Students will use their knowledge about gears and gear ratios to build a machine that will play tug-o-war against another classmate’s.
To apply building techniques and knowledge about gears to an activity challenge.
RCX or NXT LEGO kits
Assortment of extra LEGO pieces, especially gears and beams
Engineer’s Planning Sheet
Preparation and Set Up:
Collect necessary materials
Arrange students into groups of 2
Decide how you will distribute extra pieces
Write design requirements on the board
Review gears, gear ratios, and torque.
Engineering Design Process
Tell students that in this challenge they will be playing tug-o-war by building a machine that can provide enough torque to pull on another machine doing the same thing. String will be tied between the two, and a machine will have to pull the other over a line of tape in order to win.
Make sure to review how gears work, gear ratios, and using gears for torque vs. speed. Also explain the engineering design process.
Tell students the requirements for their tug-o-war contenders. Examples of requirements are:
Must use gears
Must have a sensor
Allow the class to brainstorm different ideas for their machines. Have them plan out and draw their design on the engineering planning sheet.
Distribute materials and have students start building. You may have to assist students with tying string to their machine.
After the students finish building, pair up machines and tie them to either end of a string, making sure the middle of the string is right above the tape on the ground, and that both machines are equidistant from the tape.
Have the students start their machines. Whoever’s machine gets pulled over the line first, loses.
After the students finish, review the activity with the class. Have them share their ideas, ask groups to explain what the hardest part of the challenge was, etc.
Have students add more gears
Make a classwide tug-o-war competition. Whose is the “strongest”?
Allow those who lose to redesign and compete against each other again