Competitive VEX Robot Designer Skill Set 2: Builder I Terminal Objective 2.3: build a drift chassis Performance Objective: Given provided VEX components, build a drift chassis that can complete five laps around the room in less than 80 seconds. Enabling Objectives: 1. define the following terms: chassis, chain and sprocket, driving sprocket, driven sprocket, idler sprocket, drive train 2. explain the purpose of a chain and sprocket set 3. explain the relationship between gear ratios, speed, and torque 4. calculate gear ratios Laboratory Hardware: The following materials and hardware are required and unique to this lesson: Chain and sprocket set Learning Activities: 1. View PowerPoint presentation and complete Activity Sheet 2.3, Build a Drift Chassis. 2. Build a drift chassis using the guidelines set forth in Design Brief 2.3, Build a Drift Chassis. Formative Evaluation: Activity Sheet 2.3, Build a Drift Chassis, will be used to assess student progress. The answers to Activity Sheet 2.3 are as follows: Matching 1. F 2. B 3. G 4. D 5. E 6. C 7. A Multiple Choice 8. C 9. B Developed by Trevor Robinson Lesson 2.3 page 1
10. A 11. Driven Gear D Driving Gear A 12. Driven Gear A Driving Gear D Short Answer 13. Gearing can increase your speed or torque depending on the gear ratio 14. The purpose of sprockets and chain is either to transmit rotary motion between two shafts where gears are unsuitable or to impart linear motion to a track, tape etc. Summative Evaluation: Performance Assessment 2.3, Build a Drift Chassis, will be used to measure the performance objective. In addition, the following test items could be used to measure the enabling and terminal objectives on a unit or end-of-level test: 1. The tendency of a force to rotate an object about an axis. 2. The rate of change of an objects position. 3. A multiplier on torque and a divider on speed. A. gear ratio B. gear reduction C. gearing up D. adding more gears/sprockets 4. A frame that consists of motors and wheels: A. chassis. B. body. C. drive chain. D. robot. Developed by Trevor Robinson Lesson 2.3 page 2
Performance Assessment 2.3 Name: Start Date: Skill Set: Builder I Terminal Objective 2.3: build a drift chassis Performance Objective: Given provided VEX components, Build a drift chassis that can complete five laps around the room in less than 80 seconds. Performance Assessment Elements Acceptable Unacceptable 1. Build a drift chassis a) Chain drive is used to increase speed b) Robot completes 5 laps around the room in under 80 seconds Note: All items must receive an acceptable rating to pass the objective. Evaluator: Date: Developed by Trevor Robinson Lesson 2.3 page 3
Activity Sheet 2.3 Build a Drift Chassis Name: Date: Directions: Match the description or purpose of a gear in the left column with the best selection from the list of gears in the right column by writing the corresponding letter in the space provided. 1. A frame that consists of motors and wheels 2. Rotated by the sprocket connected to the source of power 3. A set of sprockets and chain connected to a source of power 4. Inserted between driving and driven sprockets 5. Used to connect two sprockets together 6. Attached to the source of power 7. A profiled wheel with teeth that mesh with a chain A. sprocket B. driven sprocket C. driving sprocket D. idler sprocket E. chain F. chassis G. drive train Directions: Circle the letter that corresponds to the correct answer. 8. The tendency of a force to rotate an object about an axis. 9. The rate of change of an objects position. Developed by Trevor Robinson Lesson 2.3 page 4
10. A multiplier on torque and a divider on speed. A. gear ratio B. gear reduction C. gearing up D. adding more gears/sprockets Directions: Use the figure below to answer questions 11 12. A B C D 40 tooth sprocket 24 tooth sprocket 15 tooth sprocket 10 tooth sprocket 11. Which two sprocket combination will gain the most torque? Driven gear Driving Gear 12. Which two sprocket combination will gain the most speed? Driven gear Driving Gear Directions: Write your answer in the space provided. 13. What is the purpose of gearing when discussing speed and torque? 14. Explain the purpose of a chain and sprocket set (drive train). Developed by Trevor Robinson Lesson 2.3 page 5