PSN-L Email List Message

Subject: Re: Re:
From: tchannel1@............
Date: Thu, 2 Oct 2008 21:13:22 -0600


Thanks, Folks, Yes this was the image I had seen before.   Thanks also =
for the various references.
Ted
  ----- Original Message -----=20
  From: meredith lamb=20
  To: psn-l@.................
  Sent: Thursday, October 02, 2008 6:47 PM
  Subject: Re: Re:


  Hi Ted,

  The "concept" or diagram you mention is possibly this:

  http://physics.mercer.edu/petepag/tilt.gif

  which is a part of:

  http://physics.mercer.edu/petepag/tiltm.html

  and the title of the above is "Tiltmeters and Angle Measuring =
Equipment" by Randall Peters

  but....I suppose you've already found such from Chris's reference.

  Take care, Meredith


  =20
  On Thu, Oct 2, 2008 at 5:11 PM,  wrote:

    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










Thanks, Folks, Yes this was the image I = had seen=20 before.   Thanks also for the various references.
Ted
----- Original Message -----
From:=20 meredith lamb
Sent: Thursday, October 02, = 2008 6:47=20 PM
Subject: Re: Re:

Hi Ted,
 
The "concept" or diagram you mention is possibly this:
 
http://physics.mercer= ..edu/petepag/tilt.gif
 
which is a part of:
 
http://physics.merc= er.edu/petepag/tiltm.html
 
and the title of the above is "Tiltmeters and Angle Measuring = Equipment"=20 by Randall Peters
 
but....I suppose you've already found such from Chris's = reference.
 
Take care, Meredith


 
On Thu, Oct 2, 2008 at 5:11 PM, <tchannel1@............>=20 wrote:
Meredith,  Thank you for your = reply and=20 encouragement.   The first sensor I spoke of was about 8 = foot tall=20 and the boom was about 4 foot, two feet on each side of the=20 ribbon.
I did not keep my notes on this = unit but=20 remember the period was massive, just moving the masses further out = on the=20 boom.
 
This present unit is only about 36" = tall and=20 the boom, one side of the ribbon only is about 6".   I = used a SS=20 thin wire instead of the band saw blade ribbon.   At this = point I=20 think it will respond similar to a Lehman with a 5 second = period.  So=20 far it behaves, just like my Lehman.
 
I will let you know, if it works = and send or=20 post the=20 = ..psn.           &n= bsp;=20 It looks promising, very simple and if it works I will rebuild it = targeting=20 a 20 second period.
 
Cheers, Ted   =20 ps..............On some web site I saw the concept of a Torsion = Spring Long=20 Period, illustrated as a box with a vertical torsion spring in the = center of=20 the box, and a boom............but the entire box was tipped, to = illustrate=20 the vertical wire/spring needed to be off vertical, not unlike the=20 Lehman
----- Original Message ----- =
From: = meredith lamb
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=20 to adjust for.

A lot of the web sites I've seen, go out of = their=20 way to describe such as antiquated, obsolete, old etc; which is = true in=20 the sense
of what is predominately used now.  On the other = hand,=20 the torsion aspect really "does away" with a few of the normal = pesky pivot=20 problems
that are found in other seismometers/tiltmeters; and = that=20 alone is a good adjustment and/or labor saving = positive.

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

Take care,=20 Meredith
  
On Wed, Oct 1, 2008 at 10:38 PM, <tchannel1@............> wrote:
I am exploring the subject of a = torsion=20 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=20 a long vertical torsion spring. Attached both ends and pulled it = tight.
In the middle of this spring I = attached a=20 boom. On both ends of the boom I attached a mass of equal=20 value.
This boom would move around the = vertical=20 axis with very little effort, twisting the spring and then = reversing to=20 the other direction, rocking back and forth for a very long = time. =20 I don't remember how long but I think it was one hour = plus.
The period of oscillation = was=20 controlled by moving the masses further out on the = boom.  =20 Very long periods 30 seconds plus.  To make a long story = short, it=20 did not record any earthquakes.
 
I think I did two things = wrong.  1.=20 The booms of equal mass cancelled the movement of each = other. And=20 in this configuration the earthquake would need to spin = the house=20 to move the masses.
2. The torsion spring needed to = be tipped,=20 not vertical.
 
Here is my next = attempt.  =20 1.  I removed the boom, which formed a (+) on the vertical = torsion=20 spring and replace it with a short pendulum boom, this time on = one side=20 only.
it looks like a T on its side ( = l-)
2.  I contained the = vertical torsion=20 spring in a strong box about 12"x12"x36".  This retains all = the=20 parts and I can add tension to the spring, and mount the magnet = and=20 coil
3.  I placed three = leveling legs on=20 the 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=20 pendulum which is now (Off Horizontal).
 
The pendulum I am using is only = about 6"=20 long, and I get a period of about 5 seconds. I could get 20 = seconds=20 with a 18" boom. But my box could only accommodate a 6"=20 boom.
 
 It is now running as a = test......I=20 will see if it will record earthquakes.
It is sensitive to me moving = around the=20 room, and to drafts and tilts.
 
I have seen something similar = somewhere on=20 the web, but I can't fine it.   This is all I could=20 find.   If someone has tried this please email = me.  =20 Thanks, Ted
 
Torsion Seismometer Wood=20 Anderson
 
 
http://www.data.scec.org/Module/s3inset3.html<= /DIV>



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