Drivetrains

Drivetrains

A drivetrain is the moving base of a robot. It includes the wheels, motors, gears, and frame that let the robot travel around the field. Picking the right drivetrain is one of the most important decisions your team makes — it affects how fast, how strong, and how maneuverable your robot will be.

There are four common drivetrain types in VEX robotics:

• Tank Drive
• Mecanum Drive
• X-Drive
• H-Drive

Why does this matter?

The drivetrain you choose shapes every other decision on the robot. A slow, powerful drivetrain suits pushing matches. A fast, agile drivetrain suits games that require quick movement and precise positioning.

Tank Drive

Tank Drive is the most classic and simple drivetrain. The left wheels are controlled by one set of motors, and the right wheels are controlled by another set — just like the tracks on a military tank!

• How it moves: To go straight, both sides spin forward together. To turn, one side spins forward while the other spins backward.
• Pros: Great traction and pushing power. Hard for opponents to shove around. Also easy to build and easy to code.
• Cons: Cannot slide directly sideways — it must turn to change direction.

Mecanum Drive

Mecanum Drive uses 4 special mecanum wheels. These wheels have small rollers attached at a 45-degree angle around the rim. By spinning the four wheels in different combinations, the forces cancel out in certain directions and push the robot sideways!

• How it moves: Spin all four wheels in specific combos to move in any direction — forward, backward, left, right, and diagonally — without turning the robot.
• Pros: Very agile. Great for quickly lining up with a goal or game piece.
• Cons: More complex to code, and the 45-degree angle means some pushing force is wasted — it cannot push as hard as a tank drive.

X-Drive

An X-Drive uses four regular omni wheels, but each wheel is pointed outward at a 45-degree angle, making the robot look like the letter “X” from above.

• How it moves: Like mecanum drive, it can move in any direction by combining different wheel speeds.
• Pros: Extremely fast — about 1.41 times faster than tank drive using the same motors! Also very agile and great at turning quickly.
• Cons: Complicated to build correctly (must be a perfect square), and has low pushing power because the force is split between directions.

H-Drive

H-Drive looks like a normal tank drive, but with one or two extra wheels mounted sideways in the center of the robot. From above, it looks like the letter “H.”

• How it moves: The outer wheels handle forward, backward, and turning like a normal tank drive. The center sideways wheel is controlled by a separate motor and handles sliding left and right.
• Pros: Simpler to code than X-Drive or Mecanum. Keeps full tank drive pushing power when going forward, but can still slide sideways.
• Cons: If the field is slightly uneven, the center wheel may lose contact with the ground and stop working. Also requires an extra motor just for the center wheel.

Each drivetrain type needs different code and controls to drive well. Make sure your programming matches your drivetrain choice!