Lessons Learned From Gemini North: Monitoring the Gemini South Shutter Drive Units

Active monitoring of the drive units on the Gemini South dome are ongoing in order to avoid the failures which recently occurred at Gemini North. These include an exhaustive review of bearing lubrication procedures, as well as a re-evaluation of the loads acting on the bearings. Bearings are now well lubricated and the loads acting on them are confirmed to be within manufacturer specifications. In this photo, Pablo Díaz, Mechanical Engineer, inspects the drive unit at Gemini South.

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Gemini North Back on the Sky Tonight!

The Gemini North telescope will resume scientific operations tonight after an unscheduled shutdown due to the failure of a dome shutter drive unit. The Gemini engineering team was able to repair the unit on their original schedule and minimize down-time to Gemini North operations.

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Drive Box Work Continuing – On Schedule

Seven days after removing the Drive Box, the Drive Box assembly has been repaired, refurbished, and reassembled. Both Gearboxes within the Drive Box have been extensively tested in preparation for the re-installation of the Drive Box back into the shutter. Gemini North is still on schedule to return to normal operations by the end of next week.

In the meantime, watch this video illustrating the difficulties of accessing the Drive Box unit on the Gemini dome!

Shut Down Update #3 Drive Box is Down!

With the arrival of the crane as scheduled on Tuesday at Gemini North, the summit staff (on Wednesday) removed the shutter Drive Box assembly. Now that the Drive Box is safely in the workshop, the team is working on repairs to the Drive Box in order to replace the failed spherical bearing and shaft.
See the Canada-France-Hawaii Telescope’s Webcam view showing a live view of the action at: http://cfht.hawaii.edu/webcams/index.php?cam=cfhtdome
 
View from the dome platform, taken just after the Drive Box assembly was clear of the shutter.

View from the dome platform, taken just after the Drive Box assembly was clear of the shutter.

The crane lowers the Drive Box attached to the lifting fixture.

The crane lowers the Drive Box attached to the lifting fixture.

Harlan U. helps “land” the Drive Box outside of level 1,

Harlan Uehara helps “land” the Drive Box outside of level 1.

 

 

Gemini North Dome Repair: Update 5/30/14

Gemini staff are making good progress on preparations to physically lock both the top and bottom shutters in place, which must be done before the left (from the outside looking in) shutter Drivebox can be removed.  This is being done by the addition of a total of four shear angle plates with structural bolts, connected to the enclosure structure, that exceed the loading requirements.

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Gemini Senior Optical/Mechanical Technician Clayton Ah-Hee inspects the shutter Drivebox as preparations are made to remove it from its housing on the Gemini North dome next week.

The team also reports that they are on track to safely remove the Drivebox next week.

Gemini North Dome Suffers Critical Failure – Update #1 – May 23, 2014

A mechanical failure of a key drive unit high on the outer side of the Gemini North dome will force a shutdown of operations until the unit is repaired. It is expected that the repair will take on the order of a month to complete due to the difficulty of accessing the drive unit.

The mechanism, which works in tandem with an identical unit on the opposite side of the Gemini observing slit, appears to have suffered the same fate as the unit’s companion that failed in late 2013. Gemini’s Director, Markus Kissler-Patig expects that the repair will proceed more quickly since we now understand how to make these repairs.  “Because these drive units are used at both telescopes we urgently need to understand the cause of the failure in order to avoid this happening again in the future. Fully understanding the problem is our highest engineering priority.”

This image shows the drive unit, in which a critical bearing has been sheared causing its alignment to skew (lower aqua-colored box) and render the unit inoperable. The entire mechanism weighs about 4 tons and must be removed from the dome for servicing.

This image shows the drive unit, in which a critical bearing has been sheared causing its alignment to skew (lower aqua-colored box) and render the unit inoperable. The entire mechanism weighs about 4 tons and must be removed from the dome for servicing.

Gemini is currently informing all PIs of active Gemini North programs. The repair will not impact the planned visiting instruments DSSI and TEXES scheduled for July and August of this year. In addition, we are investigating options to minimize impact on the overall scientific productivity by moving work forward from the maintenance shutdown scheduled for September 2014.

Watch this blog for regular updates on this repair work.

During the similar repair in January of this year, the crane used to remove the unit is shown in place. In this instance, the identical unit on the left side of the observing slit will be repaired. For details on the repair earlier this year, see: http://www.gemini.edu/node/12160

During the similar repair in January of this year, the crane used to remove the unit is shown in place. In the current instance, the identical unit on the left side of the observing slit will be repaired. For details on the repair earlier this year, see: http://www.gemini.edu/node/12160