Fractured front cog?

On Mon, 5 Jul 2004 11:03:27 CST, "Daniel Kelly \(AKA Jack\)"
wrote:

Dear Bikers,

I fear my bike has a fracture in its front cog. I first noticed something
was wrong when I heard the front cog hitting against the front derailleur
once every revolution of the pedals. It turned out the front cog was
actually bent and so "wobbled" as it rotated, relative to the front
derailleur. Closer inspection showed that the front cog was a little loose
and could be jiggled a little. The join between the front cog and the right
pedal was clearly loose.

I took the right pedal off and found a little crack in the front cog. Some
photos are he

http://www.xlk.org.uk/forum/modules....view_album.php

Is this a fracture? If so, how dangerous is it? Can I ride my bike with
this fracture? Do I need a new front cog & right pedal?

Thanks,
Jack

That link doesn't work for me. At anyrate, be sure and carry extra duct
tape in case the cob breaks 30 miles frome home, eh? ;-D

-B

Badger_South wrote: {OP snipped}

That link doesn't work for me. At anyrate, be sure and carry extra
duct tape in case the cob breaks 30 miles frome home, eh? ;-D
****

That's just corny advice!

Bill "sure you meant 'cogg' ;-) " S.

"S o r n i" wrote: (clip) Bill "sure you meant 'cogg' ;-) " S.
^^^^^^^^^^^^^^^
I think he really meant "chainring." :-)

I couldn't get the link to work, either, but I would not ride with a
chainring that might fail. Not only do you risk being stranded with nothing
but a roll of duct tape--if it happens when you are pressing hard on the
pedal, you could hurt yourself. :-(

Leo Lichtman wrote:
"S o r n i" wrote: (clip) Bill "sure you meant 'cogg' ;-) " S.
^^^^^^^^^^^^^^^
I think he really meant "chainring." :-)

I was referring to Badger's typo ("cob"), which you snipped (and then
referred to the OP).

Bill "you butchered Badger badly buddy" S.

Arg!

Try these links:

http://www.ucl.ac.uk/~ucgadak/fracture1.jpg
http://www.ucl.ac.uk/~ucgadak/fracture2.jpg
http://www.ucl.ac.uk/~ucgadak/fracture3.jpg

Thanks!
Jack



"Daniel Kelly (AKA Jack)" wrote in message
...
Hi guys,

Thanks for all your replies.

Sorry about the failed link. It turns out my web hosts have taken their
servers off-line for some maintanance. It should be back online soon.

In the mean time, I'll try to attach a pic to this mail.

Thanks,
Jack



"Leo Lichtman" wrote in message
...

"S o r n i" wrote: (clip) Bill "sure you meant 'cogg' ;-) " S.
^^^^^^^^^^^^^^^
I think he really meant "chainring." :-)

I couldn't get the link to work, either, but I would not ride with a
chainring that might fail. Not only do you risk being stranded with
nothing
but a roll of duct tape--if it happens when you are pressing hard on the
pedal, you could hurt yourself. :-(

On Mon, 5 Jul 2004 18:58:03 +0100, "Daniel Kelly \(AKA Jack\)"
wrote:

Hi guys,

Thanks for all your replies.

Sorry about the failed link. It turns out my web hosts have taken their
servers off-line for some maintanance. It should be back online soon.

In the mean time, I'll try to attach a pic to this mail.

Thanks,
Jack

Hey Jack, hope you didn't mind the bit of teasing. Given that the bike is a
somewhat 'delicate' piece of machinery but with often great stress placed
upon the components, as a rule of thumb, if you find -anything- wrong with
either the frame or the components, get it repaired or replaced as quickly
as possible. Luckily, this is an easily replaced component. In fact you can
use this opportunity to upgrade to a better piece of componentry, something
lighter or stronger.

Metal has interesting properties, toughness, ductility, brittleness,
resistant to compression in a certain plane, but not in other planes. When
you're dealing with a machined part which is also cut out to reduce weight,
you may have a very strong part as is - but if you have a fracture in that
part, it may become unusually weak.

Certainly we're not dealing with stresses like those in fast moving parts
like airplane propellers, but consider what others have said - if the part
fails in the middle of a fast downhill, or as you put pressure on it to
cross a busy street - well, you're playing with fire. Always, always check
out your ride, and if you notice something 'odd', it's prudent to stop and
check it out. You may not see an obvious fault, but in this case it's
staring right at you. If you're 10 miles from home, you could take a risk
and go slowly and cautiously, but I would strongly advise you get it
replaced before you ride it again.

