In a message dated 2007/08/05, barry_lotz@............. writes:

> Do you think the sensor position is very sensitive to ground tilt like a 
> Lehman when it's near the unstable point (long period)? 

Hi Barry,

       That is correct. The principle is the same, whether you reduce the 
centring force by reducing the angle of the suspension axis, or by balancing out 
the lateral pendulum forces. The main consideration is the period extension 
ratio, between the adjusted pendulum and that you would get from a simple 
vertical pendulum of the same dimensions. 

       A period ratio of x10 is fairly easily achieved. Ratios of more than 
x20 require very good suspensions, a rigid frame and careful adjustment. Not 
particularly difficult, but a bit more advanced / better engineered than the 
original 1976 Lehman concept. 

       I suggest that you use NdFeB magnetic damping and a copper damping 
blade. You can adjust the damping by choosing the thickness of  the damping 
blade, varying how much of the copper blade is covered by the damping magnets and 
by varying the separation of the magnet poles.

       Regards,

       Chris Chapman   
In a me=
ssage dated 2007/08/05, barry_lotz@............. writes:



Do you think the sensor positio=
n is very sensitive to ground tilt like a Lehman when it's near the unstable=
 point (long period)? 




Hi Barry,



       That is correct. The principle is the s=
ame, whether you reduce the centring force by reducing the angle of the susp=
ension axis, or by balancing out the lateral pendulum forces. The main consi=
deration is the period extension ratio, between the adjusted pendulum and th=
at you would get from a simple vertical pendulum of the same dimensions. 


       A period ratio of x10 is fairly easily=20=
achieved. Ratios of more than x20 require very good suspensions, a rigid fra=
me and careful adjustment. Not particularly difficult, but a bit more advanc=
ed / better engineered than the original 1976 Lehman concept. 



       I suggest that you use NdFeB magnetic d=
amping and a copper damping blade. You can adjust the damping by choosing th=
e thickness of  the damping blade, varying how much of the copper blade=
 is covered by the damping magnets and by varying the separation of the magn=
et poles.



       Regards,



       Chris Chapman