HMF

I have a random question that's not really bike related, but I don't know where to go to find an chemical engineer's forum and I know that there are some engineers in here.

So I bought this clamp recently to start taking videos with my flip camera while riding (read: poor man's GoPro). I mounted itto the top tube nicely and took some good footage recently and all is good. But I after a few uses I noticed that the bracing side of the clamp is bending outward quite a bit. Funny thing is that I thought the whole assembly was made of aluminum and could possibly crush my top-tube, so I thought I was being careful when clamping it.

Anyway. There weren't any stress fissures in the material so I decided to try bending it back. I bent it back to nearly where it used to be and it still seems pretty good. I know that if it were made of aluminum as I had thought, it would probably would have just failed immediately. But as it turns out it is fiber-glass reinforced nylon. Does anyone know anything about this material? Can it take this kind of bending? It seems okay right now...

saverin

If you value your camera, I would recommend getting a new clamp. By bending the clamp back into shape, you have weakend the material further and if it bent on its own from normal use it, is just going to bend easier.

HMF

I guess I don't really value the camera, so it doesn't matter. I think I'd be more pissed at having wasted money on a clamp. Is that weird?

Campag4life

The technical term is fiber reinforced nylon. I have designed products with it. The fiber filiments give the nylon its tensile and bending strength...just like with a carbon fiber bicycle. But the thing is...once any material yields...fiber reinforced nylon included, then bending it back...will only cause it to yield again...and generally at a lower stress point as it fatigues. So the design of the clamp isn't robust enough for the pressure you are clamping at...or the load of the camera....would have to better learn of how the clamp is bending and why.
If you prize the camera, I suggest you invest in another clamping scheme.

nhluhr

fiber reinforced polymer that has been bent past its yield point is now basically just polymer. So what you have is now approximately as strong as if it were just the nylon.

Runner 1

Chemical engineer here! For curiosity's sake, I dug up the stress-strain curve of fiber reinforced nylon:



It seems to me like you should probably get a new clamp.

EDIT: On second thought, you may have not applied enough stress to push it past its yield point, although I wouldn't risk it if you have an expensive camera mounted to it.

lazerzxr

You have locked in residual stress by bending it, therefore it is stressed even when not in use meaning it will bend under less load than it did the first time

vettracer

Well If he didn't push it past it's "Yield" point, he would not have had to bend it back.


To the OP, Cheep clamp, not fit for your use. As other posters have said it is now weaker than before.