In a message dated 2007/06/05, tchannel@.............. writes:

>  Ben and Chris,   This is great information,  Thanks, for your response.
> 
Hi Ted and anyone trying to make a simple vertical spring system,

       Suppressing sideways and rotational movements of the mass can be 'a 
pain'. It is easier to do this if you use an extension rod to join the mass to 
the spring and place everything in a vertical Al tube. Try modifying the simple 
design shown at http://mariottim.interfree.it/doc02v_e.htm in this way. It is 
also possible to use two circular iron disks separated by say 4 square / 
rectangtular NdFeB magnets, connected all with the same polarity, or a large disk 
magnet with a central hole.
       For the sensor coil, wind two side by side coils with a similar number 
of turns, about 2 to 4 x the length of the magnet separation and connect them 
in opposition - not so that the fields add. It is not difficult to make 'a 
sensor' this way, but to make a 'good' one is more difficult. It is easier to 
make a frame and use a LaCoste type arm and suspension.
       Geophones are designed with spiral leaf springs to keep the moving 
copper cylinder mass and the coils aligned axially. This principle can be 
extended to a simple vertical by using very thin horizontal parallel brass shim leaf 
'springs' at the top and the bottom of the mass to keep it aligned axially and 
to prevent any pendulum sideways movement, with the main axial load still 
taken by a vertical coil spring.
       It is no longer a simple spring / weight system, but it may be the 
simplest system which works satisfactorily.

       Regards,

       Chris Chapman   
In a me=
ssage dated 2007/06/05, tchannel@.............. writes:



 Ben and Chris,   Thi=
s is great information,  Thanks, for your response.



Hi Ted and anyone trying to make a simple vertical spring system,



       Suppressing sideways and rotational mov=
ements of the mass can be 'a pain'. It is easier to do this if you use an ex=
tension rod to join the mass to the spring and place everything in a vertica=
l Al tube. Try modifying the simple design shown at http://mariottim.interfr=
ee.it/doc02v_e.htm in this way. It is also possible to use two circular iron=
 disks separated by say 4 square / rectangtular NdFeB magnets, connected all=
 with the same polarity, or a large disk magnet with a central hole.

       For the sensor coil, wind two side by s=
ide coils with a similar number of turns, about 2 to 4 x the length of the m=
agnet separation and connect them in opposition - not so that the fields add=
.. It is not difficult to make 'a sensor' this way, but to make a 'good' one=20=
is more difficult. It is easier to make a frame and use a LaCoste type arm a=
nd suspension.

       Geophones are designed with spiral leaf=
 springs to keep the moving copper cylinder mass and the coils aligned axial=
ly. This principle can be extended to a simple vertical by using very thin h=
orizontal parallel brass shim leaf 'springs' at the top and the bottom of th=
e mass to keep it aligned axially and to prevent any pendulum sideways movem=
ent, with the main axial load still taken by a vertical coil spring.

       It is no longer a simple spring / weigh=
t system, but it may be the simplest system which works satisfactorily.



       Regards,



       Chris Chapman