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Hi Tom,<br><br>
This is the same problem with the new Compact-Trilliums.
Nanometrics used a 1/4" x 20 thread/bolt instead of tight, fitting
machine threads. (I presume to cut costs) Thus the
tightening-disk is more important than before to stabilize the
seismometer. Thus rotating the tightening-disk against the
base of the C-Trill needs to be very firm and they supply a wrench to do
this where before a good strong finger tight was good.
However, because the seismometer is light-weight (2.5 lbs) it is easy to
push it off its orientation/position even on a rough surface.<br><br>
Mark<br><br>
<br>
At 18:26 1/14/2011, Tom Yelin wrote:<br><br>
<blockquote type=cite class=cite cite="">The OEM mounting/restraining
bolts for these units have about<br>
1-2mm play when inserted through the hole in the unit's chassis.<br><br>
Paul Bodin and I are concerned that even with the nut<br>
tightened, in the case of large ground motions there will be<br>
an increased chance that the unit will shift (albeit<br>
not my much) relative to the mounting point.<br><br>
The hole appears to be just shy of 12 mm in diameter.<br>
Has anyone been concerned enough about this issue<br>
to find an alternate bolt? If so, do you have<br>
the size on record, and perhaps a supplier, too?<br><br>
Sorry, but I am inherently lazy and trying to avoid<br>
a trip to the local fasterner store.<br><br>
<br>
Tom<br><br>
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Mailing Address:<br><br>
<br>
Tom Yelin, U.S. Geological Survey<br>
c/o University of Washington<br>
Dept of Earth & Space Sciences<br>
Box 351310<br>
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Shipping Address:<br>
(For UPS, FedEx and other services that<br>
do not accept box numbers)<br><br>
Tom Yelin<br>
University of Washington<br>
Dept. of Earth & Space Sciences<br>
70 Johnson Hall<br>
Seattle, WA 98195-1310<br><br>
Phone: 206-553-1937<br>
Fax: 206-553-8350<br><br>
email: yelin@ess.washington.edu<br><br>
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