From: Greg Ralston <gregr@atp.biochem.usyd.edu.au>
  To  : RASMB@bbri.harvard.edu
  Date: Thu, 24 Oct 1996 10:02:52 +1000

Overspeed disks

Dear RASMBers,

I don't know how prevalent the problem is among others, but we have gone through
several overspeed disks. Everything is OK for low speed runs, but attempts to do
a velocity run at 60,000 rpm leads to a "faulty overspeed disk" message.

We have put a ring of felt around the rotor stand to avoid abrasion, and we are 
very careful to avoid scratching or damaging the ring on the lower surface of 
the rotor.

For a time, I suspected that the black was not black enough. It always LOOKED 
pretty black, and attempts to enhance it with texta colours or higher tech 
methods failed.

We then twigged to the fact that the bright areas were not bright enough. Gentle
polishing of the bright sectors with a typewriter eraser removed the layer of 
oil and grime, and polished up the scratches. When treated this way, a ring that
originally failed at 54,000 functioned happily for several runs at 60,000 rpm 
before needing repolishing. 

We now have a couple of disks on hand just in case, but our rate of replacement 
has dropped dramatically.


 


Greg Ralston
(Associate Professor)

Phone (61 2) 351 3906
Fax   (61 2) 351 4726

e-mail: G.Ralston@biochem.usyd.edu.au 

Department of Biochemistry
University of Sydney
Sydney, NSW, 2006
Australia