Autodesk's VEX® Robotics Curriculum
Unit 11: Creating a Tank Tread Drive
1 Overview
In Unit 11: Creating a Tank Tread Drive, you learn about tank tread drivetrains. You build a simple tank tread drivetrain, and modify that drivetrain to complete a given challenge using the design process and problem-solving techniques. You then document your process and report on your findings and learning.
Unit Objectives
After completing Unit 11: Creating a Tank Tread Drive, you will be able to:
■ List the advantages and disadvantages of tank tread drives. ■ Animate the installation of the tank tread kit using Autodesk Inventor Professional software. ■ |Apply the knowledge from the Unit 11: Creating a Tank Tread Drive > Think Phase to build a tank tread drivetrain.| ■ Create tank tread drivetrains of varying design.
Prerequisites and Resources
Related resources for Unit 11: Creating a Tank Tread Drive 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 ■ Unit 8: Friction and Traction ■ Unit 9: Drivetrain Design 1 ■ Unit 10: Drivetrain Design 2
Key Terms and Definitions
The following key terms are used in Unit 11: Creating a Tank Tread Drive.
Term Definition
Bogey Wheel One of a number of modern tank-tread double-wheels used as an Idler/Tension Wheel.
Frames Per The measurement of frequency at which Inventor Studio produces unique, Second consecutive images.
Idler (Tension Component that transmits no power but guides or tensions a track, belt, or rope. Wheel)
2 ■ Autodesk's VEX Robotics Unit 11: Creating a Tank Tread Drive
Term Definition
Render The process of producing an image or animation based on user-defined parameters such as fps, lighting style, and scene style.
Tank Tread Individual links combined together to form a continuous section. On the robot, the tank tread distributes the vehicle's weight more evenly, enabling the robot to maneuver in loose sand, or on spongy surfaces that would otherwise cause the robot to sink.
Tank Tread A drivetrain which utilizes a continuous track as a drive member; this track is Drive driven by one or more drive sprockets.
Timeline Specifies the duration in seconds for each of the actions that comprises an animation. Plays the actions in an animation in sequence, or plays actions specified in the timeline. When opened, activates the last animation.
Track A series of connected treads, drive sprocket(s), idler(s)/tension wheels(s), and sometimes support rollers and suspension components when necessary.
Tread One of a series of connected components that make up a track.
Required Supplies and Software
The following supplies and software are used in Unit 11: Creating a Tank Tread Drive:
Supplies Software
VEX Classroom Lab Kit Autodesk® Inventor® Professional 2011
Tank Tread Drivetrain built in the Unit 11: Creating a Tank Tread Drive > Build Phase
Notebook and pen
Work surface
Small storage container for loose parts
4’x4’ of open floor space
Measuring tape
Masking tape or duct tape
3-4” high obstacle
Overview ■ 3 VEX Parts
The following VEX parts are used in Unit 11: Creating a Tank Tread Drive > Build Phase:
Quantity Part Number Abbreviations
2 ANG-HH22-15-SK RevA A15
1 Antenna-Holder AH
1 Antenna-Tube AT
2 BATTERY-STRAP BST
6 BEARING-FLAT BF
12 BEARING-RIVET BR
4 Double Bogie Wheel TBD
4 DRIVE-WHEEL TS15
1 MICROCONTROLLER VMC
37 NUT-832-KEPS NK
1 RECEIVER RX75
4 SCREW-632-0250 SS2
20 SCREW-832-0250 S2
9 SCREW-832-0375 S3
8 SCREW-832-1000 S8
4 SHAFT-3000 SQ3
8 SHAFT COLLAR COL
140 TANK-TREAD-LINK TL
1 VEX-Motor MOT
4 ■ Autodesk's VEX Robotics Unit 11: Creating a Tank Tread Drive
Academic Standards
The following national academic standards are supported in Unit 11: Creating a Tank Tread Drive.
Phase Standard
Think Science (NSES) ■ Unifying Concepts and Processes: Form and Function ■ Physical Science: Motions and Forces ■ Science and Technology: Abilities of Technological Design
Technology (ITEA) ■ 5.8: The Attributes of Design
Mathematics (NCTM) ■ Measurement: Understand measurable attributes of objects and the units, systems, and processes of measurement. ■ 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
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.
