PM natural model...

[iacob alex]

 
....is a common first degree lever  ,also (Earth-Moon system).

    -fulcrum (barycenter)
    -fixed arm (with Earth)
    -variable arm (with Moon moving between long arm/405.000 km and small arm/362.600 km )

   E pur si muove...

        Best wishes for 2012 !  / Alex                                                               

[iacob alex]

.....we have on the sky,as an idea of the perpetuum mobile.Take a brief look on youtube (a short animation ) at:
  http://www.youtube.com/watch?v=W47Wa7onrIQ&feature=related
If we have the first design ( a leveraged pendulum),now we can think for a second "sight"/"step":  a double leveraged pendulum.
This can be the beginning of a "1,2,3...."  long story...
.....and yet it moves ! ("Eppur si muove !").
    All the best! / Alex

[iacob alex]

.....at : https://youtu.be/uGBANgbRkws
     The leverage concept is introduced at ( 0:31-0:39 ) time...
     Al_ex

[DreamThinkBuild]

Hi Iacob Alex,

A inward seeking system (centripetal) can be displaced into precession with an outward seeking system (centrifugal). 

Examples:

https://i.imgur.com/zYgvx4n.gifv

https://i.imgur.com/SwGhVro.gifv

[iacob alex]

 Hi DreamThinkBuild !
So..."weebles wobble,but they don't fall again " , at : https://en.m.wikipedia.org/wiki/Weeble
Al_ex