By the fatigue tests of bicycle spokes subjected to repeated tensile loads, the following results are obtained:
1. Since the fatigue fracture of bicycle spokes begins with a crack at the root of the head, the shape and condition under which this part contacts with the spoke hole in the wheel hub seriously affect the fatigue strength.
2. The surface of the fracture on the head of spokes in this test shows the same appearance as that which actually occurs, but is quite different from the one obtained by static tensile test. The reason is that the fracture in the latter test occurred by shear stress.
3. The fatigue limit of sample spokes (240kg being the static tensile strength) was 85kg, and corrosion with acids, sea water etc. decrease the fatigue strength.
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