I'm flashing back to a cub scout project that involved creating a simple wooden crane with a magnet (made from a carriage bolt, I think) electrified by a six volt battery you could switch on and off to pick up and dump metal "junk". Perhaps a basic crane kit could be modified using a similar approach? The container crane mentioned above is wondrous but costs several hundred dollars. I created a nonfunctional electromagnetic crane for a junk yard that simulates a crushed car held over a car crusher. A working model would be fun!
Ralph