The measurment of momentum

[ljogle]

Since I am new at this, I am wondering if I am in the right place. I am in the middle of a project and have a need to better understand flywheel momentum. Can someone help me with the math and physics of such mechanical devices?

[swansont]

Sure.

 

Flywheels mean rotation, and so you want angular momentum, L. [math]L = I\omega[/math], where I is the moment of inertia and omega is the angular speed. Compare that with linear momentum, p=mv. Mass changes to the moment of inertia, which takes into account the mass distribution.

 

You can see why this matters by looking at another equation. [math]\vec{L} = \vec {r}\times \vec{p}[/math], so a particle farther from the axis of rotation has more angular momentum than an identical particle moving at the same linear speed, but closer to the axis. IOW, the placement of the mass matters to the angular momentum.

[ljogle]

Thank you,

 

But what I am trying to understand is, what input force is necessary to maintain momentum, once optimum momentum is acquired. In other words, if a flywheel of 18" dia., rotates at 1800 rpm's, x momentum will be achieved, therefore x force is required to start rotation, x force is required to develop momentum and x force is needed to maintain momentum and that is what I am trying to understand. Is there a solution that allows one to find this necessary input force.

 

again, thank you,

[swansont]

You'd need to know what the losses are, because no force is necessary to maintain momentum. You just need to counteract the other force (or torques) in the system. If you had an ideal system, multiplying the torque and the time will give you the momentum, if the torque is constant.

[ljogle]

You make some good points, but I do not know how to access loss factors other than normal atmospheric effects as I am not working within a vacuum, and I am using modern bearing technology unrelated to automotive requirements. I guess I need to hire a mathmetician to complete this project, but I am having difficulty finding a potential candidate. If you have any suggestions they would be certainly appreciated.

 

Thank you,