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
=
DIV>
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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