Notes from Bill McBride's visit 11_7_2021

Owned by Gary Foster
Last updated: Nov 17, 2021
3 min read

Ground Floor

Vibration isolation is critical. Look out for a report any crossover connection between the enclosure and Coude or Mount.

Coude Cable Wrap

Coude Cable wrap has 2 cables in one slot. If the cables get dirty they can bind and not slip within the cable wrap slot.

  • Cables should be inspected and verified to be slack within the cable wrap. Overtension, or excessive slack can cause cables to bind and become damaged.

  • Cables and cable wrap should be cleaned on Preventive Maintenance (PM).

Bill changed mount cable wrap. Coude wrap should be changed to match. Can someone provide more detail?

There is a Cable Wrap auto-greaser near the ladder.

  • Grease and greasing operation should be inspected and verified on PM.

Coude Wrap Delta Chain

There is a Delta Chain section between the Coude tower and cable wrap to prevent tension relief if the Cable Wrap does not synchronize with Coude tower position .

  • Cables and cable wrap in the Delta Chain should be cleaned, inspected and verified to be slack within the cable wrap.

  • Operation of the Delta Chain should be tested and verified on PM.

Coude Encoders

There is an encoder tape around the Coude. It is scaled to report position within 40 microns. There are 4 coude encoder tape reading heads. The encoder is interpolated by 4096 (or 8192?) so reads to around 5 or 10nm.

Encoder heads are mounted at 90° intervals.

Runout of the Coude tower can be calculated by measuring the difference in counts between two encoders opposite each other.

  • We can add logic to the controller calculate runout. This data can be logged to monitor performance and accuracy of the Coude mechanical rotating assembly

  • Encoder tape should be inspected and cleaned on PM. This requires removing the tape covers.

  • The procedure is somewhere in our documentation. We need to locate this procedure.

If encoder tape must be replaced:

  • There's an installation fixture and procedure. We need to locate both.

  • Installation of new tape requires some rollers. Heidenhain will loan rollers for tape installation.

Coude Accelerometers

Qty (4) 3 axis Accelerometers are installed on the Coude. They are connected to a Data Acquisition System in Rack 6. The DAS is networked to a switch. There's another one on the mount.

  • We can collect and log accelerometer data

  • We need the subnet connection info.

There’s a lightning detector near mezzanine door.

  • Battery is dead, needs to be replaced.

Crane at clean room door is is supported from overhead. It is connected to the Coude and to the enclosure. This transmits vibration from Enclosure to Coude.

  • Crane mount needs to be modified to not connect to the Enclosure.

Utility level cable wrap

Dust causes cables to bind.

  • Cables need to be cleaned on PM. Cables need cleaning.

Delta chain has excess slack.

  • Cables need to be adjusted.

Air Knife

Air knife is a source of vibration.

Air knife cabinet is on the telescope side so may be a problem.

Enclosure cable wrap

Enclosure cable wrap rollers can rust and seize. Causes dragging and vibration. Can detect by seeing scratches on the wrap bed.

  • Need to inspect cable wrap rollers on PM.

  • Need to inspect truck rollers on PM.

  • Cables and slots need to be cleaned on PM.

There's an alignment fixture and control unit for the Heidenhain encoder.

  • Need to locate alignment fixture and control unit.

There's a procedure to align mount motor gear to the drive wheel somewhere. Also must adjust commutation of the drive.

  • Need to locate the alignment procedure.

Telescope level

Cooler cabinet is hard bolted to deck.

  • Need to install vibration isolation.

Mount has multi position locking pins. 2 pin positions, check for balance before removing pin.

  • Need to locate the locking pin documentation an procedure.

  • Shutter crawlers should be greased on PM.

  • Enclosure azimuth lightning brushes resistance should be checked on PM.