Shaft vibration, deflection, and bending stress
The size of shaft was greatly reduced to match it to small pairs of bearings.
The lateral vibration of the shaft at hub position was analysed as an
‘overhanging load with simple supports’ (Shigley) beam with
the rotor as a lumped mass load. The shaft is supported by a pair of bearings.
To make calculation easier, the shaft cross section was assumed constant.
The resulting frequency is well above the maximum rotor rpm. The calculated
fatigue stress is 20% higher than the endurance limit so the shaft won’t
live forever. Also, the deflection calculated might be too high as the
conservative constant cross section and weakest Aluminum alloy were assumed.
The assumed hub to upper bearing distance a = 2.5cm, distance between
bearings l = 40cm, and smallest shaft diameter D = 7mm.
Lateral vibration of shaft
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