I finished off the week with the fourth revision of the art bot. I have struggled with vertical reach of the pen in revisions 01-03. I even had a version 03b that did not get photographed. It returned to the design of Rev 01 but was too erratic and abandoned. Rev 04 changed the design completely and returned to the design of the Balancing Robot. I hope with more of a vertical reach the robot might draw a larger picture.
Here are some detailed photos of the gearing and design.
Those are two big LEGO weights at the bottom of the robot, between the wheels. Speaking of wheels, I am also challenged by the design of the pen tray at the bottom of the whiteboard. It is scalloped. This makes the wheels wander. I am thinking I should use my LEGO railroad parts and build a rail line for it to go up and down on. This would help focus all the power into the tasks of moving and drawing; I see a lot of energy expended as the robot wanders slightly off course and bumps into the board or drags some part of itself against the board. Rails would ensure proper placement of the pen against the board, too, another frequent challenge. The original Senseless Art Bot ran on sheets of particle board, so this accommodation to the robot's locomotion would be acceptable.
Here is some footage of the robot being tested.
Rev 04 also marks the start of using Scratch as the programming environment! Right now the program would just draw a line on a whiteboard. Soon the robot will have many procedures!