Wednesday, September 18, 2019

Craft Stick Motorized Car



Materials:
• bottle caps
• straw
• paperclips
• Hobby motor
• 1 AA battery
• Solid core wire (we like telephone wire)
• craft stick
• tape
• a broccoli rubber band, or inner tube cut off
• wooden dowel or bamboo skewer

Tools:
• scissors
• wire strippers
• hammer
• nails
• hot glue gun




Make a hole in bottle cap by hammering a nail through the middle of the cap.  Push the motor’s axle through the hole.  It should be a tight fit.  If it is not a tight fit hot glue the cap in place. We found that a 3D nail makes the perfect size hole for the axle of the motor we use. 


  

Use scissors to enlarge holes for rear wheels if using a dowel. If using bamboo skewers it is not necessary to enlarge the hole. 





Cut dowel to preferred length.  Cut straw an inch smaller than dowel.  Insert dowel into straw and glue rear wheels to dowel. The second photo shows us using corks for wheels and a bamboo skewer for the axle.  
Wheel axle should spin freely in straw.




Glue or tape rear wheel assembly to craft stick.



Cut wire into two and strip ends of wires.  Attach each wire to a paper clip.  Pull rubber band lengthwise over the AA battery.



Tape battery to craft stick.





Hot glue motor to end of craft stick and attach wires to motor tabs.




Your car is ready to go!


Things to do and notice: 

  • Cars might go “backwards” if the polarities (negative and positive) of the battery are attached to the motor in a certain way.  If this is the case switch paperclips position on the battery.
  • The weight of the battery helps the front wheel gain traction. Using a piece of bicycle inner tube can also help with this.  If the front wheel jumps around too much try adjusting the position of the battery. 

Concepts Involved:


  • Electrical circuit is a path for the electrical current to flow.
  • Conductors and insulators:  Paperclips and copper wire make good conductors; they allow electricity to flow through them with little resistance.
  • Friction is the force between two objects as they move over one another. 
  • Static frictional force for the front wheel to move the car forward (or backward).  Kinetic frictional force keeps the object in motion.  The initial force that starts something to move is always greater than the force needed to keep it moving.  The rear wheel assembly has little friction as the axle moves around in the straw.

Focus Questions:

1.      How else can you make the car turn on and off? Try making a different switch.
2.      Would the car go faster with a bigger front wheel or bigger rear wheels?
3.      Does it matter if the car goes forward or backwards?  Is it faster one way or another?