Electric Bike Front Wheel Skewer Axle Failure
It could be a surprise to users that the front axle on an electric bike is a small skewer. The skewer holds the front wheel to the front fork. Read Consulting Performed a failure analysis of a quick release skewer front axle of an electric bike. The skewer failed suddenly while the bike was in use and the front wheel came off causing the bike to crash. The skewer is a 0.190” diameter steel pin that passes through the wheel and is fastened at the other end with a large nut. To tighten the axle, the nut is screwed down to be “snug”; then the cam lever on the other end is folded down (it is important to note that the lever provides a mechanical advantage). If the axle is too loose, the lever is lifted; the nut is tightened a bit more and the lever is folded down. In the end, the lever supplies the ultimate skewer tightening force. This force depends on the strength of the person assembling the wheel. In this case, the tightening force generated by tightening caused a tensile overload failure of the skewer. The remaining half of the skewer exhibited the “cup” half of a “cup and cone” tensile overload failure commonly found in mild steel. See the pictures below.
