Hi all,

With a crossed rod hinge/suspension, one can easily set the rotating rods
placement
on the lengths of the two outer rods by using acouple shaft collars on them=
,
that are
adjusted/moved/placed as desired in relation to the sensors used below near
the
mass. This is being written in the sense of a S-G, or vertical hanging mass=
;
but the
approach is also quite applicable for a vertical or a "hanging gate"
(Lehman)
horizontal seismometer.

As this type of suspension will physically rotate or move in the directions
of desired
sensing, it only remains for the bottom of the pendulum mass to be manually
offset, say, ~1" from its desired resting spot/zero; while shoving and then
gently
releasing the upper portion of the pendulum hinge against the shaft collars=
.
When
you gently manually allow the mass end of pendulum to go back to zero
(gravity),
or whatever zero spot, it will rotate slightly away from the shaft collars,
and thus
it will be at a set operating position, and can then freely rotate. One can
use about
any distance desired, but, irregardless; for a normal operating environment=
,
about
any reasonable distance amount will be far more than what the response of
the
pendulum/mass would normally be for any seismic event. The installed shaft
collar will have to be placed on the appropriate side of the center
rod/boom/mass
to allow this to work of course. For a more consistent "zero" placement, on=
e
could entertain having a spaced and anchored contact angle bracket down nea=
r
the mass for this offset zero adjustment.

One would have to be aware that this resulting spacing won't be very much;
so
one will have to watch our for interferring dirt/hair etc., that could get
inbetween
the shaft collars and the rotating hinge/rod/pendulum/mass, and degrade its
enertia response.

A crossed rod hinge suspension will also have a lateral (non-rotating,
sideways)
position to be aware of. Normally the position won't change once set on the
two
outer rods. One could also a shaft collar/s "near too, but not touching",
one or
both of the two outer rods; or another mechanical variety of visual
alignment near
to one end of the center rod. Here; one might entertain the use of a thin
temporary shim spacer inbetween one shaft collar and one of the two outer
rods; for the initial adjustment and withdraw the shim spacer before any
adjustment of the "zero" as described above. Going abit further, one could
place two more shaft collars on the two outer rods, for temporary "locking"
of
the hinge pivot, during the moving and eventual placement setup of such
seismometer.

Take care, Meredith Lamb
Hi all,



With a crossed rod hinge/suspension, one can easily set the rotating rods p=
lacement

on the lengths of the two outer rods by using acouple shaft collars on them=
, that are

adjusted/moved/placed as desired in relation to the sensors used below near=
 the 

mass.  This is being written in the sense of a S-G, or vertical hangin=
g mass; but the

approach is also quite applicable for a vertical or a "hanging gate&qu=
ot; (Lehman)

horizontal seismometer.



As this type of suspension will physically rotate or move in the directions=
 of desired

sensing, it only remains for the bottom of the pendulum mass to be manually=
 

offset, say, ~1" from its desired resting spot/zero; while shoving and=
 then gently

releasing the upper portion of the pendulum hinge against the shaft collars=
..  When

you gently manually allow the mass end of pendulum to go back to zero (grav=
ity),

or whatever zero spot, it will rotate slightly away from the shaft collars,=
 and thus

it will be at a set operating position, and can then freely rotate.  O=
ne can use about

any distance desired, but, irregardless; for a normal operating environment=
, about

any reasonable distance amount will be far more than what the response of t=
he

pendulum/mass would normally be for any seismic event.  The installed =
shaft

collar will have to be placed on the appropriate side of the center rod/boo=
m/mass

to allow this to work of course.  For a more consistent "zero&quo=
t; placement, one

could entertain having a spaced and anchored contact angle bracket down nea=
r

the mass for this offset zero adjustment.



One would have to be aware that this resulting spacing won't be very much; =
so

one will have to watch our for interferring dirt/hair etc., that could get =
inbetween

the shaft collars and the rotating hinge/rod/pendulum/mass, and degrade its=


enertia response.



A crossed rod hinge suspension will also have a lateral (non-rotating, side=
ways)

position to be aware of.  Normally the position won't change once set =
on the two

outer rods.  One could also a shaft collar/s "near too, but not t=
ouching", one or

both of the two outer rods; or another mechanical variety of visual alignme=
nt near

to one end of the center rod.  Here; one might entertain the use of a =
thin 

temporary shim spacer inbetween one shaft collar and one of the two outer
rods; for the initial adjustment and withdraw the shim spacer before any
adjustment of the "zero" as described above.  Going abit fur=
ther, one could

place two more shaft collars on the two outer rods, for temporary "loc=
king" of

the hinge pivot, during the moving and eventual placement setup of such

seismometer.



Take care, Meredith Lamb