tiedown positions during telescope painting
Tiedown jack 4 failed on 28may08 with broken ball
grooves in two places near the middle of the jack run. This jack had
only 3 years of service. The previous jack at td 4 lasted for 8 years
before it failed.
The tiedown motion was limited for part of the
painting project because the distomats were not operational. To see
where the jacks were situated, i plotted the jack positions for td
12,4,8 for 01may07 thru 01dec07.
Jack positions during
painting project (.ps) (.pdf):
There were two positions when the tiedowns were
- Position 0" is with the jack all the way up (little tension).
position 24" is the jacks all the way down (hi tension).
- top plot: tiedown position vs date
- bottom plot: tiedown position vs dayno.
If the failed position midway through the jack was caused because we
sat at 10" for a while, you might also want to check the extremity
where the jack sat at 4 inches for 35 days (although the tension would
have been less here).
- jul-aug 30 days at tdpos=10
- aug-sep 35 days tdpos=4 inches.