calculating from hp, torque, and rpm how much mass a vibrating motor w

[MidniteRambler]

EE by degree and thrown into this problem.

Need formulas for how much mass a vibrating motor will move.

known are the characteristics of the motor.

Hp
Torque
rpm

Any help appreciated

Many Thanks
MidniteRambler

 

[BobM3]

Not sure what you mean. Are you driving the motor with a cyclical (vibrating) command or is the motor vibrating and you need to figure out an isolation mass to isolate it?

 

[MidniteRambler]

We wish to use an eccentric motor much like on a pager or cell phone and are trying to figure how much mass it will shake noticeably enough for someone to wear on their arm with a strap and be alerted that the motor is vibrating.

The mass to be shaken is the case for the motor andthe accompanying electronics.

Good question, I should have had that in there at first!!

Many Thanks,
MidniteRambler

 

[electricpete]

The unbalance force is m*r*w^2 where m*r is the eccentric mass times its radius.

Depending on the dynamics of the system (masses, other springs, and frequencies), the force transferred to the person may be less.

The ability of a person to sense vibration undoubtedly depends on frequency (motor speed) as well.


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[Tmoose]

Season the unbalance with resonance and the transmitted force can be much greater. Antennae length, LC circuits, an unbalanced tire at 63 mph, or a nice long intake manifold (

http://victorylibrary.com/graphics/intake-300.jpg)

are examples how resonance makes itself known in my life sometimes for good and sometimes for evil.

I'd cheat and first measure the vibration (frequency and amplitude) of nice devices' buzz alarm.

 

[zifos]

You might start with a motor and vary unbalanced weight and frequency (change RPM using speed controller) until you get a vibration that will wake you up. Its probably easier just to cheat (like Tmoose suggested) but maybe you can make it better...

Then you have the "ideal" frequency and amplitude for a vibration alarm. The frequency is easy to scale to what ever mass you need (should be the same).

You can reproduce the amplitude by comparing the force (m*r*w^2) of the vibrator to the mass (resistance to move) of the vibratee (electronics, housing, battery, etc.) You should then know the m*r needed (w is based on frequency). Increase m and decrease r or decrease m and increase r as desired (i.e. big r little m = light weight; big m little r = small).

The motor RPM will be known (frequency desired) and the motor torque will be whatever is needed to maintain acceleration (r*w^2) of the m selected to produce the desired force (force = m*a).

I may have missed something but someone more skilled (and more awake) then I will hopefully correct it.