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Autodesk's VEX® Robotics Curriculum Unit 8: Friction and Traction

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Autodesk's VEX® Robotics Curriculum Unit 8: Friction and Traction Autodesk's VEX® Robotics Curriculum Unit 8: Friction and Traction 1 Overview In Unit 8: Friction and Traction, you modify the differential tricycle to participate in a tractor pull. You learn about the concepts of friction and traction while applying your knowledge of the design process to solve a given problem. The physics concepts of friction and traction must be considered in countless real-world applications. In STEM Connections, one scenario is presented involving friction and traction in the design of a snowmobile. After completing the Think Phase and Build Phase in Unit 8: Friction and Traction, you will see how concepts regarding friction and traction come into play in the real world. Objectives After completing Unit 8: Friction and Traction, you will be able to: ■ Explain the difference between static and kinetic friction and list the factors that determine traction. ■ Create a VEX tire in Autodesk Inventor Professional. ■ Have a robot ready to compete in a “tractor pull” and be proficient in making simple modifications to VEX robots. ■ Take advantage of the principles of friction and traction to modify a robot to pull a greater amount of weight. Prerequisites and Resources Related resources for Unit 8: Friction and Traction are: ■ Unit 1: Introduction to VEX and Robotics ■ Unit 2: Introduction to Autodesk Inventor ■ Unit 4: Microcontroller and Transmitter Overview ■ Unit 5: Speed, Power, Torque, and DC Motors ■ Unit 6: Gears, Chains, and Sprockets ■ Unit 7: Advanced Gears Key Terms and Definitions The following key terms are used in Unit 8: Friction and Traction: Term Definition Chamfer A placed feature that bevels a part edge and is defined by its placement, size, and angle. Coefficient of The ratio of maximum frictional force between two surfaces to the force holding Friction them together. Term used to describe the "grippyness" of two surfaces meshing together. Slippery objects have a very low coefficient of friction. 2 ■ Autodesk's VEX Robotics Unit 8: Friction and Traction Term Definition Component A part or subassembly placed into another assembly. Assembly components may be single parts or parts combined that operate as a unit (or subassembly). Components may be treated as parts within other assemblies. Dimension Parametric dimensions that control sketch size. When dimensions are changed, the sketch resizes. Dimensional constraints may be expressed as numeric constants, as variables in equations, or in parameter files. Fillet A placed feature applied to edges and corners of a 3D model. A fillet feature is defined by its type, radius, and placement. Friction The resistance that one surface or object encounters when sliding against another. iFeature Features, sketches, or subassemblies that can be used in more than one design are designated as iFeatures and saved in a file with an IDE extension. Kinetic The frictional force which opposes the motion of an object while it is moving. Friction Mirror Sketch geometry that is copied across a centerline. sketches Normal Force The amount of force holding two surfaces together. For an object sitting on a level surface, this value is equivalent to the objects weight as caused by gravity. Opacity Is the measure of how opaque or see-through an assembly component is. Pattern Multiple instances of a placed or sketched feature arrayed in a specified pattern. Patterns are defined by type (rectangular or circular), orientation, number of features, and spacing between features. Plane A two-dimensional (flat) part face. Profile A closed loop defined by sketched or reference geometry that represents a cross section of a feature. An open profile defined by sketched segments, arcs, or splines may define a surface shape or extend to boundaries to close a region. A profile may enclose islands. Projected Geometry (model edges, vertices, work axes, work points, or other sketch Geometry geometry) projected onto the active sketch plane as reference geometry. May include edges of a selected assembly component that intersects the sketch plane when it was cut in an assembly cross section. Properties A characteristic of a Microsoft Windows file that can be manipulated from an application or Microsoft Windows Explorer. Properties include author or designer and creation date and may also be unique properties assigned by applications or users. Specifying properties can be useful when searching for part or assembly files. Revolve A solid feature created by revolving a profile around an axis. Overview ■ 3 Term Definition Section View In an assembly, a view of the model defined by temporarily hiding portions of components or features on one side of a specified cutting plane. Static Friction The