Power Generation for the Better Water Maker:

Subsystems Design Review

October 29, 2013

Agenda● Concept Selection

o Treadleo Bike

● Subsystems

● Engineering Requirements

● Proof of Concept

● Budget/Cost Analysis

● Project Plan to DDR

Problem StatementThe Better Water Maker was developed to disinfect water in nations

with high mortality rates due to poor water and sanitation systems. The goal of our team is to provide a low cost, efficient power generation system for the Better Water Maker that does not tire the user, while it is fun and easy to use.

Concept Selection• The original selection

was too much like re-inventing the wheel

• From there, we toyed with a mechanical treadle design

• Finally, we worked back towards a more reasonable design

Treadle Pump• Used in developing

world for irrigation

• Piston-Cylinder System

• Difficult to translate into power

Mechanical Treadle

Treadle Lathe

Arc Trainer

Treadle Sewing Machine

Our Design: Treadle

After careful consideration,

we decided to move back to

the bike design.

Subsystems• Seating• Power Train• Electronics• User Interface• Sanitation System Interface• Structural Components• Manuals• Testing• Risk Analysis

Engineering RequirementsFunction

Importance Units

Range Goal Value CN Fulfilled

ER1 Cost 9 USD 0-200 150 CN7, CN8

ER2Generated Power 9 W, V 23-29 27.5, 14.3

CN1, CN14, CN17

ER3 Shipping Size 3 weight CN4ER4 Training Time 3 minutes 5-30 10 CN16

ER5 Ease of Repair 3 minutes 20-60 30CN7, CN10, CN16

ER6 Effort Required 9 n/aLow Intensity

CN2, CN12, CN13

ER7 Weight 3 lb CN3, CN16

ER8Number of Installers 3 People 1-3 1

CN3, CN7, CN10, CN16

ER9 Number of Tools 3 Tools CN7

ER10 Unit Life 3

Gallons Treated >180,000

CN5, CN6, CN9, CN10, CN15, CN16

ER11 Support User 9 lb

40-200 130 CN5, CN12

ER12

Can Hook Up to 12V Car adapter 9 Binary Yes Yes CN14

Proof of Concept“Historically, two treadles were used for some tasks, but even then the maximum output would have been quite small, perhaps only 0-15 percent of what an individual using pedal operated cranks can produce under optimum conditions.”

(Wilson, “Understanding Pedal Power”, 1986)

Proof of Concept• “A person can generate four times more power (1/4 horsepower

[hp]) by pedaling than by hand-cranking.”

• “Pedal power enables a person to drive devices at the same rate as that achieved by hand-cranking, but with far less effort and fatigue.”

• Test Plan - run motor with a second motor to determine required torque

• Our power requirement = 23 to 29 Watts

(Wilson, 1986)

Schematic

*P13417 Design

potentially wooden gearbox versus plastic

1-4 motors

ergonomic recumbent seat, potentially adjustable

will re-evaluate effectiveness

4 gears and 1 sprocket inside of gearbox

Block Diagram

Mechanical Analysis• RPM output of 7424• Max torque value of 3.7 lbf-ft

o Low stress on shaft

*Calculations made using Shigley’s Design of Machine Elements

Electrical Details of Pump and Bulb● 12V nominal system

○ Operates closer to 14V○ Voltage is limited to 14.3V in current design

● Pump turns on after ~10s, bulb draws power immediately○ Controlled using a capacitor

● Resistance of system with pump off = ~9.3Ω● Resistance of system with pump on = ~7.17Ω

Electrical Systems in the Generator● DC Motors

○ Possibility of using from 1 to 4 DC motors● Regulator Circuitry

○ Limits voltage to a max value■ Current design limits voltage to 14.3V■ We would like this raised to 15V

● LED user interface○ Display information to the user

Regulator Circuit● Would like to make use of Team 13417’s design

○ Limits voltage at 15V● 1 inductor● 5 capacitors● 10uF to 100uF ● 3 diodes● 4 ICs● 2 switching regulators, 2 amplifiers

Selection of DC Motors● Run tests at different RPM ● Develop a voltage to RPM ratio for each motor

or set of motors● Need to generate 15V under load at a

reasonable RPM● Once a motor configuration is selected, the gear

ratios in the gearbox can be finalized○ Gear ratio is based on 50-60 RPM user input

Risk Assessment: Design

Risk Assessment: Ergonomics

Risk Assessment: Project Planning & Shipping

Risk Curve● Add risks as they arise● Review and adjust

risks on Fridays● Superimpose lines to

stay on track● Current value = 105

Feasibility• Parts are readily available

o Standardized sizes

• Design aspects are fundamental

• High RPM, high efficiency

Test PlanER2: Generated PowerER4: Training TimeER5: Ease of RepairER6: Effort RequiredER8 and ER9: Number of Installers and

Tools

Bill of Materials (BOM)

BOM for Power Generation System

BOM for User Interface

Budget

Cost Analysis• This is not an actual cost

estimate, preliminary cost estimate.

• Many of the component’s manufacturers have not responded or have not been contacted.

• Yellow=Variable Pricing

• Orange=Worst Case Pricing

Project Plan• List of tasks that

will be completed before the Detailed Design Review

• An action item log is also maintained to delegate more specific tasks

Project Plan

Manuals• Template is prepared• Pictures are the main ingredient• User Manual will contain:

o The Use Of the BWMo Setting Up the BWMo Properly Using the BWMo Maintainng the BWMo Troubleshooting and Repairing the BWMo Parts and Toolso Contact Information

Questions?