Chinertown
Chinese Carbon MTB => 29er => Topic started by: carbonazza on November 19, 2015, 05:14:02 AM
-
Last week during my Wednesday night ride, I felt on the side with all my weight on the frame.
It happened already quite a few times, but a rock was just there to welcome my seatstay, that broke in two pieces.
Obviously my co-riders mocked its Chinese origins. Next time buy a real bike, etc.
I'm sure, under the same conditions, any of their carbon bike would had suffered the same fate.
The seatstay are the thinner tubes in general, and it was a very unlucky fall.
(http://i.imgur.com/3Kb62aL.jpg?1)
I wish you never hear a cracking frame noise. It is a very sad sound.
While I fixed my frame in the past, when my chainstay was hit.
This one looked impossible to fix, to then ride it with confidence.
Sooo, I contacted Peter, who happened to just have a CS-041 19" in stock :)
Hopefully he should ship it soon.
The frame, a new crank and a new seatpost depleted my road bike savings I was slowly accumulating for next spring :(
-
Whow, bad impact. I hope you're okay. No injuries ?
Good to see the Y at the back of the seatpost tube isn't broken. Not that weak peace as everyone thought.
I'm also sure a brand name frame wouldn't survive the impact.
-
Just a grazed and swollen ankle, but nothing really bad. Thanks for asking!
-
Glad you came out ok. Frames are replaceable.
Good thing is you get to build another bike. ;D
You should cross section the 256 to see what's inside. ;)
-
I wish you never hear a cracking frame noise. It is a very sad sound.
I have heard that sound, but thankfully it was not my bike, it was a demo, and I had noticed some cracking before I took it out. Mentioned it to the guy, he said go ahead and ride it. I did, it broke. It's quite a sound indeed.
Glad to hear you're okay!
-
Unexpected expenses are the worst! Good to hear you didn't get seriously hurt, at least.
You should cross section the 256 to see what's inside. ;)
I'd also be interested in this. Not sure how much trouble it would be, though. Possibly quite a bit.. Guess it would depend on what kind of tools you have on hand. Wouldn't blame you for not wanting to mess with it.
-
I remember the shop guys cross section-ing a Cannondale Super Six. I think they just used a hacksaw. I doesn't take much to cut through carbon bike parts. ;D ;D
-
When you cut it wrap some tape around it before you take the saw to it
-
As sad as it is, I always take benefit of such misfortune to... upgrade the bike ;D
Good to read you are OK. A broken leg is more difficult to replace.
-
Yes, I have, you know this excitement we all know, again.
Choosing a new frame, new components, cleaning thoroughly all re-usable parts, etc. and... the coming build.
I do not really like to cut carbon, and breathe its dust... but for the "science" I will try.
Thanks all for your support.
-
I cut and grind various metals and carbon for work. Obviously outside is best but also try using a nice pedestal fan next to your work area. It will clear the dust from your breathing air. Seems simple enough but surprisingly a lot of people don't use it.
-
Do it for science! :D
-
very sad news carbonazza :-(
fortunatly you are OK, and that's the most important thing
enjoy your new build ;-)
-
If you've got one, a abrasive saw is by far the best way to cut carbon. If not, as was mentioned, cutting carbon isn't terribly difficult. :D
-
The CS-041 frame arrived today. In perfect conditions.
As many others have already experienced here.
Peter is a very good(and patient) person to deal with.
Now, build time !
As I was without frame, I gave my lefty for maintenance, but they detected an oil leak.
A tiny scratch on the down tube.
It means the very expensive down tube/axle part is toast :( ... but under warranty :)
This will leave me some time to cut the 256 in two.
But currently the weather is quite horrible here to work outside.
So a little of patience will be required ;)
-
This will leave me some time to cut the 256 in two.
But currently the weather is quite horrible here to work outside.
So a little of patience will be required ;)
Most threads around here require patience! Lol. Someone starts a build thread and we sometimes don't see it finished for months. I actually like that dynamic of this forum, I tend to get invested in everyone's builds this way, it seems.
Another positive of this is we'll have a direct comparison between the 256 and 041. Now we just have to wait for you to break the 041 frame, and then we'll also have cross sectioned frames to compare ;D
-
This will leave me some time to cut the 256 in two.
