Power to rotate shaft in bending

[Simon Cohen]

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)

 

[vin300]

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.

 

[astrokreng]

To calculate the amount of power needed to slowly rotate a shaft under bending moment, we need to consider two main factors: the bending moment and the rotational speed. The bending moment is a measure of the force applied to the shaft that causes it to bend, while the rotational speed is the rate at which the shaft is turning.

First, we need to determine the bending stress on the shaft caused by the bending moment. This can be calculated using the formula σ = M*c/I, where σ is the bending stress, M is the bending moment, c is the distance from the neutral axis to the outermost fiber of the shaft, and I is the moment of inertia of the shaft. The moment of inertia can be calculated using the formula I = π*r^4/4, where r is the radius of the shaft.

Next, we need to consider the rotational speed of the shaft. This will determine the amount of work being done per unit time, which is the definition of power. Power is calculated using the formula P = W/t, where P is power, W is work, and t is time. Since we are assuming slow rotation, we can ignore the centrifugal forces caused by deflection and focus on the work being done to overcome the bending moment.

Therefore, the amount of power needed to slowly rotate a shaft under bending moment can be calculated using the formula P = M*ω, where P is power, M is the bending moment, and ω is the angular velocity (in radians per second) of the shaft.

In order to determine the exact amount of power needed, we will also need to know the span between the support bearings and the size of the shaft. This will allow us to calculate the distance c and the moment of inertia I, which are both necessary for the calculations.

In conclusion, to calculate the amount of power needed to slowly rotate a shaft under bending moment, we need to consider the bending stress, rotational speed, and other factors such as shaft size and span between support bearings. With this information, we can accurately determine the power required to rotate the shaft in bending.