Gary,

Good observation.  Most force-feedback instruments use quite low 
masses.  The effective mass of the STS-2 is shown as 0.161Kg.  And 
Sean-Thomas' STM-8 used around 0.5Kg, which is on the high end of the 
range.  You will want to design the support spring to get a natural period 
in the 2-6 second range.  The performance you get after turning on the 
feedback is not strongly influenced by what you use as a natural period for 
the spring-mass.

Regards,
Brett


At 05:52 PM 8/29/2008 -0700, you wrote:
>
>  I have one question, if I have 8 to 10 Kg of mass on the pendulum, I 
> would think I m going to need quite a amplifier-driver to keep the 
> pendulum stationery during events.


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