In a message dated 2008/08/18, tchannel1@............ writes:

> Hi All,   Just a thought...Has anyone explored a simple 36"? pendulum, say 
> having a 2? second period, then containing the pendulum in a fluid. The 
> pendulum still should move from side to side, but with a longer period? I have no 
> idea, how to do this, or what the result would be.  

Hi Ted,

       The period of a pendulum depends on the inertial mass and on the 
acceleration force. The mass M stays constant, but the the acceleration force will 
be reduced by (1 - the density ratio of the liquid to solid). Suspending a 
pendulum in a fluid will show much greater damping, but it is also likely to show 
up turbulence effects from the moving liquid and a non linear response, 
depending on the amplitude. One problem with liquids is the very high temperature 
coefficient of the viscosity. An oil damped pendulum has a working temperature 
range limited to about +/-5 F!!

       The period of a pendulum may be lengthened by reducing the centreing 
force, like a garden gate suspension or a folded pendulum, or by using a 
suspension linkage which gives an increased effective length, like the Romberg.

       Regards,

       Chris Chapman   
In a me=
ssage dated 2008/08/18, tchannel1@............ writes:



Hi All,   Just a thou=
ght...Has anyone explored a simple 36"? pendulum, say having a 2? second per=
iod, then containing the pendulum in a fluid. The pendulum still should move=
 from side to side, but with a longer period? I have no idea, how to do this=
, or what the result would be.  




Hi Ted,



       The period of a pendulum depends on the=
 inertial mass and on the acceleration force. The mass M stays constant, but=
 the the acceleration force will be reduced by (1 - the density ratio of the=
 liquid to solid). Suspending a pendulum in a fluid will show much greater d=
amping, but it is also likely to show up turbulence effects from the moving=20=
liquid and a non linear response, depending on the amplitude. One problem wi=
th liquids is the very high temperature coefficient of the viscosity. An oil=
 damped pendulum has a working temperature range limited to about +/-5 F!!


       The period of a pendulum may be lengthe=
ned by reducing the centreing force, like a garden gate suspension or a fold=
ed pendulum, or by using a suspension linkage which gives an increased effec=
tive length, like the Romberg.



       Regards,



       Chris Chapman