Gimbaled Gyroscope: Do I Need Constant Torque?

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Discussion Overview

The discussion revolves around the operational mechanics of gimbaled gyroscopes, specifically focusing on the torque requirements from the gimbal motor when accelerating the flywheel, regardless of its rotational state. The scope includes conceptual understanding and technical explanations related to gyroscopic motion and torque application.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether the same torque is needed from the gimbal motor to accelerate the flywheel when it is rotating compared to when it is not.
  • Another participant asserts that the torque from the gimbal motor does not accelerate the flywheel but instead causes precessional motion at a constant angular velocity, indicating that torque must be adjusted to change precession velocity.
  • A later reply points out a potential issue with the diagram presented, suggesting that the input couple causes precession about a perpendicular axis, which may not align with the observed motion.
  • One participant expresses confusion regarding the fixed position of the gimbal motor and questions the feasibility of precession, asking if there is a difference in required torque when the flywheel is rotating versus when it is stationary.
  • Another participant claims that the same amount of torque is needed to accelerate the flywheel regardless of its rotational state, but notes that the gyroscopic couple will create a bending moment on the gimbal shaft.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between torque and precession, with some asserting that torque requirements change based on the flywheel's state, while others maintain that the same torque is necessary regardless of rotation. The discussion remains unresolved with competing perspectives on the mechanics involved.

Contextual Notes

There are indications of missing assumptions regarding the diagram and the specific mechanics of the gimbal motor's fixed position, as well as the implications of gyroscopic motion on torque requirements. The discussion does not clarify these aspects fully.

Viroos
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Hi !
I have very basic question about gyroscopes: do I need same torque from gimbal motor to accelerate the flywheel whenever it's rotating or not ? (and the gimbal motor is attached to the floor)

cmg.jpg


Thanks in advance :)
 
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The torque applied from the gimbal motor is not going to accelerate it, it is only going to cause precessional motion at a particular constant angular velocity. You'd have to change the torque to change the velocity of precession. The couple is equal to moment of inertia times the cross product of velocity of precession and vel. of spin.
There's something wrong with your diagram. The input couple causes precession about a perpendicular axis but this kind of motion is not possible from what is seen in the drawing.
 
Last edited:
That's what is confusing me-the gimbal motor is fixed to the floor, so the precession is impossible and the only possible rotation is "omega", and that's exactly the problem-is there any difference in the gimbal motor torque when the flywheel is rotating and when it's not ?
 
The same amount of torque will be required to accelerate the flywheel irrespective of whether it's rotating or not, but the gyroscopic couple will produce bending moment of the gimbal shaft.
 

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