Determine moment of Inertia from resistance

In summary, the conversation revolves around calculating the starting torque required to move a drum weighing 2000kg and with a diameter of 1200mm at 6rpm. The tension of 3000N acting on the drum is also a factor in determining the torque. The participants discuss different methods, such as using a gear box or a sprocket arrangement, to reduce the required torque. However, they also clarify that the moment of inertia of the drum is not affected by these factors and is solely determined by the mass and distribution of the drum.
  • #1
barvas11
32
0
Hi Guys,
I am trying to calculate a starting torque required to move the drum at 6rpm that weights 2000kg and has 1200mm in diameter.

There would be no problem to do this calc in normal circumstances as I can find a moment of inertia formula for a pipe in my book.

But in this case there is a tension of 3000N acting on the rim of my drum.

What will be the formula for the moment of inertia in this case?

Thanks
 
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  • #2
The moment of inertia of the drum is not affected by the tension. However, overcoming this tension will figure significantly in the torque required to spin the drum.

What is this tension? Is it friction?
 
  • #3
Hi,
No it's a wire injected in the steel coil tube and I am trying to take it out. I am currently building a special machine for it and need to select the right type of motor. I was thinking of powering the drum with light duty bonfiglioli gear box housed from one side of the drum or having a sprocket arrangement with the ratio 6:1. Sprockets would significantly drive down the torque but the gearbox would suit much better for this arrangement.

Yes that's right the tension will increase the torque value significatly but I don't know by how much.
 
  • #4
Well, as a first guess, I would say 3000N times the radius of the drum.
 
  • #5
Thanks,
Have you got any idea how to incorporate a sprocket ratio into my torque calc?

Diameter of the wheel that moves the drum has 38mm and drum has a diameter of 1200mm

I incorporated the ratio into my moment of inertia of the drum.

So the formula would be the following: I=Id*(38/1200)^2

Id is the moment of inertia of the drum

What do you think of that?

Thanks for your thoughts
 
  • #6
The inertia of the drum is a physical property of the mass of the drum and how that mass is distributed about the axis of rotation.
 
  • #7
It is but how does my pulley ratio affect that property?
 
  • #8
That's what I am trying to say: the inertia property is NOT affected by pulley ratios. The torque required to turn the drum will be affected by the pulley ratio, but not the inertia.
 

1. What is moment of inertia and how is it related to resistance?

Moment of inertia is a physical property that measures an object's resistance to changes in its rotational motion. The higher the moment of inertia, the more difficult it is to alter an object's rotation. Resistance, in this context, refers to the object's resistance to changes in its rotational motion.

2. How is moment of inertia calculated from resistance?

The moment of inertia can be calculated using the formula I = MR², where I is the moment of inertia, M is the mass of the object, and R is the distance from the axis of rotation to the object's center of mass. This formula assumes that the object has a uniform density and all the mass is concentrated at the center of mass.

3. What is the difference between moment of inertia and moment of resistance?

Moment of inertia and moment of resistance are often used interchangeably, but they refer to different concepts. Moment of inertia is a physical property of an object, while moment of resistance is a measure of the force required to resist a change in an object's motion. In simpler terms, moment of inertia is a characteristic of the object itself, while moment of resistance is a measure of its resistance to external forces.

4. How does the moment of inertia affect the rotational motion of an object?

The moment of inertia plays a crucial role in determining the rotational motion of an object. A higher moment of inertia means that an object will require more torque (rotational force) to accelerate or decelerate its rotational motion. This means that objects with higher moments of inertia will have slower rotational speeds and take longer to change direction compared to objects with lower moments of inertia.

5. Can the moment of inertia be changed?

Yes, the moment of inertia can be changed by altering the mass distribution of an object or by changing the axis of rotation. For example, if the mass of an object is concentrated closer to the axis of rotation, the moment of inertia will be lower compared to the same object with the mass distributed farther away from the axis. Similarly, if the axis of rotation is changed, the moment of inertia will also change accordingly.

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