Bicycle rear gears - sudden failure

[Wozzaaah]

The pressure of the in-built rear mech springs is quite a lot, for a start.

It's really not that much at all, think about how it's designed to move sideways, just finger or thumb pressure and the backwards tension is just enough to stop the chain from sagging.

Just out of interest, have you examined the chain in detail at all? Any tight links, loose pins/plates, unusual wear?

 

[Mr Mike]

Simple fix to it all George, Just man up and run the bike single speed, the only thing you gotta worry about then is the chain snapping, No gears no worries...... Get on it!!!!

 

[chap]

George, the part that failed isn't made out of glassfibre.
As has been suggested, it's most likely a plastic that's "glass filled" with chopped strand fibre. That's why it's a composite material.

There's some info on this page that pertains to injection moulding (how that component looks to have been made), all be it for a different material.
Point 3 under the heading Foaming test describes different types of bubbles; also the pics at the bottom help explane.

I must say that your fracture looks matt finished from the pic, and small bubbles like in the acceptable image?!

 

[Drains]

I love this thread. I want to have its babies.

Flippant? Moi?

Sorry George, I know you'll hate that. Serious question - have you examined the rest of the bike (eg the chain), as has been mentioned more than once in this thread, to see if there might be reasons causing this part to fail, other than the inherent weakness of which you have accused it?

 

[the snooper]

come on drains SNAP out of it

 

[brightspark]

I love this thread. I want to have its babies.



Flippant? Moi?

it certainly pulls the posts and views in

 

[the snooper]

im suprised george hasnt tried to make a mould from the old one and cast one form fibreglass and resin

 

[GeorgeB]

im suprised george hasnt tried to make a mould from the old one and cast one form fibreglass and resin

Telepathy or what? I was looking closely at the device a few hours ago, to see if it might be possible to remake the bit which cracked. It would be difficult for sure; not least in getting the alignment right. The first problem will be getting the pins out which fix that bit to the rest of the rear mech. I can't start hammering it about, or cutting it free, until I've exhausted complaints and any hope of a free replacement from the bike shop.

 

[Drains]

Now I want twins. It's just so good!

 

[GeorgeB]

George, the part that failed isn't made out of glassfibre.
As has been suggested, it's most likely a plastic that's "glass filled" with chopped strand fibre. That's why it's a composite material.

There's some info on this page that pertains to injection moulding (how that component looks to have been made), all be it for a different material.
Point 3 under the heading Foaming test describes different types of bubbles; also the pics at the bottom help explane.

I must say that your fracture looks matt finished from the pic, and small bubbles like in the acceptable image?!

The human resources linked to this forum never cease to amaze me. How on earth did you track that link down? I agree - it does look like Campagnolo might have used the Dupont material, or something similar. But whatever it was - It FAILED. It wasn't strong enough. How about making suspension arms for cars out of plastic? Are you from Clanfield near Horndean in Hampshire?

 

[GeorgeB]

Serious question - have you examined the rest of the bike (eg the chain), as has been mentioned more than once in this thread, to see if there might be reasons causing this part to fail, other than the inherent weakness of which you have accused it?

Not yet, but it's a good suggestion and I will, within the next few days.

 

[Drains]

Oh. George. One thing.
How long was the bike guaranteed for?

 

[Chickenjohn]

Telepathy or what? I was looking closely at the device a few hours ago, to see if it might be possible to remake the bit which cracked. It would be difficult for sure; not least in getting the alignment right. The first problem will be getting the pins out which fix that bit to the rest of the rear mech. I can't start hammering it about, or cutting it free, until I've exhausted complaints and any hope of a free replacement from the bike shop.

George, why stop at the derrailer, why not make the WHOLE bike out of fibreglass. Wheels, frame, tyres, chain cassette and all!

Carry a small fibre glass repair kit with you whilst cycling and you will be able to repair virtually any small breakage, even to bones and teeth.

 

[GeorgeB]

George, why stop at the derrailer, why not make the WHOLE bike out of fibreglass. Wheels, frame, tyres, chain cassette and all!
Carry a small fibre glass repair kit with you whilst cycling and you will be able to repair virtually any small breakage, even to bones and teeth.

You don't get it, do you? Ridicule, dumbing down this thread - please refrain. It makes me especially grateful to the numerous members who've made very valid and helpful suggestions.

 

[Shox Dr]

You don't get it, do you? Ridicule, dumbing down this thread - please refrain. It makes me especially grateful to the numerous members who've made very valid and helpful suggestions.

Quiet frankly George. (And I think I can speak for a great deal of us on here) No WE don't get it. I admire your tenacity, however misplaced. You either have way too much time on your hands or...

 

[GeorgeB]

Quiet frankly George. (And I think I can speak for a great deal of us on here) No WE don't get it.

OK - point taken. End of thread. And so nobody will learn how it all turned out. For anyone who might have been interested, blame it on a small minority of kill joys. Thank you again to the majority who had something useful to say.

 

[Wozzaaah]

And so nobody will learn how it all turned out.

I don't think anyone's really bothered George, all that can be said has been said, mostly good advice, some a bit tongue-in-cheek.
Good luck trying to get an FOC replacement, if you do manage to get one then good on you.
I won't bother to close the thread as it'll fizzle out of it's own accord if you've no intention of posting the conclusion.