Hi all,

The report on using VHS tape cassette spacers is unfortunately
bad.  I find there is too much variations of the exterior/interior sizes of
the
VHS tape guides/spacers, and; of the diameter variations along the lengths
of the hardware store mounting bolts to "easily" consider using such for
crossed rod pivots.  The crossed rod on such tend to "walk" over time
and oscillations, away from their initial positions due to differences of
level height, diameters and possibly minor weight shift movement of the
spacers themselves on the bolts.

Nevertheless I did setup acouple variations of such, and they oscillated
from 5 to 6.5 hours; from their initial offset....which is a reflection of
the
smooth surfaces (pivot) low friction.

Meredith Lamb


On 7/5/06, meredith lamb  wrote:
>
>  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,
 
The report on using VHS tape cassette spacers is unfortunately
bad.  I find there is too much variations of the exterior/interior sizes of the
VHS tape guides/spacers, and; of the diameter variations along the lengths
of the hardware store mounting bolts to "easily" consider using such for
crossed rod pivots.  The crossed rod on such tend to "walk" over time
and oscillations, away from their initial positions due to differences of
level height, diameters and possibly minor weight shift movement of the
spacers themselves on the bolts.  
 
Nevertheless I did setup acouple variations of such, and they oscillated
from 5 to 6.5 hours; from their initial offset....which is a reflection of the
smooth surfaces (pivot) low friction.
 
Meredith Lamb 

 
On 7/5/06, meredith lamb <paleoartifact@.........
> wrote: 


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