Hi Chris,

I'm a complete novice in this field, but I would like to build a decent =
seismograph that could detect local and strong distant tremors. I've =
looked around on the net, but have not seen something I was sure I could =
build AND that would work well.

Do you have any suggestions?

Regards,

Beno=EEt Evans


On 2010-03-10, at 12:23, ChrisAtUpw@....... wrote:

> In a message dated 10/03/2010, kevans@............ writes:
> Does anyone have an opinion on the Pop Sci seismograph plans from =
1965? Could it be modernized and be useful today?
> =
http://www.popsci.com/archive-viewer?id=3DWiYDAAAAMBAJ&pg=3D135&query=3Dea=
rthquake+detector
> Regards,
> Beno=EEt Evans
> Hi Beno=EEt,
> =20
>     The short answer is not without a complete redesign. This kit was =
designed before semiconductor amplifiers became readily available, or =
personal computers and digital recording were invented. To view the =
background microseisms, you need a gain of ~x1,000, but the lever gives =
only about x4. The suspension needs to be changed to either a plane on a =
ball or to crossed rollers. Point in a dimple and knife blade types are =
NOT satisfactory. NO damping is provided.
>     While you can use heavily varnished wood for the frame, 3" x 1" x =
1/8" section Aluminum U Channel with 1/8" thick corner plates are easy =
to fabricate. Use SS bolts from a boat/marine supplier to prevent =
corrosion. The frame needs to be very rigid. Quad NdFeB magnet blocks =
give very 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)
>     Pi =3D 3.14159, g =3D 9.81 m/s/s, L is in m (0.56m for 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 has a 3" x 3/4" section Al bar frame. I use a SS scalpel blade =
rolling on a 1/2" SS ball bearing on the upright and a 1 kg brass mass =
(non magnetic). DON'T mount the ball on the end of the arm. We have =
'come a very long way' in seismometer design since 1965.
>    =20
>     Are you looking for a seismometer design?
> =20
>     Regards,
> =20
>     Chris Chapman


Hi =
Chris,

I'm a complete novice in this field, but I =
would like to build a decent seismograph that could detect local and =
strong distant tremors. I've looked around on the net, but have not seen =
something I was sure I could build AND that would work =
well.

Do you have any =
suggestions?

Regards,

Be=
no=EEt Evans


On 2010-03-10, at =
12:23, ChrisAtUpw@....... =
wrote:




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 =
readily=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 =
gives 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 =
plates=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://jc=
lahr.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_prototy=
pe.jpg This=20
has a 3" x 3/4" section Al bar frame. I use a SS scalpel blade =
rolling on a=20
1/2" SS ball bearing on the upright and a 1 kg brass mass (non =
magnetic).=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



=