1. Planning



View the entire  “Deep Dive” episode by using the following links.

Please answer the following questions based on the videos and your understanding of the Engineering Design Process (EDP).

1. What was the problem the engineers at IDEO were asked to solve?

They were asked to solve the concerns and problems a typical shopping trolley possesses, such as issues with child safety and theft.

2. Name two constraints that they had to deal with.
Time constraint and cost of production constraint (it had to be of similar price of typical trolleys)

3. What were two of the major concerns/issues the teams discovered from their research?
Child safety, as injuries were commonplace with current trolleys. Theft, as many trolleys had been stolen due to its convenient function of having wheels and being able to carry large loads.

4. IDEO uses several methods, processes and ideas to generate alternative solutions.  What two principles or approaches appealed to you the most? Why?
The concept of drawing whatever comes to mind on a piece of paper to be displayed at the front. The concept of voting was feasible too. With random sketches titled around the problem, the group can easily amass ideas and build upon them. The list of solutions would then be not as exhaustive. Voting allows the general consensus of people to be decided without much conflict and the most feasible idea to surface among the hundreds of other ideas.

5. How were the possible solutions prototyped and tested?
Among hundreds of ideas and alternatives, the group conducted a vote to determine the most feasible product, which was reliable and can be built in a day. They were further splitted into subgroups, where they built mock-ups on areas of concerns. With mock-ups presented, they could extract ideas from each of them and combine them into the final product. With the final product ready, they showcased them to grocery stores for their approval and feedback.

6. Was there a redesign step in the IDEO project? What was the final outcome?
There was a redesign step, where crude mockups were constructed to show their intended function in real life. The group then picked out the essential ideas from within and recombined then into the final product. The final outcome was a mixture of the key concepts they earlier on had constructed.

1.2 Assignment of roles

Project Manager: Wai Kit

Drivetrain Engineer: Praveen

Wheel Engineer: Michael Chun

Chassis Engineer: Timothy Cheong

1.3 Brainstorming

Engineering Goals
Develop a MouseTrap Car with the following specifications:
Uses only the MouseTrap provided as the only energy source
Has a maximum length of 30 cm, width of 10 cm, and a height of 10 cm
Can travel a minimum distance of 5 meters carrying an egg (the egg will be provided by the teacher)
All time-lines have to be adhered  

LIST ANY KEY TERMS OR ISSUES THAT CAME UP DURING BRAINSTORMING.  This does not have to be neat or even organized. It gives you a way to keep track of any idea you may have had. Include separate notes, google sketches, etc. if you have them. (Attach separate sheets if needed)

→ Issue with power of mousetrap
- Due to suspicion that the mousetrap was not powerful enough, it is wise to make a lightweight car
→ Cost of car
- School has easily obtainable materials, such as bottle caps. Recycled CDs from home make good wheels
→ Weight of car
- To reduce the weight of the car, we can use lightweight PVC pipes and attach them to the mousetrap itself (chassis)
→ Bigger drive wheel
- More inertia hence car will travel further

1st Idea
Wheels- Back wheels- two CDs, separated by a bottle cap, with duct tape taped on the circumference, for each wheel.
Front wheel- Yogurt drink cap
Body- Mousetrap itself
Axles- Pencil Shafts
Mechanism- Mouse trap with fishing wire attached to the axle of the rear axle.
“Seat”-egg carton
2nd Idea
Wheels- Back wheels- two CDs, separated by a bottle cap, with rubber (gloves) taped on the  circumference, for each wheel.
Front wheel- Yogurt drink cap
Body- Two parallel sticks, with the mousetrap sitting on it and axes inserted through
Axles- Copper Rods
Mechanism- Mouse trap with a cotton twine attached to the rear axle
“Seat”- Wire shaped like a cup

3rd Idea
Wheels- Back wheels- two CDs, separated by a bottle cap, with duct tape taped on the    circumference, for each wheel.
Front wheel- Yogurt drink cap
Body- Corrugated board
Axles- 2B Pencil Shafts
Mechanism- Mouse trap with a cotton twine attached to the rear axle
“Seat”-egg carton

5.7 Bibliography

J.Balmer, A. (2012, January 20). Mouse trap cars: Making a big wheel. Retrieved from http://www.docfizzix.com/topics/construction-tips/Mouse-Trap-Cars/making-big-wheel.shtml

J.Balmer, A. (2012, January 17). Mouse trap cars: Decreasing friction. Retrieved from http://www.docfizzix.com/topics/construction-tips/Mouse-Trap-Cars/decrease-friction.shtml

bamimsam. (2008, March 30). Mouse trap car- 112 ft.. Retrieved from https://www.youtube.com/watch?v=iiV2zzdon50

E. George, P. (2009, March 7). How three-wheel cars work. Retrieved from http://auto.howstuffworks.com/three-wheel-car.htm

Smartkitty314. , Mr handsome, , & Maluniu (2009, November 14). How to adapt a mousetrap car for distance. Retrieved from http://www.wikihow.com/Adapt-a-Mousetrap-Car-for-Distance

1.4 Decision Making Matrix

Design Idea #1
Design Idea #2
Design Idea #3
Time to produce
Availability of materials
Cost to produce
Ease of use
Environmental impact


Idea 2 has the highest value and hence we are designing it.

