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Carbon Frame - Tap test. What do you think?

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Carbon Frame - Tap test. What do you think?

Old 10-14-09, 07:52 PM
  #26  
nycphotography
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Originally Posted by Fat Boy View Post
I work with carbon structures quite a bit. As a first cut, this is actually a pretty decent way to determine if it's OK or not. It's more of a way to see if the carbon had delaminated from some sort of core (often foam or honeycomb), but could be used on tubes as well. The deal with tubes is that if you've hit it hard enough to mess it up, it will usually have a massive tear, dent or kink in the tube (and, yes, you can 'dent' a carbon structure, it is not always a catastrophic failure) that will be pretty much impossible to ignore.

So, if you take a screwdriver and tap it on a part of the frame that you know is good, it'll give you a certain sound which will be very sharp. Move around the entire bike. It will continue to sound the same way unless you get to a bad spot which will sound very flat. I don't know how else to describe it, but if you get to a bad spot, they really stand out.

Incidently, the is a reasonable way to do non-destructive testing on a lot of things. Steel parts will often 'ring' when hit with a screwdriver (assuming you aren't damping the vibrations by holding the piece in your hand). If the piece is cracked, it won't ring. Again, a little hard to describe, but very apparent once you come across it in real life.
And this process is helped considerably by a $10 stethoscope.
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Old 10-14-09, 07:53 PM
  #27  
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Originally Posted by cap View Post
Oh Dear Lord,

That's SOP from the FAA? Do I have to watch out for guys walking around under the plane with a quarter on my next flight? Fantastic.
Count your blessings.
Here in Cleveland they hit it with a ball peen hammer and look for daylight inside the wing.
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Old 10-14-09, 08:23 PM
  #28  
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Originally Posted by vettefrc2000 View Post
should be supplemented with additional NDI techniques ( i.e.,
ultrasonic or other approved NDI methods)
I think they key thing is that tapping it is not going to be sufficient. I didn't mean to dismiss it entirely.
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Old 10-14-09, 08:49 PM
  #29  
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Actually it is sufficient.
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Old 10-15-09, 01:18 AM
  #30  
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Originally Posted by bobthib View Post
Indeed, I used the other seat stay as a control. There was no difference in the sound of the two. Several people in this forum and others have suggested this is a very good method.

Microscopic examination with a magnifying glass is also a good way, looking for damage to the carbon layer. This too appears fine. The damage appears limited to the paint and primer layers.

The plan now is to cover the "wounds" with a clear coat, apply bondo and sand down smooth. I'll then either mask and spray with black paint, or better yet, find an appropriate decal(s) to cover the spot and the corresponding area on the other seat stay.
Bondo? I hope you are joking...
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Old 10-16-09, 10:37 AM
  #31  
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Originally Posted by rooftest View Post
Bondo? I hope you are joking...
Why not? What's wrong with bondo as a filler (to fill the paint/primer void, not a hole in the CF)

FYI - I have decided to cover it with clear coat and leave the scar for all to see so I can monitor the area for cracking.
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Old 06-03-19, 02:58 PM
  #32  
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well done.

ride on & for future reference coin tap will suffice.
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Old 06-03-19, 03:15 PM
  #33  
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Originally Posted by '02 nrs View Post
ride on & for future reference coin tap will suffice.
The actual F is this? A TEN YEAR OLD THREAD resurrected to tell the OP the tap test is good? Is the OP still a poster here? Still alive? I'm honestly curious how you found this thread, realized it was 10 years old, and wanted to give the OP some advice? Is the "tap test for carbon frames" your passion? Anything on the subject you have to comment on? It's akin to finding some random ancient thread, and adding a comment like "I agree!" So strange...

Also, you have 2 posts in 9 years, the second one being this. Did this post actually happen in 2009, and got stuck in some time warp black hole thing, only to be spit out in 2019?
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Old 06-03-19, 04:47 PM
  #34  
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Old 06-03-19, 10:37 PM
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I was really hoping that this was the OP coming back to share that their bike was fine, and is still going strong...
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Old 06-04-19, 12:07 AM
  #36  
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Originally Posted by grafik1979 View Post
I think that the sounds are different in different spots of the bike, depending on the diameter of the tubing at that particular spot
I think we are mistaking pitch for timbre or resonance. Damaged carbon lacks a certain level of resonance to its sound.
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Old 06-04-19, 03:48 AM
  #37  
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Originally Posted by wipekitty View Post
I was really hoping that this was the OP coming back to share that their bike was fine, and is still going strong...
Another reason why I wish that an old thread (say > 1 year) should only be bump-able by the OP.
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Old 06-04-19, 07:47 AM
  #38  
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This thread is tapped out. Move on, nothing to see here.
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Old 06-04-19, 09:07 AM
  #39  
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For me, the resurrection of the thread was worth it when I read this:

Originally Posted by bobthib View Post
I figure I'll probably just ride the crap out of it and if it fails (and I survive) I'll consider the replacement then.
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Old 06-04-19, 10:20 AM
  #40  
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10 yr update from OP

Well, tempes fugit. It's been 10 yrs since that incident occurred. I've probably put on 30k miles, and it's still my main ride. In fact, I just bought a HVLP paint sprayer for my patio furniture project and it worked so well, I'll be tearing it down and repainting it. At that point I'll bondo or epoxy the blemish before painting, so I'll put another 30k on it!
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Old 06-04-19, 07:33 PM
  #41  
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This was worth reading just for the OP's response a decade later.

Zombie thread haters gonna hate. Some of us enjoy old braaaiiinnnsss. shrug.jpg
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Old 06-05-19, 03:27 PM
  #42  
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Originally Posted by bobthib View Post
At that point I'll bondo or epoxy the blemish before painting, so I'll put another 30k on it!
I'd suggest making sure you use a flexible filler suitable for parts that flex.... ask your local body shop for guidance. Something they would use on a bumper cover would probably be best.

It's fun to come back 10 years later and review the "I'd get rid of the car. That much damage it won't be any good. You may have dented the frame *" comments in hind sight.

* Tin Men
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Old 06-05-19, 05:24 PM
  #43  
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the actual tap test is good imo. if you can interpret the sounds that is.

you can also push the parts with your thumbs/bend/stretch the parts to know if its cracked.

to be honest you only need to understand one single thing: if the part is cracked then its weaker there and then there will be a difference there compared to the rest of the frame no matter how you "test it", because thats the defintion of a crack. its not continous no more.. should be easy to check imo. even without coins.
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