Power to rotate shaft in bending

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SUMMARY

The discussion focuses on calculating the power required to slowly rotate a shaft under a bending moment, emphasizing that this is distinct from torque transmission. Key parameters include shaft size, span between support bearings, bending moment value, and RPM. The moment of inertia is calculated using the formula I=M{[R^2]/4 + [L^2]/12}, which, when multiplied by angular acceleration, provides the necessary torque. Power is defined as the product of force and velocity, with the relationship between force and torque being F=T/r, indicating that power inversely varies with the distance from the center of rotation.

PREREQUISITES
  • Understanding of bending moments in mechanical systems
  • Familiarity with moment of inertia calculations
  • Knowledge of angular acceleration and its relationship to torque
  • Basic principles of power and force in rotational dynamics
NEXT STEPS
  • Study the calculation of moment of inertia for various shaft geometries
  • Learn about the dynamics of bending moments in rotating shafts
  • Explore the relationship between torque, power, and RPM in mechanical systems
  • Investigate methods for measuring and applying torque in practical applications
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Mechanical engineers, design engineers, and students in mechanical engineering who are involved in the analysis and design of rotating shafts under bending loads.

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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