Bicycle light generator

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Report 2: Research, Opportunities and Concepts


Executive Summary

Bicycle light generators are used to power battery-less safety lights mounted on bicycles. Safety lights are important to bicycle enthusiasts alike as they provide the necessary lighting to traverse a road as well as inform auto drivers of the bikers presence at night. The generator converts the energy put into the bicycle in the form of a pedaling motion into an electric current through the friction developed by the generator’s contact with the wheel of the bicycle.

The purpose of the bicycle light generator project is to dissect and understand the design processes behind this product. Our goal is to study this product thoroughly in order to engineer a modification that will result in an improvement in its functionality.

The product we choose to disect was the Cycle Force 6 Volt Bicycle Generator Light Set. This kit included a bottle dynamo or generator, headlight, taillight, mounting brackets, and wiring. By dissecting the product, we were able to notice several desgin improvement possibilites. One possibility was the current generator powered bicycle light set does not have a means of storing power. As a result, these generator powered bicycle lights do not operate when the bicyclist is not pedaling and could be hazardous when the stopped at a traffic light. In an attempt to incorporate a power storing functionality, we will also be studying a hand-crank generator powered flashlight whose product dissection can be found below. Using the same principles as a generator powered bicycle lights, these flashlights also have a rechargeable battery pack that is able to store power; thus, allowing the user to operate a light without having to input energy at the same moment.

The next step after our preliminary observations, we were able to brainstorm several ideas on design concepts as well as perform a question and answer survey. of the 51 completed surveys, 37% own a bicycle, 47% purchased within price range of $100-$300, and 24% ride at night at least few times a week. These results reinforce the need for and substantiate a market for self-powered bicycle lighting systems. In additon, using the results of the survey, we were also able to identify the most popular functionalities the end-user would like to incorporate including: 1. Charge indicator 2. Power storing capacity 3. Self-powered 4. Adjustable brightness 5. Detachable feature 6. Light-sensitive sensor 7. Turn signals

By incorporating the our own design ideas, the results of the survey, as well as market research on competitors and current technology used, we were able to introduce 5 design ideas. These ideas are a power storage ability, creating closed circuit without the bike frame, detachability & charge indicator & power button, chain mounted generator, and turn signals. Our goals in these designs are to eliminates wear on tires by introducing a brand new way to power the generator, incorporate end user preferences to make better overall product, and introduce and improve safety aspects within the system.

The Project

The major function of a bicycle lighting system is seeing and to be seen. It is dangerous riding a bicycle without adequate lighting, especially at night. A bicycle lighting system can illuminate the path in front of the rider, and alert anyone within the lamp’s range. There are many lighting systems available in the market, and each has their own trade offs. The least expensive bicycle headlights use a tungsten filament lamp, and more expensive models use the brighter alternative halogen lamp. LEDs are sometimes used for its inexpensive and high lumen-per-watt nature, but its limited light output can be a serious disadvantage. Bicycle lighting systems are usually powered by a battery pack or an electrical generator. The battery pack could be disposable or rechargeable. A dynamo lighting system has unlimited duration, but its maximum power output is relatively low.

Product Requirements

1. Able to illuminate a path of certain distance in front of the rider
2. Able to alert other people of the rider’s presence
3. Able to be mounted on a bicycle’s frame easily
4. Able to withstand temperatures extremities and different weather conditions
5. Durable and tough enough to withstand minor impacts and various road conditions
6. Light in weight so it does not add to the rider’s burden
7. Runs on either batteries or an electrical generator

Customer Needs

1. Brightness of the lamp
2. Small size
3. Light weight
4. Durability
5. Long lasting battery
6. Low additional pedaling effort


The installation of the power generation is probably the most difficult part. The user has to first analyze the structure of the bike and choose a location to mount the headlight. Since the light mounting mechanism is not universal, a hole on the front fork is required for mounting with an additional screw. User can also purchase a set of universal mounting device for the installation of the front and rare lights. The generator should be positioned vertically and that the roller connects with the middle part of the tire. The grounding screw on generator bracket must be screwed in completely to make contact with the metal of the bicycle frame. To complete the power generator circuit, connect headlight wire and tail light wire with generator terminal by pressing down the metal connector on the generator and put wires through the metal hole, then release the connector so the metal part of wires get stuck in that hole. It is very important that the generator and the lights are properly grounded to metal parts on the bike. The tail light can be fastened to rear frame stay of bicycle. Finally, press lever on the generator downward so the roller touches the tire. Before riding the bike, be sure that all screws are tight and that the wires and generator are clear of all moving parts. To activate the front and rare lights, user would have to rotate pedals by riding the bike.

