PSN-L Email List Message

Subject:
From: tchannel1@............
Date: Wed, 1 Oct 2008 22:38:06 -0600


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









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

[ Top ] [ Back ] [ Home Page ]