1.5 Design rationale and notes

The back wheels are designed to be larger in circumference than the front wheels. This is because the energy from the mousetrap is transferred to the back wheels. This allows the loads of the car to be spread equally among all four wheels. The larger wheel allows the car to travel at a higher top speed and hence can travel a longer distance when the energy of the mousetrap diminishes. The wheels are made of 2 CDs, duct tape and bottle caps. The wheel is 2 CDs spaced out from one another with the use of bottle caps, the gap is then sealed up completely with the use of duct tape. With the spacing and duct tape, there would be a bigger surface area of the wheel in contact with the ground and more friction for the same surface area, this would increase the friction between the wheels and the ground significantly and thus allow more of the kinetic energy to move the car forward and thus the car would be able to accelerate faster.

Chassis Material
The chassis would be made out of PVC pipes. The frame would be two PVC pipes of 30cm along the length of the vehicle.  Each of the pipes would have two holes of diameter 0.8cm drilled 1.5 cm from each end. The purpose of the chassis is to be able to hold the axles and wheels. And the reason for using PVC pipe is because its strong and relatively light. Due to it being hollow, there is less surface area present that poses air resistance.

Chassis Shape
The Chassis would be two PVC pipes of 30cm attached along the length of the mousetrap. This length is for spacing out the axles so that the wheels do not collide.

Location of Mousetrap
We placed the mousetrap at the front of the car to allow the string to stretch for a larger length, which allows more energy from the mousetrap to be transferred to the wheels. Hence, the car would be able to travel a larger distance.

The axles would be 2 circular copper rods with length of at least 20cm. The circular shape is to ensure that the friction between the axle and the chassis (0.8cm holes) is minimised to allow for smooth motion and the reduction of energy used to overcome friction. This enables our vehicle to travel a larger distance.

String type and attachment
For the string attached to the mousetrap and axle, we use cotton twine due to its rough and strong nature. It is also relatively cheap. The rough surface of the cotton twine would enable it to have a better grip when coiled around the axle. This means that the string is taut at all times and the axle would rotate accordingly. Thus, this would increase the total amount of kinetic energy transferred from the mousetrap to the axle, allowing for better acceleration. The strong nature of the cotton twine reduces the chance of it snapping while the car is moving forward.

1.6 Materials used

Where is it used?
It is used as the engine of the car
It stores elastic potential energy which would be converted to kinetic energy, which would be used to move the car forward
2 PVC Pipes
It is used to support the car and connect the front and back wheels.
It is a strong and lightweight material that can ensure that the chassis of the car is strong does not break easily and does not carry unnecessary weight due to its material and hollowness.
2 pairs of CDs
It is used as the back wheels. There will be two back wheels, each wheel will consist of two CDs and masking tape. Bottle caps are used to space out the two CDs/
CDs have a large diameter, which allows the car to travel further with lesser energy than a smaller diameter . CDs are also lightweight and and do not break easily. The use of 2 CDs is to increase the surface area of the wheel in contact with the surface of the ground, thus ensuring that there is more grip and the car would be able to accelerate faster.
Masking Tape, gloves
Used along the circumference of the back wheel (CDs)
Masking tape added along the circumference of the wheels would increase the friction between the circumference of the wheel and the surface of the ground. This would increase the traction and the car would be able to accelerate at a faster rate and in turn travel further (all rotations would be involved fully in moving the car).
Coiled into a loop to be used as a “seat” for the egg, to contain and transport the egg.
Wire is made to specifically fit the egg so that it does not fall off while being transported. It is also lightweight.
2 Yogurt Bottle Caps
It was used as the front wheels.
Yogurt bottle caps have a smaller diameter than CDs and bigger diameter than other bottle caps, making it the ideal material to make a wheel. This size ensures that the car does not require so much energy to overcome inertia, thus there is more energy to power the car.
Copper Rod
Used as the axle of the wheels.
The circumference of the copper rod is small. This makes the axle rotate a greater number of times for the same length of string used, which in turn makes the car have a higher top speed.
Cotton Twine
Used as a medium to transfer the energy from the mousetrap to the axis of the wheels.
As the mousetrap cannot power the wheels directly, the cotton twine allows kinetic energy from the mousetrap to be transferred to the axles, due to the rough surface of the cotton twine, it would be able to transfer more of the kinetic energy to the axle, as compared to a smoother string.
Bottle Caps
Also used to space the 2 CDs of 1 back wheel apart

Used to space the 2 CDs of a wheel apart, so that the wheel with the duct tape around its circumference would have more surface area in contact with the ground. This allows for more friction and the car can accelerate faster.

1.7 Preliminary Sketch (Using Google Sketchup)

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