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Busted Carbon - Help Please?

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Busted Carbon - Help Please?

Old 02-15-22, 05:44 AM
  #51  
bulgie 
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Originally Posted by FBOATSB View Post
Un uomo duro.
Not to disparage DD's hardness, but legend has it that the first time Jacquie Phelan was ever beaten in a MTB race, it was by Cindy Whitehead who accomplished that previously-impossible feat despite having her seatpost break and saddle fall off in mile one of a 50-mile race. She rode 49 miles standing (in high mountains) and vinced the invincible.

Anyone who remembers that day better, please do correct any mistakes I made. My unreliable memory is why I called it a "legend" but I think it might actually be true!

Mark B
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Old 02-15-22, 06:04 AM
  #52  
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Originally Posted by bulgie View Post
Not to disparage DD's hardness, but legend has it that the first time Jacquie Phelan was ever beaten in a MTB race, it was by Cindy Whitehead who accomplished that previously-impossible feat despite having her seatpost break and saddle fall off in mile one of a 50-mile race. She rode 49 miles standing (in high mountains) and vinced the invincible.

Anyone who remembers that day better, please do correct any mistakes I made. My unreliable memory is why I called it a "legend" but I think it might actually be true!

Mark B
That's very true and well documented Sir!
https://mmbhof.org/cindy-whitehead-buccowich/
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Old 02-15-22, 06:13 PM
  #53  
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60 miles worth of test riding over all sorts of surfaces has me convinced: the fix is in



After the first 20 miles I stopped worrying and put the saddle out of my mind; was nice to feel that confident in the repair and enjoy the ride for the remainder of the day. Success!

DD
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Old 02-15-22, 06:45 PM
  #54  
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Gotta love a happy ending.
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Old 02-15-22, 07:03 PM
  #55  
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Great success! Nice to see something put back into service that might otherwise be scrapped, especially a cool saddle like that.
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Old 02-15-22, 07:39 PM
  #56  
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Originally Posted by tricky View Post
Great success! Nice to see something put back into service that might otherwise be scrapped, especially a cool saddle like that.
I wholeheartedly agree - plus, all my spares are currently 1500+ miles to the northwest!

DD
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Old 02-15-22, 07:53 PM
  #57  
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Originally Posted by FBOATSB View Post

That's very true and well documented Sir!

https://mmbhof.org/cindy-whitehead-buccowich/
"I decided to go for a training ride without my seat..."

Some training ride! Trained her brain to ignore 49 miles of pain, more like it

Now that's a hard individual.

DD
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Old 02-15-22, 09:56 PM
  #58  
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Originally Posted by Drillium Dude View Post
Found this stuff:



Carbon fiber was called out specifically in the compatibility list. Dries tan, not clear, but what the hey - the repair site is on the underside of the saddle so I don't really care.

Finishing up the prep work with a little more sanding of the mating surfaces. I figure as the interference fit is pretty tight, I'm going to get a goodly amount of epoxy squeezing out. With that in mind, I have wet paper towels and Q-tips standing by

The fix will be completed tonight and I'll wait until tomorrow to road test. Feeling pretty confident, however, now that I've found a bonding agent specifically for plastic to CF.

DD
JB also offers one specifically for carbon to metal. I glued an FD braze-on tab to a carbon frame. I waited 2 weeks, then picked up the frame and swung it around by the braze-on tab. Works just fine. Of course, prep filing and sanding preceded the epoxy application. Now the head tube is cracked. Murphy.

As far as saddles, I ride cheap Toseek carbon from China. I worry more about the rails.
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Old 02-15-22, 11:17 PM
  #59  
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Never tried that "plastic" flavor of JB Weld but based on nothing more than 1st hand experience and superstition I would have picked OTHER than the trad "metal-powder-infused" gray JB Weld and gone with something I trust more for odd and different materials (Loctite/Henkels industrial epoxies for example).
But this JB seems to have worked with CF so here's hoping the repair lasts, certainly the price was right!
My rule of thumb is: unless you really need quick-curing epoxy always choose the slowest cure that will work for the job. It's generally going to be stronger and more durable.
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Old 02-15-22, 11:24 PM
  #60  
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A good test of the epoxy will be to take it on a century ride.

If it breaks in the first 10 miles, then you'll only have 90 more miles to do standing up, or balancing on those spindly seat rails.



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Old 02-16-22, 12:06 AM
  #61  
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Great work! Even looks good.

To me, it looked as though the crack went all the way thru the outer shell. Apparently, I assumed too much. That the shell was still in one piece (or could be made whole again) was essential to a successful repair.

An interesting thread for me.

Gratz!
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Old 02-16-22, 12:25 AM
  #62  
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Love it when somebody fixes a high end vintage part and gets it back on the road.

Good job, Jeff.
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Old 02-16-22, 01:20 AM
  #63  
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Originally Posted by unworthy1 View Post

Never tried that "plastic" flavor of JB Weld but based on nothing more than 1st hand experience and superstition I would have picked OTHER than the trad "metal-powder-infused" gray JB Weld...
Me, neither - in fact, the gray, metal powder infused JBW is the kind I'm used to and used recently on the exterior garage light repair (which is metal, btw). I'd heard JBW made various epoxies, so I didn't go immediately with the remaining gray stuff but went shopping instead. When I found the CF version, I was pretty stoked. Perusing the Interwebs today, I found out it's also available in black; that would've looked better, of course.

