PART A

THE DESIGN BRIEF

Construct a mousetrap or siege machine. The building and testing will be documented, with pictures through the different stages of building and testing: no more than three photos, they must document the process.

DESIGN DEVELOPMENT

INITIAL DESIGN IDEAS

The initial brainstorming was based on internet research, my own person life experiences with design/ building and drew from knowledge of my own schooling. Three design sketches were draw and each was evaluated against the purpose of using it as the focus of a class activity designed around movement and force.

EVALUATION OF DESIGNS

Design 1: this long wheel base design is designed for maximum distance. The extension of the lever arm provides less force but more distance. With the longer arm more string will be pulled off the axel allowing for the wheels to turn more times hence greater distance.

Pros: greater distances to measure

Con: needs large area to complete activity, extra expense of materials – wood, bushes, drilling of axel holes in the wood, added wood weight.

Design 2: This compact design is based on the ease of the build.

Pros: Limited materials need, compact design, easy construction, limited expense, light weight.

Cons: None

Design 3: This was designed as a wide wheel base providing extra stability.

Pros: Stability

Cons: Expense, extra weight, cost of materials,

THE DESIGN CHOICE

After researching many viable options of siege machines and mousetrap cars combined with consultation with my children the compact mousetrap car was chosen. It was an easy and effective way of using a device (mousetrap car) to gather data then applying a mathematical equation to give a solution. So on reflection I believed I could meet the design brief in a DMA with a mousetrap car.

PLANNING

DESIGN SPECS

During the research stage I discovered that the materials used would have a large impact on the final performance of the mousetrap car. The heavier the materials used the more force needed, it was decided to utilise the lightest materials possible in the construction. An initial design focus was to design a mousetrap car for maximum distance, to allow for this design the axils placement would need to be a distance from the mouse trap lever arm with the lever arm being extended to align with the axil for maximum distance but provide less force, see design 1 above. This design was ruled out due to the increase weight the timber would add, the drilling of holes for the bushes needed to decrease axel friction, cost and the space required to complete the activity. Design 3 was ruled out due to the same constrictions that design 1 had with the weight being the most critical factor. Design 2 was chosen due to its compact design and minimal materials needed. This design is an easy for students to build themselves and requires only a hot glue gun to complete. No cutting and drilling of timber. The time it wold take to build this design is not prohibited in using in a science unit of work.

This design will be used within a unit of work where students will build this model a conservative materials approach will be used.

MATERIAL EXPLORATION/GATHERING

The materials used in this design have been mainly recycled with only the mouse trap purchased specifically for this project.

PRE-BUILD DESIGN

The initial design was based off this sketch with changes and modifications in materials and design being made throughout the build.

CONSTRUCTION PROCESS

ESSENTIAL MANUFACTURING SKILLS

The mousetrap car build will use a variety of tools and skills associated with those tools. They are as followed:

Grinder – cutting wheel Vice - grasping objects Stanley knife – cutting out slot in mousetrap Hot glue gun – gluing wheels, bushes, axel hook

Scissors – cutting balloons

Note: The skills used in this design are for this particular model only. If used as a unit of work purchased items such as washers and steel axels will be substituted with no cutting necessary.

FABRICATION PROCESS

Screwed eye hooks into mouse trap frame Cut 2 pegs down for axels Cut 4 conduit clamps to be used as washers for wheels and axel Ground down conduit clamp washers Cut off plastic mouse trap hook Secured zip tie and glued in place with hot glue (zip tie is used as the axel hook for the string) Glued conduit washers on to wheels (DVD’s) Slid bushes (brass washers) onto axels and glued Attached braided fishing line to mouse snapper arm and tied end loop Cut balloons and secured over wheels Ran first test

TESTING

The initial test was successful with only minor modifications needed. The balloons on the wheels provided traction, the torque (power) was proficient enough to drive the car forward. A modification made was to give the car a wheel alignment. This was done by adjusting the wheels until they spun smoothly with no noticeable wobble and applying extra hot glue to keep the correct balance. Upon retesting the car wheel balance corrected the deviation.

I was happy with the distance covered in the tests which I knew could be used in classroom sized area or something similar. I could have adjusted the lever arm length to match up with the axel creating more torque but was happy with the power output and the distance covered in the tests.

During the construction of the mouse trap car I came across some obstacles which I was able to resolve quite easily such as noticing before time that the zip tie axel hook would hit the mouse trap when the wheels turned, so I cut a slot in the mousetrap to alleviate the potential issue. Another potential issue was trying to keep the mousetrap from sliding from side to side on the axels. This is where washers were used as a bush to decrease any sideways movement, by using steel washers as bushes the potential friction was reduced and efficiency increased.

ACHIEVING THE DESIGN BRIEF

The mousetrap racer building stages and testing has been documented via video which is embedded below this document (direct link: http://youtu.be/J2HfH-pFcPU )

CONCLUSION

The process of conducting a DMA with this design brief has giving me valuable insight into what is needed to achieve an outcome and the applicable process involved. I now feel confident in linking and incorporated DMA approach into differing curriculum strands and teaching approaches. This process I will be using in the development of my teaching pedagogy.