Summary

My version of a gondola (penholder) for a simple vertical plotter. See also the bead chain gear in my objects.
http://www.thingiverse.com/thing:467647

See both objects in action in this video:
https://www.youtube.com/watch?v=LPdCCa383Jw

There is also a slightly more complicated v4 here:
http://www.thingiverse.com/thing:478346

These models (and some electronic stuff) are all you need to build your own vertical plotter. Sandy Nobles (creator of Polargraph) great Instructables is a good point to start:
http://www.instructables.com/id/Polargraph-Drawing-Machine/?ALLSTEPS

This is iteration 3 of the gondola. Far from perfect, still a work in progress.
Features:

• Bead chains can be fixed with M3 bolts
• Pen can be fixed with M4 bolt
• Enough place to glue servo for pen lift
• M3 hole for counterweight at the bottom (M5 would be better, could use M5 nuts then as weight)

You can see some more pictures here (text in german, sorry):
http://www.makerblog.at/2014/09/vertikalplotter-im-selbstbau-teil-1-polargraph-kritzler-makelangelo-und-co/