Calculating torque required to rotate objects

In summary, the speaker is seeking help with building a robot that involves shooting a foam bullet from a Nerf gun at different angles. They are looking for the torque required to rotate the gun and have provided details such as the weight and dimensions of the gun, as well as the radius of the motor's shaft. They are seeking guidance on how to calculate this torque and are given a formula to use.
  • #1
XepheraGeeb
2
0
I don't have any background in any physics past high school, so I was wondering if someone could help me figure something out.
I'm trying to build a robot that involves shooting off a foam bullet from a Nerf gun at different angles. I want to have a motor attached to the center of the gun, turning it around so it can shoot between 0 degrees (straight) and 90 degrees (up). Now I want to figure out what kind of motor I need to do this, but for that I need to know the torque required to rotate the gun.

To make calculations easy, I think it would be easiest to assume that the gun is a perfect rectangular prism weighing 1.00 KG (it won't be that exact weight of course, but I thought it would be faster if I was shown how to do the calculations first then I could plug in the real numbers) 30 CM long, 10 CM wide, and 5 CM thick. The motor would have a shaft with a 2 CM radius (might look something like this: http://www.engineersgarage.com/sites/default/files/imagecache/Original/wysiwyg_imageupload/28714/Servo-motor-insight1.jpg) and would be placed in the center of the side of object.

To give you a picture of what it all looks like: At 0 degrees the gun is parallel to the ground and oriented straight like someone would hold a gun, so the object has a depth of 10 CM (it's width), 5 CM wide (it's thickness), and 30 CM long. At 90 degrees, it's now facing up so it has a depth of 30 CM (it's length), 10 CM long (it's width) and is still oriented so that it's 5 CM wide.

To recap:
-I'm assuming the gun is a perfect rectangle
-1 KG mass
-30 CM long, 10 CM wide, 5 CM thick
-2 CM shaft radius on motor
-Motor is connected to the center of the side of the gun
-trying to find the torque required to rotate the object 90 degrees, against gravity

If anyone could show me how to calculate this, or just point me in the right direction that would be helpful! Thanks.
 
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  • #2
Well, I think the torque required depends on the angular acceleration you want for the gun.
Torque = I * alpha, where I = mass moment of inertia and alpha = angular acceleration (consistent units)
You should be able to find formulas for mass moments for common shapes and axis of rotation by searching.
That might get you started.

Cheers,
Terry
 
  • #3
Thanks Terry, I'l check it out
 

1. What is torque and why is it important in rotating objects?

Torque is the measure of the force that causes an object to rotate around an axis. It is important in rotating objects because it determines how much force is needed to overcome the resistance and make the object rotate.

2. How do you calculate torque required to rotate an object?

The formula for calculating torque is: torque = force x distance. This means that the torque required depends on the amount of force applied and the distance from the axis of rotation.

3. What units are used to measure torque?

Torque is typically measured in Newton-meters (Nm) or pound-feet (lb-ft). These units represent the amount of force needed to produce a certain amount of torque at a given distance.

4. How does the shape and size of an object affect the torque required to rotate it?

The shape and size of an object can affect the torque required to rotate it because they determine the distribution of mass and the distance from the axis of rotation. Objects with a greater mass or a larger distance from the axis will require more torque to rotate.

5. Can the torque required to rotate an object be reduced?

Yes, the torque required to rotate an object can be reduced by changing the distance from the axis of rotation or by using a different shape or material that distributes the mass differently. Additionally, using gears or levers can also reduce the amount of torque needed to rotate an object.

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