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 -----
Sent: Thursday, October 02, =
2008 6:47=20
PM
Subject: Re: Re:
Hi Ted,
The "concept" or diagram you mention is possibly this:
which is a part of:
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 ----- =
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
=
BLOCKQUOTE>
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