Old Salty required frequent pushes to continue navigating the rough waters and strong winds of the high seas. Most of the time he would just sit dead in the water until a passerby gave him a push and sent his ship rocking back and forth.
I was experimenting with Flexinol wire's (Commonly known as Muscle Wire) application for a client's project, when I thought that "motorizing" the sailor would be an excellent real world test of the wire's function. The sculpture was brought to life using a piece of .003 inch Flexinol wire, controlled by a Pic 12F675 microcontroller. The Flexinol wire contracts in length when a current is applied to it. The difficult aspect of using it though, is that it only contracts 4% of it's length, and it needs a significant force to stretch it back to it's normal length. A spring placed at one end solved these problems, and allows the boat to rock back and forth like normal when someone manually pushes it.
The Pic12F675 controls the on and off time of the current applied to the wire. Depending on the variables used for the on and off time, either Chaotic Motion or Resonance Motion is achieved. Chaotic Motion is caused when the off time of the wire is not the same as the period of the pendulum. Due to the springs ability to absorb energy, the boat will rock, come to a complete stop, and swing very slowly in a random fashion. When the off time is the same as the period of the pendulum, then the ship enters Resonance where every activation of the wire rocks the boat further. To keep the motion interesting, the microcontroller is programmed to loop through subroutines of different lengths of on and off times.
Below: Spring attached to a hair thin piece of Flexinol wire near the fulcrum point of the ship.
Below: Flexinol wire can be seen to the left of the mast. The ground wire is wrapped around the mast.
Below: Pic 12F675 in the center of the board. 5V regulator on the left side of the board, and Relay on the right side.
The mechanism had to be repaired twice in the first 3 days. The first time the Flexinol broke near the crimp point. Looks like I had damaged it when crimping. Flexinol is very tough wire for it's size, but can still be cut easily if you are not careful. The second time, the wire carrying current to the flexinol broke near the crimp due stress fracture from constant flexing of the bare wire. This was fixed by wrapping with heat shrink to make sure that any flexing happened where the wire was insulated. Since then it has worked nonstop for weeks.
The protoboard was replaced with a soldered circuit board installed in a tiny project box.
Compact Control Box
Daniel Bauen Mechanical Engineering Product Design :: Contact: