Building with VEX V5 Motor Groups – VEX Library

When building a custom VEX V5 Robot, sometimes you just need more power. One easy way to do this is to add another motor. These two motors working together are known as a motor group.

How motor groups are mechanically tied together

In order for two motors to work together they need to be mechanically connected in some manner.

Some methods of connecting motors together mechanically include:

Angled view of two Motors sharing the same parallel drive shaft.

Both motors share the same drive shaft.

Angled view of two Motors sharing the same set of gears.

Both motors share the same gear set.

Angled view of two Motors sharing the same chain and sprocket system.

Both motors share the same chain and sprocket system.

Angled view of two Motors that are each powering a Motor on the same side of a Drivetrain.

Both motors have wheels on the same side of the drivetrain.

The importance of motor spin direction

When two motors are working together it is very important that the direction each motor is spinning does not fight with one other. The orientation of the motors to one another will determine which direction each will need to spin. A typical robot arm with two motors working together to lift the arm is an example of how this works.

Angled view of two Motors that are connected to Gears and are powering a robotic arm from either side. In this case, the motors should spin in opposite directions. A label indicates that the drivem gear on the right must spin counterclockwise.

In this case, the driven gear attached to the right side of the arm will need to rotate counterclockwise for the arm to lift. Since the driving gear needs to rotate in the opposite direction of the driven gear on the arm, the right motor of the arm will need to spin the smaller driving gear in a clockwise direction.

Angled view of two Motors that are connected to Gears and are powering a robotic arm from either side. A label indicates that the driven gear on the left must spin clockwise.

However, on the left side of the arm the driven gear will need to rotate in the opposite direction or clockwise. This also means the left motor will need to spin in the opposite counterclockwise direction.

Angled view of two Motors that are each powering a Gear and facing each other. Arrows indicate that the Motors must spin in opposite directions.

As a general rule, if the two motors in a motor group are facing each other as in the application with the arm above, the spin of one motor in the motor group will need to be reversed so the motors do not fight against one another.

Angled view of two Motors that are each powering a Gear and facing the same direction. Arrows indicate that the Motors must spin in the same direction.

If the motors are facing in the same direction, then both motors in the motor group will need to spin in the same direction.

VEXcode V5 Devices Motor Group menu after the Motor ports have been selected. There are options to change each motor's drive direction, and the option to reverse the second motor has been selected and is highlighted.

When using VEXcode V5, it is very easy to reverse a motor within a motor group. This can be done when you are adding the motor group as a device.
For more information on configuring a motor group in VEXcode V5, view this article from the VEX Library.

Applications in which motor groups will be helpful

The principles of mechanical advantage tell us whenever:

More weight needs to be lifted.
More distance needs to be traveled.
More speed is needed.
More force will be needed.

These principles can be seen with robot arms as well as drivetrains.

Robot arms

Angled view of a V5 Single-swing Arm with a passive scoop added to the end of it.

A single swing arm may be able to lift light things with a single motor. However, if the arm needs to lift a heavy object, a second motor may be necessary.

Angled view of two Motors powering a 6-Bar Arm.

When designing advanced arms such as a six-bar or a double-reverse four bar, two motors will be required. This is because these arms are capable of lifting objects higher and faster.

Drivetrains

Angled view of a Drivetrain that has four Motors each powering a wheel.

When designing a drivetrain you may want to go faster, climb steeper, or push more with your robot. A four motor drivetrain will allow you to accomplish this.

Screenshot of the Drivetrain 4-motor option in the VEXcode V5 Add a Device menu.

VEXcode V5 has a DRIVETRAIN 4-motor device which will allow you to program your drivetrain.
For more information on configuring a 4-Motor Drivetrain, view this article from the VEX Library.

However, a 4-Motor Drivetrain device limits your robot turns to pivot turns. If your robot navigation requires different turns, motor groups can allow these.

Using Motor Groups for different types of turns

A skid-steer robot is a robot which turns by adjusting the speed and direction of the drive wheels on each side of the robot. The types of turns are:

Top down view of a 4-motor Drivetrain build with a circle and a point that represent its center of rotation when performing a pivot turn. The center of rotation is directly in the center of the 4 motors. VEXcode V5 Blocks project that reads When started, spin LeftDriveMotors forward and then spin RightDriveMotors reverse.

Pivot turns: this type of turn pivots on a center point between the drive wheels. This happens when the drive wheel/wheels on one side of the robot move in reverse to the drive wheel/wheels on the other side of the robot. This type of turn is helpful when the robot needs to turn in place.

Top down view of a 4-motor Drivetrain build with a circle and a point that represent its center of rotation when performing a drag turn. The center of rotation is in between the motors on the right, directly opposite the spinning motors on the left. VEXcode V5 Blocks project that reads When started, spin LeftDriveMotors forward.

Drag turns: this type of turn has the pivot point on the side of the robot. This happens when the drive wheel/wheels on one side of the robot move forward or reverse and the drive wheel/wheels on the other side of the robot do not move. This type of turn can be helpful when lining up with a game piece.

Top down view of a 4-motor Drivetrain build with a circle and a point that represent its center of rotation when performing an arc turn. The center of rotation is far to the right of the robot and not in between any set of motors. VEXcode V5 Blocks project that reads When started, set LeftDriveMotors velocity to 50% and then set RightDriveMotors velocity to 25%. Next, spin LeftDriveMotors forward and then spin RightDriveMotors forward.

Arc turns: this type of turn has the pivot point located outside of the drivetrain of the robot. This happens when the drive wheel/wheels on one side of the robot spin at a faster or slower speed than the drive wheel/wheels on the other side of the robot. This type of turn allows for a shorter travel distance when navigating around obstacles.