For the head in a 2D plotter I have 4 gears in an X configuration in the same plane. The gears are driven by belts from the outside in different combinations. The top and bottom gear can be turned in opposite direction as indicated by green arrows. Or the left and right wheels can be turned in opposite directions as indicated by the red arrows. Both of those can happen simultaneously. The gears can also be driven all in the same direction as indicated by the blue arrows. Or all directions can be reversed. This is part of a larger construct and the belt movement already has effects there so they can't be changed.
Now what I want to build is some mechanical contraption that turns the blue arrow movement into an upward (or downward if reversed) movement to rise (or lower) the pen of the plotter.
If all wheels turn anti clockwise the pen should rise. If all wheels turn clockwise the pen should lower (or vice versa).