Mecanum Drivetrain V2
This section outlines the steps required to build a mecanum drivetrain using the Mecanum Drivetrain Kit V2 (REV-45-2470). The Mecanum Drivetrain Kit V2 uses UltraPlanetary Gearboxes and Ultra 90 Degree Gearboxes for a direct drive rather than one driven with belts or chain. For instructions on how to build a mecanum drivetrain with belts and pulleys check out the Mecanum Drivetrain Kit or for a mecanum drivetrain with sprockets and chain see the Channel Drivetrain - Mecanum Upgrade.
This design is a great starting point. However, modification may be required to address the specific needs of the robot being designed.
The assembly of this drivetrain can be broken into a few sections. This allows for a team of people to work on different tasks to complete the build quicker. Each Section Begins with what parts and the quantity of parts needed to complete the steps in that section. A list of all required materials for the drivetrain is listed below.
Kit Options
This drivetrain can be built out of the following options:
FTC Starter Kit V3.1
Mecanum Drivetrain Kit V2
Full Bill of Materials
Required Tools
UltraPlanetary Gearbox Assembly
Gear Ratio Choices
The Mecanum Drivetrain Kit V2 comes with four of the UltraPlanetary Gearbox Kits with HD Hex Motors. This is an entry point into using the REV UltraPlanetary System. There are three UltraPlanetary Cartridges supporting seven different final gear reductions ranging from nominally 3:1 to 60:1. This allows for the right amount of torque for the application at hand. The motor provided already has the pinion gear pressed onto it making assembly of gearboxes easier.
When getting started with this drivetrain, it is recommended to use a nominal 20:1 Gear Ratio. This uses the UltraPlanetary 5:1 Cartridge and the UltraPlanetary 4:1 Cartridge. For more information on all gear ratio options, load ratings, and more, see the UltraPlanetary Gearbox User's Manual.
UltraPlanetary Assembly Parts Required
PART NUMBER
DESCRIPTION
QTY.
UltraPlanetary Assembly Steps
Attach the UltraPlanetary Mounting Plate to the HD Hex Motor using two 8mm Button Head Screws.
Note: Use the 2mm Allen Key to tighten these screws.
Seat the UltraPlanetary 5:1 Cartridge onto the input pinon.
Note: Placing a finger on the output of the 5:1 Cartridge and turning it helps for placement.
Seat the UltraPlanetary 4:1 Cartridge onto the UltraPlanetary 5:1 Cartridge.
Note: Placing a finger on the output of the 4:1 Cartridge and turning it helps for placement.
Seat the UltraPlanetary Output Stage onto the UltraPlanetary 4:1 Cartridge.
Note: Placing a finger on the output of the Output Cartridge and turning it helps for placement.
Insert six of the 30mm Cap Head Screws into the holes in the outer ring off the Output Cartridge.
Tighten these screws down until they are snug not tight using a 2.5mm allen wrench.
Note: The 30mm length is the 2nd longest screw provided with the UltraPlanetary Gearbox Kit.
Drive Rail Assembly
Motor Pod Assembly
Motor Pod Assembly Parts Required
PART NUMBER
DESCRIPTION
QTY.
REV-41-2081
5mm Hex Shaft, 20mm
4
REV-41-2082
UltraPlanetary Face Mount Spacer
4
M3 x 40mm Socket Head Cap Screw
16
Motor Pod Assembly Steps
Ultra 90 Degree Gearbox Installation
Insert the 20mm long hex shaft into the output of the gearbox.
Place the Face Mount Spacer on the output of the the gearbox as shown.
Note: Line up the short edge of the spacer with a flat side of the UltraPlanetary gearbox body.
Rotate the hex shaft output so that it lines up with the hex input on the Ultra 90 Degree Gearbox.
Slide the two gearboxes together. Rotate the Ultra 90 Degree Gearbox until the spacer and gearbox body line up.
Insert the 4 mounting screws in the holes on the end of the Ultra 90 Degree Gearbox. Ensure that they line up with the holes in the spacer and the gearbox.
Tighten the 4 mounting screws hand-tight. Then alternate between slightly tightening screws diagonally across from each other in an X shaped pattern.
Note: Take care not to over tighten the mounting screws.
