An Introduction to Moby: the 2021-2022 VRC Hero Bot


Each year, the V5 Hero Bot is designed from the VEX V5 Competition Starter Kit to provide teams with a starting point to play the current VEX Robotics Competition game. It is intended for experienced teams to be able to quickly assemble a robot to investigate the game's dynamics and for new teams to be able learn valuable building skills and have a robot they can customize to compete with early in the season.

The 2021-2022 VRC Game is Tipping Point. View this page for more information on the game and how it is played. This season's Hero Bot to play Tipping Point is Moby. You can view Moby’s build instructions for more information.

For game definitions used throughout this article, an overview of the game rules, and scoring, view the Game Manual for Tipping Point.

This article to introduce to Moby will include:


Scoring Capabilities

Moby can score in the following ways:

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Scoring Preload Rings into a Mobile Goal.

Each side of Moby’s Forks can hold up to two Rings, which leaves plenty of capacity to handle all three of the Preload Rings.

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Pick up Rings from the Field to score in Mobile Goals.

Rings can be picked up off the Field’s floor using Moby’s Forks.

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Lift Mobile Goals and move them into the Alliance Home Zone.

The Forks can be lowered to slide under the edges of a Mobile Goal. The Forks can then lift and pick up the Mobile Goal to be carried into the Alliance Home Zone.

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Place Mobile Goals to be elevated on the Alliance Platform.

After a Mobile Goal has been picked up it can be placed on your Alliance Platform. Note that Moby can only place a Mobile Goal on the Platform with the Mobile Goal in it's possession, this is because Moby's design cannot reach high enough to place Mobile Goals on the Platform when the Platform is already balanced.

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Elevate your robot on the Alliance Platform by driving on the platform until it is balanced.

Moby’s Forks can be used to lower the Alliance Platform when it is balanced. This will allow Moby to drive up on the platform.


Design Features

Two of Moby's prominent design features are its 2-motor direct drive drivetrain and its compound gear ratio 2-motor lift for the Forks.

2-Motor Direct Drive Drivetrain

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Moby has a 2-motor direct drive drivetrain. This makes for an easy to assemble and effective drive for the robot.

Direct drive refers to having the shaft go directly from the motor to the wheels without using gears or a chain and sprocket system.

The two motors power the rear wheels making this a rear-wheel drive robot.

For more information on drivetrains, view this article from the Knowledge Base.

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The drive wheels are Omni Directional Wheels.

Omni Directional Wheels have rollers around the circumference of the wheel which allows the wheel to roll in two directions - frontwards/backwards and sideways.

The Omni Directional Wheels will allow for easy turning of the robot. Moby turns about the center of the Forks to make lining up to Mobile Goals easier.

Compound Gear Ratio 2-Motor Lift for Forks

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Anyone who has ever tried to pick up a broom by holding onto the very end of its handle has experienced rotational torque.

With the mobile goals weighing in between 1520 grams and 1810 grams, depending on the goal, it takes a large amount of rotational torque to lift the Mobile Goals with the Forks.

This torque is generated by using a compound gear ratio.

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The first shaft has the 12 tooth driving gear which is powered by the motor.

The second shaft has a 36 tooth driven gear.

This 12 tooth gear into a 36 tooth gear provides a 3:1 gear ratio.

The second shaft rotates at 1/3 the speed of the motor, however, it has 3 times the rotational torque.

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The second shaft also has a 12 tooth gear on it which becomes the driving gear.

The third shaft (screw) has a 60 tooth driven gear attached directly to the Fork.

This 12 tooth gear into 60 tooth gear provides a 5:1 gear ratio.

Combining the two gear ratios of 3:1 and 5:1 form a compound gear ratio of 15:1

Moby has two motors in a motor group and both of them have the 15:1 compound gear ratio between the motors and the Forks. At nearly 15 times the two motors’ rotational torque, this provides plenty of rotational torque to pick up any of the Mobile Goals on the Field.


Tips and Tricks for Programming Moby with VEXcode V5

Configuring Moby's Drivetrain

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Follow the steps in this article from the Knowledge Base for general information on how to configure a 2-motor drivetrain.

To configure Moby's specific 2-motor drivetrain, select port 1 for the left motor and port 10 for the right motor.

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To ensure the settings are adjusted for Moby’s physical dimensions:

  • change the track width from 295 mm to 375 mm.
  • change the wheelbase from 40 mm to 0 mm.

Note: a 2-wheel drive drivetrain only has one drive shaft on each side of the robot, so it will have a 0 millimeter wheelbase.

For more information on track width and wheelbase, view this article from the Knowledge Base.

Configuring the Fork's Motor Group

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To control both motors together, the Fork’s motors need to be placed in a Motor Group.

For more information on building with Motor Groups, view this article from the Knowledge Base.

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Follow the steps in this article from the Knowledge Base for general information on how to configure a Motor Group.

To configure the motor group for Moby's Forks, select port 2 for Motor A and port 9 for Motor B.

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To ensure Moby's Fork motors drive in the correct direction together in the motor group, toggle the port 9 motor to reverse.

Configuring Moby's Controller

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The V5 Controller can be configured to drive Moby as well as control the Forks.

Follow the steps in this article from the Knowledge Base for general information on how to configure a controller.

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Any of the button groups on the controller can be used to control Moby’s Forks.

Note: Moby’s Forks must be configured first before configuring the controller.


V5 Competition Template

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Remember if you are planning on taking Moby to a competition, they will be using a field control system.

You will need to create your project using the Competition Template example project.

For more information on using example projects, view these articles from the Knowledge Base:


Adding V5 Sensors

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Moby’s chassis has been designed to easily add any of the V5 Sensors. The Tipping Point game robot rules allow up to 8 motors as well as pneumatics. This allows for plenty of customization to your Moby Hero Bot.

For more information on V5 Sensors, view this section of the Knowledge Base.

You can also view this article on Virtual Moby used in VRC Virtual Skills to see examples of how sensors can be added to Moby.