Here is my submission:
Spool on the carrier.
Shown upside down to see the screw as feet. The t-slot nuts and M5 nuts are shown as extra parts.
Minimum Setup (Requires extrusion be elevated such as printed feet OR have the MakerSlide upside down!):
MakerSlide or other 2040 extrusion 100 mm length minimum x 1
HNKK5-5 5mm thread t-slot nut x 4
Smooth Idler Wheel Kit x 4
M5 nut x 8
M5 screw (50mm shown) x 4
Shown Setup (shown in pictures with screws to elevate extrusion):
MakerSlide or other 2040 extrusion - 100 mm length minimum x 1
HNKK5-5 5mm thread t-slot nut x 8
Smooth Idler Wheel Kit x 4
M5 nut x 8
M5 screw (50mm shown) x 4
M5 cap screw (10mm shown) x 4
What I like about this setup is most of the parts can be sourced at the MakerSlide store such as the idler wheel kit, t-slot nut, and extrusion. The screws and nuts can be found at your local hardware store. The idler wheel are installed so you can pull them out. The idea is spool will keep the wheels from coming loose and the wheels will not touch the extrusion when installed this way.
Compliments the look of the ORD Bot by using 2040 extrusion (MakerSlide or Misumi, etc...)
Uses ORD Bot Parts or has simple BOM as listed.
Minimal Fabrication required (some printed parts OK) such as new feet to elevate the extrusion.
Easy Spool change since you are not required to stick something in the middle of the spool.
Fits multiple standard spool types by having longer screws.
Easily Portable (not attached (at least permanently) to ORD bot) because it is small and can be mated with other parts of the printer's extrusion.
It is Open Source.
Hope you folks like it!
Updated/Revision
Felt like the screw could be easily loosen, I have added an additional nut and washer to give it a tighter lock.
Revised Setup (shown in pictures with additional nut and washer):
MakerSlide or other 2040 extrusion - 100 mm length minimum x 1
HNKK5-5 5mm thread t-slot nut x 8
Smooth Idler Wheel Kit x 4
M5 nut x 12
Size #10 washer x 4
M5 screw (50mm shown) x 4
M5 cap screw (10mm shown) x 4