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National Radio Astronomy Observatory Socorro, NM VLBA Antenna Memo Series #27 Fort Davis Maintenance Visit August 14
1
National Radio Astronomy Observatory
Socorro, NM
VLBA Antenna Memo Series #27
Fort Davis Maintenance Visit
August 14
th
through 19
th
, 2000
Trip Report
Jim Ruff
8/22/00
Attachments: Azimuth Rail Survey, Servo Trip Report, Electronics Trip Report, Task Schedule
The team consisted of Steve Aragon, Ramon Gutierrez, Bob McGoldrick, Steve Tenorio, Steve
Troy, and Jim Ruff. Site Techs Gary Tobias and John Smith assisted throughout.
An apex handrail was installed.
The pintle bearing pocket was inspected for flatness. Measured TIR was 0.010. The spec is
0.012 in 90
*. The TIR of this bearing is much worse than NL or KP, but still within spec.
The FRM INA bearing was inspected for internal clearance. Clearance measured 0.0045
Elevation bearing grease catchers were installed.
The vertex house door was replaced. Ordering spec for the door is Ceco 2868, Right Hand.
The azimuth bearings were inspected and found to be OK. Outside bearings on Drives 1 & 2 and
Idler 2 were replaced about 2 years ago. The outer races were not rotated, as this had been done
previously on the old bearings and it was too soon to rotate the new ones. Note that the new
bearings had a different type of retainer. The design of this retainer makes on-antenna inspection
of the inner ring impossible.
Drive 1
Drive 2
Idler 1
Idler 2
Inner
Metal fines & flakes.
Minor pitting.
A few flakes. No pits.
No metal or pits.
Several flakes. No
pits. Moisture.
Outer New. Some fine
metal.
New. No metal.
Some flakes. No inner
ring pits. Moisture.
New. Some fine
metal. Moisture.
The Drive 1 inner bearing would probably have failed by now if not for the conscientious job
Gary and John do on greasing.
Radial positions were measured for both drive wheels. Az 1 was 299.76. Az 2 was 299.94.
These positions are within the
)1/4 spec. 2
The dichroic panel is delaminated in the corners and sagging. It appears a feed heater partially
melted the top tube. (Figures 1 & 2). This dichroic should be replaced when a new plate
becomes available.
Figure 1: Dichroic Reflector
Figure 2: Dichroic Reflector 3
The azimuth rail and grout were in good condition. Elevation readings appear to be stable. The
course focus on the Wild level was not working properly and may have caused some error in the
readings.
An original RSi bolt ID was located. It is a numeral 3 welded on the rail support plate.
Figure 3: Rail Elevation History
-30
-20
-10
0
10
20
30
40
Readi
ng: 0.001"
1
11
21
31
41
51
61
71
81
91
101
111
Bolt #
S
S
S
S
S
S
95
96
97
00
FD Azimuth Rail Elevations
Figure 3: Az Bolt ID 4
The subreflector appears to be in excellent condition.
The 3mm receiver was checked for clearance. Clearance is adequate.
Figure 5: 3 mm receiver
Figure 6: 3 mm receiver
The paint on this antenna is in excellent condition. There is very little rust, and most failures are
flaking of paint from galvanized metal. (Figures 8 & 9)
About 50% of the paint under the pedestal room was flaking off the galvanized structure. We
scraped most of the loose paint off. I recommend that the site techs borrow a water blaster from
the VLA and use it to remove the rest of the paint from this area. (Figure 7)
The mid-level handrail was repainted. (Figure 10)
A structural crack was found over the El encoder-side bearing and re-welded. (Figure 11)
Figure 4: FD Subreflector 5
Figure 7: Ped room underside, before scraping
Figure 8: Paint failure
Figure 9: Paint failure
Figure 10: Mid-level handrail before painting
When we returned to the motel Saturday night, there was a message saying that the
antenna was faulting on el overspeed and that the pedestal room was hot. Tenorio and Aragon
went back and corrected the overspeed problem. I went back and checked the MarvAir unit. All
functions on the MarvAir were working properly. A fan was used to cool the room, and no
further problems have been reported.
Figure 11: Repaired weld over El bearing 6
From:
Steve Tenorio
Subject: Servo Trip Report Ft. Davis
Date:
13 aug 00
13aug00 Day # 1
Traveled from Magdalena to Alpine Tx.
14aug00
Day # 2
Traveled from Alpine to Ft. Davis site. Unloaded truck, installed
Az. J-boxes. Trouble shot servo power fault problems. Problem
turned out to be slow blow fuse on Drive cabinet interface panel.
Started on El. # 2 j-box.
15aug00
Day # 3
Finished El. J-boxes. Checked ped. room electrical panels with IR.
Thermometer. Completed Drive cabinet pm., ACU pm, and Data
Converter pm. Changed and seated Az. brushes (armature scarred
needed a lot of work). Changed El. # 2 brushes. Checked brake
tension on all motors. Checked gear box heaters El. # 2 bad (no
current).
16aug00 Day # 4 Completed Fault test . Changed and seated El. Brushes. (armatures
scarred also needed a lot of work.) Mounted warning horn on El.
Platform j-box. Checked velocity and limits and recorded.
Completed servo test.
17aug00 Day # 5 Trouble shot El. Counting problem. (not counting correctly in slew
mode. Turned El. #2 tac. so that the strain relief is facing down.
Replaced all tac. Plugs. Changed out El. # 2 gear box heater
switch. Helped Aragon mount stow pin extension tray. Moved El.
Platform E-stop box (fried drive cabinet interface card and slow
blow fuse on az. side doing this) swapped out El. Drive cabinet
interface card, and replaced fuse. Moved stow pin engaging switch
to accommodate the new stow pin extension tray. Helped change
spiders (WITH STOW PIN ENGAGED !!!) Ty-wrapped all motor
cables. Helped Aragon install grease trays.
18aug00 Day # 6 Helped Aragon check hoist on Encoder platform. Reset antenna
stow position to 93 degrees from 87 degrees. Per site techs request.
Oked by Tom Baldwin. Helped check panel bolts. Repaired door
closer on ped. room door.
19aug00 Day # 7 Finished replacing doors on Electrical panels in ped room. Helped
Troy remove and replace ped. room A/C unit. Cleaned ped. room.
Helped mechanics grease pintal bearing and El. Bearings. Loaded
truck. Got called back from motel to trouble shoot El. Overspeed
problem. Swapped Az. and El. Drive cabinet interface cards.
20aug00 Day # 8 Traveled back from Alpine Tx. to Magdalena. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.
National Radio Astronomy Observatory
P.O. Box O, 1003 Lopezville Road, Socorro, New Mexico 87801-0387
Telephone: (505) 835-7000 Fax: (505) 835-7027
To: Jim Ruff
Subject: Fort Davis Tiger Ream Report
From: Bob McGoldrick
The Fort Davis Station is well maintained, and a considerable
amount of maintenance was completed by the Tiger Team in conjunction with the Site Techs,
Gary Tobias and John Smith. The members of the Tiger Team were Jim Ruff (PE Engineer in
charge), Ramon Gutierrez, Steve Tenorio, Steve Aragon, Steve Troy, and Bob McGoldrick.
The Site Techs leave little to find fault with around the station as is evidenced with their
clean and replace as you go attitude concerning station maintenance and upkeep. Many
improvements and maintenance issues were corrected, but some items were left for the Site
Techs to correct.
ACTION COMPLETED
1.

