FTC:Drivetrain

Drivetrain

In FIRST Tech Challenge, the drivetrain refers to the part of the robot that allows it to move around the field. It is mainly composed of motors, wheels, and a chassis to hold all these things and other subsystems together. By combining these three things together in different ways, many different types of drivetrains can be made.

Types of Drivetrains

Name	What Is It	Pros	Cons
2-Wheel	A two-wheel drivetrain consists of two moving wheels and two non-moving wheels. The design can have moving wheels in the front or the back, but they should be across from each other.	Easy to set up and fix Easy to control Good for demos or learning basics	Bad Maneuverability
4-Wheel	It has 4 wheels that are moving. This method can use 2 or 4 motors depending on the driver’s preference or how many motors subsystems will need.	Very similar to the 2-Wheel, but it’s easier to turn	Bad Maneuverability
6-Wheel	Very similar to the 4-wheel drivetrain, however, each side has 3 wheels.	Very stable Easy to go over rough terrain	Bad Maneuverability Uses a lot of power to move 6 wheels Takes up a lot of space
Tank	A tank drivetrain uses treads powered by 1-2 motors on each side.	Very stable Easy to go over rough terrain	Very bad Maneuverability Slow
Mecanum	This drivetrain requires mecanum wheels and 4 motors to work. The special wheels need to spin in different directions in order for the robot to strafe.	Precise movements Omni- Directional	Can’t go over terrain very well
Holonomic	Similar to the mecanum drivetrain except the wheels are oriented at 45° angles on the corner of the robot. This drivetrain uses Omni wheels orientated this way to allow good control over the robot.	Very maneuverable	Angled corner wheel placement makes it hard for motors to be attached
Kiwi	A triangular-shaped drivetrain that has Omni wheels on the corner (at 60° angles) or the side of the robot.	Omni-Directional Only Uses 3 motors	Can fit more things in a square robot Can’t go over rough terrain
H-Drive	This type of drivetrain has a basic 4-wheel drivetrain with Omni wheels. However, in the center are 1-2 perpendicular wheels that allow the robot to strafe. These wheels need suspension if the field uses rough terrain.	Maneuverable and sturdy at the same time	Suspension needed for middle wheel otherwise it is impossible to go over terrain Slower strafing
Swerve	Swerve Drive are a unique type of drivetrain that can be very strong in defense. THey have multiple pods that are able to rotate independently of each other providing good maneuverability while maintaining high strength and defensibility.	Strong and Manueverable Good Defense Innovative	Complex

There are also many different kits that most major FIRST part vendors will sell. These are typically very simple and easy to use, however, not very customizable.

Motors

Name	Uses	Pros	Cons
NeveRest Orbital 20 Gearmotor	Good for use in high-speed drivetrains	High speed Reliable	Can’t adjust tension for a chain drive easily Low torque
NeveRest 40	Good for use in driving	Decent Torque and Speed Easy adjustment of chain tension	Uses a D pattern axle
REV Ultra Planetary Gearmotor	High-speed subsystems and driving	Durable Easy to change the gearbox	Can’t adjust tension for a chain drive easily
REV HD Hex Motor 20:1 Planetary	High-speed subsystems and driving	High Speed	Can’t adjust tension for a chain drive easily
REV HD Hex Motor 40:1	Good for driving and for high torque subsystems	High Torque Durable	Decent speed
goBilda 5202 Series Yellow Jacket Planetary Gear Motor	Good for subsystems and driving. It can be put into a goBilda U-channel	Many options on torque and speed Uses a D axle	Can’t adjust tension for a chain drive easily
goBilda 5203 Series Yellow Jacket Planetary Gear Motor	Good for subsystems and driving. It can be put into a goBilda U-channel	Many options on torque and speed Uses a hex axle	Can’t adjust tension for a chain drive easily

Wheels

Wheels are what your robot sits on. Using certain wheels enables different types of motion. Remember that the robot doesn’t have to have all the same types of wheels. Get creative with how wheels can be used to advantage the team.

Name	Pros	Cons
Mecanum	Allows for strafing/omnidirectional movement Fast	Less stable due to rollers
Omni Wheel	Omni-directional movement Light Smaller and thinner	Less efficient total directional movement than mecanum Omni wheel’s movement has points where it is rough or harder to control due to the way the wheels are designed
Stealth Wheel	Moving is more consistent	Can only move forward and backward

If you want to learn more, here is a quick video we made that covers the wheels in more depth.

Chassis

The chassis is the base to support everything, including subsystems, on the robot. The motors and wheels are attached onto the chassis in order to move it around. It is mainly composed of strong support beams or plates connected together to form a strong base for a robot. There are many different part providers that provide the necessary parts for a chassis. There are even some kits for this.

Ways to Power the Types of Drivetrains

There are many different ways to connect wheels to motors in FTC. These types of connections, or drives, can be used to amplify power/torque or speed.

Name	What Is It	Pros	Cons
Bevel Gears	Two perpendicular gears that turn against each other. An axle is connected to each bevel gear. One axle leads to the wheels and one leads to the motor. The motor powers one gear to spin, turning the other one, therefore, turning the wheel.	Changeable speed and torque based on gear ratio Small	Not very durable, the gears can grind a lot
Chains	Two sprockets are connected together by a chain with a motor at one end. The other end has the wheel that spins with the motor. This motor is connected to a sprocket that powers the whole system. The other sprocket is connected to the wheel so it can turn and an optional sprocket can be placed in between these two to tension the chain. This tension prevents the chains from slipping off.	Customizable gear ratios to get higher speed or torque	Chains slip off easily Takes up a lot of space
Belts	This system is very similar to a chain drive except it uses belts instead of chains. Also, It doesn’t always need an additional sprocket or wheel to keep it tensioned. If it uses stretchy belts this is unnecessary.	Sometimes provides its own tension based on the type of belt you buy Changeable speed and torque based on gear ratio	Belts can slip easier
Direct Drive	The motor is connected directly to the wheel and spins with it.	Fast Takes up a very small amount of space	Motors take a lot of damage and strain Not very strong