Feedback Chain: Theoretical & Applied Mechanics

Artist and engineer Norman Tuck created this dynamic sculpture to give visitors a chance to see feedback in an instructive and playful way. A bike wheel attached to a motor, elevated high above a visitor, continuously moves a loop of linked chain around and around in a set path. A tap to the chain sends a new force through the system, and the chain responds by changing its path around the object- like a stream around a rock. When the force is removed, the chain eventually disperses the energy and returns to its normal path. By gently tapping, visitors can create some dynamic, beautiful, and unexpected reactions.

Propeller

At this exhibit, visitors pedal on a bicycle that is attached to a propeller from a DeHaviland "Otter" airplane. As the visitor pedals faster, the propeller will spin faster causing yellow weights to move outward. The weights control the angle of the propeller blades. In this position the blades slices through the air with difficulty. When this happens, it becomes harder for the visitor to pedal. When the visitor starts to pedal slower, the yellow weights move inwards changing the angle of the blades making it easier for them to slice through the air. This is an example of feedback. In this example, feedback sets limits of performance by limiting the visitor's top speed.

Sharing the Load

Suspension bridges, such as the Brooklyn Bridge or the Golden Gate Bridge, work by distributing the weight of moving vehicles and people and the vibrations from them over a series of interconnected cables and high-strength beams. All of the parts exert different forces that work together to support their load. Some parts, like the beams of the structure, have to push, or compress. The cables, meanwhile pull back under tension.

At this station visitors get to pull, push, and even hang on a rope attached to a small suspension structure. A series of LEDs indicate how much force is exerted in response by the cable and the beam of the system.