Testing torque for motor selection

It would also be helpful to know the friction coefficient of the surface, but since it is not conventional, this information may not be available. Your research on comparing the strength of motors based on watts was a good starting point, but torque is a crucial factor that needs to be considered as well. Ultimately, your goal is to find the cheapest motor that can effectively drag the ring across the surface, so it would be beneficial to continue researching and comparing different motors based on their torque capabilities.
  • #1
jloogoons
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I need to drag a ring across a surface by pulling it with a string attached to a motor. The motor will simply coil the string, or the motor will be attached to a pulley and the ring will be tied on the rope. My key problem: the surface is not conventional so there is no friction coefficient.

Basically, I know very little about physics but I've done a lot of research on this topic so I hope someone can follow my thought process and point me in the right direction. Thanks in advance.

At first, I was comparing the strength of motors based on calculating the watts. I have a hand mixer that will pull the ring across with no problem, but I have a 5 hobby motors that failed. There seemed to be no correlation to the amount of watts used by the motor. After some research, I realized torque was the missing element. But without a friction coefficient I'm not sure how to determine my required torque.

Since I need to buy the cheapest motor that will do the job, it would be nice to know the exact amount of torque required to drag this ring across the surface. I pulled out a luggage scale and measured the resistance of the ring to the surface. This involved tying one end of the rope to the scale and the other to the ring. Then, I held the surface with my left hand and the scale with my right and simply pulled the ring across. The scale showed 2 pounds of resistance.

I then measured the hand mixer that had worked so well and the scale showed 5 pounds. The hobby motor that came closest to working provides .25 inch pounds of torque according to the manufacturer.

From what I understand about measuring torque, it is simply the length of the lever multiplied by the force. Since I didn't have a lever for this exercise, I need a motor with 2 inch pounds of torque, and my hand mixer has 5 inch pounds of torque. In other words, whatever was on the luggage scale is my required torque. So I need to look for a motor with more than 2 inch pounds of torque, correct?

I hope I've provided enough information. I would really appreciate any help you can provide on this topic. Thank you.
 
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  • #2
Yes, you are correct. To determine the amount of torque required to drag the ring across the surface, you need to take into account both the force applied and the length of the lever. Since you don't have a lever for this exercise, you can use the weight of the ring and the resistance of the surface measured with the luggage scale as a proxy for the required torque. In this case, you need a motor with more than 2 inch pounds of torque to drag the ring across the surface.
 

1. What is torque and why is it important in motor selection?

Torque is a measure of the force that causes an object to rotate. In motor selection, it is important because it determines the ability of the motor to do work and overcome resistance. It is a crucial factor in determining the efficiency and performance of a motor.

2. How is torque tested in motor selection?

Torque can be tested through various methods, including dynamometer testing, load cell testing, and direct measurement using a torque wrench or torque sensor. These tests can determine the peak torque, continuous torque, and torque at different speeds.

3. What factors affect the torque requirements for motor selection?

The torque requirements for motor selection depend on factors such as the load or resistance being moved, the speed at which it needs to be moved, and the desired acceleration or deceleration. Other factors include the type of motor, gearbox, and the efficiency of the system.

4. How do you calculate the required torque for a specific application?

The required torque can be calculated by multiplying the force needed to move the load by the distance from the center of rotation to the point where the force is applied. This can be further adjusted for factors such as friction, gravity, and acceleration to determine the total torque required for the motor.

5. Can torque testing be done in real-world conditions?

Yes, torque testing can be done in real-world conditions by using instruments such as torque meters or load cells. However, it is important to note that environmental factors such as temperature and humidity can affect the accuracy of the test results and should be taken into consideration.

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