing and pink the screw. The screw presses the inner race of the bearing against the link, so the screw and inner race are one piece with the link. There is some clearance between the screw head and the triangle so that the parts can rotate with respect to each other. This assembly would be alright if the two eyelets of the triangle (only one shown) were perfectly rigid relative to each other, but that is not the case. So, what prevents the outer bearing from sliding out of the triangle eyelet (to the left) is in practice only the press force of the outer bearing race in the eyelet, as Maffly stated. Inevitably, when the triangle is submitted to lateral forces, the bearing will end up sliding to this position, where the eyelet contacts the screw head, and rubs against it as the triangle and link rotate relative to each other. After a while, clearance may build up between the outer race and the eyelet, whereby the bearing will move freely in and out... The rubbing with the screw head will cause wear and potentially loosen the screw... The situation wouldn't be improved if the bearing were pressed from the outside. The bearings should be in the link, not the triangle, as per the SC assembly shown below. Yellow is a tube for taking up some of the axial force exerted on the bearings by the screw. Here, the bearings are mounted in the link and rely on the rigidity of the link between the two eyelets. The bearings cannot slide out. Dammit, the 831 link and triangle need to be redesigned!! A not too drastic redesign would be to provide something for keeping the bearing in the eyelet, such as a retainer ring. What about the assembly of the lower link to the triangle? I haven't looked close at that yet. November 29, 2021, 04:10:44 AM |
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Re: The Shiny New AM831 Group Buy (A) Thread!
Dear All: Have a nice day. Finally we got the solution of the flexing of the frame FS-AM831. The upgrated of the new mold of triangle, if you need it, contact us. Eddy@haidelibicycle.com We also found that JJJ have the idea of the bolts to solve the problem, really thanks for his help and effort. But that's would not be our solution and cannot ensure it would be works. Thanks for all the supporting and understanding. Feel free to contact me via email. All the new order would be use the new mold. Eddy@haidelibicycle.com Best regards Eddy December 11, 2021, 04:20:39 AM |
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Re: The Shiny New AM831 Group Buy (A) Thread!
Dear All: Ah, the carbon eyelets with two bearings - similar to my fix  A lower link with through-axle. Better. Yet the link still has a cutout between the eyelets. Can do better without the cutout. So what is the upgrade policy for the purchasers of the first version? December 11, 2021, 05:02:47 AM |
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Re: The Shiny New AM831 Group Buy (A) Thread!
At first I didn't pay attention to the flex issue, as my bike and many others here were fine, so I was thinking just about few defective ones. After reading the great JJJ case study I also realize that the design is flawed and all frames potentially will show the flex issue. JJJ fix is brilliant, Haideli one much less even if they invested in a new mold for rear triangle, obtaining the same result as JJJ on the upper link and maybe making it even worse on the lower; the triangle is beefier but this isn't necessary a good thing. For sure the problem has to be solved on all frames, even the non flexing ones like mine: as haideli says carbon fiber is an anisotropic material (the paper sheet explanation); unexpected stress in unexpected direction can cause failure even with relatively low force; I would consider the frame dangerous without locking somehow the bearings in the recess. The big question is if the old triangle section is strong enough after the bearings will be locked in place. I am still positive that the fix will work and the bike will be a great bike as it is for now; for sure I don't want to invest 300$ in the new triangle or even worse 1000$ in the new haideli model. We have to accept that we are beta testers of this frame, it's part of the fun too; just I hope at the end I will have a safe and reliable bike. I am sure everybody isn't riding much due to winter season, but with the coming spring let's keep the community updated about possible failures or defects that this frame could bring. Merry X-mas to all 831 team! 
December 21, 2021, 02:16:56 PM |
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