Drive Rail Assembly
Drive Rail Assembly Parts Required
Drive Rail Assembly Steps
Mount a Universal Hex Adapter to each Mecanum wheel using 4 - M3 8mm Screws After completing this step you will have 4 assembled mecanum wheels.
Slide the following onto a 90mm long 5mm Hex Shaft. Make 2 of the Right Wheel Shaft assembly - 3mm Spacer (Or 2 - 1.5mm Spacers) -15mm Spacer -Right 75mm Mecanum Wheel -Shaft Collar The Shaft Collar should be flush with the right side of the Hex Shaft.
Slide the following onto a 90mm long 5mm Hex Shaft. Make 2 of the Left Wheel Shaft assembly - 3mm Spacer (Or 2 - 1.5mm Spacers) -15mm Spacer -Left 75mm Mecanum Wheel -Shaft Collar The Shaft Collar should be flush with the right side of the Hex Shaft.
Fasten 2 Motor Pod Assemblies with 16 - M3 6mm Hex Head Screws total in between two pieces of C Channel The output of the Ultra 90 Degree Gearbox will line up with the 2nd large (9mm) hole from each end of the C Channel
The Ultra 90 Degree Gearbox should have 4mm of thread engagement with each screw. If you do not have 6mm screws to use for your assembly, please use washers or a spacer of approximately 2mm thickness on the outside of the C Channel.
Fasten 4 - Plastic 90 Degree Brackets to the top and bottom of the back side of the C Channel facing inwards as shown in the image. Load the brackets fully with 5 - M3 8mm Hex Cap Screws and 5 - M3 Nyloc Nuts each.
Insert the Left Wheel Shaft Assembly into the Ultra 90 Degree Gearbox that is closest to the plastic brackets. Insert the Right Wheel Shaft Assembly into the Ultra 90 Degree Gearbox that is at the front of the drive rail
Secure both Wheel Shafts with a Shaft Collar
Fasten 4 - Plastic 90 Degree Brackets to the top and bottom of the back side of the C Channel facing inwards as shown in the image. Load the brackets fully with 5 - M3 8mm Hex Cap Screws and 5 - M3 Nyloc Nuts each.
Insert the Right Wheel Shaft Assembly into the Ultra 90 Degree Gearbox that is closest to the plastic brackets. Insert the Left Wheel Shaft Assembly into the Ultra 90 Degree Gearbox that is at the front of the drive rail
Secure both Wheel Shafts with a Shaft Collar
Make sure the Mecanum Wheels form an "X" shape when they have been fastened to the Drive Rails
Final Assembly
Final Assembly
Final Assembly Parts Required
Final Assembly Steps
Slide the Left and Right Drive Rail on each side of 2 pieces of 248mm C Channel
Tighten the Nyloc Nuts on each bracket to secure your drivetrain
Drivetrain Complete
Mecanum Wheel Setup and Behavior
Mecanum wheels, when properly set up on a drivetrain, allow for omni-directional movement. Each Mecanum Wheel Set (REV-45-1655) comes with a two right (REV-41-1656) and two left (REV-41-1657) mecanum wheels. This is determined by the direction of the leading edge of the rollers. If the rollers point left it is a left wheel and if they point right it is a right wheel.
Each side of the chassis needs one left and one right wheel. Mecanum Chassis also require four motors for operation.‌
To know if your Mecanum Wheels are properly configured look from the top down on the drivetrain. Following diagonal lines created from the angle of the rollers should form an "X" as shown above.‌
Mecanum Wheel Drivetrain Behavior
Running all four wheels in the same direction at the same speed will result in a forward/backward movement, as the longitudinal force vectors add up but the transverse vectors cancel each other out, as shown below.‌
When both wheels on one side of the drivetrain are moving in one direction while the other side is moving in the opposite direction results in stationary rotation of the drivetrain. The transverse vectors cancel out but the longitudinal vectors combine to generate rotation around the central vertical axis of the drivetrain, as shown below.‌
When the right mecanum wheels run in one direction while the left mecanum wheels run in the opposite direction allows for a strafing movement, as the transverse vectors add up but the longitudinal vectors cancel out.‌
Using the above concepts in tandem through varying motor power to each wheel type allows for the drivetrain to move in different, angled vectors.
