HCOE bike power classroom

Background

Students will have the opportunity to work with the McKinleyville High School (MHS) students and the Humboldt County Office of Education (HCOE) to design lectures tailored to appropriate technology. During the Spring 2017 semester Caroline Stoddard and Kelsey Summers will design a bike power project and corresponding educational curriculum to be delivered in McKinleyville, CA once per week. The intent is to design and construct a bicycle capable of producing electricity. The goal of the class is to provide students with strengths in hands on activities while working to serve the community. This pedal power project also has the potential to provide future curriculum ideas for bike power service learning projects.

Problem statement

The primary objective of this project is to develop a mechanical pedal power bike project capable of powering a blender. MHS students will participate in 50-minute lectures that will focus on the primary tenets of appropriate technology, prototyping, project design, mechanical bike blender construction building and testing. Introductory projects will include a t-shirt to tote bag and DIY notebooks. Depending on student needs, interests and time future projects could include edible garden design and/or papercrete stepping stones.

Literature Review

Creating energy from pedal power can be used as a demonstration of what harnessing the human potential can do. Throughout history, human power has been used to meet all sorts of needs. In the 1940’s manual crank devices, including human-powered radio were common but the energy generated from leg-powered devices is much greater. Soon came the advent of bicycle pedal power parts, capable of generating up to 60 Watts of power. ^[1]

That cranking or pedaling motion serves as mechanical energy that is then converted into electrical energy. ^[2]Pedal power can be used to charge a battery or used directly to assist in agricultural processes, operate tools, power blenders, washing machines, devices, light bulbs; the possibilities are vast and can be tailored to fit different objectives and needs.

Pedal power is often divided into two categories, mechanical and electrical.

Electric Pedal Power

Electrical bike power harnesses the mechanical power of pedaling and converts it to electrical energy. Electrical bike design may lose some potential energy between conversion through the generator or alternator and even more so if used in conjunction with a battery.

These schematics can be used for any bike by removing the back wheel and mounting the frame. ^[3]

Mechanic Pedal Power

Mechanical bikes use the power of the cranking motion to directly operate some mechanism.

Parts

First things first, you need a bike. Many people recommend using an exercise bike since it solves any bike stabilization issues, others have used training stands, but creating a custom frame or using cinder blocks can also accomplish mounting the bike.

There are two major modes of power transmission for bicycle attachments, chain drive and friction drive. These two drives can be used to meet the power requirements of most pedal power attachments.

Chain drives should be paired with low-speed devices. Chain drives are more efficient; a study at Johns Hopkins found efficiency rates from 81 % to as high as 96.8 %. ^[4] Chain drives are often used most because of this, however can be more costly and less accessible.

Belt drives and roller drives are the two main types of friction drives. Belt drives, can be fashioned out of recycled rubber, but eventually stretching is bound to occur especially in humid conditions. ^[5]

A pulley is the simple machine that will generate the mechanical energy. A small pulley on a generator will spin faster than a large one. The type of drive shaft the pulley will be connected to; chain or friction drive will determine the size of the pulley. ^[6]

A generator or alternator is used to create electrical energy. A permanent magnet direct current (DC) motor is typical for pedal power devices. Internal magnets create a magnetic field; generators with ratings of 500 to 1000 rpm are recommended. Using a car alternator is an option but internal electromagnets are capable of running at thousands of rpms, this pace may be too fast for pedal power needs. ^[7]

A diode is a circuit element that allows electrical current to run in one direction and not the other. ^[8]

A fuse protects the equipment. When too much current passes through a fuse it pops, also known as an open circuit. The break stops the surge from continuing and protects your electrical system. ^[9]

A battery is a container of one or more cells that converts chemical energy into electricity that is used as a source of power.

An inverter is essentially a portable electrical outlet that changes direct current (DC) to alternating current (AC). The input voltage, output voltage and frequency, and overall power handling depend on the design of the specific device or circuitry. ^[10]

A Flywheel is a heavy revolving wheel in a machine that stores the energy of your pedaling. This increases the machine's momentum and increases the available power. A heavy wheel with good bearings is recommended. ^[11]

Lever Arms can be used to increase power output. A design that has been used for past pedal power projects by Maurice Houbracken

Bike Sprocket/Elliptical Sprocket: “A disc with teeth on its circumference for driving a chain, a general term that applies both to chain rings and to freewheel cogs.” ^[12] This is what the bike chain wraps around, sprockets are measured by the number of teeth (pitch) and width. An elliptical sprocket can also increase energy output by using elliptical opposed to circular shaped sprockets. ^[13]