1. Choose a location to mount the headlight and rare light.
2. Position generator so that the roller connects with the middle part of the tire.
3. Ground the generator by screwing the bracket to the metal of the bicycle frame.
4. Connect headlight wire and tail light wire with generator terminal.
5. Wind generator cable to avoid getting entangled.
6. Press lever on the generator downward so the roller touches the tire.
7. Rotate the bike pedals to activate the generator.
8. Confirmation the activation of the front and rare lights.


The rotation of the bicycle tires causes the roller on the power generator to spin due to friction. Since the roller is connected to the shaft, it would transfer the rotational force to the motor. The mechanical force generates magnetic fields in the motor and creates a current that goes through the small metal connector. The metal screws coming out of both lights serve as grounding devices. The wire that connects the small metal connector and the bicycle lights would carry the current through the entire circuit and light up both lights.

The power generator’s output should vary with the speed of the bicycle. This variation can be limited to prevent blowing bulbs. To predict the output of power generator lights under various conditions we constructed an equivalent circuit of the system. The model below shows a voltage source Vs, an internal resistance Rint, an internal inductance Lint, and a load resistance Rload connected in series.


There are several assumptions that we made to make the analysis simpler.
- The load resistance is constant. In reality, the resistance of the light bulb increases as it warms up
- The voltage source is sinusoidal
- The internal resistance and inductance are constant

As the cycle speed increases, the voltage and frequency also increase governed by the equation Vs = k f. The reaction of the internal inductance is also proportional to frequency: Xint = 2π f Lint. To compute the overall impedance of the circuit we use Pythagoras’ theorem: Z = √((Rint + Rload)2 + (Xint)2). The current would become I = Vs / Z. This is where the notion that bicycle power generators produce a constant current comes from. If Xint is much larger than (Rint + Rload), both Z and Vs are proportional to speed, so I is constant.

The Rload in our design would be the LED light bulb. The parameters of the resistors and the LED could be calculated from this link [1]

Product Dissection: Hand-Cranked Light Generator

Part # Part name QTY Function Materials Dimensions Manufacturing Process Picture
001 Case 2
  • Protect working innards from user and also provides a way for the user to hold
  • Aesthetics
  • Houses the on/off switch
  • Houses crank for powering the motor
Plastic 8" x 2" x 2" Molded
002 Case Screws 4
  • Securely fastens two sides of the case
Metal .3" x .2" x .2"
003 Grips 2
  • Provide ergonomic support to the user
  • Hides case screws from being accessed
Plastic 12" x 5" x 3" Injection Molding
004 On/Off Button 1
  • Pushes toggle switch on and off
Rubber .5" dia. Molded
005 Crank Handle 1
  • Creates moment arm allowing an easier motion to power motor
Plastic 3" x .5" x .25" Molded
006 Crank Pivot 1
  • Allows the crank arm to be rotated circularly
Plastic 2" dia. Molded
007 Crank Washer 1
  • Attaches crank assembly to case at a fix point while still allowing rotational motion
Plastic .75" dia. Molded
008 Crank Pin 1
  • Keeps crank pivot attached to crank handle
metal .5" x .1" dia. Molded
009 Crank Knob 1
  • Provid user with a place to hold crank
  • Serves as a pin to keep crank housed inside case when not in use
Plastic .25" x .25" Molded
010 Lens Cover 1
  • Protects Led Housing
Plastic 3" dia. Molded
011 Lens Holder 1
  • Screw cap that attaches lens cap to case
Plastic 3" dia. Molded
012 LED Housing 1
  • Protects LED
  • Concentrates light into a beam
Plastic 3" x 2" x 2" Molded
013 LED Lights 1
  • Diodes that emit light
Plastic, Semiconductor .1" dia.  ??
014 LED Circuit Board 1
  • Support and connect wires to light
Silicon, Conductor 2"x2" Assembly
015 Motor 1
  • Transform the rotational energy from crank into current
Magnet, Copper wire 2" dia. Assembly
016 Gears 3
  • Changes the speed and torque input of the crank and spins the motor
Plastic Sizes vary Molded
017 Gear Housing 1
  • Attaches gears and motor to be attached to the case
Metal 3"x2" Molded
018 Motor Circuit Board 1
  • Allows current to travel from motor
  • Attaches motor to switch and battery through wires
Silicon, Conductor .25"x .25" Assembly
019 Gear Housing Screws 4
  • Fixes gear housing to case
Metal NA NA
020 Switch 1
  • Toggle button that turns the LEDs on and off
Plastic .25" dia. Stamped
021 Switch Housing 1
  • Protects switch and aligns it with on/off button
  • Allows switch to be attached to gear housing
Plastic 2"x1" Stamped
022 Rechargeable Batteries 4
  • Stores power from motor and releases when needed
Metal, Chemicals 6V Multiple
023 Indicator LED Circuit Board 1
  • Connects indicator LEDs to motor through wires and provides base for LEDs
Silicon, conductor 2"x2" Assembly
024 Indicator LED 2
  • Tells user whether batteries are fully charged or are charging
Diode NA NA

