Out of balance rotating system

[Bravemeister]

Figure Q4. illustrates a rotor assembly with out-of-balance rotor discs in planes A, B
and C. The out-of-balance mass x radius products in planes A and C are as
indicated in the figure. The out-of-balance mBrB in plane B and its angular position $\Theta$B
are such that the system is in static balance.

(a) Determine the values of mBrB and $\Theta$B.


(b) If the system is to be dynamically balanced by adding balancing masses m1r1
and m2r2 in planes A and C, respectively, determine their values and angular
positions $\Theta$1 and $\Theta$2.

Any help is much appreciated!

 

[SteamKing]

What don't you understand about part a?

 

[Bravemeister]

well how to do it, in my lecture notes I says to take moments about a point, so I chose to go about point A. so from that I drew a moment polygon. I need to find sommething called a closing vectpr, I presume so thwt from point C I cwn return to point A therefore using some angles and other maths calculate a values for the question. I just don't know how to ge the closing vector.

 

[Bravemeister]

sorry for the horrid spelling my tablet keyboard is crap

 

[SteamKing]

Check out this article. It shows several calculation examples:

http://library.worldtracker.org/Physics/Theory of Machines/Ch-21.pdf