Introduction: Mousetrap Vehicle

This instructable is not for the faint of heart, possess weak stomach, nor a phobia of calculators. Before we start, defining what a mousetrap vehicle should be done. A mousetrap vehicle, as implied, is a vehicle solely powered by the potential energy of a mousetrap(s).

There are three main types of vehicles; long range, high speed, competition. The defining characteristic of the long range vehicle is it's large drive wheel. For the high speed vehicle its, you guessed it, it's high speed. As for the competition vehicle they must comply with guidelines most likely for school or Science Olympiad.

This Instructable will be for the designing and building of a mousetrap vehicle following the rules for Science Olympiad devision C for the 2010 - 2011 academic year.

Step 1: Design

To start your design you must have nothing more than:
*a writing utensil

However, if you want to design a vehicle that you will be proud to put your school's name on you will also need:
*a graphing utility
* micrometer(if you have a thing for sig figs?)
**a good foundation in mathematics

**Those who do not possess these skills, yet. Have no fear there are countless resources at your disposal. For example the internet, public libraries, and your teachers. The internet, your on it now. Public libraries, they are free and full of helpful underpaid knowledgeable city employees know as librarians. The other option is your teachers. Who would be enthralled to have a student or non-student ask for their help and guide you. That is if you don't owe them any work.

Here is the SciOly wiki on mousetrap vehicle, an indispensable resource.

After reading the rules, read them again. The last thing you want to hear is, after all your hard work, "your disqualified." 

Step 2: Materials

Does this step need an explanation? The answer is yes.

You will need these items:
*mousetraps(different kinds)
*wood(balsa preferred)
*super glue
* lubricant(not dw-40, gt-85, or pw-50. lithium based preferred) 
*rubber bands
*fishing rod(old,cheep)
*sip ties
*fishing line
* aluminum rod

Tools needed:
*tools listed in step 1
*X-ACTO knife or utility knife
*C clamp
*measuring tape(7m min)
*spring scale
*computer or calculator

Step 3: Data Collection for Spring Constants

Lets start with a fun calculation of the spring constant of different types of mousetraps.
you will need:
*C clamp
*spring scale
*writing utensil
*anything that can do a liner regression (very helpful)

1. Make a table with three columns labeled; #, angle(deg), force(N).

2. Clamp the mousetrap to the edge of a table.

3. Measure the length of the mousetrap lever arm in meters.

4. Measure the force of at least four different angles. I used {0, 90, 130, 180}. Keep the spring scale perpendicular with the arm.

5. Repeat steps 1 - 4 for each mousetrap

6. Clean up your lab equipment

7. Create a new table with columns labeled; #, angle(rad), torque(N*m).

8. Convert the angle column from degrees to radians
     a) multiply by pi radians
     b) divide by 180 degrees

9. Convert the force column to torque
     a) multiply by the lever arm in meters

10. repeat steps 6 - 8 for the data sets of each mousetrap

Step 4: Calculation the Spring Constant With Computer

This method for calculating the spring constant will be using:
*software for data regression (I suggest QtiPlot )

1. Start QtiPlot

2. Enter the column labeled "angle" into the column labeled "x"

3. Enter the column labeled "torque" into the column labeled "y"

4. Click Analysis -> Fit Liner

5. record the a and b values, the "a" value is the spring constant.

6. repeat for the different mousetraps

Step 5: Calculating Equilibrium

Knowing the values of a and b of the different mousetraps makes this step very easy.

1. negate b

2. divide by a

3. record the value

3. repeat for each mousetrap

*we will represent this value with the Greek letter theta � measured in radians

Step 6: Calculating Potential Energy

It is yet again time to pull out the calculator.

1.  The potential energy stored in the spring of mousetrap is equal to a * ( ((pi + �)^2) - (�^2) ) 

2. repeat for each mousetrap

3. Now lean back and enjoy an ice-cold beverage (not really, you are far from finished)

Step 7: Calculating Arm Length

calculating proper arm length is very important:

you will need:
*writing utensil

the length of the arm is equal to ((the length of the track * (radius of the axle + radius of the string)) / (2 * radius of the axle))

Step 8: Velocity

We could continue and derive the formula for the efficiency of the vehicle, but that information is off limits until competition season is over. Feel free to derive it, here is a hint "Energy Conservation." 

