Technician <
[email protected]> wrote:
> JD <
[email protected]> spoke thusly...
> > When all of a sudden:
http://gallery.consumerreview.com/webcrossing/images/061003013.jpg
> Damn, that really sucks i can imagine.
> But seriously, "Just Riding Along", what really happened? i have never seen a broken crank, so i
> am curious how one would break (aside from dropping the bike from 40' and having it land solidly
> on the crank first).
http://pardo.net/pardo/bike/pic/fail/FAIL-001.html
Metal fatigue from repeated stress cycles.
A small crack starts and grows slowly. Eventually the thickness of uncracked metal is not enough to
take the stress, and blammo, it cracks the rest of the way through, even while JRA. For example,
pictures "crank-fail-011" and "crank-fail-017" at the above link. You can see that half of the break
is dark from oxidation and dirt - that's the part that was already cracked, growing slowly. The
light part is what was exposed at the moment of failure.