Thanks everyone for the excellent responses.
I'm a little surprised, however, that this rather severe "gotcha" of a
design flaw has never been addressed? Yes, Yes, I know: "Always Follow
The Instructions", but this a pretty expensive penalty for such a small
mistake. Also, I can't think of a single reason why there would be an
advantage to having the space deep inside a shipping dewar be bigger
than its neck.
We just did some measurements on a warm CX100. The neck tube inner
diameter is 70.58 mm and the puck cane I have in front of me measures
68.15 mm outer diameter. And, with a puck inserted out of alignment,
the maximum sticky-outy diameter of the cane+puck is 71.33 mm.
(basically: 3 mm wider, the height of the alignment bump) This is only a
750 micron difference! I've seen protein crystals bigger than that.
If the next step is destroying the dewar, maybe one more thing to try
would be using a sanding drum or other abrasive to widen the dewar neck
aperture? You only need to take off ~0.4 mm. In fact, a felt cylinder
painted with coarse grit diamond paste could make short work of that.
Might even work cold. Now, I have no idea how thick that fiberglass
tube that forms the neck is, but I suspect it is probably thicker than
0.5 mm. It is also a vacuum seal, an fiberglass dust is not good for
you. But with adequate safety measures I think perhaps it could be
done. Have I tried this? No. All the working dewars around me are not
mine.
I was also thinking, as a preventative measure, why not add padding? I
bought some 1 mm thick teflon mesh and we dropped a single layer of it
down inside. Took a few iterations (and it helps if someone on your
team has very small hands), but the final sheet that fits measures 280.7
mm deep and 225.72 mm in circumference. This implies a ~72 mm internal
diameter for the deeper cavity. This is ~4mm bigger than the puck cane,
and 0.7 mm bigger than the misaligned cane+puck. A properly aligned
cane, however, fits. Takes a few tries to push the teflon firmly against
the walls of the lower chamber, but after that it goes in and out
easily. With the added 1 mm of teflon on all sides, there is only 2 mm
of room left: not enough for a mis-aligned cane+puck (the alignment bump
is 3 mm). I expect that means it won't be able to pop out of place.
Now, have we tried putting a cane with no retention pin into this dewar
and gorilla tested it? No. I don't have a dewar I hate that much.
But, seems to me that adding a teflon liner to your CX100 would be
harmless, and perhaps save some of us all a lot of headaches in the future?
Just an idea for your Holiday gift lists.
-James Holton
MAD Scientist
On 12/4/2025 3:25 PM, Kevin M Jude wrote:
James, this came up on the BB a couple months ago, look for the thread
"[ccp4bb] Off-topic: call for suggestions to rescue a puck stuck in a
shipping dewar”.
*From: *CCP4 bulletin board <[email protected]> on behalf of James
Holton <[email protected]>
*Date: *Thursday, December 4, 2025 at 10:28 AM
*To: *[email protected] <[email protected]>
*Subject: *[ccp4bb] stuck puck
Anybody know any tricks for getting a puck cane out of a shipping
dewar after it got shipped without the retaining pin?
Asking for a friend,
-James Holton
MAD Scientist
------------------------------------------------------------------------
To unsubscribe from the CCP4BB list, click the following link:
https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1
<https://urldefense.com/v3/__https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1__;!!G92We9drHetJ8EofZw!edpCynZA0dj8pM3-dpzLTQbdQLdppxyxBvVAt6Q8B6tLTQwsVJgonW1Y68_WS8gvhzL-DqHkRo61koMaOZsOtDQkizM_ttbmPaY$>
########################################################################
To unsubscribe from the CCP4BB list, click the following link:
https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1
This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a mailing list
hosted by www.jiscmail.ac.uk, terms & conditions are available at
https://www.jiscmail.ac.uk/policyandsecurity/
