Calculating Torque for Steel Fixture at 90 Degrees

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Discussion Overview

The discussion revolves around calculating the torque required to rotate a steel fixture that weighs 3600 lbs and rotates 90 degrees. Participants explore the implications of the dimensions and forces involved, as well as the potential need for a gearbox to assist in the rotation.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes the fixture's dimensions and the force required to rotate it, questioning whether multiplying the force by the distance to the pivot point yields sufficient torque.
  • Several participants seek clarification on the axis of rotation, indicating that the lack of this information complicates the torque calculation.
  • Another participant mentions the need to consider static friction (stiction) when calculating the required torque, suggesting that the initial torque may need to be significantly higher than the calculated value due to this factor.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the axis of rotation and the implications for torque calculations. There is no consensus on the torque requirements or the effects of stiction.

Contextual Notes

The discussion highlights the importance of specifying the axis of rotation and the effects of static friction, which may influence the torque calculations. There are unresolved assumptions regarding the fixture's design and operational conditions.

SevenToFive
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The red section of this fixture rotates 90 degrees it weighs 3600lbs, and is 130 inches wide. It is made out of 10 inch steel channel. On the left of the drawing is the dimension of 40" and the pivot point is actually in the center.
We can rotate it by hand if you grab onto the end that is 12" and it takes approximately 30lbs force applied to the end. If we want to add a gearbox to drive this fixture would it simply be multiplying the 30lbs by 60 inches that is the end of the fixture to the pivot point? Giving me 1800 in-lbs? It doesn't seem like enough. Or am I just greatly over simplifying this? Any help is greatly appreciated.
IMG_0001.jpg
 
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You say the red section rotates 90 degrees, but you do not say what axis it rotates about. The whole question really need clarification.
 
Dr.D said:
You say the red section rotates 90 degrees, but you do not say what axis it rotates about. The whole question really need clarification.

The red section rotates around the circle which runs through the fixture where the intersection of the red section running left and right and the red portion running up and down.
 
To be sure we understand, you are actually rotating the arm vertically around the table pivot shaft, correct?
 
Hopefully this drawing will help clear things up. Thanks to everyone who replies.

IMG.jpg
 
Due to stiction (static friction), you wil probably need at least twice that torque to get it started; depends entirely on the bearings and lubricant. I still remember a textbook example from half a century ago that stated: "It takes 10 men to start a loaded railroad boxcar moving but one man can keep it moving."
 

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