Subject: Re: [sloan-25mlog 3911] Re: 2.5m obslog 20180228 (SJD 58178)
From: John Downey
Date: Thu, 1 Mar 2018 15:03:08 -0700
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> On Mar 1, 2018, at 1:37 PM, Karen Kinemuchi  =
wrote:
>=20
>=20
>> On Mar 1, 2018, at 8:31 AM, John Downey > wrote:
>>=20
>>>=20
>>> On Mar 1, 2018, at 6:30 AM, Dmitry Bizyaev > wrote:
>>>=20
>>>>>=20
>>>>> * The manipulator arm brake is not working.  The arm is =
drifting/moving on
>>>>> its own.  We will turn off the arm when not in use.  The brake is =
now
>>>>> working at
>>>>> sunrise since we warmed up to -3C.  There is a temperature =
dependence as we
>>>>> dipped down to -6C tonight and the manipulator arm brake was not =
working
>>>>> then.
>>>>> Nothing is obstructing the beam.
>>>>=20
>>>> Is this the vertical brake or the pivot brake?  The description =
sounds like
>>>> the pivot brake, but ince Bill flipped the big shock absorber over =
last
>>>> summer, loss of the vertical brake causes just a slow downward =
drift rather
>>>> that a rapid fall.
>>>=20
>>> Pivot brake
>>=20
>> Its pretty strange to have it fail in the "brake off" condition, =
since that requires the pneumatic solenoid to actuate (like when the =
beam is broken).
>>=20
>> One possibility is that the brake itself stuck off due to cold =
conditions, but it is vastly more likely that a small amount of snow got =
in the little gap where the handle is mounted to its arm - the beam has =
to go through that gap, and a small amount of snow can easily escape =
notice.
>=20
> We inspected handle and did not see any snow in the ingress/egress of =
the beam.  And at the end of the night when it reactivated, we could =
hear the brake come on when we let go of the handle.  I seem to remember =
the manipulator arm was much quieter when we were extracting one of the =
carts out as we were preparing to open.  Usually we can hear some noise =
from the solenoid during normal use.
Ok, I was also wondering about whether you'd heard all those noises.  =
The system runs on compressed air, and that too can get a little funny =
during cold weather.  If it happens again we'll take a look at the =
solenoid.=
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On Mar 1, 2018, at 1:37 PM, Karen Kinemuchi <kinemuchi@apo.nmsu.edu> wrote:On Mar 1, 2018, at 8:31 AM, John Downey <jdowney@apo.nmsu.edu> wrote:On Mar 1, 2018, at 6:30 AM, Dmitry =
Bizyaev <dmbiz@apo.nmsu.edu> wrote:* The manipulator arm brake is not working. =
 The arm is drifting/moving onits own.  We will =
turn off the arm when not in use.  The brake is nowworking atsunrise since we warmed up to -3C. =
 There is a temperature dependence as wedipped down =
to -6C tonight and the manipulator arm brake was not workingthen.Nothing is obstructing the beam.Is this the vertical brake or the =
pivot brake?  The description sounds likethe pivot =
brake, but ince Bill flipped the big shock absorber over lastsummer, loss of the vertical brake causes just a slow =
downward drift ratherthat a rapid fall.Pivot brakeIts pretty strange to have it fail in the =
"brake off" condition, since that requires the pneumatic solenoid to =
actuate (like when the beam is broken).One possibility is that the brake itself stuck =
off due to cold conditions, but it is vastly more likely that a small =
amount of snow got in the little gap where the handle is mounted to its =
arm - the beam has to go through that gap, and a small amount of snow =
can easily escape notice.We inspected handle and did not see any snow in the =
ingress/egress of the beam.  And at the end of the night when it =
reactivated, we could hear the brake come on when we let go of the =
handle.  I seem to remember the manipulator arm was much quieter =
when we were extracting one of the carts out as we were preparing to =
open.  Usually we can hear some noise from the solenoid during =
normal use.Ok, I was also wondering about whether you'd heard all those =
noises.  The system runs on compressed air, and that too can get a =
little funny during cold weather.  If it happens again we'll take a =
look at the solenoid.=
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