Foundations for Vibrating Machines

[ChadKhan0245]

To Whom It May Concern,

Is anyone familiar with the Design of Structures and Foundations for Vibrating Machines by Suresh Arya, Michael O'Neill, and George Pincus?

In the examples the equation used for the magnification factor is for the Constant Force Excitation. Ref Table 1-4

Can anyone tell me when one would use the Rotating Mass Excitation for the Magnification Factor?

I have included a pdf copy of the reference material

Thank You

Chad Corkern

 

[WARose]

In the examples the equation used for the magnification factor is for the Constant Force Excitation. Ref Table 1-4

Can anyone tell me when one would use the Rotating Mass Excitation for the Magnification Factor?

That for reciprocating/centrifugal machines like motors.

 

[ChadKhan0245]

Mr. Warose,

In the reference material A/O'N/P example 2 on sheet 99 is the "Foundation Block for Centrifugal Machine" and it uses the constant force equation for the magnification factor. I am wondering when one would use the rotating mass excitation equation from table 1-4.

Thanks

Chad C.

 

[WARose]

In the reference material A/O'N/P example 2 on sheet 99 is the "Foundation Block for Centrifugal Machine" and it uses the constant force equation for the magnification factor. I am wondering when one would use the rotating mass excitation equation from table 1-4.

They really don't say which equation they are using. I assume you've calculated it and it matches the constant force eq?

[red]EDIT:[/red] I ran it myself and got something (a lot) closer to the constant force equation than the other equation. Not sure why. This book does have a errata list.....but nothing is down for p.13, or 99-101. So this may be a undiscovered error.

[red]EDIT #2:[/red] Then again, I'm not 100% sure which operating speed they are comparing the natural frequency to (to obtain the "r" value). If they are checking it at resonance......then "r" equals "1" and (in that case) the constant force and the rotating mass equations are identical for magnification.

 

[ChadKhan0245]

Mr. Warose,

The justification for the use of the constant force equation for the magnification factor is show on page 100 part D, and I agree with their logic.

I am trying to understand when one would use the Rotating mass equation for the magnification factor.

Thank You

 

[WARose]

The justification for the use of the constant force equation for the magnification factor is show on page 100 part D, and I agree with their logic.

Like I said in my Edit #2 (above).....I'm not sure what operating frequency they are checking it at.

But most people do check the magnification for when it passes through resonance. The operating frequency in this example is well above the resonance.....so I assume that is what they are doing.

I am trying to understand when one would use the Rotating mass equation for the magnification factor.

I've seen it used all the time for fans, motors, etc. Just looked at a set of old calcs of mine where I used it for a fan.

 

[WARose]

By the way, let me say something else about this reference.....it's good.....but I wouldn't take it as the gospel ok? (I.e. the absolute final word.) There are a number of things that they do in that book that I (a guy who has a couple hundred vibrating foundations out there with his seal on it) wouldn't do. It takes experience to do this stuff.