Product Dissection: Bicycle-Mounted Light Generator

The Cycle Force 6 Volt Bicycle Generator Light Set includes a dynamo or generator (001), headlight (012), taillight (022), mounting brackets (004,005), and wiring. The dynamo is mounted on the fork of the bike and placed such that the roller (010) on the end is in contact with the profile of the tire. This position allows the roller from the generator to turn when the wheel is in motion; thus, turning the shaft of the generator and inducing a current. One other noticeable design feature is the existence of a spring lever (017), which allows the user to position the roller/generator against the tire when so desired.

The current then travels through two wires to the headlight and taillight. The headlight is mounted on the front shaft and the taillight is meant to be placed where traditional reflectors are placed. The circuit is completed through the frame of the bike by being in contact with the mount.

In conclusion, we were able to determine the light set was manufactured as cheaply as possible. All the screws, nuts, bolts, and washers were interchangeable except for one smaller screw on the generator mount. From a design perspective we were also able to identify several opportunities for improvement. For one, the circuit is completed through the bike frame which may pose problems if the bike frame is non conductive. In addition, it was very difficult to assemble, and when operating the light, its intensity tended to fluctuate based on the speed of the rotating tire.

Part # Part name QTY Function Materials Dimensions Manufacturing Process Picture
001 Generator Assembly 1
  • Convert the rotational energy from biker into an electrical current
Metal 4" x 2" x 3" Assembly
002 Generator Hole 1
  • Serves as a place for generator to be connected to the generator mount
Metal .25" dia. Stamped
003 Generator Metal Connector 1
  • Conducts electricity from spring inside generator
  • Works with spring for easy installation of wire
Metal .1" x .1" x .1" Stamped
004 Generator Mount (Back) 1
  • Allows generator to be attached to bicycle
Metal 3" x .5" x .25" Stamped, Bent
005 Generator Mount (Front) 1
  • Allows generator to be attached to bicycle
Plastic 3" x .5" x .25" Stamped, Bent
006 Generator Mount Hex Screw 1
  • Provide Extra support when mounting generator to bicycle fork
Metal .25" x .25"dia NA
007 Generator Mount Nut 2
  • Keeps generator mount screw from falling out
Metal .25" dia. Molded
008 Generator Mount Screw 1
  • Connects to pieces of generator mount together
Metal 2" x .25" dia. NA
009 Generator Mount Washer 2
  • Relieves the pressure exerted by the nut onto the mount by increasing the area on which the force is exerted
Metal .25" dia. Stamped
010 Generator Roller 1
  • Touches wheel to create friction and rotate the generator shaft
Plastic .75" dia. Molded
011 Generator Spring 1
  • Conducts electricty from generator
  • Works with metal connector for easy installation of wire
Metal .2" dia. NA
012 Headlight Assembly 1
  • Lights the path in front of the bicyclist
Plastic 2.5" x 5" dia. Multiple
013 Headlight Light bulb 1
  • Emits Light from electricity produced by the generator
Filament, Metal .1" dia.  ??
014 Headlight Case 1
  • Serves as a base for light bulb
  • Connects headlight to generator through a wire
Plastic 2"x 3" Molded
015 Headlight Cover 1
  • Protects lightbulb, Diffuses light into a larger beam
Plastic 2" x 5" dia. Molded
016 Headlight Mount 1
  • Allows headlight to be attached to bicycle
Metal 4" x .25" x .25" Stamped, Bent
017 Lever 1
  • Allows the user to switch the position of the generator creating an "on/off" functionality
Metal 3"x2" Stamped
018 Lever Case 1
  • Protects the spring in the lever from rusting
Plastic 1" x .5" Molded
019 Lever Spring 1
  • Allows movement of the lever
Metal 2" x .25" dia. NA
020 Reflector Back 1
  • Provide user with an area to mount the reflector on the bicycle
  • Serves as a base for the light bulb
Plastic 3" x 1" x 1" Molded
021 Reflector Cover 1
  • Protects reflector light bulb
  • Provides a red color to light emitted
Plastic 3"x1" x 1" Molded
022 Reflector Light Assembly 1
  • Serves to warn others of biker's presence
Plastic, Metal 3" x 1" x 2" Assembly
023 Reflector Light Screw 1
  • Allows the reflector light assembly to be connected to bicycle
Metal 1.5"x .25" dia. NA
024 Reflector Light bulb 1
  • Emits light
Filament, Metal .2" dia. NA

Design for Manufacture and Assembly

The generator bicycle light set parts are designed in such a way that they are overall favoring their manufacturing processes and assembly. Most parts are very easy for disassembly because of the maintenance requirement. However, the parts that does not usually require maintenance are build in a way that is hard for disassembly.


