What Is the Torque Required to Rotate a Disc Between Two Static Discs?

AI Thread Summary
The discussion centers on calculating the torque required to rotate a disc positioned between two static discs. The initial scenario involves two identical discs with a coefficient of friction of 0.4 and a force of 10kN, leading to a calculated torque of 200Nm for rotation. When a third disc is added between the two outer discs, the torque required to rotate the middle disc is confirmed to be the sum of the resistances from both contact faces, resulting in a total of 400Nm. Participants agree on the necessity of considering both contact points for torque calculations. The conversation emphasizes the importance of understanding static rotation torque in engineering applications.
RichyRich85
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Hi everyone

This is my first post on the forum. I work in engineering and use this forum to answer questions from time to time.

I am looking for confirmation of my understanding of static rotation torque (not something I deal with in day to day work).

Imagine 2 identical discs or washers that can rotate. The i/d is 0.095m and o/d is 0.105m. The coefficient of friction is 0.4. They are held together by an invisible force of 10kN. I believe the torque required to start rotation is (coefficient of friction x radius x force) 0.4x0.05×10000=200Nm

Next scenario: A third identical disc is inserted between the other two, and the two outer discs are unable to rotate. The same invisible 10kN force is applied on both of the outer discs. Would the torque required to rotate the middle disc be the same 200Nm, or would it be the sum of the 2 contact faces, I.e. 400Nm. I believe the latter, but just wanted to check.

Thanks in advance.
Richard
 
Engineering news on Phys.org
Yes, the two torque resistances will add.
 
haruspex said:
Yes, the two torque resistances will add.

Thank you haruspex. I appreciate the feedback.
 

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