PSN-L Email List Message
Subject: Re: Homebrew AS-1 seismometer
From: John or Jan Lahr JohnJan@........
Date: Sun, 27 Mar 2005 21:17:20 -0700
Good job of finding a spring! Do you have some photos of your
unit? I think it would be good
to post some, along with your spring details, on my web site. Are
you using AmaSeis? If so,
it would be interesting to save a 24-hour screen image of the next good
sized event. We could
compare it to one of the local AS1 posted here:
At 07:49 PM 3/27/2005, you wrote:
completed a homebrew AS-1 seismometer.
I must say the most challenging part was trying
to find a boom support spring.
Having no engineering degree so I was left to
do the trail and error method. I got very lucky. I just had a new LOWES
lumber/hardware store open very close to me.
Being a new store their stock was full and
complete. I found a spring manufactured by Century Spring Corp.
The part number on the package is "C-219". I purchased
two of these springs.
I had to do some resizing of these springs. The
spring is 4.5" long. I cut about 3/8" off of each coil. I then
spread the coils of each spring just far enough apart to mesh them
together (about a 1/2" overlap.) I happened to have a
1/2" i.d. x 1" spacer in my junk bin so I slid the spacer over
the meshed coils so they will not separate.
I ordered a coil and magnet for Larry. The
amplifier is from the following URL
http://users.viawest.net/~aloomis/seismom.htm a power supply
for this amplifier
can be found at
When I started this project I requested a
catalog from Century Spring. I can not find a spring with a C-219 part
number, but there is a spring with the part
number of 302 that is a very close match. Another spring that
could be tried is the 119. This one would have to be cut to the desired
length. Century Spring has
a minimum order of $30.
I must say that the sensitivity appears to be
superb as compared to my Lehman (but it's never been quite right after I
All of the mechanical bits were purchased from
If you would like more information please
contact me at n0ssy@...........
and not through the PSN list server.
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