FIRST Robotics - Minibot

Since this was an off season project I wanted to try some designs that our team had never used before. The beavertail design was a known FRC design that used plastic tubing capture balls from the ground and store them in the robot. This design works by dragging balls to the center of the mechanism with tubing and pulley assemblies on the sides. Then a main stretch of tubing drags the tennis balls into the robot. I used Onshape to design all the custom parts and create the entire assembly.

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We were going to add a ramp to this design so the tennis balls could get the chassis and into the robot, but our initial testing showed us that the beavertail design was not effective. the tubing was not gripping or centering the tennis balls well enough, and it was clear that this design was not going to work.

We decided the intake needed a complete redesign, and we chose a modified verson of a mechanum grip intake mechanism. We have used similar intakes in the past, and they have worked well and are more simple to build.

This design uses mechanum wheels, which have one directional angled rollers imbedded in the wheels. These effectively grip and center balls by pushing them against the robot's safety bumper. Once centered, I decided to use plastic tubing to carry the balls up and over the bumper. Because the mechanum wheels would predictably center and position the tennis balls, using tubing here would be effective and could drag the tennis balls along a ramp.

I also made this design in Onshape, importing parts like the motors, bearings, and mechanums while creating parts like the sideplates, ramp, spacers, and the tubing.

Intake V2 Side Plate

This intake design requred custom sideplates to support the mechanum grip shaft, the tubing shafts, and the motors. I made this part in Onshape and used construction lines to map out the geometry to determine the best locations for the band, mechanum, and motor shafts.

When possible, we like to test our custom parts via rapid prototyping before making the final version. I laser cut two of these plates out of cardboard to test the geometry. We assembled this intake design with the cardboard plates and determined that the mechanums would successfully capture the tennis balls and the tubing grip them with the right amount of compression.

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Once I finalized the design for this piece, I used our CNC mill to cut the final sideplates out of lexan, a flexible material that keeps its shape. I chose to use lexan for the plates because it is durable and its flexibility does well with impacts.