The Electronics Inspection Sheet was completed, except where Tom Baldwin left specific
instructions to leave for him on a later visit.; this is a FRM to Station Building electronic
inspection.
2.

A new RH sensor over the recorders for Contempo temperature control was installed by
Steve Troy.
3.

Strain reliefs for all cables needing strain relief in the Cable Wrap were installed; three
holes were drilled in the top-plate(just below the bulkhead ceiling) to hang the strain
relief by John Smith and Bob McGoldrick.
4.

Bob McGoldrick was trained by John Smith on decontaminating, cleaning and talcing the
Cable Wrap after hanging the strain reliefs.
5.

The Pedestal Room bulkhead feedthroughs (adjacent to the outside Pintelbearing Room
bulkhead) were found to have some water damage on the inside/outside wall surfaces.
One PVC feedthrough was replaced by Gary Tobias, and several were pluged. The large
feedthrough on the bottom had come unglued from its fitting, and it was reattached with
the standard two-piece plumbers adhesive by Bob McGoldrick, but the amount of PVC
fitting to work with was insufficient to provide an idea joint; the joint cured but it moved
a little before doing so. The joint was caulked liberally along with the other bulhead
joints, and found to be leak free.
6.

Bob McGoldrick inspected both site Tape Recorders and looked at some Recorder Test
results to determine if any major work would be needed, and found that the machines
were operating satisfactorily at that time.
7.

Jim Ruff relaced the dish anemometer roll pin blocks with replacement blocks and new
bolts rather than roll pins; He had the machine shop modify old blocks prior to the visit,
and plans to take the old blocks back for modification prior to the next trip.
8.

John Smith and Bob McGoldrick