Are you sure nobody can fix your 256 ? I think it can, but it won't be beautiful.
Most threads around here require patience! Lol. Someone starts a build thread and we sometimes don't see it finished for months. I actually like that dynamic of this forum, I tend to get invested in everyone's builds this way, it seems.
I'll start a new thread within days. :) Got a new 650B frame for my daugther from Peter. She will build the bike by herself (and me).
-
@MTB2233, yeah a friend told me the same.
And if I don't want to repair it, he would take the frame and do it gladly.
I'm sorry all scientific fellows here, but I'm not sure it will be cut in two after all.
-
Well of course if you can get it fixed, then that's what we would all do. Looking at those pics, I wouldn't have even considered repair an option, but I guess I have a lot to learn about carbon.
-
I would think for the cost of a repair (I would imagine it would be at least $250?), the increased risk you'd be assuming by repairing it, the reduced cosmetic appeal of the repair (subjective), and the added weight of the repair, you'd be better off just ordering a new frame.
These frames are cheap enough to throw away in situations such as this. No OEM would ever begin to think about repair in this situation. A chip or crack, maybe, but complete and multiple fractures? Nope.
Plus, Peter is a good guy and deservers more business! ;D
EDIT: Here is an interesting article on the subject: http://www.bicycling.com/maintenance/bicycle-repair/calfees-carbon-frame-repair
Perhaps my fears are not very founded. Though the cost aspect is correct,
"Simple repairs typically cost between $200 and $500. Complicated fixes are more expensive, and recreating the original paint can increase the price dramatically. At a certain point, buying a new frame may be a better investment. "
-
Also, was the bike still rideable after this? I realize that sounds silly, but I am curious if you could very carefully ride the bike in this state off the trail? With one side intact and the fairly stiff/strong left side chainstay...
-
Yes, I came back to the car riding.
Albeit slower, as each serious bump caused the wheel/tire to tilt, and scrape the chain stay.
-
I am not an expert on carbon fibre bike frames. It can be just the image quallity too. However, this is not how I remember broken composite materials to look like (simple fiberglass, kevlar and kevlar/carbon mix of racing kayaks' shells). Without trying to stir any shit, does it not look like there is too much of resin and very little of fibre in that broken seat stay? Or am I completely wrong?
-
I am not an expert on carbon fibre bike frames. It can be just the image quallity too. However, this is not how I remember broken composite materials to look like (simple fiberglass, kevlar and kevlar/carbon mix of racing kayaks' shells). Without trying to stir any shit, does it not look like there is too much of resin and very little of fibre in that broken seat stay? Or am I completely wrong?
Hmm, not sure. Hard for me to see. Is that a known cost cutting tactic in the carbon industry?
-
I am not an expert on carbon fibre bike frames. It can be just the image quallity too. However, this is not how I remember broken composite materials to look like (simple fiberglass, kevlar and kevlar/carbon mix of racing kayaks' shells). Without trying to stir any shit, does it not look like there is too much of resin and very little of fibre in that broken seat stay? Or am I completely wrong?
Hmm, not sure. Hard for me to see. Is that a known cost cutting tactic in the carbon industry?
"Known" - I would not go that far. Let's say conceivable. But more than blunt cost cutting it may be simply a manufacturing issue. The quality of any composite material, no matter the fibre part of it, is measured as the fibre:resin ratio. The higher, the better. Basically what you desire is the resin to penetrate in between the fibres with no "empty" space left and then as much of the resin as possible to be removed again. Vacuum is used for high-end boat shells. Probably quite labourious, time consuming and requiring sofisticated machinery. Don't know exactly how much it all applies to bike frames but would not imagine there should be much of a difference.
Again, not an expert, just my 2 cents.
-
@MTB2233, yeah a friend told me the same.
And if I don't want to repair it, he would take the frame and do it gladly.
I'm sorry all scientific fellows here, but I'm not sure it will be cut in two after all.
After successfully repairing a broken carbon seatstay on my Salsa Mamasita, I'd definitely try to repair that frame too!
-
One interesting thing is that the frame remained strong around that junction of the two seat stays that I've seen a few guys concerned about. The impact was just a few inches from that area.
