Author Topic: Broken frame  (Read 15017 times)

Izzy

Re: Broken frame
« Reply #15 on: November 23, 2015, 06:33:08 PM »
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

MTB2223

Re: Broken frame
« Reply #16 on: November 24, 2015, 02:03:34 AM »
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).

carbonazza

Re: Broken frame
« Reply #17 on: November 25, 2015, 02:41:43 AM »
@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.

Sitar_Ned

Re: Broken frame
« Reply #18 on: November 25, 2015, 07:51:56 AM »
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.

Vipassana

Re: Broken frame
« Reply #19 on: November 25, 2015, 03:09:55 PM »
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. "
« Last Edit: November 25, 2015, 03:16:10 PM by Vipassana »

Vipassana

Re: Broken frame
« Reply #20 on: November 25, 2015, 03:22:58 PM »
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...

carbonazza

Re: Broken frame
« Reply #21 on: November 25, 2015, 04:55:49 PM »
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.

seahog32

Re: Broken frame
« Reply #22 on: November 30, 2015, 12:33:08 PM »
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?

Oolak

Re: Broken frame
« Reply #23 on: November 30, 2015, 01:21:26 PM »
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?

seahog32

Re: Broken frame
« Reply #24 on: November 30, 2015, 02:53:02 PM »
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.

rvc

Re: Broken frame
« Reply #25 on: December 03, 2015, 08:13:28 PM »
@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!

MTNRCKT

Re: Broken frame
« Reply #26 on: December 07, 2015, 08:14:04 AM »
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.

SportingGoods

Re: Broken frame
« Reply #27 on: December 08, 2015, 07:55:02 AM »
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...

Rigid_Bloke

Re: Broken frame
« Reply #28 on: December 08, 2015, 08:16:23 AM »
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.

Patrick C.

Re: Broken frame
« Reply #29 on: December 08, 2015, 09:50:41 AM »
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. 

 
« Last Edit: December 08, 2015, 09:58:05 AM by Patrick C. »