How Do Gyroscopic Forces Affect Flywheel Torques?

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    Flywheel Forces
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Discussion Overview

The discussion revolves around the calculation of bending torques on a rotating flywheel, specifically focusing on the effects of gyroscopic forces. Participants explore the relationship between the moment of inertia and the resulting torques when the flywheel is rotated about different axes.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant seeks assistance in calculating bending torques on a rotating flywheel, providing details about the disc's radius, mass, and angular velocity.
  • Another participant questions the term "bending torque," indicating a lack of familiarity with the concept in the context of flywheels.
  • A different participant clarifies that bending torque is orthogonal to the rotating torque, using an analogy related to a front-wheel-driven car.
  • One participant reiterates the initial conditions of the rotating disc and emphasizes that only the moment of inertia around the spinning axis is relevant to the relationship being discussed.
  • A reference to a lecture by professor Walter Lewin is provided, suggesting that the formula for the relationship is presented there, though deriving it is stated to be beyond the lecture's scope.
  • A link to an external article is shared, which purportedly contains a derivation of the relevant formula for gyroscopic effects.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the concept of bending torque and its relation to gyroscopic effects. There is no consensus on the definition or implications of bending torque in this context, and the discussion remains unresolved.

Contextual Notes

Some assumptions about the definitions of bending torque and its application to rotating systems are not fully articulated. The discussion also lacks a clear derivation of the relationship between the moment of inertia and the resulting torques.

doodaa
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Hi there,

I need to calculate bending torques on a rotating flywheel. Not sure how to do this. Anyone who can help?

I have a disc with radius r and mass m rotating with omega_z. This means that the moment of inertia is m*r^2/4 for x and y-axis and m*r^2/2 for z axis. (Z-axis is the "natural" center axis of the disc).

If I rotate the spinning disc around the x-axis (or y-axis) I will feel a torque in the y-axis (or x-axis) due to gyroscopic effects. But how does it relate?
 
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I'm not very familiar with flywheels. What do you mean by "bending torque"?
 
Well, flywheel or not. Let's just assume it is a rotating disc. Bending torque is ortoghonal to the rotating torque. For exampel, if you have a front wheel driven car the rotating torque accelerates the car and the bending torque turns the wheel.
 
doodaa said:
Hi there,
I have a disc with radius r and mass m rotating with omega_z. This means that the moment of inertia is m*r^2/4 for x and y-axis and m*r^2/2 for z axis. (Z-axis is the "natural" center axis of the disc).

If I rotate the spinning disc around the x-axis (or y-axis) I will feel a torque in the y-axis (or x-axis) due to gyroscopic effects. But how does it relate?


A discussion of that relation is presented by professor Walter Lewin in lecture 24 of his classical mechanics series, available as a youtube video:
http://www.youtube.com/watch?v=zLy0IQT8ssk"
At 14 minutes into the lecture the discussion of a spinning disk starts.

Remarkably, only the moment of inertia around the spinning axis figures in the relation you are asking about.


Professor Lewin just presents the formula, deriving the formula is beyond the scope of that lecture.

In case you are curious about a derivation, there is one in an article on my own website: http://www.cleonis.nl/physics/phys256/gyroscope_physics.php"
 
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