Create a new document - Add a new cube:
Apply these settings to the cube:
Create another cube (or duplicate the one you have) and set these settings to the new one:
Place the new cube like in the image below:
Create a new Cogwheel:
Change the Plane to XZ:
Set the Cogwheel to these settings:
Create a Extrude Nurbs object:
Place the Cogwheel as a child to the Extrude nurbs:
Modify the settings of the Extrude Nurbs to match these:
Now, duplicate the boxes you created earlier and place them at the top, you should now have something like this:
Add a floor, and a light, and you’ll get something like this: