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VEX IQ Curriculum - Mechanisms

Drivetrains (Grades 4-8)

Mobile and Competition robots will vary greatly depending on the tasks they are designed for. However, one thing common among them is that they usually have some method for moving. The robotic subsystem that provides the ability to move is often known as a Drivetrain. Drivetrains may come in many different forms – two examples are wheels or treads (like a tank). The wheeled, rolling drivetrain is the most common one found in competition robotics and one of the most popular in the entire industry.

Drivetrain Design

The most basic, multi-functional competition robot Drivetrain design consists of:

  • A rectangular Chassis (the structure of a mobile robot that holds wheels, motors, and/or any other hardware used to make up a Drivetrain)
  • Two Motors
  • Four Wheels
  • Gears transmitting Power from the Motors to all Wheels

The Clawbot IQ Standard Drive Base is one example that you can build. However, Drivetrains can come in all shapes and sizes - some don’t provide power to all wheels, use different types of wheels, or are not even a rectangular shape! Whatever the details of your Drivetrain, you should always be aware of a property known as Turning Scrub.

Turning Scrub is the friction that resists turning. This friction is created from the wheels dragging sideways on the ground as a robot (or other mobile vehicle) turns. The greater the Turning Scrub in a Drivetrain, the harder it is for a robot to turn. Turning Scrub in a basic Drivetrain can be easily managed and minimized in two ways:

1. Make sure that the Wheelbase (distance between Drivetrain wheels) is wider (side-to-side) than it is long (front-to-back):

VEX IQ Turning Scrub

2. Use different wheel and/or tire types to reduce the friction of Turning Scrub:

VEX IQ Turning Scrub