Drivetrain and Framing Possible configurations of a robot base, and pros and cons of each. Robotics 101

Robot Base Overview The robot Base generally has three major components: −Frame −Drivetrain −Controls Robot base construction −Standard KOP frame Flexible, low cost, but heavy −Custom designed thin gage aluminum Very lightweight, not flexible to changes, built from CAD Good success with this style of base in past years Will use this base style again unless game requires something different −Climbing over obstacles, open front for collector mechanism, etc.

Robot Base Overview The robot “Drivetrain” has several major components: −Wheels or Tracks −Motor or Engine −Transmission/Gearbox −Chains/Belts A robot needs a robust base and drivetrain to: −Move quickly and efficiently −Push other robots out of the way −Precisely control where it is so that it can perform tasks −Provide stable base to mount scoring mechanism −Easy access to controls and battery change −Low center of gravity #1 Rule- Our robot should never tip over

Wheel Options Traction wheels- coefficient of friction close to 1 −AndyMark standard KOP wheels Low cost, good traction, can’t replace tread Plastic wheel frame may break −AndyMark Plaction wheels Higher cost, excellent traction, replaceable tread Plastic wheel frame may break −AndyMark Performance wheels Much higher cost, excellent traction, replaceable tread Very durable −VEXpro Colson wheels Low cost, great traction, can’t replace tread Very durable for low price point

Wheel Options Lower Traction Wheels −Omni Wheels Low sideways friction (rollers), decent forward/reverse traction Very easy to push robot around −Used when turning is more important than pushing −Mecanum Wheels Rollers at 45 degree angle so robot can drive in all directions Highly maneuverable but easy to push robot around Difficult to program

Drivetrain Layout Principles Center of Gravity −Mass concentration and where it is acting on your robot Center of Turning −Point at which the robot will rotate about Effective Wheelbase −Wheelbase in contact with the ground WB COG COT

Axle Options Cantilevered Side Supported “Live” “Dead”

Drivetrain Options 6 Wheel Tank Drive with “Dropped” Center Axles −Relatively easy to turn and drive straight Can turn in place with 2 CIM’s per side −Most popular choice among FRC teams −Standard design for Team 1507

Drivetrain Options West Coast Drive (WCD) −Cantilevered Axles −Direct Drive to One Wheel, #25 Chain to other Live Axles −Hex Axles −Fast Removable Wheels −Welded Tube Chassis

Drivetrain Options 4 Wheel Swerve Drive −Robot can drive in all directions, incredibly maneuverable −Very complex to design, build, and program −Would require off-season to develop if we wanted to pursue this option

Drivetrain Options 4 Wheel Omni Drive −Wheels 45 Degrees in Corners of Chassis −Very Maneuverable −Loss of pushing force in all directions compared to a tank drive Kiwi Drive −Wheels 120 Degrees apart −Very Maneuverable −Loss of pushing force in all directions compared to a tank drive

Drivetrain Options Mecanum Drive −Wheels located in same orientation as a 4WD −Uses Force Vectors from wheel rollers to translate −Expensive −Fairly easy to build with COTs wheels −Difficult to program effectively −Requires a lot of Driver Training

Six Wheel Robot Base Linkage Wheel Motor Gearbox Motor Gearbox High traction wheels CIM Motors Belts or Chains: Transfer Power To Wheels Transmission/ gearbox

Gearbox Function Gearbox Wheel Motor Single speed gearbox Standard KOP Ratio: 12:1 Torque From Motor Increased By 12X Speed from Motor Reduced 12X Gearbox Function: Convert Motor Speed to Wheel Torque through a series of gears 2 speed shifting speed gearbox Low gear = 6:1 ratio for pushing High gear = 24:1 ratio for speed Pneumatics used for shifting gears

Team 1507’s Base and Drivetrain CAD demo of last year’s robot AndyMark Scavenger Hunt