frictional force that opposes the motion of an object before it starts moving. Template An assembly, part, or drawing file that contains predefined file properties. To create a file based on a template, you open a template file, create the content, and then save it with a unique file name. Predefined properties can include visible default reference planes, customized grid settings, color scheme, drafting standards, and so on. Traction The friction between a drive member, wheel, and the surface it moves upon. The amount of force a wheel can apply to a surface before it slips. Tread The pattern on the surface of a tire. Required Supplies and Software The following supplies and software are used in Unit 8: Friction and Traction: Supplies Software VEX Classroom Lab Kit Autodesk® Inventor® Professional 2011 One assembled differential tricycle built in the Unit 7: Advanced Gears > Build Phase One modified and assembled differential tricycle from the Unit 8: Friction and Traction > Build Phase Notebook and pen Work surface Small storage container for loose parts 6’x12’ of open floor space Masking tape Measuring tape 36” of 1/8” Braided nylon and polyester cord or equivalent rope/string 4 ■ Autodesk's VEX Robotics Unit 8: Friction and Traction VEX Parts The following VEX parts are used in Unit 8: Friction and Traction > Build Phase: Quantity Part Number Abbreviations 1 BEAM-2000 B2 2 SCREW-832-0250 S2 1 SCREW-832-0750 S6 1 SPACER-THIN SP1 1 VEX-12-TOOTH-GEAR G12 4 WASHER-DELRIN WP Academic Standards The following national academic standards are supported in Unit 8: Friction and Traction: Phase Standard Think Science (NSES) ■ Unifying Concepts and Processes: Form and Function; Change, Constancy, and Measurement ■ Physical Science: Motions and Forces ■ Science and Technology: Abilities of Technological Design Technology (ITEA) ■ 5.8: The Attributes of Design Mathematics (NCTM) ■ Alegbra: Analyze change in various contexts. ■ Measurement: Understand measurable attributes of objects and the units, systems, and processes of measurement. ■ Problem Solving: Apply and adapt a variety of appropriate strategies to solve problems. ■ Communication: Communicate mathematical thinking coherently and clearly to peers, teachers, and others. ■ Connections: Recognize and apply mathematics in contexts outside of mathematics. Create Science (NSES) ■ Unifying Concepts and Processes: Form and Function ■ Physical Science: Motions and Forces ■ Science and Technology: Abilities of Technological Design Overview ■ 5 Phase Standard Technology (ITEA) ■ 5.8: The Attributes of Design ■ 5.9: Engineering Design ■ 6.12: Use and Maintain Technological Products and Systems Mathematics (NCTM) ■ Numbers and Operations: Understand numbers, ways of representing numbers, relationships among numbers, and number systems. ■ Algebra Standard: Understand patterns, relations, and functions. ■ Geometry Standard: Use visualization, spatial reasoning, and geometric modeling to solve problems. ■ Measurement Standard: Understand measurable attributes of objects and the units, systems, and processes of measurement. Build Science (NSES) ■ Unifying Concepts and Processes: Form and Function; Change, Constancy, and Measurement; Evidence, Models, and Explanation ■ Physical Science: Motions and Forces ■ Science and Technology: Abilities of Technological Design Technology (ITEA) ■ 5.8: The Attributes of Design ■ 5.9: Engineering Design ■ 6.10: Troubleshooting, Research, and Development, Invention and Innovation, and Experimentation in Problem Solving Mathematics (NCTM) ■ Numbers and Operations: Compute fluently and make reasonable estimates. ■ Algebra: Analyze change in various contexts. ■ Geometry: Use vizualization, spatial reasoning, and geometric modeling to solve problems. ■ Measurement: Understand measurable attributes of objects and the units, systems, and processes of measurement. ■ Measurement: Apply appropriate techniques, tools, and formulas to determine measurements. ■ Problem Solving: Build new mathematical knowledge through problem solving. ■ Problem Solving: Solve problems that arise in mathematics and in other contexts. ■ Problem Solving: Apply and adapt a variety of appropriate strategies to solve problems. ■ Connections: Recognize and apply mathematics in contexts outside of mathematics. 6 ■ Autodesk's VEX Robotics Unit 8: Friction and Traction Phase Standard Amaze Science (NSES) ■ Unifying Concepts and Processes: Form and Function; Change, Constancy, and Measurement; Evidence, Models, and Explanation ■ Physical Science: Motions and Forces ■ Science and Technology: Abilities of Technological Design Technology (ITEA) ■ 5.8: The Attributes of Design ■ 5.9: Engineering Design ■ 6.10: Troubleshooting, Research, and Development, Invention and Innovation, and Experimentation in Problem Solving Mathematics (NCTM) ■ Numbers and Operations: Compute fluently and
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