Broken Bicycle Cranks

More broken cranks under 000.html.


Bullseye crank. Note: the cranks are of welded steel.

Picture from as of 2003/01/01. ``09.07.99: ... we were just setting off on another hike, accelerated up the road and CLANK the crank arm snapped ... Bummer. Anyway the Pace is very old and can only take Bullseye cranks so I'm trying to find another arm to put on them.'' Not sure the age of the broken crank, but elsewhere the page notes ``17.09.2000 ... Mondo Mike emailed me saying he had a set of Bullseye cranks that I could have ... the diameter of the set he sent was approx 0.2mm bigger than my old set, so they didn't go through the old bearings.''

The spindle diameter may be a clue to the age. The crank appears to be a left-side (splined) crank which broke near the spline band clamp. Likely the failure contributors included high loads (greatest leverage), heat affected zone (in the weld), and flexing of the splined clamp. Without closer examination it is not possible to determine the deeper nature of the failure.

See also FAIL-003.html