Summary

See it in action!
https://www.youtube.com/watch?v=KuehkVUGT5I

This is a simple crane I designed to sit on top of a Bachmann flat car and attach to the stake holes.
For motorized version you'll need 3 electric motors (10mm x 12 mm width) - I used Greartisan geared motors available on Amazon https://www.amazon.com/Greartisan-74RPM-Torque-Reduction-Gearbox/dp/B07FVSR5QS/
For R/C control you can use any 3 or more channel receiver that'll fit inside, I used this one https://www.amazon.com/dp/B0B3DHWW2M
You'll also need some thin rods or nails for the axles, thread or mini chain for the rigging and a rubber band for the crane rotation.
The crane battery compartment is designed to accept a rechargeable battery pack the size of 2x3 AA batteries.
I used this gravity hook https://www.thingiverse.com/thing:1607199
There is a counterweight pocket on the back of the cab that can be filled with weights as desired to achieve good crane balance.
Since I'm not using any bearings to keep the design simple, I recommend using teflon lubricant on all moving parts to prevent binding.

Depending on your printer specs, for proper fitment might be necessary to adjust Horizontal Expansion to -0.1mm if things fit too tight or +0.1mm if too loose.