Power SourceStopping Mechanism

Circuitry & DrivetrainSafety FeaturesCost

Iodine Clock Reaction

Stopping Mechanism1. Solution changes color from clear to

dark blue2. Rate Law = 1.18×10-4 [IO3

-][HSO3-]

3. Increasing concentration of iodate or bisulfite will shorten the time for the solution to turn dark, as shown in Fig. 1.

The iodide ion is generated by a slow reaction between iodate and bisulfite:

Rate-determining step: The iodate in excess will oxidize the previously generated iodide to form iodine.

However, the iodine is reduced immediately back to iodide by the bisulfite:

IO3-(aq) + 3HSO3

-(aq) à I-(aq) + 3HSO4

-(aq)

IO3-(aq) + 5I-(aq) + 6H+

(aq) à 3I2 + 3H2O(l)

I2(aq) + HSO3-(aq) + H2O(l) à 2I-(aq) + HSO4

-(aq) + 2H+

(aq)

When the bisulfite is fully consumed, the iodine will survive, causing the solution to darken.

Drifter is powered by a zinc-alkaline battery with the overall reaction of:Zn(s) + 2MnO2(s) à ZnO(s) + Mn2O3(s)

Secondary containment for the batteries prevents leakage of chemicals.

Syringes reduce the potential for spills and provide an easy, accurate delivery of reactant.

Secondary containment for the stopping mechanism chemicals is compact and provides reliable housing for the photoresistor and light bulb.

In the case of an emergency, flipping the large red switch will cause the car to stop.

All circuit components are housed to prevent chemical contact.

The gearbox cover serves as protection from moving parts.

The photoresistor detects light passing through the solution and triggers the relay to open the circuit once the solution turns dark blue. This cuts off power to the motor, causing the car to stop.

Environmental Impact

Car DescriptionDrifter employs a zinc-alkaline battery reaction to generate electrical energy, which is then used to power a motor. The stopping mechanism utilizes an iodine clock reaction, which turns dark after a given amount of time, triggering the photoresistor to cut power to the motor.

Anode CathodeZn(s) + 2OH-

(aq) à ZnO(s) + H2O(l) + 2e- 2MnO2(s) + H2O(l) + 2e- à Mn2O3(s) + 2OH-(aq)

Zinc and a gelling agent are added to a KOH solution.

Manganese dioxide, water, and a conductor are mixed to create a

stable reaction substrate.

The reaction generates about 1.5 V and 2.0 A per cell. Three cells are attached in series to obtain the power necessary

to move Drifter to the finish line.

H2OKOH solution

Zn

Gelling agent

ConductorMnO2

Each substrate is spread thinly onto a copper plate, forming the anode and cathode of the battery.

The entire cell sandwiches a fabric separator that serves as a salt bridge to facilitate ion flow.

Completed cell

Electrolyte

Separator

Use of rapid-prototyping technology such as 3D printing and laser cutting reduces wasted material while ensuring precision.

DRIFTER

Figure 1: Volume of Solution B vs. Time

Time (s)

V B(m

L) y = 152.4x-0.63

R2 = 0.990

18

16

14

12

10

8

6

4

2

00 50 100 150 200 250

Battery

M

Photoresistor detects light Solution cuts off light

Acknowledgements

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4

5

6

1

2

34

5

6

The gearbox motor has a gear ratio of 1:41.7 and an overall gear reduction ratio of 1:183.5.

Copper Plates & Separator

Anode

Cathode

Chassis & Drivetrain

Electrical

Stopping Mechanism

$ 74

$164

$112

$200

$60

$40

$650Total Cost

• All materials are abundant in nature• Emission-free power source• Copper is reused, reducing waste• Highly efficient chemical energy

conversion

A Special Thanks to: Professor Roseanna Zia, Professor Lynden Archer, Cornell School of Chemical and Biomolecular Engineering, Cornell College of Engineering, Cornell Student AIChE Chapter, The Leeds Family, Alumni Family

Cornell ChemE Car Team Members: Daniel Recalde, Charles Wan, Sophie Le, James Dong, Christine Soong, Dhruv Ragunathan, Reginald Lin, Courtney Bui, Doris Chen, Neil Mehta November 8, 2015

2015 ChemE Car National Competition - Salt Lake City, UT

Total Cost:

$650