Curricular Activity Template NAME: Cadence Ellington University: Boston University Email: cadence@bu.edu Activity Title: Black Out Racers Grade Level (s): 8 th -12th Approx. Time: 2-3 hours Subject Areas: Physics, Mathematics, and Engineering Standards: (Please list by number using the following abbreviations: Earth and Space Science (ESS), Life Science (LS), Physical Science (PS), Technology/Engineering (TE), Mathematics (M)) 1)TE 2)PS 3)M Description of Activity (please limit to 250 words): This activity is a great introduction to Lego Mind Storms. The students learn about gears, gear ratios, and gear advantage. Students also learn the basic concept behind motors and build a motor generator. Every thing they learn in the lesson is later applied to complete the challenge. Begin by introducing the gears that come in the kits, and instruct the students to build gear trains using gears, axles, and beams. Let the groups explore what happens to one gear as the other is rotated. Have them notice spin direction and speed, and then lead them on a class discussion of the findings. This activity leads easily into a structured lesson on understanding and calculating gear ratios. Next show the students the Lego motors and discuss how a motor works. Show the class that is you connect two motors together and spin one axle, it drives the other. This is a simple motor generator. Have each group assemble two motor generators, and introduce the challenge. The Challenge is to use what they know about gears to design a racer powered by motor generators to complete an obstacle course. I generally design a simple course with straight-aways and a few turns. Try to keep it simple, even the simplest courses are tricky. Allow your students as much time as possible to design, test, and improve their design.
Implementation (classroom organization, presentation, other implementation comments): Have a separate table for each kit to avoid mixing parts. This Activity can be squeezed into a one hour class, but it is tight. I would strongly recommend using 2-3 hours for the lesson to allow student more time to build, test, and rebuild. The most learning occurs when they think it through, test several design ideas, and improve on them. If they are too rushed, groups often don t used the gears their advantage. Materials (include vendor information if appropriate): 1 Lego Mind Storm Kit per group 4 Lego motors for each group
Name: Student ID: Date: Gear ratios: Gear ratio: Ratio of how many times gear 1 turns to how many times gear 2 turns. i.e. a 1:2 ratio means is you spin gear one once, gear two spins twice. [number of turns of the driver]:[number of turns of the follower] Gear ratios can be expressed in two equivalent forms: a:b where a and b are integers (whole number) 1:c where c can be any rational(fraction) number To convert from a:b to 1:c, c=b/a. Example 1: first gear has 10 teeth and second gear has 20 teeth If you spin gear 1 once, gear 2 spins times Scale to integer form Example 2: first gear has 15 teeth and the second gear has 10 teeth If you spin gear 1 once, gear 2 spins times Scale to integer form
Another Approach Counting gear teeth Gear one has A teeth and gear two had B teeth Simplify the fraction B = A X Y Then the ratio is X:Y Example 3: first gear has 3 teeth and the second gear has 12 teeth A= B A = B= simplify A B, Y X = Convert to 1:? Example 4: first gear has 40 teeth and the second gear has 30 teeth A= B A = B= simplify A B, Y X = Convert to 1:?
Gearing Up and Gearing Down Gearing up : increasing the number of revolutions per driver rotation Also increases the rpm (rotations per min) Gearing up occurs when a<b in the gear ratio a:b Use: gives more speed Gearing down (Gear reduction): reducing the number of revolutions per driver rotation Also reduces the rpm (rotations per min) Gearing down occurs when a>b in the gear ratio a:b Use: gives more power Questions: Is it gearing up or gearing down? (circle one) Ex 1: gear ratio: : up or down Ex 2: gear ratio: : up or down Ex 3: gear ratio: : up or down Ex 4: gear ratio: : up or down Gear trains When 3 or more gears are connected in a row, it is referred to as a gear train. Only the first and last gear contribute to the gear ratio. Therefore, calculating the gear ratio will the same, only using the first and last gear.
Gear Ratios Worksheet Using the gears in the kit answer the following the questions. You will need the 40 tooth, 24 tooth, 16 tooth, and 12 tooth gears. Express the ratios in the form you prefer. gear 1 gear 2 ratio Gearing up or down? 1) 40 24 / up down 2) 24 40 / up down 3) 40 16 / up down 4) 12 16 / up down 5) 16 24 / up down 6) 24 24 / up down
Challenge: Build a motorized cart to complete an obstacle course using a maximum of four motors. construct two motor generators use two motors to power and steer your cart use two motors for hand cranks choose gear ratios to optimize the speed and control, on your cart and hand crank do not use your RCX test your design THE COMPETITION WILL BEGIN 10 MINS BEFORE THE END OF CLASS.