Overview ■ 5
Phase Standard
Build Science (NSES) ■ Unifying Concepts and Processes: Form and Function ■ Physical Science: Motions and Forces ■ Science and Technology: Abilities of Technological Design
Technology (ITEA) ■ 5.8: The Attributes of Design ■ 5.9: Engineering Design ■ 6.11: Apply the Design Process
Mathematics (NCTM) ■ Measurement: Understand measurable attributes of objects and the units, systems, and processes of measurement. ■ Connections: Recognize and apply mathematics in contexts outside of mathematics.
Amaze Science (NSES) ■ Unifying Concepts and Processes: Form and Function ■ Physical Science: Motions and Forces ■ Science and Technology: Abilities of Technological Design
Technology (ITEA) ■ 5.8: The Attributes of Design ■ 5.9: Engineering Design ■ 6.11: Apply the Design Process
Mathematics (NCTM) ■ 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. ■ Communication: Communicate mathematical thinking coherently and clearly to peers, teachers, and others. ■ Connections: Recognize and apply mathematics in contexts outside of mathematics.
6 ■ Autodesk's VEX Robotics Unit 11: Creating a Tank Tread Drive Think Phase
Overview
This phase describes the characteristics of a tank tread drivetrain. It reviews advantages and disadvantages of these systems.
Phase Objectives
After completing this phase, you will be able to:
■ List the advantages and disadvantages of tank tread drives.
Prerequisites
Related phase resources are:
■ Unit 5: Speed, Power, Torque, and DC Motors ■ Unit 8: Friction and Traction ■ Unit 9: Drivetrain Design 1
Required Supplies and Software
The following supplies are used in this phase:
Supplies
Notebook and pen
Work surface
Think Phase ■ 7
Research and Activity
A tank tread drive is a drivetrain that uses a continuous track as a drive member; this track is driven by one or more drive sprockets.
Sometimes people incorrectly refer to tracks as treads. Treads are actually components of the tracks, not the tracks themselves. Many treads are used to make up a track. Tracks are made up of treads, the drive sprocket, idlers/tension wheels, and if required, support rollers and suspension components. Track drive systems have been around since the early 1900s, but their major usage did not happen until World War I when a variety of different vehicles were developed to traverse the diverse terrains of Europe. Their diverse evolution continued in World War II and continues today.
The M3 Half-Track was an armored personnel carrier during WWII.
8 ■ Autodesk's VEX Robotics Unit 11: Creating a Tank Tread Drive
Track Drive System Advantages
One of the major advantages of a track drive system is the large contact area with the surface being traversed, effectively spreading the weight of the vehicle out over a large area so it does not sink into the surface. In fact, military tanks put less force on the ground per square inch than a person’s foot. Because of this, tracks provide substantial advantages in soft, muddy, sandy, rocky, and loose terrain such as snow.
The M1A2 Abrams tank uses the double-ramp configuration.
They can also carry heavy loads which might sink on a wheeled vehicle. A famous example of this is the crawler-transporter used by NASA to carry space vehicles to the launch pad. The crawler-transporter can be seen below.
The NASA Crawler Transporters are two of the world's largest vehicles.
Image credit: NASA KSC
Think Phase ■ 9
Another advantage tank tread drives have is their continuous contact patch from front to back. This enables them to cross over rough terrain without getting hung up or high-centered. Wheeled vehicles may end up riding down into ruts or holes that a tank tread drive will go right over.
Rubber road inserts can be clearly seen on XM1's treads. The XM1 was the only prototype for the M1A1 Abrams tank.
Wheeled vehicles have a small contact patch with the ground, whereas tank tread drive vehicles have a large contact patch. Wheeled vehicles have great traction on hard surfaces like pavement, but on loose surfaces the force of the wheel is applied to a small area. If the force is great enough, it will cause the ground to break away and the vehicle will lose traction. The tank tread drive applies the force over a larger area, and as such the ground does not break away and the vehicle does not lose traction. For this reason, some vehicles rely on tank tread drives for higher traction.
Large earthmoving equipment use large durable metal treads.
10 ■ Autodesk's VEX Robotics Unit 11: Creating a Tank Tread Drive
Tank tread drives, unlike wheels, can also have varying angles of approach and departure. Different track profiles are good for different applications. When designing a track profile, it is important to account for surface and terrain conditions (slope of terrain, size of possible obstructions, surface material, and so on).
A basic track profile with just two sprockets is shown below. This is extremely low profile but has a very low angle or approach and angle of departure. It is not good for climbing objects, but it has all the other advantages described above.
