A doplo figure can fit in it

Easy to print toy excavator with a few non printable parts

For the axis: 6mm rod (I used alu) could be a screw as well. 

for the z axis rotaton use an m8 screw and nut

You can also use skateboard bearings, but a 3d printable supplement part is also available 

To make it complet you will also nead a rubery rope for the back that pulls a pit on the arm.