AMMRLers,
I wanted to mention another unrelated spinning problem we've encountered,
but the other spinner post was so long I thought I should put it by itself.
Some other issues we've had with spinners relate to a batch of replacements
we purchased a little over a year ago. They were made out of a different
material than the originals (it seemed to chip easier) and had slightly
different specs (mass and diameter). One result was that, if the users got
the spinners mixed up, spinning and ejecting became a problem which some of
them tried to solve by adjusting the air pressure at the regulator on the
wall, usually creating a bigger problem for the next user. We wanted
consistent behavior from all of the spinners to minimize any air pressure
adjustments. In addition, neither of the two styles seemed to spin or eject
reliably at low temperatures (below -40/-50 deg. C or so). Another
observation of the new spinners was that, it was possible for them to get
stuck at the top of the barrel (wedged at a slight angle) after the user had
given the insert command. Based on the observations of the user who was
using the spectrometer the last time the glass insert of our Nalorac quad
probe was shattered (there's a lot already in the archives about this), I
believe this is what happened: he hit insert, the spinner got stuck at the
top of the barrel until after the slow-drop air turned off, and then
subsequently dropped, cracking the glass insert.
After some correspondence with David Cross at Rototec-Spintec regarding
these problems he agreed to let us try the two new spinners he was working
on (made out of PET and PEEK). They can be seen and read about at:
http://www.rototec-spintec.com/products/prod_area/tab_02_01_04_01.htm
They have worked great. We have one of each kind; they are well matched,
and don't require any air adjustments when switching between the two. The
PEEK version is the one we use for user samples (the PET model holds our
standard sample in the magnet between users) and has been used successfully
spinning samples as low as -60 deg. C without any problems. Also, as far as
sticking at the top of the barrel is concerned, it simply can't be done.
The surface is so smooth that no matter how hard I tried, I couldn't get it
to stick. With the fiberglass ones it was quite easy. Hopefully we won't
see another shattered glass insert for quite some time.
Best of all, at ~$70 - $140 depending on model and quantity, they are
relatively cheap. Sorry to sound like a commercial, but I'm quite pleased
with them.
Cheers,
John T.
Tomaszewski, John
NMR Facility Coordinator
Indiana University
800 E. Kirkwood Ave.
Bloomington, IN 47405-7102
(812) 855-4478
Received on Fri Aug 09 2002 - 11:35:42 MST