I designed this Mobile to bolt onto the side of my sons cot. The reference cot is an IKEA unit with top rail dimensions of 20mm x 35mm. Depending on the bolt length you use it could fit taller rails, but the OnShape files are available for you to modify freely. I rounded all the edges on the bottom bracket to make it safer.
The part "Gantry Base/Top Clamp" is the bottom section of the gantry and the top clamp combined, the tolerance between the two creates a contained bearing/rotational point, I printed this with a BigBox Pro with minimal supports and the bearing works smoothly (I had to use a fair bit of force to free it after printing). This allows you to rotate the unit away from the cot.
Hardware required (See attached photo):
2 x M4 Cap-head bolts (I used 30mm long ones)
2 x Flat nuts (These might not be required as there is enough "bite" in the bottom clamp)
The gantry sections require some glue (I didn't bother with fancy joints for this section. The center hanging piece uses dovetail joints (May also require glue) and requires 5 of the Baby Mobile - Arm 1 pieces.
OnShape files: https://cad.onshape.com/documents/eb4c23f1efeecfa3e56b22d7/w/21289a410a44bcda0ef8227c/e/e35dbc96f0c1f60dcd96a719
Let me know if I missed anything :)
Used Simplify 3d with standard settings for my printer. Printed in PLA. Supports only really required for the top clamp (Under the clamp and some around the bearing area overhang).