Teaching bike power

Pedal power has been used as an educational tool to teach students the basics of energy and power. Exercises can be tailored to highlight mechanics or electricity function, energy efficiency, or environmental concerns. Bike power also gives rise to appropriate technology (AT) and utilizing human power to meet our needs. AT is an important topic to teach youth because it incorporates hands on learning, simple design, maintenance, low cost and local knowledge base. AT uses local resources to solve problems and provide services for people. ^[14]

Client Criteria

We are waiting for administrative approval at the Mckinleyville school and a meeting with the teachers from the TLC classroom until we establish project criteria. While planning this project our objective is to remain mindful of the students individual grade levels, since the classroom is a mix of middle schoolers with varying skills and interests. Criteria and constraints are based on information provided by MHS teachers and students.

Criteria	Constraints	Weight (1-10)
Educational value	energy basics	9
Low skill	user friendly	7
Size	kid friendly	5
Movability	in and out of classroom	3
Parts	recycled/locally sourced	6
Reliable	function when needed	9
Low Cost	fit within budget	6

System Examples

CCAT has contributed plenty to pedal power innovations. Some designs include bike power blenders, tools, and larger scale projects like the Mobile Energy Operations Wagon (MEOW).

Foodshare.net offers great instructions for creating a bike power blender tailored to meet educational objectives.^[15]

Maya Pedal offers great examples of how bike power can generate real solutions. Bicimaquinas have been designed to pump water, mill grains, shell nuts and de-pulp coffee. Fact sheets, instructions and sketch-up models are available for many of the designs. ^[16]

Prototyping

Construction

Tentative timeline

Project Tentative Timeline

Action	Date Completed	Date Actually Completed
Approved to work with school (TB test and fingerprinting)	02/20/17	02/17/17
Meet teacher- establish criteria	02/24/17	3/7/17
Curriculum design and structure	03/01/17	03/08/17
1st Bike power class in Mckinleyville- Teach student what AT is DIY tote bag/notebooks	03/03/17	03/23/17
Make a prototype or two	02/19/17	02/19/17
Project Budget	02/26/17	05/06/17
Purchase all materials for bike project	03/01/17	04/29/17
2nd Bike power class in Mckinleyville- intro to bike power and prototyping, brainstorming	03/10/17	03/30/17
3rd class- planning, parts, design discussed with the students	03/24/17	04/06/17
4th class- parts and begin building	03/31/12	03/31/12
5th class-parts and begin building	04/07/17	MHS spring break (04/20/17)
6th class- building and testing	04/14/2017	MHS class canceled (04/27/17)
7th class- testing, smoothie party, student/teacher feedback	04/21/17	05/04/17
Final write-up, evaluation of project success, lessons learned	05/07/17	05/09/17

Costs

Our costs accrued from this project will be minimal. A criteria of our project is to use all locally sourced and recycled goods. CCAT has been generous enough to donate about half of the required materials for our pedal power project. A big thank you! As we move forward with acquiring materials we may find better options and opportunities to ensure that our project uses the most easily accessible local resources.

Quantity	Material	Source	Cost ($)	Total ($)
1	Bike	CCAT (donated)	0.00	0.00
1	Blender	Thrift Store	8.00	8.00
1	Bicycle Rear Rack	CCAT (donated)	0.00	0.00
1	Bicycle Stand for Stationary Blending	ebay	30.00	30.00
1	Wood Board 12" x 5"	CCAT (donated)	0.00	0.00
1	Metal Plate	CCAT (donated)	0.00	0.00
2	Wood Screws	CCAT (donated)	0.00	0.00
4	Bolts 1/4" x 2"	Ace Hardware	0.80	3.20
4	Washer 1/4"	Ace Hardware	0.20	0.80
4	Nut 1/4"	Ace Hardware	0.25	1.00
1	Threaded Rod 3/8"	Ace Hardware	8.00	8.00
1	Transmission Wheel	CCAT (donated)	0.00	0.00
1	Old Bike tube	CCAT (donated)	0.00	0.00
1	Wood Glue	CCAT (donated)	0.00	0.00
Total Cost				$51.00

Operation

Instructions

Instructions for use are pretty straight forward. Pedaling turns the back wheel which spins against the rotating rod attached to the skateboard wheel powering the blender. Make sure the blender is fully seated and that pedaling is consistent and slow.

Conclusion

Team

• Kelsey Summers
• Caroline Stoddard

References