Hi Chris, and Others,   My problems with my new Lehman, have been =
resolved, I think......

I had one obvious problem:   At 20 seconds the arm would drift, left or =
right and I would need to reset it every two days.  The legs were =
threaded into the base, but loose, a lot of free play.  Knowing this I =
added a standard nut to lock the leg, which I would only finger tighten, =
this had always worked in the past.

What was happening is that the leg was moving itself.   Chris pointed =
out using two different materials would cause this.  But on other units =
it was never an issue.
In this case I removed the hex nut and added a wing nut.  After adj. I =
finger tighten the wing nut, nice and tight, and it has not drifted =
since.

The second problem:  At 20 seconds, I was missing all but large =
earthquakes, those were coming through just fine.   Chris suggest the =
arm might be sticking.  I could see nothing which resembled sticking.

I don't know if this was the cause and effect, but I fixed it:

First this is not the best Lehman I have ever built.  Its okay, and with =
little effort I got the 20 seconds, but I am not sure I could get 22.  =
However at 20 something was sticking. =20
I think at 20 it was so near infinity, it was almost flat.   At infinity =
it would never move to center, the arm would just stay where you placed =
it.  At 20 seconds it would move to center, if the event was large =
enough to overcome the inertia, but smaller earthquakes would not do =
this.=20

I reduce the period to 15 seconds, and it is working great.  I record =
6.2M Iceland, and 4.1M California.   I could, now increase the period to =
16,17,18 etc and retest.   I will see how it performs at 15 for a while.

Just wanted to share.








Hi Chris, and Others,   My =
problems with=20
my new Lehman, have been resolved, I think......
 
I had one obvious problem:   =
At 20=20
seconds the arm would drift, left or right and I would need to reset it =
every=20
two days.  The legs were threaded into the base, but loose, a lot =
of free=20
play.  Knowing this I added a standard nut to lock the leg, which I =
would=20
only finger tighten, this had always worked in the past.
 
What was happening is that the leg was =
moving=20
itself.   Chris pointed out using two different materials =
would cause=20
this.  But on other units it was never an issue.
In this case I removed the hex nut and =
added a wing=20
nut.  After adj. I finger tighten the wing nut, nice and tight, and =
it has=20
not drifted since.
 
The second problem:  At 20 =
seconds, I was=20
missing all but large earthquakes, those were coming through just=20
fine.   Chris suggest the arm might be sticking.  I could =
see=20
nothing which resembled sticking.
 
I don't know if this was the cause and =
effect, but=20
I fixed it:
 
First this is not the best Lehman I =
have ever=20
built.  Its okay, and with little effort I got the 20 seconds, but =
I am not=20
sure I could get 22.  However at 20 something was sticking. =20

I think at 20 it was so near infinity, =
it was=20
almost flat.   At infinity it would never move to center, =
the arm=20
would just stay where you placed it.  At 20 seconds it would move =
to=20
center, if the event was large enough to overcome the inertia, but =
smaller=20
earthquakes would not do this. 
 
I reduce the period to 15 seconds, and =
it is=20
working great.  I record 6.2M Iceland, and 4.1M =
California.   I=20
could, now increase the period to 16,17,18 etc and retest.   I =
will=20
see how it performs at 15 for a while.
 
Just wanted to share.
 
Thanks for the help. =20
Ted