Hi all,

Heyyyyy...this part seemingly has real potential !  If you even vaguely have
followed last
years emails on crossed rod pivot/hinges; this might be something you can
also try
during any bored or curious moments.

Its within common VHS video tape cassettes.  Most all cassettes use two tape
spacer/
guides, that appear to be ultra smooth stainless steel.  The minority can be
plastic.
Most of them appear to be punched/stamped out of sheet metal and then formed
into a round tube; and then they appear to have been further smoothed to
where they
don't damage the video tape moving over their surfaces.  The rarest
spacer/guide is a
complete cut off tube.  You can open the release latch on the side of the
cassette to
view parts of these tubes behind the tape.  You can generally easily open to
remove
them by first removing 5 small phillips head screws on the bottom of the
cassette
itself.  The rare cassette might be plastic welded shut.

The main point here being the very smooth surface of these metal tubes is
what one
absolutely needs for a crossed rod pivot.  Naturally, the contact points
won't be over
the lengthwise joint.  Being as they are essentially tubes, one can use
bolts and
nuts to seat/mount them, which is also very convenient.  If you only use
these, you
only need 4 (2 cassettes) tubes; 2 for running in one spaced apart
direction, and 2
"cross rod" (right angle to the other two) to attach to either side of the
boom you
use.  They appear to all be ~ .630" length (16.0mm), .225" outside diameter
(5.75mm),
..190" inside diameter (4.90mm), with a wall thickness of .0175" (.5mm).

The second main point here, is that from testing a variety of solid rod kind
of
material late last year; their low friction level is absolutely amazing.
This means
greater seismic sensitivity especially for the low level mass enertia
offsets we
either can or can't sensor pickup with a majority of "home brew"
seismometers.

Credit Chris Chapman for bringing up the "crossed rod pivot" subject late
last year!

I intend to try such first as another "test table top edge" setup
eventually; where
there is only the pivot arrangement, and a test boom and mass.  This would
be a
gravity vertical hanging mass pendulum.  Its not really a S-G per-say; as
S-G's use
flexible strips of metal (torque limiting) as the
pivots...which...essentially....make
them kind of partial accelerometers.  This would be a horizontal directional
sensing
unit.  Will get back with you all later....with the specific test model
results; whether
its good, bad, or somewhere inbetween, as compared to solid rods tests of
the past.

Meredith Lamb
Hi all,
 
Heyyyyy...this part seemingly has real potential !  If you even vaguely have followed last 
years emails on crossed rod pivot/hinges; this might be something you can also try
during any bored or curious moments.
 
Its within common VHS video tape cassettes.  Most all cassettes use two tape spacer/
guides, that appear to be ultra smooth stainless steel.  The minority can be plastic.
Most of them appear to be punched/stamped out of sheet metal and then formed
into a round tube; and then they appear to have been further smoothed to where they
don't damage the video tape moving over their surfaces.  The rarest spacer/guide is a
complete cut off tube.  You can open the release latch on the side of the cassette to
view parts of these tubes behind the tape.  You can generally easily open to remove
them by first removing 5 small phillips head screws on the bottom of the cassette
itself.  The rare cassette might be plastic welded shut.
 
The main point here being the very smooth surface of these metal tubes is what one
absolutely needs for a crossed rod pivot.  Naturally, the contact points won't be over
the lengthwise joint.  Being as they are essentially tubes, one can use bolts and
nuts to seat/mount them, which is also very convenient.  If you only use these, you
only need 4 (2 cassettes) tubes; 2 for running in one spaced apart direction, and 2
"cross rod" (right angle to the other two) to attach to either side of the boom you
use.  They appear to all be ~ .630" length (16.0mm), .225" outside diameter (5.75mm),
.190" inside diameter (4.90mm), with a wall thickness of .0175" (.5mm).
 
The second main point here, is that from testing a variety of solid rod kind of 
material late last year; their low friction level is absolutely amazing.  This means
greater seismic sensitivity especially for the low level mass enertia offsets we
either can or can't sensor pickup with a majority of "home brew" seismometers.
 
Credit Chris Chapman for bringing up the "crossed rod pivot" subject late last year!
 
I intend to try such first as another "test table top edge" setup eventually; where
there is only the pivot arrangement, and a test boom and mass.  This would be a
gravity vertical hanging mass pendulum.  Its not really a S-G per-say; as S-G's use
flexible strips of metal (torque limiting) as the pivots...which...essentially....make
them kind of partial accelerometers.  This would be a horizontal directional sensing
unit.  Will get back with you all later....with the specific test model results; whether
its good, bad, or somewhere inbetween, as compared to solid rods tests of the past.
 
Meredith Lamb