Peak Performance

ACTIVITY HEADER

 

 

 

Name of Activity Peak Performance
Author Jay Clark
Keywords NXT, car, course, fastest, flat, inclined, gear, gear ratios, torque, speed, optimization, building, drive gear, driven gear, 1 Hour Total
Subject NXTs
Grade Level K, 1, 2, 3, 4, 5, 6, 7, 8, 9+
Time 1 Hour Total
Brief Description Students must gear their NXT car to complete the course the fastest. The course consists of a flat section and an inclined section.
Lesson Objectives: To learn about gear ratios, gearing for torque vs gearing for speed, optimization, and building.
Materials Needed: NXT kit
Ramp
Computers running MINDSTORMS
Preparation and Set Up: Prepare one or more courses – With a flat beginning and an incline ending. The length of both sections will determine the optimum gear ratio. To allow for extensions, set up other courses with varying distances of the course components.
Necessary Background Using gear ratios students can gear their cars for more torque or more speed. If the drive gear is bigger than the driven gear, the car will be geared for speed. If the other way around, it will be geared for torque.

A car geared for torque will be slower, but will climb better. A car geared for speed will be quick, but might not be able to climb the ramp.

Vocabulary:

Gear Ratio – The ratio of the speed of rotation of the drive gear of a gear train to that of the driven gear.

Drive Gear- The gear attached to the source of torque. (Usually the motor).

Driven Gear – The gear that receives motion from the drive gear.

Optimization – Finding a balance between design concerns that yields the best solution.

Procedure Introduction – 10 Minutes Ask students if they’ve ever used gears before. More than likely, they’ve driven a 10 speed bike before, and never knew how the gears worked. Introduce students to gears and gear ratios. Using a pre-made gear train, show them the size of the drive gear and the driven gear, and ask if the driven gear will spin faster or slower than the drive. If they are having trouble seeing it, ask them for every one rotation of the drive gear, how many times does the driven gear rotate? Explain torque vs. speed. ie. tugboats – high torque, low speed. Handheld fans- high speed, low torque. Introduce the concept of optimization. Introduce the activity Activity – 40 minutes Clean up/ Wrap up – 10 minutes

  • What was easiest? What was hardest?
  •  What would you have done differently?
  •  What were some good ideas you saw that other groups came up with?
Extensions: Have the students try a different course with different dimensions and slopes.
Reference 1 http://sites.tufts.edu/stompactivitydatabase/files/formidable/e.jpg
Reference 2 http://sites.tufts.edu/stompactivitydatabase/files/formidable/f.jpg

Bicycle Unit: Bike Gears

ACTIVITY HEADER

 

 

 

Name of Activity Bicycle Unit: Bike Gears
Author STOMP
Keywords bicycle, gear ratios, gears, gearing up, gearing down, teeth, cogs, drive gear, follower
Subject Non-LEGO
Grade Level 4, 5, 6
Time 1 Hour Total
Brief Description Students will be introduced to gears using a real bike as an example. Students will use this knowledge to do an activity about gear ratios.
Lesson Objectives: - To relate the concepts of gears, gear ratios, and gearing up and down to actual bikes.
Materials Needed: - At least one road bike.
- As many trainers as bikes.
- Measuring tape.
- Activity worksheets.
Preparation and Set Up: - Set up the bike(s) on the trainer(s).
- Place a mark on the rear wheel using tape or chalk.
- Make enough worksheet copies for each student.
- Arrange students in groups if there is more than one bike to look at.
Necessary Background Gears are wheels with teeth, or cogs. These teeth come in contact with each other and interlock so that when one gear turns the other gear also turns. Interlocking gears of different sizes turn at different rates. The gear that is manually turned is called the drive gear. The other gear is connected to a wheel or axle that needs to be turn; this is called the driven gear or follower.

On a bike, gears are connected by a chain. The driver is the gear connected directly to the pedal. The back wheel of the bike is connected to the pedal by a chain. Usually there is a mechanism on the handle bars that changes the gear ratio; in other words, moves the chain to gears of different sizes on the driver and driven gears.

Gear ratios are a set of two numbers that tell how fast one gear will spin in relation to the other gear. A gear ratio is a direct function of the number of cogs on each gear. To calculate a gear ratio, count the number of teeth on the drive gear and divide it by the number of teeth on the driven gear.

Bicyclists gear up and down depending on the conditions of where they are riding. Gearing up is when a bicyclist chooses a high gear ratio; there are more teeth on the drive gear than then driven gear. This means that you go very far on one pedal, but can be good when you want to climb hills. This is because with one pedal, the wheel on the back gear spins several times. Gearing down is when a bicyclist chooses a low gear ratio and there is a lower gear ratio closer to 1:1. This means that for each pedal the rear wheel turns a lot; a bicyclist can not go far, but each pedal provides more power. Gearing down is good for going uphill, or just starting out.

