Power to rotate shaft in bending

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To calculate the power needed to slowly rotate a shaft under a bending moment, one must consider the shaft's size, span between support bearings, bending moment value, and desired RPM. The torque required to initiate rotation is derived from the moment of inertia, which is calculated using the formula I=M{[R^2]/4 + [L^2]/12}, and is multiplied by angular acceleration. Power is only necessary until the shaft reaches the desired RPM, after which it can be maintained with varying force based on the torque and distance from the center of rotation. The relationship between force and torque indicates that as the radius increases, power decreases for the same torque. Understanding these dynamics is essential for accurately determining the power requirements for rotating a shaft under bending moments.
Simon Cohen
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How do you calculate amount of power needed to slowly rotate shaft under bending moment? This is not related to transmittal of torque.

Given:
shaft size
span between support bearings
bending moment value
rpm

Assume: slow rotation (ignore centrifugal forces caused by deflection)
 
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Simon Cohen said:
How do you calculate amount of power needed to slowly rotate shaft under bending moment? This is not related to transmittal of torque.

Given:
shaft size
span between support bearings
bending moment value
rpm

Assume: slow rotation (ignore centrifugal forces caused by deflection)
To set a stationary shaft into rotation needs application of torque.
Do you need the shaft to rotate around the central axis along its length or the central axis perpendicular to length?
"Bending moment" is torque.
The moment of Inertia, given by I=M{[R^2]/4 + [L^2]/12) muliplied by angular acceleration gives the torque that you know.
Power is supplied only until it accelerates.Fdx/dt is the power, but to produce the same rpm with the same torque F varies as F=T/r, where r is the distance of point of application of force from the centre, power varies inversely as r for the same torque.
 
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