Team:  Team Leader - Fred McChesney

              Time Keeper - Patrick Rambo

              Facilitator - James Allen

              Gatekeeper - Nick Williams

              Recorder - Ramon Vallejo

Sponsor:  Engineers for a Sustainable World

Advisor:  Tom Colledge

EXECUTIVE SUMMARY:

Engineers for a sustainable world has proposed a project to develop an energy recovery system utilizing treadmills, cross trainers, and stationary bicycles.  At gymnasiums and health spas across the county, people are expending energy with no beneficial purposes except personal health.  This project is intended to design a system which will be able to interconnect multiple pieces of aerobic equipment to recovery so that energy will be recovered and gym costs will be decreased.

Preliminary ideas were a drive shaft design and an air pneumatic pump design.  For efficiency, cost, and safety considerations the alternator being directly connected to the treadmill fly wheel was chosen.  The alternator, mounted to the treadmill base by an adjustable bracket, will be connected to the fly wheel shaft via a flexible shaft connector.  The alternator will then run to an AC/DC inverter and the energy will be stored in a 12 volt deep cycle battery.  The battery will be housed in an aesthetically pleasing storage container to ensure safety.

The main goals of designing this system are to safely and efficiently extract useful energy, while remaining aesthetically pleasing.  After the design stage is over, a prototype will be built to demonstrate how the system will operate.  The total cost for design and construction of the prototype will be no more than $600.

OBJECTIVES:                                               

1. To dissect an existing treadmill and/or stationary bicycle to ascertain the basic components and operational characteristics while understanding its function and purpose. 

2. To design a mechanism or device that will allow for the efficient and safe extraction of useful energy from it.

3. System must be aesthetically pleasing.

4. To design a system to permit multiple machines functioning together to produce sufficient energy to make the undertaking economically feasible.

5. To design an energy storage unit capable of storing energy gathered from multiple pieces of equipment.

6. Build a prototype of the sample machine along with an analysis of output power.

OPERATIONAL DESCRIPTION:

       The treadmill requires electricity to run.  Electricity drives a motor and the motor in turn drives a belt.  The belt then drives a conveyor.  The conveyor is the part of the treadmill which a person runs on.  The motor also has a flywheel attached to its shaft which provides an inertial force to keep the motor’s speed constant.  To recover energy from this system, an alternator is retrofitted to the shaft of the motor on the same side as the flywheel.  The two shafts are coupled using a flexible shaft coupling which compensates for any shaft misalignment which may occur during the retrofitting.  The alternator then connects to a deep-cycle battery which stores the recovered energy.  The battery then connects to an inverter which transforms the 12 VDC into 120 VAC.  Once the electrical energy is in AC form, it can be used to drive electrical components such as a television, lights, a radio, and etc.  The fitness cycle already has an alternator mounted onto the frame.  No retrofitting is required, 10 gauge wire was connected from the alternator to the deep-cycle battery.

Figure 1:  Picture showing how the alternator connected directly to the flywheel shaft on the treadmill via helical coupler.  The alternator will be used to charge a 12V deep cycle battery. 

DETAILED DESIGN:

• 12 Volt Alternator
  • Minimum speed requirement:  1400 rpm
• Helical Coupler
  • Maximum angular displacement:  10°
  • Maximum torque capability:  218 in-lbs
• Inverter
  • Conversion:  12V DC to 120V AC
  • Maximum power output:  600 W
  • Amperage:  5A
• Deep-Cycle Battery
  • Minimum Voltage:  12 Volts
  • Reserve Capacity:  160 minutes
• Electrical Wire & Components
  • Minimal requirement for components:  10 gauge

ANALYSIS:

• Energy Recovery of Treadmill
  • Measure power required run the treadmill.
  • Measure power output of treadmill generator.

• Energy Recovery of Bicycle
  • Measure current and voltage output of bicycle generator
  • Calculate power production

RESULTS:

Total Power Recovered

Prec = Pbout + Pgout = 65.8W + 72.9W = 138.7W