Here some details.
The pen-lift function is based on a “Micro Mini Servo SG37 ” , I bought two for about 7€ from Ebay. With hot-glue I attached a part of a “loose-leaf-binder” as a quick-and-dirty solution for the function prototype. Some plywood and osb-board do the rest ..
The motor holder is a simple holder from the Do-it-yourself-shop ( German: Obi Baumarkt ) , it is a holder for wooden-beams, I used some brackets so that i could see the motors -normally they are not needed, only a few Euros, too.
The plastic wheel is a cheap part from Ebay.
The servo-control is based on the idea of a “servo-tester” with a “PIC” Microchip controller, but I want to get rid of the wires to the pen-holder, I’m thinking about a simple remote control and maybe two AA-sized batteries on the pen-holder ..