Tank Tread Drive 4
Adding a bogey wheel assembly turns the front of the vehicle into a ramp, making it a better climber. This is called a single ramp configuration.
Think Phase ■ 11
An additional bogey wheel assembly creates a ramp on the back of the vehicle as well. This enables the machine to go over large obstacles either forward or backward. This is called a double ramp configuration, and is commonly found on military and construction vehicles.
The simplest and most recognizable single-track vehicle is the snowmobile. It provides a wide contact surface that enables it to move over snow with cleats to provide traction. This design must provide another mechanism for steering because the track can only provide forward or backward force.
Track systems using two tracks are the most common. They steer by braking or reversing one set of treads. The vehicle turns into the braked or reversed track. Since tanks are steered in this manner, this method is referred to as tank drive.
Multiple-track drives are complex and versatile machines. Some incorporate the use of “flippers” to provide maximum flexibility and obstacle-climbing ability. Some say that flippers got their name from the flippers that marine mammals have, but the name is more likely coined from the flippers in a pinball machine. They share the same basic shape. Multiple-track drives are complex and are used primarily on sophisticated machines.
12 ■ Autodesk's VEX Robotics Unit 11: Creating a Tank Tread Drive
Tank tread drives have a number of disadvantages as well. Tracks are ideal for a variety of situations, but they do have limitations. Because they contain so many moving parts, these drives are full of friction and require a lot of lubrication and maintenance. They are also difficult to change when compared to a tire. To change out one bad tread, the entire track must be removed. This is a difficult and time-consuming job.
Tracks do not have the cushioning effects of air-filled tires, so the ride can be really rough. Often tank tread drives require some additional form of suspension.
Tracks, although strong and very reliable, can be thrown off of their drive sprockets. That is why tank drive systems need to be designed to take severe punishment and stay on the vehicle.
Although the tank treads in the VEX Robotics Design System differ from treads in real life in many ways, VEX Treads are not subject to the lubrication and maintenance needs of real tracks. However, they do require proper tensioning. VEX Tank Treads come with four primary components: the tank tread links, drive wheels, single bogey wheel assemblies, and double bogey wheel assemblies. These components can be used to create a variety of tread profiles and configurations designed to overcome any obstacle a robot encounters.
The VEX GameBot uses a double-ramp track configuration.
Think Phase ■ 13 Create Phase
Overview
In this phase, you learn how to create an animation for assembling the tank tread kit. The animation will be used to demonstrate how to convert the VEXplorer from wheels to tank treads.
The completed exercise
Phase Objectives
After completing this phase, you will be able to: ■ Animate the installation of the tank tread kit.
14 ■ Autodesk's VEX Robotics Unit 11: Creating a Tank Tread Drive
Prerequisites
Before starting this phase, you must have:
■ A working knowledge of the Windows operating system. ■ Completed Unit 1: Introduction to VEX and Robotics > Getting Started with Autodesk Inventor. ■ Completed Unit 2: Introduction to Autodesk Inventor > Quick Start for Autodesk Inventor.
Technical Overview
The following Autodesk Inventor tools are used in this phase:
Icon Name Description
Animate Fade Controls the visibility of a component during a given time frame.
Go to Start Sets the current time to zero, which is the start of the animation.
Play Plays the animation. Changes to Stop Animation during playback. Animation
Render Specifies general settings for rendering animations. Animation
Required Supplies and Software
The following software is used in this phase:
Software
Autodesk Inventor Professional 2011
Create Phase ■ 15
Exercise: Animate the Tank Tread Installation
In this exercise, you learn how to create an animation for installing the tank tread kit. The animation will be used to demonstrate how to convert the VEXplorer from wheels to tank treads.
Make the Tank Tread Kit Invisible The completed exercise
In this section of the exercise, you start the animation by making all the tank tread components invisible. Open the File
1. On the Environments tab, Begin panel, click You have been given the task of showing how the Inventor Studio. tank tread kit is installed on a VEXplorer robot. To do this, you use Inventor Studio to create a high quality
animation of the parts and their location on the 2. In the browser, right-click Animations. Click robot. New Animation.