  • There are no complex geometries in plastic parts. They used two parts injection molding to create most parts.
  • Metal parts are made from stamping, which is easy to mass produce.


  • Assembly plastic components (Lights) are simple. They are built with sockets to minimize the use of screws.
  • Many parts are used for both electrical and mechanical purpose to reduce the number of parts.
  • Screws, bolts, nuts and washers are used to secure parts that may require future disassembly/adjustment.
  • Used bicycle frame to finish circuits for lights. Save material -> reduces cost.
  • Generator parts were bolted on -> not meant for disassembly.


  • Most sub-assemblies are easy to identify and disassemble (besides the generator).
  • Disassembly for light parts was intuitive for easy replacement of light bulbs.
  • Phillips screw driver is sufficient to take apart most parts (besides the generator).
  • Generator is assembled through internal sockets. It is merely impossible to take it apart without damaging its function.

The manufacturing, assembly, and disassembly process is designed for minimal parts. The lightsets low price had clearly demonstrated its ability to be mass produce at low cost. The overall product has very little room for improvement in DMA. However, due to some component's assembly process, there may be an environmental impact. We will further analyize its DFE in later section.

Failure Modes and Effective Analysis

There are many possible failure modes can occur in this generator bicycle light set. In this FMEA section we will point out the 4 most important modes that can seriously affect this product's core functions or user's safety.

The generator bicycle light set is made for the purpose of enhancing rider's safety during low visibility time. Therefore, many of its function failure modes will directly effect the user's well being through failure to provide light. These modes include friction loss on roller, open circuit for lights, wheel jamming from generator, and burned out light bulbs. The failure of these are often not harmful to the user's well being, however, they do increase the chance of occurrence of personal injuries.

Therefore, we recommend for indepth inspection, research and improvement on the following failure mode presented.

Item and Function Failure
Effects of Failure S Cause of Failure O Design Controls D RPN Recommended
Responsibility Comment
Contact Roller Friction Loss - Roller can no longer provide sufficient friction to power the generator
- Fails to light up the bulbs
7 - Severe road condition (wet, mudding, etc.)
- Worn out roller
8 Test in various road condition
- Wet
- Muddy
- Icy
- Greasy
8 448 - Redesign roller or the entire power generating system (ie, use pedaling shaft to generate power rather than wheel profile).
- Select durable material
- Design roller contact profile to improve performance in severe road conditions.
Design Engineers The loss of friction on roller in this generator design is inevitable. It is likely that current design is already close to optimal. To fix this may require redesign of the entire generating system.
Bicycle Frame Open circuit for lights Fails to light up the bulbs 7 - Non-conductive frame due to its material or coating 4 N/A 1 28 Redesign light circuit: Complete closed circuit with wires rather than bicycle frame - Design Engineers
- Customers
This can also be minimized if the manufacture provides warning message to notify the users regarding to this failure possibility before purchase.
Mounting Bracket for Generator Unable to hold generator in place while wheel in motion - Jams the wheel
- Damage Wheel rims and generator
- Personal injury
9.5 - Loose bolts
- Worn contact surface
- Vibrations
- Faulty installation
6 Test for durability in different conditions 6 342 - Redesign mounting bracket: Use washer with teeth
- Redesign the entire generator system
- Design Engineers
- Customers
This failure mode may minimize through improvement, however, its damage severity is too great to only minimize. Redesign the entire system will be optimal.
Bulbs Burned out - Unable to deliver light source when needed 7 - Bulb life spam
- When travel at high speed the generator provides power exceed bulb limit
6 - Standardize generator that can only generate power under the constraint of the bulb specs 9 378 - Provide a voltage regulator to eliminate this failure mode - Provide higher wattage light bulbs Design Engineers If use a voltage regulator it can also provide constant light brightness rather than variation through wheel speed.

Design for Environment

Overall this generator bicycle lighting system is designed to be environmental friendly. It has little complex components, most are recyclable and most importantly, it is battery less! However, few of its design can still cause environmental damage. We will further analyze these issues from our DFE below and recommendation will be made within each bullet.

Environmental Problems

  • Light Bulbs - The current light bulb has short life spam. This implies it will require constant replacement of light bulbs. Each replacement of light bulb is more use of materials, and energy to produce it. Therefore, we recommend to upgrade the light bulbs to LED or halogen bulbs to reduce the frequency of bulb replacement as an investment to the environment.
  • Design for Disassembly - The generator is not made to be disassembled. This infers that the part will be difficult to repair and the salvage cost of the materials will be high. If parts can be made dissectible it will greatly improve its environmentally friendly value.
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