Introduction: Regenerative Braking for Bicycle Safety

If you have always wanted to generate electricity on your bicycle but wished for a way that would not add extra work and resistance to your bike ride, then this project is for you. 
We will build a regenerative brake for a bicycle, based on 2 geared motors which will power a functional ultra bright LED stop light/safety flare for your ride.
The intention of this project is to create an elegant mix of sustainability and personal transportation safety.
We wish to enhance bicycle safety by alerting visually all vehicles around you, that you are braking, making them aware of a possible change in your trajectory,  whether it is because you wish to make a turn or just slow down or stop.

It will require no extra pedal stroke effort as we will be harvesting the energy that usually gets released as heat from friction.
It will require no extra buttons, or switches as we wish to keep the cockpit of the bicycle the same, and maintain the mode of operation.
No batteries required.

This tutorial requires some soldering, light dremel work and basic circuitry (i.e connecting LEDs in parallel).
Lets go to the next page for materials.

Step 1: Materials and Tools

Here are the materials sourced.

2 mini gear motors(24:1) from
Aluminum Mounting Hub for 3mm Shaft Pair, 2-56 Holes from Pololu
Mini Metal Motor bracket from Pololu
Various nuts and bolts 

Architectural Aluminum (alloy 6063), Rect Bar W/ Rounded Edge, 1/8" Thk X 5/8" W X 6'l
from McmasterCarr

Plexiglass 1/4 in at 10x10 in 
UltraBright LEDs (Radioshack)
Speaker wire( Radioshack)
Heat Shrink (Radioshack)
Electrical tape (Radioshack)

hex set
Socket wrench
Drill, some bits,
Soldering iron,
Lasercutter (optional)
Dremel + various bits
Wire stripper

Step 2: Assembling the Assembly

1.Take your aluminum flat bar and measure with your micrometer/ruler how long the arms need to be from the center of the brake pad.
    For us it was 4 inches long.
    Mark where you need to drill holes to mount it to the brake assembly and at what angle you will need to mount the motor to make      contact with the tire. For us it was 120 degrees.

2. Once you have all the measurements, take your Dremel and cut the aluminum bar as you marked earlier.
    Drill the holes and dry fit the assembly to make sure it all fits. Both pieces act symmetrically so they will need to be the same lengths.
    Remember that the holes for mounting the motor mount will be much smaller than the holes needed to mount it to the brake so use       the appropriate drill bits for each.
    Be safe and use cutting fluid, goggles and gloves for all of the above.

3.If everything fits than bolt on each motor mount bracket to each of the cut aluminum bar.
   Insert each motor into the mount and make sure they are facing the correct direction in order to make contact with the tire.
   Use the provided bolts to secure the motor in in the mounting bracket.

4. Now that everything is mounted you should have 2 aluminum bars with a motor attached to each. Take the aluminum hubs,
    place them snuggly in a vice and notch each very gently with a Dremel and a cut off wheel so that they have a little grab to the tire.
   Avoid making it too sharp if you value the life of your sidewalls.

5. Once that is done, place the hubs onto the motors and gently tighten down with the worm hex nut. Be careful with this as it is prone    to stripping.

Your assembly is now complete. 

Step 3: Electrical

Ok in the previous step we assembled the motors to the aluminum bars.
Now it's time to solder wires to the motors, run the wires on the frame and connect the LEDs.

1. Take 2  lengths of 12- 48in double stranded speaker wire(Radioshack) and strip the ends. Add some heat shrink, cut to size to make      sure it covers all exposed wire and insert into the wire.

2. Solder to the motor leads and use a heat gun/hair dryer to shrink around the connection.
    Check continuity and that everything works and is making contact. Do this to both motors.

3. Take your LEDs and solder them together in parallel. We put one in front and 3 in the back. Extend a connection for later

We didn't use any capacitors or resistors as we didn't see them as necessary in this circuit.

Step 4: Putting It All Together

1. Attach your ready assembly to the brake calipers.
It is advisable that you keep your brake pads in case you need to make an emergency stop at some point. 

2. Run the wiring under the frame with all the gear cables etc that exist, using either electrical tape or coiling it around the cables to avoid any problems or entanglements.

3. Connect the left generator to the front light and the rear LEDs to the right generator.
Test the assembly and make sure there is no drag when the brake is not depressed. The main point of this mechanism is to hack the pre-existing brake and turn the brake lever into a sort of self generating switch. 
Adjust your brakes for the necessary clearance.

Congrats, you should be all done now.

Step 5: Some Video and Final Thoughts

We find it a very successful project and hope that you do as well.
Its a simple way to add much more visibility and safety to your biking without sacrificing the quality of your ride or having to add batteries.
The added weight was negligible at around 150 grams.

Here is a video of the in action.

Spring Bike Contest

Second Prize in the
Spring Bike Contest