1. Make IFI_Unit11.ipj the active project file.
2. Open VEXplorer_Module.iam.
3. Expand Animations. Right-click Animation1. Click Activate.
3. On the View tab, Appearance panel, click the arrow below Visual Style. Click Shaded.
16 ■ Autodesk's VEX Robotics Unit 11: Creating a Tank Tread Drive
4. On the Animate panel, click Fade. Set the Length of the Animation
In this section of the exercise, you set the length of
5. In the browser, select Shaft_Collar:1. Hold the animation to 15 seconds.
down the SHIFT key, select TankTread:1. All the 1. On the Animation Timeline, click Animation components in between are also selected. Options.
2. Under Length, for Seconds, enter 15.
3. Click OK. The timeline is set to 15 seconds.
Make the Shaft Collars Visible
1. On the Animate panel, click Fade.
2. In the browser, select Shaft_Collar:1 and 6. Under Action, for End, enter Shaft_Collar:10.
00 3. Under Time, for End, enter 1.
7. Click OK. 4. Under Action, for End, enter 100.
5. Click OK.
6. On the Animation Timeline, click Go to Start.
7. On the Animation Timeline, click Play Animation.
The shaft collars appear in the first second of the animation.
Create Phase ■ 17
Make the Drive Wheels Visible Play the Animation
1. On the Animate panel, click Fade. 1. On the Animation Timeline, click Go to Start.
2. In the browser, select Drive_Wheel:1 and 2. On the Animation Timeline, click Play Drive_Wheel:2. Animation.
3. Under Action, for End, enter 100.
4. Under Time, click Specify. All the parts appear between zero and twelve seconds.
Create a Camera
1. On the ViewCube, click Home.
2. On the Animation Timeline, click Go to Start.
3. In the browser, right-click Cameras. Click Create 5. For Start, enter 1. Camera from View.
6. For End, enter 3. 4. In the browser, right-click Camera1. Click
7. Click OK. Visibility to turn off the visibility of the camera.
8. On the Animation Timeline, click Go to Start. 5. On the Animation Timeline, move the slider to 12 seconds.
9. On the Animation Timeline, click Play Animation.
Make the Remaining Parts Visible 6. Select Camera1 from the list.
1. Using the workflow from the previous steps, use Animate Fade and the following settings to make the parts visible.
Part Name Settings
On the ViewCube, click the top-front corner. 7. Shaft_Collar:11 and 12 3s to 4s
NUT-832-KEPS:1 and 2 3s to 4s
Hexagon Screw:1 and 2 4s to 6s
IDLER-WHEEL:1 5s to 8s
Tank Tread:1 8s to 12s
18 ■ Autodesk's VEX Robotics Unit 11: Creating a Tank Tread Drive
8. On the Animation Timeline, click Add Camera ■ Four Color from the Lighting Style list. Action. ■ YZ Reflective GP from the Scene Style list.
7. Close the dialog boxes.
8. Save the file.
9. Close the file.
9. Move the slider to 15 seconds.
10. On the ViewCube, click the top-left corner.
11. On the Animation Timeline, click Add Camera Action.
12. On the Animation Timeline, click Go to Start.
13. On the Animation Timeline, click Play Animation.
Render the Animation
1. On the Render panel, click Render Animation.
2. On the Output tab, under Time Range, click Entire Animation.
3. Select the Launch Player check box to start the media player when the animation is complete.
4. Click Render.
5. Save the file as my_video.
6. This animation was created using 30 frames per second and took many hours to render. The settings were: Click OK. The Render Output dialog box is displayed. This animation will take a few minutes to render. To view a high quality rendering, navigate to the Video Demonstration folder for this exercise.
Create Phase ■ 19 Build Phase
Overview
In this phase, you build a simple tank tread drivetrain.
Phase Objectives
After completing this phase, you will be able to:
■ Apply the knowledge from the Unit 11: Creating a Tank Tread Drive > Think Phase to build a tank tread drivetrain.
20 ■ Autodesk's VEX Robotics Unit 11: Creating a Tank Tread Drive
Prerequisites and Resources
Before starting this phase, you must have:
■ Completed Unit 11: Creating a Tank Tread Drive > Think Phase.