DD
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Old 02-16-22, 01:23 AM
  #64  
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Originally Posted by CliffordK View Post

...then you'll only have 90 more miles to do standing up.
Ha ha - believe me, I got an early enough start that a century could easily have been on the cards today, but my toes wouldn't have made 9 miles standing up, let alone 90, had this fix not worked. Lucky for them, it did

DD
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Old 02-16-22, 01:30 AM
  #65  
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Originally Posted by Bad Lag View Post
Great work! Even looks good.

To me, it looked as though the crack went all the way thru the outer shell. Apparently, I assumed too much. That the shell was still in one piece (or could be made whole again) was essential to a successful repair.

An interesting thread for me.

Gratz!
Thanks!

Understood - and I totally agree. That's why I added the detailed photos and write-up; I figured the early pics probably didn't tell the story very well. I feel very lucky that the main shell didn't suffer any cracks; if it had, I'd have erred on the side of caution and retired it - wouldn't want a failure that might result in some half-arsed vasectomy (as another BF wit suggested in an earlier post).

Apparently this failure isn't all that uncommon with the early versions of this saddle. Later models had a different - and one assumes, more reliable - anchoring system at the nose.

Glad this thread was interesting; and hopefully informative as well. Perhaps somebody else might have a similar failure years from now, dust off this thread, and get their fix, too.

DD
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Old 02-16-22, 01:32 AM
  #66  
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Originally Posted by gugie View Post
Love it when somebody fixes a high end vintage part and gets it back on the road.

Good job, Jeff.
Thanks, Mark. I knew you'd understand, as one who "fixes" old vintage bikes and gets them back on the road

DD
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Old 02-16-22, 10:46 AM
  #67  
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Originally Posted by Bad Lag View Post
$550!, Ouch!

I have no idea of your level of experience designing and using fiber laminates and epoxy resins. These are my thoughts on the matter.

1. Don't forget to put doublers (plies of material over the break) on the outside, too. Without those, IMO, the saddle will likely break again. Weight on the "nose" will show up as a tensile load in the outer doubler plies (which is what you want). Without external doublers, the crack will just open up again and all your work underneath will be for naught. Fibers work best in tension, not compression.

2. Fabric is nice (easier) because you get fibers in two directions built into it. Unidirectional tape is more work but will also work well. Uni tape is thinner but much more directional in its properties (strong longitudinally, very weak tranverse).

3. If you are unfamiliar with layup, get a resin/hardener system with a long working time, a long pot life. They may be slower to cure but give you the time you need to get it right.

4. In designing your fiber plies and overall layup, be sure to maintain symmetry (same plies on both side) to keep it straight and true. Also, maintain balance or it may twist.

5. That fitting appears to be a stress riser, a sharp edge - little or no "fairing in" to the bottom of the seat, no extra plies (doublers) to spread the loads.

I hope some of this helps in some way.

You can do this repair for less than $550 but it will have to be a labor of love (don't factor in your cost of labor).
I did notice that there seems to be no real gradual planar transition between the edges of the nose slot piece and the top shell, which most likely cause stress concentration and failure of the CF and resin at the joints.
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Old 02-16-22, 10:51 AM
  #68  
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Originally Posted by Drillium Dude View Post
... I found out it's also available in black; that would've looked better, of course.DD
Paint, flat black paint is what you seek. :-)
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Old 02-24-22, 09:21 PM
  #69  
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Originally Posted by Bad Lag View Post

Paint, flat black paint is what you seek...
Yes, that definitely did the trick:





Added a few new coats of clear lacquer to the other side, too:



DD
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Old 02-25-22, 02:31 PM
  #70  
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A small, perhaps useful hint on that saddle usage:
Most seat posts have lower cradles that are only 1" to 1.25" long on the bottom side of the rail, and often not "continuous."
They only "grab" the rail at two distinct points, fore and aft, matched by two grab points on top of the rail.

While this may support the rails and keep the saddle in one place, I'm not at all sure how it affects those rails under real world use.

I try to find (mostly) Cannondale seat posts, which have a lower cradle that is a) solid from front to rear and b) twice as long as most lower cradles.
This tends to support that saddle rail, from underneath, nearly the entire clamping distance available.
Of course, the top clamp is almost never that long, but I sometimes can use the Cannondale post's upper clamp, which is also longer than most, on some two-bolt models. I don't use the post itself, but rather, the lower clamp on posts I have that it fits. About 75%, and all my aftermarket carbon ones that use upper/lower cradles.

This all may be just visuals, but I like the peace of mind with a long lower cradle under my rails, most of which are carbon these days.
Perhaps the same setup on your seat post would relieve some of the stress on those rails?

Engineers may now chime in to prove me undoubtedly wrong. It happens.

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Old 02-25-22, 11:57 PM
  #71  
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Originally Posted by bamboobike4 View Post

A small, perhaps useful hint on that saddle usage...they only "grab" the rail at two distinct points, fore and aft, matched by two grab points on top of the rail...
Although not an engineer, I do agree that a lower saddle cradle which supports the rail across a greater distance rather than just two points would be less likely to contribute to rail breakage. That said, engineers design these things to work with components across the spectrum, so I'd assume most saddle rails are designed to take the stresses inherent in (generally) all seatpost cradle types.

Even so, I don't trust tubular steel/titanium or carbon saddle rails, period. Give me a solid steel or titanium rail any day of the week and twice on Sunday

DD
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