PSN-L Email List Message

Subject: Re: Popular Science Seismograph plans (1965)
From: ChrisAtUpw@.......
Date: Wed, 10 Mar 2010 12:23:09 EST


=20
In a message dated 10/03/2010, kevans@............ writes:

Does  anyone have an opinion on the Pop Sci seismograph plans from 1965?=
=20
Could it be  modernized and be useful today? =20
_http://www.popsci.com/archive-viewer?id=3DWiYDAAAAMBAJ&pg=3D135&query=3De=
arthquak
e+detector_=20
(http://www.popsci.com/archive-viewer?id=3DWiYDAAAAMBAJ&pg=3D135&query=3De=
arthquake+detector)=20
=20
=20
Regards,

=20
=20
Beno=EEt Evans






Hi Beno=EEt,
=20
    The short answer is not without a complete  redesign. This kit was=20
designed before semiconductor amplifiers became readily  available, or per=
sonal=20
computers and digital recording were invented. To view  the background=20
microseisms, you need a gain of ~x1,000, but the lever gives only  about=
 x4. The=20
suspension needs to be changed to either a plane on a ball or  to crossed=
=20
rollers. Point in a dimple and knife blade types are NOT  satisfactory. NO=
=20
damping is provided.
    While you can use heavily varnished wood for the  frame, 3" x 1" x 1/8=
"=20
section Aluminum U Channel with 1/8" thick corner plates  are easy to=20
fabricate. Use SS bolts from a boat/marine supplier to prevent  corrosion.=
 The=20
frame needs to be very rigid. Quad NdFeB magnet blocks give very  good=20
performance with a damping blade or a sensor coil. See drawings at=20
_http://jclahr.com/science/psn/chapman/lehman/index.html_=20
(http://jclahr.com/science/psn/chapman/lehman/index.html)=20
    The period of a pendulum T =3D 2xPixSQRT(L / gxSinA)=20
    Pi =3D 3.14159, g =3D 9.81 m/s/s, L is in m (0.56m for  1.5 sec),=20
suspension angle A is about 1/3 degree.
    Have a look at=20
_http://jclahr.com/science/psn/chapman/2008%20lehman/lehman_prototype.jpg_=
=20
(http://jclahr.com/science/psn/chapman/2008%20lehman/lehman_prototype.jpg)=
  This  has a 3" x 3/4" section Al bar frame. I use a SS=20
scalpel blade rolling on a  1/2" SS ball bearing on the upright and a 1 kg=
=20
brass mass (non magnetic).  DON'T mount the ball on the end of the arm. We=
 have=20
'come a very long way' in  seismometer design since 1965.
   =20
    Are you looking for a seismometer design?
=20
    Regards,
=20
    Chris Chapman




<=
FONT id=3Drole_document   color=3D#000000 size=3D2 face=3DArial>
In a message dated 10/03/2010, kevans@............ writes:
Does=20 anyone have an opinion on the Pop Sci seismograph plans from 1965? Could= it be=20 modernized and be useful today?=20
http://www.popsci.com/archive-viewer?id=3DWiYDAAAAMBAJ&pg= =3D135&query=3Dearthquake+detector
Regards,
Beno=EEt Evans
Hi Beno=EEt,
 
    The short answer is not without a complete=20 redesign. This kit was designed before semiconductor amplifiers became rea= dily=20 available, or personal computers and digital recording were invented. To= view=20 the background microseisms, you need a gain of ~x1,000, but the lever give= s only=20 about x4. The suspension needs to be changed to either a plane on a= ball or=20 to crossed rollers. Point in a dimple and knife blade types are NOT= =20 satisfactory. NO damping is provided.
    While you can use heavily varnished wood for= the=20 frame, 3" x 1" x 1/8" section Aluminum U Channel with 1/8" thick corner pl= ates=20 are easy to fabricate. Use SS bolts from a boat/marine supplier to prevent= =20 corrosion. The frame needs to be very rigid. Quad NdFeB magnet blocks give= very=20 good performance with a damping blade or a sensor coil. See drawings= at = http://jclahr.com/science/psn/chapman/lehman/index.html
    The period of a pendulum T =3D 2xPixSQRT(L /= gxSinA)=20
    Pi =3D 3.14159, g =3D 9.81 m/s/s, L is in m= (0.56m for=20 1.5 sec), suspension angle A is about 1/3 degree.
    Have a look at http://jclahr.com= /science/psn/chapman/2008%20lehman/lehman_prototype.jpg This=20 has a 3" x 3/4" section Al bar frame. I use a SS scalpel blade rollin= g on a=20 1/2" SS ball bearing on the upright and a 1 kg brass mass (non magnet= ic).=20 DON'T mount the ball on the end of the arm. We have 'come a very long way'= in=20 seismometer design since 1965.
    
    Are you looking for a seismometer design?
 
    Regards,
 
    Chris Chapman

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