Carbon Frame - Tap test. What do you think?
10-14-09, 07:52 PM
#26
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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.
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.
10-14-09, 08:49 PM
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Actually it is sufficient.
10-15-09, 01:18 AM
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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.
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.
10-16-09, 10:37 AM
#31
Legs; OK! Lungs; not!
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06-03-19, 02:58 PM
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well done.
ride on & for future reference coin tap will suffice.
06-03-19, 03:15 PM
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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?
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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06-03-19, 04:47 PM
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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...
06-04-19, 03:48 AM
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Another reason why I wish that an old thread (say > 1 year) should only be bump-able by the OP.
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06-04-19, 09:07 AM
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06-04-19, 10:20 AM
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Legs; OK! Lungs; not!
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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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06-04-19, 07:33 PM
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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
Zombie thread haters gonna hate. Some of us enjoy old braaaiiinnnsss. shrug.jpg
06-05-19, 03:27 PM
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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
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.
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.