-
I am not an expert on carbon fibre bike frames. It can be just the image quallity too. However, this is not how I remember broken composite materials to look like (simple fiberglass, kevlar and kevlar/carbon mix of racing kayaks' shells). Without trying to stir any shit, does it not look like there is too much of resin and very little of fibre in that broken seat stay? Or am I completely wrong?
You are not wrong at all. I don't mean that Chinese vendor intentionally use less carbon but it is difficult to use a lot of it. The proof is that Cube considers a significant accomplishment to produce a 68% Carbon containing frame. Here is their marketing :)
"C:68 Carbon Fiber Technology
CUBEs highly innovative new C:68 carbon fibre technology allows us to build better bikes than ever. Typically,
carbon fibre frames are around 60% carbon fibre, with the rest being the resin that bonds the fibres together. By distributing carbon fibres evenly, we can make thinner layers within the frame and reduce the amount of resin. Those fibres are a mixture of Ultra High Modulus, High Modulus Spread Tow and Intermediate Modulus carbon, each chosen for the needs of the particular area of the frame. Nanoparticles within the resin itself allows it to be distributed more evenly when under pressure in the frame mould. The result is a range of frames with 68% carbon fibre, lower weight, higher stiffness, more fun."
That tells me that low-end material, probably used here, is a weaker material then what you would find in latest frames from Cubes, Cannondale, Specialized, etc...
-
That tells me that low-end material, probably used here, is a weaker material then what you would find in latest frames from Cubes, Cannondale, Specialized, etc...
This just a "hunch" of yours, or you have actual knowledge of such things? Not trying to start anything, serious question. Because what I got out of your post was that most carbon frames would have similar carbon to resin ratios due to the general difficulty in manufacturing them with increased carbon and decreased resin - even your basic Specialized and Cannondales.
Sounds like CUBE has a "highly innovative" process that improves these ratios, and I agree that would be an improvement and possibly worth paying for, but it wouldn't really be highly innovative if all of the other bike company's frames already had these improved carbon/resin ratios, as you imply they do.
-
The big names may be using a more expensive prepreg, but the effect on the frame or on what the rider feels will be negligible IMO. The designs may be better, but that's a separate argument and can be very subjective. If they have 68% fiber versus 60% fiber, that could save about 100 g on a 1 kg frame, assuming the design uses the same amount of fiber (for equal strength and stiffness) and that they are able to use the higher fiber % composite for the entire frame. The actual savings is probably less. Most of the stuff they put out about carbon fiber is marketing speak.
I work for a company that makes a high performance thermoplastic resin. Most of our material goes into molded and extruded parts, but we also make composite tapes. I'm not a composites expert, but I think I am smarter than your average bear on composites and materials in general. To me, the best measure of quality control is how well the fibers are wetted out. If the fracture has a lot of 'dry' fibers sticking out or obvious delamination between the layers, that means it was poorly made and failed at a lower stress or strain than it should have. It's tough to tell from the pictures, but it looks like the material was pretty well made. If you smashed the seat stays of a name brand frame with a rock I bet you'd see the same thing.
Carbonazza, any chance for some close ups of the fracture surfaces? Also, where did the rock hit the frame? At one of the fractures, or in between?
edit- also, if anything is highly innovative in the carbon fiber, it's done by the fiber maker or prepreg maker and is available to all bike makers willing to pay for it.
-
Patrick, that is very interesting. It is already dark here.
I'll post better pictures tomorrow morning.
-
Good stuff Patrick. The general bike buying public really has no idea what goes into the production of a carbon frame...including me. You just have to take the word of the manufacturers on how the frame is made. If you buy a $3k frame...you just have to assume that the materials and research you expect are actually in the frame.
I'm real curious to see a Specialized (or any big brand) frame cross sectioned and compared to a well known open mold (non bootleg) China frame. Done by a third party with no brand bias.
