FRC 2021 Game Bot Design

Diag. R17.1: 3D Printing of Swerve Module Components

Given the usage of 3D printed plastic wheels, a goal of the robot was to keep weight to a minimum.

The overbumper intake when retracted keeps the robot dimension within sizing restriction. During game play, it can be raised and lowered to protect the intake. The captured Power Cells are guided by mecanum wheels and filtered toward the custom gateway. 

With filtering happening at the intake, the Power Cells are fed directly to the linear indexer and conveyed to the single vertical flywheel. 

The hooded single flywheel is constructed of evenly spaced ThunderHex stock pieces running the width of the flywheel. This is in contrast to the use of a solid curved plate for most hooded flywheels. In this instance, because the game object is rather large, the gaps between the rods in the hooded flywheel do not pose an issue. 

Robot Design Learnings

What Worked Well

This robot represents an improvement over Ref 1. The macro design conception of this robot seeks to overcome the limitation of the earlier iteration while still working within the budget constraint.

The team attempted the transition to a Swerve Drivebase. The swerve drivebase is a worthwhile investment for any team as it allows the robot considerably more flexible movement. Programming for a Swerve Drivebase is significantly more complicated than a tank drivebase, but once the knowledge base is built, the code can be recycled from year to year. This represents a progress in the team's capability.

Having learnt in Ref 1 that a wall is needed at the intake to guide the ball towards the centre feeder for the indexer, this robot was designed with a backwall at the intake. However, see below on the limitation when executing this design

What Could Be Improved

Working within the budget constraint, 3D printing was deployed for a number of components. There is a reason why 3D printing is predominantly used for prototyping. 

3D printing wheels with the initial 50% infill setting to reduce printing time had a significant drawback. Within a few hours of usage, the center around the axle had warped and cracked relative to the perimeter of the wheel. The wheels were reprinted with 80% infill and lasted a while longer. Despite that, by the end of the season, (at the end of the recordings for the COVID-19 at Home challenges), other 3D printed components such as the pulleys were damaged, rendering the swerve drive barely usable. 

The indexer and launcher for this robot functioned well enough. However, the wall at the intake was not constructed of a sufficiently rigid plate (calibrated for cost and weight). At certain positions, the wall flexed backward resulting in the ball jumping over the intake's barrier rather than moving along the wall to go through the gate. 

Diag. R17.2: Mecanum Wheeled Intake Pathing