Meredith,  Thank you for your reply and encouragement.   The first =
sensor I spoke of was about 8 foot tall and the boom was about 4 foot, =
two feet on each side of the ribbon.
I did not keep my notes on this unit but remember the period was =
massive, just moving the masses further out on the boom.

This present unit is only about 36" tall and the boom, one side of the =
ribbon only is about 6".   I used a SS thin wire instead of the band saw =
blade ribbon.   At this point I think it will respond similar to a =
Lehman with a 5 second period.  So far it behaves, just like my Lehman.

I will let you know, if it works and send or post the .psn.             =
It looks promising, very simple and if it works I will rebuild it =
targeting a 20 second period.

Cheers, Ted    ps..............On some web site I saw the concept of a =
Torsion Spring Long Period, illustrated as a box with a vertical torsion =
spring in the center of the box, and a boom............but the entire =
box was tipped, to illustrate the vertical wire/spring needed to be off =
vertical, not unlike the Lehman
  ----- Original Message -----=20
  From: meredith lamb=20
  To: psn-l@.................
  Sent: Thursday, October 02, 2008 3:29 PM
  Subject: Re:


  Hi Ted,

  Sorry...I couldn't find anything along the specific line you mention =
either..especially the flat ribbon spring variety.  If I read you email =
right;
  the very height you're using makes it a "giant" representation; and =
that likely makes it much more responsive as you're seeing, and
  to be fair the stresses involved will likely show all kinds of =
metal/structure creep over time which you'll have to adjust for.

  A lot of the web sites I've seen, go out of their way to describe such =
as antiquated, obsolete, old etc; which is true in the sense
  of what is predominately used now.  On the other hand, the torsion =
aspect really "does away" with a few of the normal pesky pivot problems
  that are found in other seismometers/tiltmeters; and that alone is a =
good adjustment and/or labor saving positive.

  Yes indeed...explore away.....there is likely a world of different =
flat ribbon or round wire sizes material one could try.

  Take care, Meredith
    =20

  On Wed, Oct 1, 2008 at 10:38 PM,  wrote:

    I am exploring the subject of a torsion spring sensor again.  I say =
again because I have tried this approach before with no success at all.
    I took a long band saw blade cut it to form a long vertical torsion =
spring. Attached both ends and pulled it tight.
    In the middle of this spring I attached a boom. On both ends of the =
boom I attached a mass of equal value.
    This boom would move around the vertical axis with very little =
effort, twisting the spring and then reversing to the other direction, =
rocking back and forth for a very long time.  I don't remember how long =
but I think it was one hour plus.
    The period of oscillation was controlled by moving the masses =
further out on the boom.   Very long periods 30 seconds plus.  To make a =
long story short, it did not record any earthquakes.

    I think I did two things wrong.  1. The booms of equal mass =
cancelled the movement of each other. And in this configuration the =
earthquake would need to spin the house to move the masses.
    2. The torsion spring needed to be tipped, not vertical.

    Here is my next attempt.   1.  I removed the boom, which formed a =
(+) on the vertical torsion spring and replace it with a short pendulum =
boom, this time on one side only.=20
    it looks like a T on its side ( l-)
    2.  I contained the vertical torsion spring in a strong box about =
12"x12"x36".  This retains all the parts and I can add tension to the =
spring, and mount the magnet and coil
    3.  I placed three leveling legs on the base of the box.  Now I can =
tip the vertical spring (Off Vertical).    Similar to tipping a Lehman, =
pitching up or down.
    The spring now at an angle, contains a pendulum which is now (Off =
Horizontal).

    The pendulum I am using is only about 6" long, and I get a period of =
about 5 seconds. I could get 20 seconds with a 18" boom. But my box =
could only accommodate a 6" boom.

     It is now running as a test......I will see if it will record =
earthquakes.
    It is sensitive to me moving around the room, and to drafts and =
tilts.

    I have seen something similar somewhere on the web, but I can't fine =
it.   This is all I could find.   If someone has tried this please email =
me.   Thanks, Ted

    Torsion Seismometer Wood Anderson


    http://www.data.scec.org/Module/s3inset3.html








Meredith,  Thank you for your =
reply and=20
encouragement.   The first sensor I spoke of was about 8 foot =
tall and=20
the boom was about 4 foot, two feet on each side of the =
ribbon.
I did not keep my notes on this unit =
but remember=20
the period was massive, just moving the masses further out on the=20
boom.
 
