How to Calculate Torque for Rotating a Supported Vertical Load?

  • Thread starter Thread starter thesnesinator
  • Start date Start date
  • Tags Tags
    Inertia Torque
Click For Summary

Discussion Overview

The discussion centers around calculating the torque required to rotate a supported vertical load, specifically in the context of designing a 3-axis robot. Participants explore various formulas and considerations related to torque, moment of inertia, and the effects of friction and weight.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • Tim seeks a formula for calculating the torque needed to rotate a dead weight on a thrust bearing.
  • Berkeman provides the equation τ = I α, explaining the relationship between torque, moment of inertia, and angular acceleration.
  • Tim questions the initial angular acceleration of a stepper motor setup, proposing a value of 1.57 rad/s² based on a 100Hz input pulse.
  • Another participant emphasizes the importance of including frictional forces from the thrust bearing in the torque calculation.
  • A different participant suggests that the torque can also be calculated using T = F.R, where F is the weight and R is the horizontal radius from the pivot, without considering acceleration.

Areas of Agreement / Disagreement

Participants present multiple approaches and formulas for calculating torque, indicating that there is no consensus on a single method or formula. The discussion remains unresolved with various perspectives on the factors to consider.

Contextual Notes

Some participants highlight the need to account for friction and weight in the torque calculations, while others focus on the moment of inertia and angular acceleration. The discussion reflects differing assumptions about the conditions under which torque is calculated.

thesnesinator
Messages
2
Reaction score
0
Hi I am designing a 3 axis robot but need help with one calculation.

How do you calculate the torque required to rotate a supported vertical load.

For instance the torque required to rotate a dead weight sitting on top of a thrust bearing. I am looking for some formula from mechanical design books but haven't found anything.

Sorry about asking such a basic question.

Regards,
Tim
 
Engineering news on Phys.org
thesnesinator said:
Hi I am designing a 3 axis robot but need help with one calculation.

How do you calculate the torque required to rotate a supported vertical load.

For instance the torque required to rotate a dead weight sitting on top of a thrust bearing. I am looking for some formula from mechanical design books but haven't found anything.

Sorry about asking such a basic question.

Regards,
Tim

Welcome to the PF, Tim. The equation you are looking for is:

[tex]\tau = I \alpha[/tex]

Where tau is the torque, alpha is the angular acceration in radians/s^2, and I is the Moment of Inertia:

http://en.wikipedia.org/wiki/Moment_of_inertia

.
 
Thanks Berkeman,

If I'm using a Stepper motor that has an input pulse of 100Hz (90 degrees a second in this setup) is my initial acceleration 1.57 rad per second^2?
 
thesnesinator said:
Thanks Berkeman,

If I'm using a Stepper motor that has an input pulse of 100Hz (90 degrees a second in this setup) is my initial acceleration 1.57 rad per second^2?

If the motor swings 90 degrees in a second, that is an angular velocity omega:

[tex]\omega = \frac{\pi}{2}[/tex] radians per second.

The acceleration would be during the time it takes to go from omega = 0 to omega = PI/2 rad/s. The angular acceleration is the change in the angular velocity with respect to time.
 
thesnesinator said:
Hi I am designing a 3 axis robot but need help with one calculation.

How do you calculate the torque required to rotate a supported vertical load.

For instance the torque required to rotate a dead weight sitting on top of a thrust bearing. I am looking for some formula from mechanical design books but haven't found anything.

Sorry about asking such a basic question.

Regards,
Tim

Don't forget to include the frictional force from the thrust bearing.

http://www.roymech.co.uk/Useful_Tables/Tribology/Plain_Bearing Friction.html

CS
 
Umm, don't forget to in include the weight either T = F.R . Which would be the "torque required to rotate a supported vertical load" as described in the first thread. Where F is the weight of the item and R is the horizontal radius of the load from the pivot position (without acceleration).
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
4K
  • · Replies 5 ·
Replies
5
Views
5K
Replies
9
Views
2K
  • · Replies 22 ·
Replies
22
Views
6K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 2 ·
Replies
2
Views
4K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 8 ·
Replies
8
Views
3K
Replies
3
Views
5K
  • · Replies 13 ·
Replies
13
Views
4K