LEGO provides a great rapid prototyping environment! I completely changed the design of the Whiteboard Bot after thinking it over last night. I decided to try the pendulum design from the original Senseless Art Robot.
Here is another example of its artistic talent.
The pendulum produces some good random designs but the range is smaller than the Rev 01 design. The robot moves and marks but the marks are too concise.
I am going back to the idea of a free-swinging arm that is governed by a cam. I want to include a smarter "return system" that gets the randomly swinging arm back into position and making art.
One design issue I have not yet tackled is how the pens are connected to the bots and the shape of the pen's nub.