This present unit is only about 36" =
tall and the=20
boom, one side of the ribbon only is about 6".   I used a SS =
thin wire=20
instead of the band saw blade ribbon.   At this point I think =
it will=20
respond similar to a Lehman with a 5 second period.  So far it =
behaves,=20
just like my Lehman.
 
I will let you know, if it works and =
send or post=20
the=20
..psn.           &n=
bsp; It=20
looks promising, very simple and if it works I will rebuild it targeting =
a 20=20
second period.
 
Cheers, Ted    =
ps..............On=20
some web site I saw the concept of a Torsion Spring Long Period, =
illustrated as=20
a box with a vertical torsion spring in the center of the box, and a=20
boom............but the entire box was tipped, to illustrate the =
vertical=20
wire/spring needed to be off vertical, not unlike the =
Lehman

  
----- Original Message ----- 
  From:=20
  meredith lamb 
  
To: psn-l@.............. 
  
Sent: Thursday, October 02, =
2008 3:29=20
  PM
  
Subject: Re:
  


  
Hi Ted,

Sorry...I couldn't find anything along =
the=20
  specific line you mention either..especially the flat ribbon spring=20
  variety.  If I read you email right;
the very height you're =
using=20
  makes it a "giant" representation; and that likely makes it much more=20
  responsive as you're seeing, and
to be fair the stresses involved =
will=20
  likely show all kinds of metal/structure creep over time which you'll =
have to=20
  adjust for.

A lot of the web sites I've seen, go out of their =
way to=20
  describe such as antiquated, obsolete, old etc; which is true in the=20
  sense
of what is predominately used now.  On the other hand, =
the=20
  torsion aspect really "does away" with a few of the normal pesky pivot =

  problems
that are found in other seismometers/tiltmeters; and that =
alone is=20
  a good adjustment and/or labor saving positive.

Yes =
indeed...explore=20
  away.....there is likely a world of different flat ribbon or round =
wire sizes=20
  material one could try.

Take care, Meredith
   =


  
On Wed, Oct 1, 2008 at 10:38 PM, <tchannel1@............>=20
  wrote:

  

    

    
I am exploring the subject of a =
torsion spring=20
    sensor again.  I say again because I have tried this approach =
before=20
    with no success at all.
    
I took a long band saw blade cut it =
to form a=20
    long vertical torsion spring. Attached both ends and pulled it=20
    tight.
    
In the middle of this spring I =
attached a boom.=20
    On both ends of the boom I attached a mass of equal =
value.
    
This boom would move around the =
vertical axis=20
    with very little effort, twisting the spring and then reversing to =
the other=20
    direction, rocking back and forth for a very long time.  I =
don't=20
    remember how long but I think it was one hour plus.
    
The period of oscillation was =
controlled=20
    by moving the masses further out on the boom.   Very long =
periods=20
    30 seconds plus.  To make a long story short, it did not record =
any=20
    earthquakes.
    
 
    
I think I did two things =
wrong.  1. The=20
    booms of equal mass cancelled the movement of each other. And =
in this=20
    configuration the earthquake would need to spin the house to =
move the=20
    masses.
    
2. The torsion spring needed to be =
tipped, not=20
    vertical.
    
 
    
Here is my next =
attempt.   1.  I=20
    removed the boom, which formed a (+) on the vertical torsion spring =
and=20
    replace it with a short pendulum boom, this time on one side only.=20
    
    
it looks like a T on its side (=20
l-)
    
2.  I contained the vertical =
torsion=20
    spring in a strong box about 12"x12"x36".  This retains all the =
parts=20
    and I can add tension to the spring, and mount the magnet and=20
    coil
    
3.  I placed three leveling =
legs on the=20
    base of the box.  Now I can tip the vertical spring (Off=20
    Vertical).    Similar to tipping a Lehman, pitching =
up or=20
    down.
    
The spring now at an angle, =
contains a pendulum=20
    which is now (Off Horizontal).
    
 
    
The pendulum I am using is only =
about 6" long,=20
    and I get a period of about 5 seconds. I could get 20 seconds =
with a=20
    18" boom. But my box could only accommodate a 6" =
boom.
    
 
    
 It is now running as a =
test......I will=20
    see if it will record earthquakes.
    
It is sensitive to me moving around =
the room,=20
    and to drafts and tilts.
    
 
    
I have seen something similar =
somewhere on the=20
    web, but I can't fine it.   This is all I could =
find.  =20
    If someone has tried this please email me.   Thanks,=20
    Ted
    
 
    
Torsion Seismometer Wood =
Anderson
    
 
    
 
    
http://www.data.scec.org/Module/s3inset3.html<=
/DIV>