■ Unit 1: Introduction to VEX and Robotics ■ Unit 4: Microcontroller and Transmitter Overview ■ Unit 5: Speed, Power, Torque, and DC Motors ■ Unit 6: Gears, Chains, and Sprockets ■ Unit 7: Advanced Gears ■ Unit 8: Friction and Traction ■ Unit 9: Drivetrain Design 1 ■ Unit 10: Drivetrain Design 2
Required Supplies and Software
The following supplies are used in this phase:
Supplies
VEX Classroom Lab Kit
Notebook and pen
Work surface
Small storage container for loose parts
Optional: Autodesk Inventor Professional 2011
VEX Parts
The following VEX parts are used in this phase:
Quantity Part Number Abbreviations
2 ANG-HH22-15-SK RevA A15
1 Antenna-Holder AH
1 Antenna-Tube AT
2 BATTERY-STRAP BST
6 BEARING-FLAT BF
Build Phase ■ 21
Quantity Part Number Abbreviations
12 BEARING-RIVET BR
4 Double Bogie Wheel TBD
4 DRIVE-WHEEL TS15
1 MICROCONTROLLER VMC
37 NUT-832-KEPS NK
1 RECEIVER RX75
4 SCREW-632-0250 SS2
20 SCREW-832-0250 S2
9 SCREW-832-0375 S3
8 SCREW-832-1000 S8
4 SHAFT-3000 SQ3
8 SHAFT COLLAR COL
140 TANK-TREAD-LINK TL
1 VEX-Motor MOT
Activity
Build a Tank Tread Drive
In this activity, you build a simple tank tread drivetrain. In the next phase, you will modify this drivetrain to climb an obstacle.
As you work on building this project, have some of your team members focus on expanding their expertise using Autodesk Inventor software. Later in the curriculum, you will be challenged to come up with your own creative solutions for robot design. You will save time and maximize your ability to create winning solutions if your team understands how to leverage the power of digital prototypes using Inventor.
22 ■ Autodesk's VEX Robotics Unit 11: Creating a Tank Tread Drive Note: Team members can download a free version of Autodesk Inventor Professional software to use at home, so you can come to class prepared to build and test your best ideas! To do this, simply join the Autodesk Education Community at www.autodesk.com/edcommunity.
1. Bolt together two Chassis Bumpers [A15] and two 25 Hole Chassis Rails [R25].
The completed model is as shown:
Build Phase ■ 23
2. To complete the next step: ■ Using Bearing Rivets [BR], attach two Bearing Flats [BF] to the 25 Hole Chassis Rails. ■ Bolt a Motor [MOT] to each of the 25 Hole Chassis Rails.
The completed model is as shown:
24 ■ Autodesk's VEX Robotics Unit 11: Creating a Tank Tread Drive
3. To complete the next step: ■ Using Bearing Rivets, attach two Bearing Flats to a 25 Hole Chassis Rail. ■ Bolt two Double Bogie Wheels [TDB] to the 25 Hole Chassis Rail. ■ Repeat to form a second assembly.
The completed model is as shown:
Build Phase ■ 25
4. Bolt the assemblies from step 3 to the main assembly from step 2.
The completed model is as shown:
26 ■ Autodesk's VEX Robotics Unit 11: Creating a Tank Tread Drive
5. To complete the next step: ■ Insert 3” Shafts [SQ3] into each of the four open holes in the Bearing Flats. While doing this, slide a Collar [COL] up between the Chassis Rails on the 3” Shaft. ■ On the outside of the Chassis Rails, slide a Plastic Washer [WP], a Tank Tread Sprocket [TS15], and a Collar. ■ Ensure that the Shaft is inserted into the motor clutch or bearing block fully, and tighten the Collars.
The completed model is as shown:
Build Phase ■ 27
6. To complete the next step: ■ Bolt two 5x15 Plates [P15] to the Main Chassis. ■ Bolt Battery Straps [BST] to the rear Chassis Bumper.
28 ■ Autodesk's VEX Robotics Unit 11: Creating a Tank Tread Drive
7. To complete the next step: ■ Bolt a VEX Microcontroller [VMC], an Antenna Holder [AH], and a Receiver [RX75] to the Main Chassis Assembly. ■ Plug the Left and Right Motors into Motor Ports 2 and 3 respectively. ■ Plug the Receiver into RX1. ■ Attach a Battery through the Battery Straps located on the rear Chassis Bumper and plug in to Battery Port.
Build Phase ■ 29
8. Install the Tank Tread Links [TL].
30 ■ Autodesk's VEX Robotics Unit 11: Creating a Tank Tread Drive
9. Your Tank Tread Drive is ready for action. Take it for a test drive, and pay careful attention to how it handles varied terrain!
Build Phase ■ 31 Amaze Phase
Overview
In this phase, you modify your tank tread drivetrain to climb an obstacle.
