(Corey, Hugh, Nicole, Scott)

Since the HAM10 door needed to pulled off for BSC4 extraction, we took this opportunity to check and level the HAM10 Support Tubes.  The Support Tube elevation was recently changed when Stop Links were installed on all H2 LVEA Scissors Tables (here's an entry to how it was done on BSC Scissors Tables). 

After going inside HAM10, and checking the Support Tube level we saw that the Tubes weren't level (so, setting the Scissors Tables to the Stop Link elevation DID NOT level the Support Tubes).

Checking The Elevation

To come up for a way to diagnose level in the future, various surveys were taken of the Support Tube.  Surfaces of the Support Tube are available external to the HAM chamber.  With the optical level, elevations of the ends of the Support Tube were taken (there's a surface of the Support Tube available between the V-Block and Bellows).  With these elevations, we were able to check elevation and see where we needed to go to set the elevation of the Support Tubes.

Setting The Elevation

The Support Tubes can be raised and lowered via the Scissors Tables (there are adjustment screws accessible inside the Piers).  To make the move, Dial Indicators were mounted such that they referenced the Accelerometer Plates on the ends of the Support Tube (see attached photo).  With the elevations taken above, we had targets for where each end of a Support Tube roughly needed to be.  So at each Pier, one person raised/lowered the Scissors Table while another person monitored the Dial Indicator.  All four Scissors Tables were adjusted to get each Support Tube end to where it needed to be.  We were able to get these within 0.002-0.004" of each other. 

An External Support Tube Check-- We Appear To Have A Technique

To confirm whether our external level adjustment truly did level the Support Tubes, once again, we went into the chamber and took optical measurements.  A scale was sighted as it was set on the bolt hole boss surfaces (these are highly machined surfaces and ideal for checking level).  Additionally, we also looked at machined surfaces of the Support Table.

With a Design (aka target) Elevation of 4.878", we had the following elevation readings (taken from two different spots...some were taken twice):

• NE Support Tube:  -0.008"
• NW Support Tube:  -0.008"
• SE Support Tube:  -0.004"

---then level was moved to sight the SW corner, and we got these readings from a different sight location:

• NE Support Tube:  -0.011" (2nd sighting taken)
• NW Support Tube:  -0.011" (2nd sighting taken)
• SW Support Tube:  -0.013"

So, the Tubes were within 0.006" of each other, and they were roughly 0.010" low. 

These appear to be acceptable results and prove to be an option for checking/setting Support Tube elevations for other HAM chambers.  Hugh mentioned we may want to bias the Support Tubes up, just to account for any compression which may occur when the HAM-ISI is installed.

After this work was completed, the HAM10 door was re-installed.