Hello Folks at PSN,   A good thing about the group, is that you can ask =
about most any issue, and get help....  Damping a large mass, which does =
not come up too often, is one problem I had recently.    Dave, it sounds =
like you are getting good  advise.    I was using a 15 pound mass, and =
had the same problem.  I used, the magnet sandwich like Chris suggested, =
I just needed to make the damper more powerful then usually........Dave =
if you have the damper plate and damper magnets in your hand.... can you =
feel the eddy as you move the plate?  If you mass is large this eddy =
must feel very powerful to work......That is my two cents worth.    By =
the way this is the first and the last big mass for me....I saw no =
benefit, but this was a special project.

I have great fun designing different sensors.   Not highly =
sophisticated, as some of the members, but simple things I can handle.   =
"The Big Lebowski" is my latest.   Made from a car leaf spring and a =
bowling ball.........as a result, I also needed a powerful damper....  , =
I made this vertical for Boise State University.  It is a simple one =
second vertical.........works just fine.

 I have no way to post pictures, but if you are interested, and you =
email me I can send a picture and or a word doc. with several pictures =
and description.

Cheers,  Ted       Tchannel@............
  ----- Original Message -----=20
  From: Christopher Chapman=20
  To: psnlist@.............. ; dave.nelson@..................
  Sent: Saturday, July 30, 2011 8:39 PM
  Subject: Re: New Seismo


   dave.nelson@...............
  Subject: Re: New Seismo


  hi Chris
         Am really at the end of the rope here ... just total =
frustration...  spent all day=20
  yesterday improving the period got down to 11 sec. set up a magnetic =
dampening system
   with a strip of aluminium  1.5cm wide going in between the 2 magnets.
    The only thing that seems to achieve is dropping my period from 11 =
sec down to=20
  ~ 7 sec.  It doesnt appear to do any actual dampening  as the unit =
will just go on=20
  oscillating for ages and just slowly dying down on its own  see...=20
  http://www.sydneystormcity.com/screen%20dump.bmp

   Hi Dave,

      I can't see from your photo how the magnet is mounted to interact =
with the Aluminium=20
  blade, or what sort of magnet it is. Can you explain further, please ? =
What thickness is=20
  the aluminium sheet and is it soft Aluminium or hard Aluminium Alloy, =
please ? I use 1/16"=20
  thick copper sheet, but you can use 1 mm thick sheet. Aluminium is =
weakly dia-magnetic.=20
  The damper should NOT reduce the period ! This suggests that the =
magnet is attracted to=20
  something on the arm ?

      Look at the drawings of my damper system. IT WORKS JUST FINE !=20
      See http://www.jclahr.com/science/psn/chapman/lehman/index.html=20

  ****BTW  I did take your bottom pivot advice. I have a flat steel =
plate on the end of the=20
  boom against the ball in the vertical


      Are the ball bearing AND the steel plate BOTH made of HARDENED =
Stainless Steel, please ?
  I use a medical Swann-Morton scalpel blade cut to a convenient length =
using a Dremmel silicon=20
  carbide cutting disk. Ordinary steel will rust and Austenitic =
stainless is too soft --- if=20
  you can file it, it is no good !=20

     The reason that I am querying this, is that I can set the period of =
my Lehman to 25 seconds=20
  DEAD EASILY ! I have run it at a period of 60 seconds !=20

  ****maybe you can help further ?   :)

      Does this help ? Let me know.=20

      Regards,=20








Hello Folks at PSN,   A good =
thing about=20
the group, is that you can ask about most any issue, and get =
help.... =20
Damping a large mass, which does not come up too often, is one problem I =
had=20
recently.    Dave, it sounds like you are getting =
good =20
advise.    I was using a 15 pound mass, and had the same=20
problem.  I used, the magnet sandwich like Chris suggested, I just =
needed=20
to make the damper more powerful then usually........Dave if you have =
the damper=20
plate and damper magnets in your hand.... can you feel the eddy as you =
move the=20
plate?  If you mass is large this eddy must feel very powerful to=20
work......That is my two cents worth.    By the way this =
is the=20
first and the last big mass for me....I saw no benefit, but this was a =
special=20
project.
 
I have great fun designing different=20
sensors.   Not highly sophisticated, as some of the members, =
but=20
simple things I can handle.   "The Big Lebowski" is my=20
latest.   Made from a car leaf spring and a bowling =
ball.........as a=20
result, I also needed a powerful damper....  , I made this =
vertical=20
for Boise State University.  It is a simple one second=20
vertical.........works just fine.
 
 I have no way to post pictures, =
but if you=20
are interested, and you email me I can send a picture and or a word doc. =
with=20
several pictures and description.
 
Cheers,  =
Ted     =20
 Tchannel@............

  
----- Original Message ----- 
  From:=20
  Christopher=20
  Chapman 
  
To: psnlist@.............. ; dave.nelson@...............=20
  

  
Sent: Saturday, July 30, 2011 =
8:39=20
  PM
  
Subject: Re: New Seismo
  


  

  

  

  

  

   dave.nelson@...............
Subject:=20
  Re: New Seismo


  
hi Chris
       Am really at =
the end=20
  of the rope here ... just total frustration...  spent all day=20
  
yesterday improving the period got down to 11 sec. set up a =
magnetic=20
  dampening system
 with a strip of aluminium  1.5cm wide =
going in=20
  between the 2 magnets.
  The only thing that seems to achieve =
is=20
  dropping my period from 11 sec down to 
~ 7 sec.  It doesnt =
appear to=20
  do any actual dampening  as the unit will just go on 
  
oscillating for ages and just slowly dying down on its =
own =20
  see... 
http://www.sydneystormcity.com/screen%20dump.bmp
<=
BR> Hi=20
  Dave,

  
    I can't see from your photo how the magnet =
is=20
  mounted to interact with the Aluminium 
  
blade, or what sort of magnet it is. Can you explain further, =
please=20
  ? What thickness is 
  
the aluminium sheet and is it soft Aluminium or hard =
Aluminium Alloy,=20
  please ? I use 1/16" 
  
thick copper sheet, but you can use 1 mm thick sheet. =
Aluminium is=20
  weakly dia-magnetic. 
  
The damper should NOT reduce the period ! This suggests that =
the=20
  magnet is attracted to 
  
something on the arm ?
  
 
  
    Look at the drawings of my damper system. =
IT WORKS=20
  JUST FINE ! 
  
    See http=
://www.jclahr.com/science/psn/chapman/lehman/index.html 

  
****BTW =20
  I did take your bottom pivot advice. I have a flat steel plate on the =
end of=20
  the 
boom against the ball in the vertical

   
     =20
  Are the ball bearing AND the steel plate BOTH made of HARDENED =
Stainless=20
  Steel, please ?
  
I=20
  use a medical Swann-Morton scalpel blade cut to a convenient =
length using=20
  a Dremmel silicon 
  carbide=20
  cutting disk. Ordinary steel will rust and Austenitic stainless is too =
soft=20
  --- if 
  you=20
  can file it, it is no good ! 
   
    =20
  The reason that I am querying this, is that I can set the period of my =

  Lehman to 25 seconds 
  DEAD=20
  EASILY ! I have run it at a period of 60 seconds =
! 
  
****maybe=20
  you can help further ?   :)

     =20
  Does this help ? Let me know. 
   
     =20
  Regards, 
   
     =20
  Chris Chapman