Wind Powered Bicycle Phone Charger

This Instructable is my entry for the Tinkercad Student Design Contest, aimed for the Practical Inventions category.

When cycling, I often have my phone mounted on the handlebars, and use it for navigation and tracking. When going on longer trips, I've had my phone run out of charge on multiple occasions, making me wish I had a way to charge my phone while riding.

This is often done with a dynamo attached to the wheels, providing energy through friction rotating a generator. However, this was not something I wanted to do: dynamos add resistance to cycling, need long wires to go from the wheel to the handlebars, and cannot be quickly removed or attached to another bicycle. Instead, I decided to create a design using wind power, as cyclists already encounter air resistance, meaning that this would not add any additional drag.

I used Tinkercad to help with designing the product, which I mainly 3D printed, while also using some other components listed below. I've also linked all of the STL files for anyone interested in printing this design!

PLA filament: 50m

TPU filament: 5m

Thin insulated wires: 0.2m

2 compression springs: 6mm diameter, 20mm long

8 screws: 1.6mm diameter with varying lengths

2 DC generators and 2 Propellors: I used this set

1 small 5V USB voltage booster: Such as this one

4 plastic adhesive dots (optional): Such as these

Small rubber grip pad (optional): Such as these

In the ideation stage, I tried to keep in mind the following essential considerations to reach a suitable design:

Function: Should provide maximum power output at a constant 5V, and should be adjustable to fit a range of phone sizes (60x130mm to 90x170mm) and handlebar sizes (22-32mm diameter). Clipping the design onto handlebars should be fast (take no longer than 5 seconds)

Size: Entire phone screen and all side buttons should be accessible, with propellors not interfering with handlebars or brakes

Shape and form: Should be aerodynamic with curved edges where possible, possible to 3D print

Joining: Should only use nonpermanent joints, as these allow the design to be easily disassembled and separated, allowing for easier repairs and recycling

After some initial sketches, I decided to go forward with a design using 2 sideways propellors, which would help generate more power, with the turbines spinning easily due to the wind always being in the same direction (straight towards the bicycle).

Creating a low fidelity cardboard model allowed me to test the design on a real bicycle with a phone, helping me make some necessary improvements leading up to the final design.

Before creating the final prototype, I wanted to test that the simple circuit I had planned worked. Using a multimeter connected to the circuit, I was successfully able to generate a steady voltage output of 5.06V when one or both of the propellors were spun.

Design on Tinkercad

Separated components on Tinkercad

This is the final design I reached, as shown in Tinkercad, which has space for all the electrical components to fit tightly. The design is quite large (180mm long), but it has to be this big for the propellors to be out of the way.

It is made up of 7 3D printed components: 3 main bodies, 3 phone holder pieces, and a flexible clip that attaches to the handlebars of any bicycle. Next, I created STL files of each component, ready to be printed.

*It took me a few iterations of testing to ensure all the tolerances in the design were ideal. The parts should fit together well, but only if the same electrical components and print settings are used.

I used the Ultimaker Cura slicer and my Artillery Genius 3D printer to print all parts of the design.

I used black PLA filament for these 3 main bodies. These bodies already have small holes in them to make screwing them together easier, as well as space for the phone holders to slide out to a certain extent.

Important print settings to use for these parts to ensure all tolerances are correct are the following:

Layer height: 0.2mm

Initial layer height: 0.3mm

Line width: 0.4mm

Infill: 25%

I used red PLA filament to print the phone holder parts. The 2 side holders have slots for compression springs.

I used the same print settings for these parts as for the main body pieces.

I used red TPU filament for clip, finding that TPU at 25% infill is flexible enough to fit different handlebar diameters while still attaching tightly to the handlebars to prevent rotation.

I used the same layer height, width and infill as for the PLA parts, but at a higher temperature and flow rate.

The image above shows how all the components, including the soldered circuit and generators, fit together. This should also show how the compression spring system is designed to hold phones tightly in place. The USB output is easily accessible at the back of the design.

The pieces are joined together with eight 1.6mm or 1/16" diameter screws, where indicated by the ready made holes in the prints. Wider holes at the bottom of the design allow the tops of these screws to be well hidden.

*When soldering the circuit, keep in mind that the propellors will face outwards and therefore spin in opposite directions.

Attaching the TPU clip is simple, as there is a slot for it to be slid into as shown above. This clip covers 2 screw holes and partly hides 2 more.

Likewise, the propellors can just be pushed into the axles that are coming out sideways from the design. I spray painted the propellors red to maintain the black and red colour scheme.

I noticed that while the side phone holders do firmly grip the phone, phones without rubber cases can still slightly move around. I added more grip to the design with 4 plastic adhesive dots, which are recessed using holes that were already printed on the design.

Furthermore, I wanted to ensure that the design would not rotate or slip on handlebars, even on a bumpy ride. To increase the grip, I added rubber grip pads to the clip as shown above. I tested this with weights, and just one clip was able to hold 1.3kg horizontally before sliding (compared to just 400g without the pads). Therefore, adding these grip squares ensures that the design is very sturdy on the handlebars, while still being quick to attach and remove.

This is what my final 3D printed prototype looks like.

The design fits well onto different handlebars, not interfering with the brakes or handlebars. Both propellors start spinning at a speed of around 10km/h, well below a normal cycling speed. The generators provide a steady 5V output, albeit at a low wattage, meaning that fully charging a phone would take a long time, although this product can extend the time it takes for the phone's battery to run out.

To increase the power generation, a more efficient generator could be used, as the one I used is intended for small DIY projects, rather than serious energy generation. Perhaps another future modification could be to add a battery or power bank to the design, which could be charged either by cycling or prior to a trip to ensure that phones could be charged more quickly.