[ANSS-netops] ANSS-netops Digest, Vol 25, Issue 2
John R. Evans
jrevans at usgs.gov
Tue Jan 18 18:46:40 UTC 2011
Hi Mark,
Again, worry about strains introduced into the sensor. At some level, every accelerometer is a strainmeter, so best use manufacturer specs for torque, and demand them if not supplied. Alternately, watch the sensor outputs for offsetting of their baselines as you tighten and stop just short. If that does not supply a tight enough anchor, we better look into the matter and also consider the divot option (extra field pain, I realize). I have had poor results from dabs of epoxy on the legs so won't suggest that. RTV or a thin piece of neoprene might work however.
Cheers,
John
John R. Evans
Normally at: Intermittently at:
U.S. Geological Survey USGS/ASL
345 Middlefield Rd, MS-977 P.O. Box 82010
Menlo Park CA 94025 Albuquerque NM 87198-2010
650-329-4753 505-846-1793
jrevans at usgs.gov Cell: 408-209-6219
There is no problem so great or grave that it cannot be
much diminished by a nice cup of tea. (Bernard-Paul Heroux)
I got nasty habits; I take tea at three. (Mick Jagger)
On 17 Jan 2011, at 04:00, anss-netops-request at geohazards.usgs.gov wrote:
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> 1. Re: mounting bolts for RT 147-01/3 accelerometer
> (Mark E. Meremonte)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sun, 16 Jan 2011 16:57:36 +0000
> From: "Mark E. Meremonte" <meremonte at usgs.gov>
> To: Tom Yelin <yelin at ess.washington.edu>,
> anss-netops at geohazards.usgs.gov
> Subject: Re: [ANSS-netops] mounting bolts for RT 147-01/3
> accelerometer
> Message-ID: <OF0D3140B9.99061058-ON8725781A.005D2A81 at usgs.gov>
> Content-Type: text/plain; charset="us-ascii"; Format="flowed"
>
> 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 fastener 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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>>
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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
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