Thursday, July 19, 2012

Scribbling Machines

• Skewers
• Dowels
• Popsicle sticks
• Clothes pins
• Cups
• Cardboard tubes
• Pipe cleaners or wire
• Masking tape
• Rubber bands of various sizes
• Straws
• Hobby motor
• Annealed steel wire
• AA batteries

• Hot glue gun
• Wire cutters
• Wire strippers

Scribbling machines are simple drawing machines which use a small motor to move a pen or pens around a pad of paper to create interesting patterns.  The idea of scribbling macines is not a new one in our experimentations we've found that having a restricted pool of material to build with creates more interesting patterns and more importantly machines that are truly adjustable. Adjustability is valuable from a an educational perspective because it encourages iteration and an understanding of how changes in form effect changes in movement.

The most important element of a scribbling machine is motive power, this consists of a hobby motor,
 two telephone wire leads (fine solid copper wires), a AA battery and a rubber band to hold the wires in place on the battery. Broccoli rubber bands work well to hold the wire on the battery, but they can be hard to find so we tend to cut up old track bike inner tubes to make our own rubber bands.  There are a couple of options to get the machine to move around the paper. Sticking a section of hot glue stick on the motor shaft to make a counter weight will create a vibrator.  The amount of vibration can be adjusted by centering the motor shaft more or less in the glue stick. We found wood screws work well to make a pilot hole in the glue stick. The other option is direct drive where the motor shaft or a wheel is in direct contact with the pad of paper.  The former makes more jittery chaotic patterns, where as the second method can make more Spirograph like drawings. In general we consider this to be a mechanics projects not a electricity project, as it is the motion of the machine not the circuit that is the focus of the activity.

Apart from that, there is no specific way to build build a scribbling machine, outside of the goal of making a structure to attach a pen to the motor. The activity itself is really adjusting the machine and figuring out how different changes in form effect the quality of the drawing and then taking that information to adjust the characteristics of the drawings. Here are a few models we tried out:

This is a very simple configuration, a toilet paper roll with clothes pins as pen holder claws and the motor/counter weight and battery attached on top. Originally it didn't have the skewer, but it did not produce very interesting drawings. Adding the skewer reduced ground friction and added some simple height adjustability which made for more interesting drawings.    

This version has a pen on one side and motor and battery on the other with a bottle cap skid in the middle. Because of the position of the motor this model can be configured as a vibrator or a direct drive by making the glue stick just long enough to touch the paper which makes for a really bouncy energetic motion (as seen below).  Changing the position of the bottle cap skid is another way to change this machine's behavior.    

This model is particularly jittery, with the pen coming in and out of contact wit the paper, as no part of its pipe cleaner structure is very ridged. Although the battery skid can't be moved the wire part of the structure can be bent and adjusted in an infinite number of ways to change behavior.

This is a direct drive model where the motor shaft is directly in contact with the paper.  It tends to make circular spiral patterns as the motor and pen rotate around the clothes pin skid. Adjusting the pen height and angle and moving the center skid around can change the pattern produced dramatically.  

Further experiments:

• Try separating the motor and pen with something flexible (sting or wire) so the pen gets dragged around.

• Confine your scribbling machine to a pen, pieces of wood or a cardboard box with no top or bottom works well and will lead to a higher concentration of line where the machine hits the walls.   

• Tether your machine with string to a point with a string and a thumb tack, this has a similar effect as the pen, with the bonus of the string possible changing length over time as  it wraps around the machine or the tack.

• Tether two machines to each other with string. Will they work together, fight each other, of orbit in some new combined motion?

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