Vocabulary:
Gears
Cogs
Teeth
Gear Ratio
Drive Gear
Driven Gear
Gear up
Gear down

Procedure
  1. Choose the large gear in the front, and the small gear in the back.
  2. Have the students count the number of cogs on both gears.
  3. Slowly turn the pedal one time and see how many revolutions the rear wheel makes (using the marker on the rear wheel to see the revolutions).
  4. Calculate the gear ratio by dividing the number of cogs on the front gear by the number of cogs on the rear gear.
  5. Based on the fact that circumference = 2*pi*radius determine how far the bike would have gone in one revolution of the pedal
    1. Measure the radius of the wheel.
    2. Multiply the radius by 2*pi (6.28).
    3. Multiply this number by the number of revolutions that the wheel made for one pedal.
  6. Have students fill out the attached worksheet for different gear ratios.
  7. Demonstrate cadence and ease of pedaling for each setting.
  8. When the students have completed the worksheet, bring the class together for discussion. Ask students:
    1. What happened to teh gear ratio as the rear gear got larger adn larger?
    2. Did that make it easier or harder for the cyclist to pedal?
    3. Which of the tested gear ratios would you want to use to climb a big hill?
    4. Which of the tested gear ratios would you want to use to go down a hill really fast?
Extensions or Modifications: - Have students calculate how far a person’s feet travel in one rotation (circumference of the circle that you foot would make in the air using the length of the pedal as the radius).

- Have students use the gear ratios to calculate how far a bike can go with one pedal in a high gear ratio (e.g. 1 to 4, or a low gear ratio 1 to 1).

Reference 1 http://sites.tufts.edu/stompactivitydatabase/files/formidable/gear1.pdf
Reference 2 http://sites.tufts.edu/stompactivitydatabase/files/formidable/gear2.doc
Reference 3 http://sites.tufts.edu/stompactivitydatabase/files/formidable/gear3.pdf

Gears

ACTIVITY HEADER

 

 

 

Name of Activity Gears
Author Laurie Cormler
Keywords gears, axles, Drive Gear, Follower Gear, Gear Ratio, Gear Trains, Simple Machines
Subject LEGO Building
Grade Level K, 1, 2, 3, 4, 5, 6
Time 1 Hour Total
Brief Description Students will learn about gears through hands on exploration with LEGOs and a worksheet.
Lesson Objectives: - Familiarize students with gears.
- Learn how gears can be useful.
Materials Needed: One Homemade LEGO kits for each group:
- Kit should contain several gears of each size (about 5 of each).
- Kit should contain many axles (10 – 20) and bushings (20 – 30).
- Kit should contain a “challenge wall” – This wall should be a collection of beams with holes about 4 inches tall and 6 – 8 inches wide. On the top left corner attach a gear with an axle and a bushing.
- One activity worksheet per student.
Preparation and Set Up: - Create homemade LEGO kit.
- Make photocopies of worksheets.
- Arrange students in pairs.
- Distribute materials.
Necessary Background The engineering design process is an eight step process that engineers use to design:

Step 1. Identify the need/problem

Step 2. Research the need/problem

Step 3. Develop possible solutions

Step 4. Select the best possible solution

Step 5. Construct a prototype

Step 6. Test and evaluate the solution(s)

Step 7. Communicate the solution(s)

Step 8. Redesign

Vocabulary:
- Gears
- Drive Gear
- Follower Gear
- Gear Ratio
- Gear Trains
- Simple Machines

Procedure
  1. Explain gears to the class
    1. Talk about how gears are simple machines – a device that helps people do work
    2. Talk about how gears connect to each other with interlocking teeth.
    3. Show that different sized gears have a different number of teeth – This means that one turn of a big gear will turn a small gear more than one turn.
    4. Explain what a gear ratio is. A gear ratio is the number of teeth on the drive gear compared to the number of teeth on the follower gear. Teeth on drive gear: Teeth on follower gear
    5. Explain the difference between gearing up and gearing down and their purpose:
      1. Gearing up mean that for ever revolution of the drive gear the follower gear turns more than one revolution – this is used to make something move faster and gives less power to whatever is attached to the follower gear.
      2. Gearing down means that for every revolution of the drive gear, the follower gear turns less than one revolution – this is used to give more power to whatever is attached to the follower gear because it moves slower with the same power as the drive gear.
    6. Explain that gears are used to slow down or speed up motors in cars, give bikes more resistance up hills, make watch hands move at different speeds etc.
  2. Pass out the gears to the students so they can have a close look.
    1. Have students count the number of teeth on each sized gear.
    2. Have students do the Gear Ratio Worksheet and activity (attached).
  3. Explain to students how when one gear is turned clockwise, the other gear turns counterclockwise.
    1. Pass out the ‘Gears Worksheet’ (attached).
  4. Explain the final challenge of the activity.
    1. Show students the “challenge wall” with one gear at the top left.
    2. Tell students that they must add gears to the wall so that when you turn a driver at the bottom right, the top left gear will turn.
Extensions or Modifications: - Have students make the top left gear turn clockwise when the bottom right gear is turned counterclockwise.
- Add a spindle attached to a net over a LEGO man on the top left gear that the students have to turn with the other gears. Have the challenge be to free the LEGO man by adding a Gear Train to the lower right of the wall so that when it is turned the net is lifted.
Modifications:
Reference 1 http://sites.tufts.edu/stompactivitydatabase/files/formidable/gears1.pdf
Reference 2 http://sites.tufts.edu/stompactivitydatabase/files/formidable/gears2.pdf
Reference 3 http://sites.tufts.edu/stompactivitydatabase/files/formidable/gears3.pdf

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