I had a bent brake lever from running into the side of a bridge, avoiding a
pedestrian. I didn't get it fixed right away, b/c I was upgrading my ride,
but when the bike mechanic saw it he said I was lucky I didn't try to
straighten it, b/c being aluminum, it would likely have snapped off. That
would have been fun, 10 miles from home and only one set of brakes! ;-)

-Badger




"Leo Lichtman" wrote in message
...

"S o r n i" wrote: (clip) Bill "sure you meant 'cogg' ;-) " S.
^^^^^^^^^^^^^^^
I think he really meant "chainring." :-)

I couldn't get the link to work, either, but I would not ride with a
chainring that might fail. Not only do you risk being stranded with
nothing
but a roll of duct tape--if it happens when you are pressing hard on the
pedal, you could hurt yourself. :-(

Leo wrote: I think he really meant "chainring." :-)
^^^^^^^^^^
I was referring to Badger's typo ("cob"), which you snipped (and then
referred to the OP).
^^^^^^^^^^^^
Sorry, Sorni...I always do that, since I assume that everyone reads these
posts in order. I did get your joke, and thought it was funny. My line
might have been, also, with better timing.

Leo Lichtman wrote:
Leo wrote: I think he really meant "chainring." :-)
^^^^^^^^^^
I was referring to Badger's typo ("cob"), which you snipped (and then
referred to the OP).
^^^^^^^^^^^^
Sorry, Sorni...I always do that, since I assume that everyone reads
these posts in order. I did get your joke, and thought it was funny.
My line might have been, also, with better timing.

Ba-rumdum!

Bill "just back from a fast (for me) 40-miler" S.

On 5 Jul 2004 21:55:08 GMT, Werehatrack wrote:

On Mon, 5 Jul 2004 11:03:27 CST, "Daniel Kelly \(AKA Jack\)"
wrote:

I fear my bike has a fracture in its front cog. I first noticed something
was wrong when I heard the front cog hitting against the front derailleur
once every revolution of the pedals. It turned out the front cog was
actually bent and so "wobbled" as it rotated, relative to the front
derailleur. Closer inspection showed that the front cog was a little loose
and could be jiggled a little. The join between the front cog and the right
pedal was clearly loose.

I took the right pedal off and found a little crack in the front cog. Some
photos are he
[snipped]

Is this a fracture?

Yes. It looks like you've got a typical non-repairable crank set
there. The large and small sprockets (also called chainrings) are
both riveted to the middle-size one, and the middle sprocket has the
splines broached into the center to mate with the hub. Unfortunately,
these almost never can be disassembled nondestructively, and no
replacement parts for the individual pieces are sold in any event.

Great answer! Had all the specifics that other replies (including my dumb
comments about metal fatigue, heh) lacked. Very informative.

-Badger

Hi Badger,

Many thanks for your replies. All very useful.

Thanks,
Jack.



"Badger_South" wrote in message
...
On 5 Jul 2004 21:55:08 GMT, Werehatrack
wrote:

On Mon, 5 Jul 2004 11:03:27 CST, "Daniel Kelly \(AKA Jack\)"
wrote:

I fear my bike has a fracture in its front cog. I first noticed
something
was wrong when I heard the front cog hitting against the front
derailleur
once every revolution of the pedals. It turned out the front cog was
actually bent and so "wobbled" as it rotated, relative to the front
derailleur. Closer inspection showed that the front cog was a little
loose
and could be jiggled a little. The join between the front cog and the
right
pedal was clearly loose.

I took the right pedal off and found a little crack in the front cog.
Some
photos are he
[snipped]

Is this a fracture?

Yes. It looks like you've got a typical non-repairable crank set
there. The large and small sprockets (also called chainrings) are
both riveted to the middle-size one, and the middle sprocket has the
splines broached into the center to mate with the hub. Unfortunately,
these almost never can be disassembled nondestructively, and no
replacement parts for the individual pieces are sold in any event.

Great answer! Had all the specifics that other replies (including my dumb
comments about metal fatigue, heh) lacked. Very informative.

-Badger