Phase Objectives
After completing this phase, you will be able to:
■ Modify robots based on new design constraints. ■ Create tank tread drivetrains of varying design.
Prerequisites and Resources
Before starting this phase, you must have: ■ Completed Unit 11: Creating a Tank Tread Drive > Think Phase. ■ Completed Unit 11: Creating a Tank Tread Drive > Build Phase. ■ Have an assembled Tank Tread Drive from Unit 11: Creating a Tank Tread Drive > Build Phase.
Related phase resources are:
■ Unit 1: Introduction to VEX and Robotics ■ Unit 4: Microcontroller and Transmitter Overview ■ Unit 5: Speed, Power, Torque, and DC Motors ■ Unit 6: Gears, Chains, and Sprockets ■ Unit 7: Advanced Gears ■ Unit 8: Friction and Traction ■ Unit 9: Drivetrain Design 1 ■ Unit 10: Drivetrain Design 2
Required Supplies and Software
The following supplies are used in this phase:
Supplies
Tank Tread Drivetrain built in the Unit 11: Creating a Tank Tread Drive > Build Phase
Notebook and pen
4’x4’ of open floor space
Measuring tape
32 ■ Autodesk's VEX Robotics Unit 11: Creating a Tank Tread Drive
Supplies
Masking or duct tape
3-4” high obstacle
Evaluation
In this challenge, you modify your tank tread drivetrain in an effort to climb a 3 to 4” high step.
Modification Instructions: ■ Take an exact measurement of your obstacle. A good example of an obstacle is a stack of textbooks. The surface of the obstacle should be wider than the robot. You will need to know this number to help design your modifications. ■ Brainstorm ideas of how you can possibly climb the obstacle. Record these ideas in your engineering notebook. ■ Sketch out some of your ideas. ■ Look back to the Think Phase from this unit to gather some possible ideas. Perhaps do some research and look at pictures of real life tanks. ■ Evaluate your ideas, and choose the one you think is best. ■ Implement your idea by modifying your tank tread drivetrain.
Obstacle Testing ■ Place your obstacle on the ground. ■ Drive your robot towards the obstacle. If the obstacle moves when the robot contacts it, you may need to tape it down to the ground. ■ If your robot successfully climbs the obstacle, you have completed the challenge. If not, examine what caused the robot to fail, and try modifying your robot accordingly.
Engineering Notebook
List three ideas/designs you had for modifying the robot to complete the challenge. For each idea, include a sketch and list of reasons why the idea was feasible, and a list of potential problems with the idea. ■ Rate each idea/design on the basis of its feasibility, complexity, and chance to succeed. ■ Explain the reason behind your choice of a final idea. What made this idea better than the others? ■ How would you modify your robot if the step was increased to ~6”.
Presentation
If your design was successful in completing the challenge, give a presentation on the key feature that enabled the robot to climb the obstacle.
If your design was unsuccessful, give a presentation on problems with your design. How would you change this design if given the time?
Amaze Phase ■ 33 STEM Connections
Background
Tank tread tracks are often used to move and maneuver bulldozers. These tracks are usually made of metal treads and therefore require regular lubrication and maintenance. But as mentioned in this unit, the advantage of the tank tread drive design for bulldozers is significant.
Science
■ What materials should a bulldozer tank tread be made out of? ■ What are the advantages of some materials over others? ■ Consider that some materials are more durable but perhaps less efficient. ■ Would your chosen material require lubrication or constant maintenance?
Technology
■ Some bulldozers with tank tread tracks cannot drive on roads, so they have to be transported from site to site by a big truck. ■ Can you think of a way to make a tank tread track convertible to allow for road travel? How would it work?
34 ■ Autodesk's VEX Robotics Unit 11: Creating a Tank Tread Drive
Engineering
■ Why can a bulldozer drive over material like sand or mud, which otherwise might cause a truck to get stuck?
Math
■ A description of the side view of a simple tank tread is as follows: Start with a three-foot by eight- foot rectangle. At each of the four corners, center a circle with a one-foot radius (representing the wheels). Wrap the whole thing with a single, tight band (the tread). ■ How long is the band? Suggestion: Make an accurate diagram; break the band into straight parts and curved parts. ■ Advanced version: Draw a side view of a tread vehicle, such as a tank or bulldozer, with as many wheels as you like, placed however you want. Compute the length of the tread.
STEM Connections ■ 35