-
Again, I'm no expert in composite failure modes, but nothing I've seen would stop me from riding my Chiner frame. There is a lot of info out on the web, but it can be tough to sift through and find anything relevant. It may be describing a completely different process than making bike frames, but this paper has a few pictures of broken test bars- http://www.scielo.br/scielo.php?pid=S1516-14392005000100016&script=sci_arttext - the loading method has a big influence on what the fracture looks like as well as the layup. Particularly interesting (to me, anyway) was the conclusion-
"In general, the flexural and shear tests showed that the matrix type caused greater influence on the mechanical properties than the carbon fabric arrangement type. The F584/PW and F584/8HS laminates showed the highest flexural strength values than the F155 epoxy ones. This behavior is attributed to the higher toughness of the F584 matrix, which was modified with a thermoplastic"
Which makes sense, since the fiber is so much stronger than the matrix the overall strength depends on how well it holds together. I guess instead of talking about the carbon fiber the bike companies should talk about their new toughened epoxy resin, but that doesn't impress people like "Ultra Super High Modulus Carbon Fiber".
-
(http://i.imgur.com/gLcrn9r.jpg)
Here are some close up pictures of the bits.
(http://i.imgur.com/WTFXaox.jpg)
(http://i.imgur.com/uGI1gDC.jpg)
A plastic bag remained inside the frame. Probably the ones used to compress the wall against the mold.
(http://i.imgur.com/bNLKiND.jpg)
(http://i.imgur.com/G7S0bP4.jpg)
(http://i.imgur.com/bltFabL.jpg)
(http://i.imgur.com/l0Ppb64.jpg)
The rock hit between 3 - 4
-
A plastic bag remained inside the frame. Probably the ones used to compress the wall against the mold.
Uh, huh, yeah, right, sure. Nice way to try to explain how your stash got all the way down there. Upside, it's probably still good. ;D
(and yes, that probably is remnants of the compression bag but I like my story better)
-
Thanks for posting the pics, but you probably gave the gram counters an aneurysm seeing that bag left in there. Probably an extra 10 g in there, or more if you count all the tubes :)
I'll ask some coworkers about the pics, but based on the description of the crash I still think it performed as expected.
-
@cmh, I'm afraid we are all part of a global opium traffic and should all get our frame inspected :o
@Patrick, so we finally found where the famous "frame weight: XXXX g +/- 50g" comes from.
It depends on the quantity of plastic bag left in the frame ;D
It is the only place( the other seat stay being intact... ) where I saw a plastic piece, and it must be stuck in an irregularity inside, as I couldn't pull it out.
-
Sucks that the bladder is left in like that. I've seen pictures of China carbon wheels with the bladder left in. How much more work is it to pull them out...or is it that once the part is molded...the bladder can't be pulled out? ::)
I have a Cervelo and a set of Zipp wheels...I hope that there are no plastic bags left in them. :o :o
-
Do we really care if the plastic bag bladder is left in? It weights basically nothing. Its presence has no performance degradation. It will never be seen in normal use. It might actually serve to help damp noise reverberation.
I also fail to see where/how you're supposed to reliably pull it out from after assembly? ??? You cannot from the dropout end. And getting it out through that coming seat stay junction on the 256 has to be damn near impossible.
I see it as a non-issue and I bet it occurs on frames routinely, Chinese design or not.
-
On the Chiner frame...not really...but on the more expensive stuff yes.
If I pay an "X" amount for a high end product...I'd be pretty irritated to find leftover production tools left inside my frame.
To each their own.
-
On the Chiner frame...not really...but on the more expensive stuff yes.
If I pay an "X" amount for a high end product...I'd be pretty irritated to find leftover production tools left inside my frame.
To each their own.
But if you're in a situation such as this where the only way you know a bag was left inside is to break your frame. Will you ever know if a Bag was left?
-
How about I put it this way. I don't like the idea of production tools being left inside my frame. Is that easier to accept?
-
How do you like the idea of non-structural foam adding weight to your XX crank arms?
-
Although the weight can be neglected, I'm also quite shocked about plastic being left inside. I don't think it supposed to be there :) Could be true that big brands have the same from time-to-time, but this is the first time I ever saw it... Apart from the weight, thinking about condensation as well although with carbon, that doesn't matter anyway. Just doesn't seem right :)
How about the rest of the frame, does it look ok (hard to tell from the photo's, but carbon seems pretty dense with now delamination issues on the inside). That is nice to see :)
-
It may just be impossible to extract the bladder from some of the tubes as they're closed
bladder in a rim is just sloppy QA, because there're plenty of spoke holes, but seatstay may not have any after leaving the mold (depending on whether it's made separately or the frame is monoqoque)