Lego Duplo marble elevator

My kids and I love to make Lego Duplo marble circuits. Once you create enough big circuits you start wondering if there is a way to make it run indefenitelly with a marble elevator.
We tried the screwy kind where the balls get lifted inside a tube. Those didn't work as I expected. Even tried to make a new one of that kind and more of the same. Then, I saw a video of lego technic where they used a chain to lift the balls and hit my mind as a good way for Lego Duplo.

In this model you need one unit of each STL you see, but you will also need:

For the upper end of the lifter:
· 2 bearings of 3x8x3mm for the end gear, the one you find up top the lifter.
· 1 screw of 3mm x 32-35mm for the upper gear.
· 1 hexagonal nut for the 3mm screw. 5mm between planes.

For the chain:
· 2 screw of 30mm long and 3mm thickness. Each 2 will be used to "get" the balls.

For the motorized base:
· 2 bearings of 5x10x4mm for the bottom gear.
· 1 screw of 42-45mm long and 5mm thickness.
· 1