This is my attempt for creating an 8x10 inch development spool for being used in the larger JOBO 25xx series of development tanks (typically used in JOBO CPE/CPA/CPP or ATL rotational film processors).
It is derived/upscaled from my 13x18cm spool for Paterson development tanks (see here: https://www.thingiverse.com/thing:3465241).
*** this can be used for 18x24cm sheet film, too
8x10 jobo spool (2x)
8x10 jobo brace 1 (3x) or 18x24 jobo strebe (3x)
8x10 jobo brace 2 (4x) or 18x24 jobo andrucksteg (4x)
8x10 jobo axis base (1x)
8x10 jobo axis extension (1x)
a little bit plastic glue
As I didn't have an original axis during design, I assumed the JOBO axis to be the same diameter as PATERSON, so the holes for the axis are slightly too big. Therefor I created the two axis parts - modify the axis extension to adapt the length to your own development tank.
I created and printed this spool for a friend (I don't shoot/develop 8x10), so the spool is currently only "dry tested" with some sheets of already developed film. But I am quite conscious that it works well under real world conditions.
Update 2019-03-29: I got feedback that the two parts for 18x24cm were some millimeters two long. I updated both, so that they are 180mm long (assuming 18x24 film has a real width of 178mm).
use your preferred one ABS or PETG
make sure the film rails of the spool are clean&smooth. Use folded sandpaper to achieve this.
print the "8x10 jobo axis base" with support - all other parts do not need supporting structures.
Take one spool and glue all 3 "brace 1" parts to it - there's virtually only one way to do this.
Then glue the second spool on top.
Glue the 4 "brace 2" parts to it with the nose to the inside.
If in doubt how to glue together the things, just see the original picture.
Hint for 18x24cm:
do not glue the 4 "brace 2 / andrucksteg" parts to the edges of the spool but about 3-4mm back from the edge.