PSN-L Email List Message

Subject: Re: Re:
From: "meredith lamb" paleoartifact@.........
Date: Thu, 2 Oct 2008 18:47:05 -0600


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



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 -----
> *From:* meredith lamb 
> *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
>
> 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.
>> 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
>>
>
>
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" 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@............> 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 -----
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
  
On Wed, Oct 1, 2008 at 10:38 PM, <tchannel1@............> 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.
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
 
 



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