This week we focus on drivetrains. The VEX IQ curriculum has a great introductory lesson on drivetrains.

Friction

Wheel Friction

Wheel friction can slow down a drivetrain. You want to reduce the friction of the tires rubbing on the beams.

Watch the video below to see how easy it is to reduce friction with a washer.

Turning Scrub

Turning scrub is friction that keeps the chasis from turning. Turning scrub can also cause the robot to drive erratically. The highest friction is from the front tires.

Hands on Activity with Friction

  1. Wheel Friction
    1. Have students put a wheel on a beam with a shaft and rubber shaft collars.
    2. Have the students do the same as above, but then put a washer in between the wheel and the beam.
  2. Turning Scrub
    1. To reduce turning scrub, students can explore omni-directional wheels.
    2. If you don’t have these wheels, simply remove the rubber tires from the wheels and you can also reduce the turning scrub!

Gear Ratio

Gear Ratio can be used to build faster drivetrains or slower, but more powerful drivetrains.

VEX IQ has a great lesson on Gear Ratio. Please have the students review this lesson.

This video explains gear ratio as well.

Explore more about gears and sprockets with the Beach Botz!

Hands on Activity with Gear Ratio

This activity may take several hours and can be done over multiple sessions.

Have students build a drivetrain and try to switch out the gears to have greater speed or more power. (Hint: Larger gears driving smaller gears will make the drivetrain faster.)

Questions to consider when building a drivetrain

  1. How long will your drivetrain be? Why?
  2. How wide will your drivetrain be? Why?
  3. What kind of shafts (plastic or metal) will you use for your drivetrain?
  4. What kind of wheels will you use? Why?
  5. What gears / gear ratio will you use?