Calculating the torque needed to rotate a drum

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Discussion Overview

The discussion centers on calculating the torque required to rotate a drum connected to a motor via a toothed belt. Participants explore various factors that influence torque calculations, including the drum's weight, radius, and the presence of friction or acceleration. The scope includes theoretical considerations and practical implications of the setup.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant requests guidance on calculating the torque needed to rotate a drum with specified dimensions and weight.
  • Another participant argues that the question cannot be answered without additional information, such as whether the drum is accelerating, the mass moment of inertia, and the presence of friction.
  • A later reply clarifies that if there is no friction, no acceleration, and the drum does not perform any work, then the torque required would be zero.
  • Concerns are raised about the feasibility of the motor's placement under the drum given the configuration of the belt, questioning whether the belt is horizontal or vertical.
  • Further discussion highlights the potential impact of motor bearing friction and losses in the belt drive on the torque calculation.

Areas of Agreement / Disagreement

Participants express differing views on the necessary conditions for calculating torque, with some emphasizing the need for more information while others propose scenarios where torque could be zero. The discussion remains unresolved regarding the specific torque calculation due to these varying assumptions.

Contextual Notes

Limitations include the lack of clarity on the drum's operational conditions, such as whether it is accelerating or performing work, and the assumptions regarding friction and the configuration of the motor and belt.

jonas_biermann
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Imagine this: You have a drum with a radius of 12cm, around that drum is a toothed belt which is connected to a motor. The drum weighs 10kg
The motor should be placed under the drum

How would I calculate the amount of torque needed to rotate the drum

I don't have any idea how to calculate this but it would be nice if somebody could answer :)
 
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This question is unanswerable with the information you've provided. It really matters a lot if the rotation is accelerating, and if so what the mass moment of inertia around the axis is, if the drum is doing any work (like if there is maybe stones inside it to be fractured or whatever), if there is friction, etc. etc.
 
Arjan82 said:
This question is unanswerable with the information you've provided. It really matters a lot if the rotation is accelerating, and if so what the mass moment of inertia around the axis is, if the drum is doing any work (like if there is maybe stones inside it to be fractured or whatever), if there is friction, etc. etc.
The accelaration is static. There are plants in the drum but the center of mass is in the middle of the drum. For my example friction can be neglected.
 
If there is no friction and no acceleration, and the drum does no other type of work, then the torque is zero
 
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jonas_biermann said:
around that drum is a toothed belt which is connected to a motor. The drum weighs 10kg
The motor should be placed under the drum
How can the motor be under the drum if there is a horizontal belt connecting them? Or are they both horizontal and the belt is vertical, and you are tumbling something inside the drum?
jonas_biermann said:
For my example friction can be neglected.
What about the motor bearing friction, and the losses in the belt drive?
 

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