[RASMB] "Sticky" fit of cells in AN-60Ti rotor

[jim.bloom.b at bayer.com]

Hi everyone,
     This is my first question for "Rasmbers" so please have pity on me!!
     I am routinely using a AN-60 Ti rotor in an XLA at 60,000 rpm.  I use the
Beckman Coulter part no. 334606 Cell Housing and Window Assembly (quartz
windows) with the part no. 306493 12 mm centerpiece, epon charcoal filled.  My
problem is that I have found that the cells fit sometimes very very tightly into
hole #3 (ie. it goes in easily about half way and then I really have to force it
the rest of the way),  moderately tightly into #2 and loosely into #1.  I
usually use the same cell in the same hole.  The cell fit has been so tight at
times that I have not been able to get it in and have been afraid that it was
permanently in there....this is on loading the cell into the rotor.  After the
spin it is no problem getting the cells out....ie. problem is before the run.  I
have thought that the cell was getting distorted so I made up a complete new
assembly and it was also tight.  Switching cells around and playing with the
same cell in twice etc. gives varying results.  I thought maybe I was tightening
the brass cell plug screws too tight and thus distorting the aluminum cell
housing but I'm not convinced of that either.  What is going on?  Has a rotor
hole become distorted?
     Anyway, the real problem is that I am afraid of getting a cell stuck inside
the hole and having no means of getting it out .  Can I lubricate outside of the
cell housing or rotor hole with say the spinkote Beckman supplies to seal the
screw ring for the cell housing?
     Jim Bloom
     Bayer Corp
     Berkeley, CA
     510-705-7760