PSN-L Email List Message
Subject: Re: New Seismo
From: "Ted Channel" tchannel@............
Date: Sat, 30 Jul 2011 22:18:21 -0600
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.
Sent: Saturday, July 30, 2011 =
8:39=20
PM
Subject: Re: New Seismo
****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
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