Building a Drivetrain

A good drivetrain is the basis of a good robot, and the foundation (quite literally) upon which everything else you create is built.

What to Design For

A good drivetrain must be very mobile on the field for that particular year's game. It has to be able to avoid obstacles, push game pieces, and be durable and reliable. Each game is different in terms of what speed, mobility, and pushing power are needed, so these three concepts should be the main focus of the design and deciding what sort of drive train to use.

Types of Drivetrains

Tank

A tank drivetrain consists of (typically) 4 or 6 wheels total placed on the chassis so that each side has either 2 or 3 wheels. The left and right sides are generally driven independently of each other with motors and a gearbox on each side. It is most usually used with high-traction wheels.

Advantages to a tank drive:

Easy to design, build, and program
Relatively inexpensive
Can be geared for speed or torque (pushing power)
Easily driven

Disadvantages to a tank drive:

Less mobility and agility
Harder to navigate the field

A tank drivetrain is what team 1261 has most frequently used.

Mecanum

A mecanum drive train is very similar to a tank drivetrain, except they use mecanum wheels (wheels with rollers attached at a 45 degree angle from the direction of rotation) as opposed to high-traction wheels, and each wheel must be driven independently of the others.

Advantages to a mecanum drive:

Very agile and easy to move about the field
Easy to design and build

Disadvantages to a mecanum drive:

Wheels and extra gearboxes make it more expensive
Less pushing power
More difficult to program
Harder to drive

Slide

A slide drive train has a similar layout to a tank drive, but with an additional wheel in the center perpendicular to the rest. All of the wheels on this drivetrain must be omni-wheels (wheels with rollers attached at a 90 degree angle from the direction of rotation) in order for it to work.

Advantages to a slide drive:

More agile, able to translate left and right
Relatively easy to design, build and program
Relatively inexpensive

Disadvantages to a slide drive:

Cost is a bit higher due to omni-wheels and extra gearbox
No real pushing power

Holonomic

A holonomic drivetrain consists of 4 wheels positioned at 45 degree angles to the frame of the robot (one in each corner). Each wheel is driven independently, and wheels are generally omni-wheels.

Advantages to a holonomic drive:

Very agile

Disadvantages to a holonomic drive:

Some additional cost for wheels and extra gearboxes
No real pushing power
More difficult to build and program
Very difficult to drive

Swerve

A swerve drivetrain consists of 4 individual wheel modules that rotate to control the robot's direction of motion. These wheels are generally high-traction wheels.

Advantages to a swerve drive:

Potential for speed or pushing power
Very agile
The best type of drivetrain for moving around the field - very versatile

Disadvantages to a swerve drive:

Extremely complicated to design, build, and program
Difficult to drive
Much more expensive