Competitive VEX Robot Designer Skill Set 2: Builder I Terminal Objective 2.2: construct a boom crane Performance Objective: Given provided VEX components, construct a boom crane that extends a minimum of twelve inches and can lift a weight ( > 5 lbs) one foot off the ground in less than thirty seconds. Enabling Objectives: 1. define the following terms: spur gear, worm gear, rack gear, pinion gear, bevel gear, driving gear, driven gear, gear ratio, idler gear, compound gear train, noncompound gear train, speed, torque 2. explain the characteristics of a gear train 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: Aluminum base to mount crane Clamp to mount base to the table Weight (>= 5 lbs) to test boom crane Learning Activities: 1. View PowerPoint presentation and complete Activity Sheet 2.2, Construct a Boom Crane. 2. Construct a boom crane using the guidelines set forth in Design Brief 2.2, Construct a Boom Crane. Formative Evaluation: Activity Sheet 2.2, Construct a boom crane, will be used to assess student progress. The answers to Activity Sheet 2.2 are as follows: Matching 1. G 2. B 3. E 4. D 5. A Developed by Trevor Robinson Lesson 2.2 page 1
6. C 7. H 8. F Multiple Choice 9. C 10. B 11. A 12. Driven Gear A Driving Gear D 13. Driven Gear D Driving Gear A Short Answer 14. Gearing can increase your speed or torque depending on the gear ratio 15. A set gears in a system, arranged to transfer rotation of one part to another 16. Compound gear trains use multiple gears per axel, where a non-compound gear train uses only one gear per axel Summative Evaluation: Performance Assessment 2.2, Construct a boom crane, 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. increasing the number of gears B. gear reduction C. gearing up D. a gear Developed by Trevor Robinson Lesson 2.2 page 2
Performance Assessment 2.2 Name: Start Date: Skill Set: Builder I Terminal Objective 2.2: construct a boom crane Performance Objective: Given provided VEX components, construct a boom crane that extends a minimum of twelve inches and can lift a weight ( > 5 lbs) one foot off the ground in less than thirty seconds. Process Assessment Elements Acceptable Unacceptable 1. Construct a boom crane a) Crane is at least 12 inches long b) Axels are supported by bearings on both sides c) Crane can lift weight 12 inches in less than 30 seconds Note: All items must receive an acceptable rating to pass the objective. Evaluator: Date: Developed by Trevor Robinson Lesson 2.2 page 3
Activity Sheet 2.2 Construct a Boom Crane 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. The main gear used in construction with VEX components 2. Rotated by the gear connected to the source of power 3. Used with a rack gear 4. Inserted between driving and driven gears 5. Transfers motion by 90 degrees 6. Attached to the source of power 7. Used to create a greater gear reduction 8. A straight, not curved gear A. bevel gear B. driven gear C. driving gear D. idler gear E. pinion gear F. rack gear G. spur gear H. worm gear Directions: Circle the letter that corresponds to the correct answer. 9. The tendency of a force to rotate an object about an axis. 10. The rate of change of an objects position. Developed by Trevor Robinson Lesson 2.2 page 4
11. A multiplier on torque and a divider on speed. A. increasing the number of gears B. gear reduction C. gearing up D. a gear Directions: Use the figure below to answer questions 12 13. A B C D 12-tooth gear 36-tooth gear 60-tooth gear 84-tooth gear 12. Which two gear combination will gain the most torque? Driven gear Driving Gear 13. Which two gear combination will gain the most speed? Driven gear Driving Gear Directions: Write your answer in the space provided. 14. What is the purpose of gearing when discussing speed and torque? 15. Explain the characteristics of a gear train. 16. What is the difference between a compound gear train and a non-compound gear train? Developed by Trevor Robinson Lesson 2.2 page 5