For our final Emily Webster and I decided to explore SMA(shape memory alloys) specifically Nitinol Wire, better known as muscle wire.

Experiment1 from AB Videos on Vimeo.

This is an alloy which has has some interesting properties. Specifically it’s an alloy that can retain a memory shape. When a charge is run through the wire, the resistance creates heat, which contracts the metal, allowing it to be a “lightweight, solid-state alternative to conventional motor-based systems.” SMA applications are widespread, and are most often used in the medical field for things like heart valves, stents and sutures.

For the final, we’d like to use this wire to create a piece which responds to it’s environment. We will harness the power of the sun to make an interactive, sustainable, local, experiential, green, organic, grass-fed, autonomous creation.

In general, the contraction percentage of the metal is about 5% of its length. Because the degree of movement is a function of its size we know we’ll be coiling the wire to increase it’s overall length. After some additional testing, we’ve gotten the wire to respond properly by giving it about 6V and 2.4 amps (4 AA batteries in series).

Some inspiration

RegenBrake is a project by Becky Kazansky and Alexander Kozovski.

Initial concept.
To use the brake calipers to drive generators to produce power.
Discreet unit of 2 geared motors per caliper, connected to an array of LEDs.

Q. what motor gearing should we use to maximize motor revolutions ?
Q. What balance of capacitance do we need, if any?

Activating the brake(pressing on the lever) puts the motor shaft to the wheel(tire). The friction turns the motors, thereby generating power to light the LEDs.
*The motors are placed on the caliper in front of the brake pads.
This is done for safety as engineering redundancy: If motors fail for any reason, the bike reverts to the default mechanism of the brake caliper.

Final Design Implementation
Once installed, we found that each motor outputs at its highest revolutions approx 12V at 1 : 24 gear ratio; more than enough to power our circuit positioned under the seat.

We like that our device is only actuated when needed. It requires very little effort from the user, as it takes advantage of lost energy that would normally be converted to heat by friction.A standard dynamo design would affect the user during the entirety of the ride, requiring extra effort to generate power.

This design, allows both the control/actuation and the power generation to happen at the same moment, thereby not requiring a separate control mechanism (i.e switch) to power the circuit. This makes for both robust/efficient minimum constraint design.

Issues
The mini gear head motors we used were well sized for the application (1.26″ x 0.63″ x 0.63), but the output shaft was very delicate 0.275″-long, 3 mm-diameter . The assembly process required us to remove the output gear from the shaft of the motor enough times that the pin holding it in place wore down, causing it to wobble. In the end, we used just one motor to generate power to our “STOP” LEDs.

Future
We wish to use both motors as a pair to generate more power for other applications.
One idea we would like to explore, is utilizing a LED projector paired to a smart phone to visually provide directions in the form of projected directional arrows and serve as a headlight to light the way at night.