Why is the driven gear's torque's direction clockwise?

  • #1
annamal
381
33
TL;DR Summary
Two gears (A and B) are spinning with their centers fixed with the left one being the driver driving the left gear clockwise. Why is the driven gear (gear B to the right) torque clockwise as well?
We have two gears A and B (left and right). Gear A is driven with a clockwise torque. Why is gear B's torque also clockwise? I would say that if gear B is driven to turn counterclockwise, the torque should be in the counterclockwise direction.
Screenshot 2023-09-12 at 7.09.39 PM.png
 
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  • #2
If the left gear is turning clockwise, the right gear will turn counterclockwise. Is the torque you are applying to A against the rotation or something?
 
  • #3
berkeman said:
If the left gear is turning clockwise, the right gear will turn counterclockwise. Is the torque you are applying to A against the rotation or something?
No. I am applying a torque just to gear A. And apparently the torque for gear B is in the opposite direction because it is some reaction torque to gear A.
 
  • #4
I assume what's being described is the force applied by gear B to gear A. If gear A applies a force downwards at the point of contact, gear B must be applying a force back against it upwards per Newton's 3rd law.
 
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  • #5
annamal said:
No. I am applying a torque just to gear A. And apparently the torque for gear B is in the opposite direction because it is some reaction torque to gear A.
Sure, just use the Right-Hand Rule for torques to help you see what is going on. Draw the force and torque vectors for each gear...
$$\vec \tau = \vec R \times \vec F$$
 
  • #6
Ah. I figured it out. The torque for the right gear is drawn as the load's torque.
 
  • #7
annamal said:
Ah. I figured it out. The torque for the right gear is drawn as the load's torque.
Correct.
Consider that the magnitude of each torque depends on the diameter (or number of teeth) of each gear.
Only the tangential contact forces mentioned in post #4 are of equal magnitude and opposite directions.

Force (or torque) and resistance to it are always a pair.
We can't talk about a driving torque, unless we have a resisting torque.
In the same way, we can't exert any weight on the floor of a free-falling elevator.

FREE-BODY-DIAGRAM-OF-TWO-GEAR.png
 

1. Why does the driven gear's torque have a clockwise direction?

The direction of the driven gear's torque is determined by the direction of rotation of the driving gear. If the driving gear rotates in a clockwise direction, the driven gear will also rotate in a clockwise direction. This is due to the meshing of the gear teeth, which causes the driven gear to rotate in the same direction as the driving gear.

2. What factors affect the direction of the driven gear's torque?

The direction of the driven gear's torque is primarily affected by the direction of rotation of the driving gear. However, other factors such as the number of teeth on each gear and the gear ratio can also play a role in determining the direction of the driven gear's torque.

3. Can the direction of the driven gear's torque be reversed?

Yes, the direction of the driven gear's torque can be reversed by changing the direction of rotation of the driving gear. This can be achieved by using a different power source or by using a reversing mechanism, such as a gearbox.

4. Why is the clockwise direction of the driven gear's torque important in certain applications?

In many mechanical systems, the direction of the driven gear's torque is crucial for the proper functioning of the system. For example, in a car's transmission, the direction of the driven gear's torque must be clockwise in order to move the car forward.

5. How does the direction of the driven gear's torque affect the overall performance of a system?

The direction of the driven gear's torque can have a significant impact on the performance of a system. In some cases, a clockwise direction may be more efficient and provide better power transfer, while in others a counterclockwise direction may be more suitable. It is important to carefully consider the direction of the driven gear's torque when designing a mechanical system to ensure optimal performance.

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