Step 9: Building the Arm

To build the arm you will need:
*fishing pole
*utility knife

1. mark on the fishing pole with the utility knife how long the correct arm length is.

2. clamp the fishing pole to a table

3. cut with hacksaw

4. sand down the sharp burr left from the hacksaw with the sandpaper

Step 10: Cleaning Bearings

To clean the bearing you will need:
*bottle with cap

1. with needle remove the dust covers of the bearings (don't throw away)

2. partially fill the bottle with the lubricant

3. place bearing in bottle

4. cap bottle and shake

5. repeat step 1 - 4 for all the bearings changing lubricant as needed

6. wipe off excess lubricant from the bearings 

7. put the dust covers back on

Step 11: Building the Wheels

To build the wheels you will need:
*super glue
*rubber bands

1. super glue washer on the center of the CD

2. stretch rubber band around the CD

3. repeat steps 1 - 2 for each CD

Step 12: Building the Drive Axle

This step requires:
*aluminium rod
*zip tie
*super glue

1. cut a 15cm segment of the aluminum rod

2. place on lathe and thread both ends

3. place the zip tie off center and tighten it

4. coat the zip tie in super glue. make sure to get super glue in the ratchet.

Step 13: Building the Front Axle

This step requires:
* threaded aluminium rod

1. cut a 15cm segment of the threaded aluminum rod

Step 14: Building (mousetrap)

remember calculation the potential energy stored in the mousetraps? Sure you do, you may have thought all that was for not. It was actually very important. You will want to use the mousetrap with the most energy stored. 

you will need:
*super glue
*utility knife

1. super glue the mousetraps together

2. remove the springs with the pliers from the arm. So that the arm moves freely

2. cut a strip of balsa wood to link the to lever arms of the mousetraps

3. epoxy the arm and cross brace on the the lever arms of the mousetraps

4. hold until epoxy sets

5. leave alone until the epoxy cures, in about ONE DAY.

Step 15: Building the Chassis

This step will require:
*utility knife
*super glue
*writing utensil
*balsa wood

1. draw a rectangle on the balsa wood
    a) with a length greater than the length of the arm plus half the length of a mousetrap
    b) and width of the diameter of the bearing

2. cut out with utility knife

3. repeat steps 1 - 2 7 times, you will have 8 strips of balsa wood.

4. super glue 4 strips together.

5. repeat step 4

6. cut out semicircles at the ends of each set of laminated strips


Step 16: Building the Cup Pusher

building the cup pusher will require:
*utility knife
*balsa wood
*super glue

1. cut two strips 1cm by around 5cm

2. super glue them together

3. cut four strips 1cm by 3cm

4. then chamfer the end of each

5. super glue two strips together

6. repeat step 4 

7. glue the two strips from steps 3 - 5 onto the first laminated strip

Step 17: Building Chassis Supports

This step requires:
*balsa wood
*utility knife

1. measure the width of the main laminated support

2. measure the width of the mousetrap engine.

3. subtract twice the width of the main laminated support from the width of the mousetrap engine

4. cut six strips of balsa wood and laminate them in sets of two

Step 18: Final Assembly

Now that we have all the parts of the mousetrap vehicle the only step left in building is piecing it together.

1. put the bearings and wheels on the axles

2. glue on the axles to the laminated balsa strips ends

3. glue the mousetraps onto the laminated balsa strips with the end of the fishing pole directly above the drive axle.

4. glue on chassis supports, one on the drive end, middle, and front

5. mount the cup pusher to the chassis support on the side with the mousetraps, the front

6. glue the free end of the fishing line onto the drive axle

7. glue on a toothpick so that one end is at most 1cm from the ground

3rd Epilog Challenge

Participated in the
3rd Epilog Challenge