[ANSS-netops] mounting bolts for RT 147-01/3 accelerometer

[Mark E. Meremonte]

Hi Tom,

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.

Mark


At 18:26 1/14/2011, Tom Yelin wrote:

>The OEM mounting/restraining bolts for these units have about
>1-2mm play when inserted through the hole in the unit's chassis.
>
>Paul Bodin and I are concerned that even with the nut
>tightened, in the case of large ground motions there will be
>an increased chance that the unit will shift (albeit
>not my much) relative to the mounting point.
>
>The hole appears to be just shy of 12 mm in diameter.
>Has anyone been concerned enough about this issue
>to find an alternate bolt?  If so, do you have
>the size on record, and perhaps a supplier, too?
>
>Sorry, but I am inherently lazy and trying to avoid
>a trip to the local fasterner store.
>
>
>Tom
>
>----------------------------------------------------------
>
>Mailing Address:
>
>
>Tom Yelin, U.S. Geological Survey
>c/o University of Washington
>Dept of Earth & Space Sciences
>Box 351310
>Seattle, WA 98195-1310
>
>
>Shipping Address:
>(For UPS, FedEx and other services that
>do not accept box numbers)
>
>Tom Yelin
>University of Washington
>Dept. of Earth & Space Sciences
>70 Johnson Hall
>Seattle, WA  98195-1310
>
>Phone:  206-553-1937
>Fax:    206-553-8350
>
>email:  yelin at ess.washington.edu
>
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*********************************************************
Mark E. Meremonte        Geophysicist    USGS/ANSS/NEIC

U.S. Geological Survey        Work: 303-273-8670   Cell: 303-478-5766
MS 966, Box 25046          Email: meremonte at usgs.gov
Denver, CO  80225             Web: http://geohazards.cr.usgs.gov

Ship:  U.S. Geological Survey, 1711 Illinois St., Golden, CO 80401
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