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FIRST Robotics - Minibot

My Senior year of high school was largely disrupted by covid. As a result my Robotics team had to drastically cut its hours and our season was largely disrupted due to the absence of a new game. To keep our members engaged, we started working on a side-project a display minibot that could pick up tennis balls. For this project, I did most of the development for our minibot's intake mechanism, including all of the CAD and designwork.

Intake V1 - Beavertail Design

Beavertail Intake CAD.JPG

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.

Intake V2 - Mechanum Grip

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.

Minibot Intake.JPG

Intake V2 Side Plate

Intake Side Plate CAD.JPG

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.

Final Test and Design Reflection

Feel free to watch the first drill test of the final intake design!

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The biggest lesson I learned from leading the design of this intake is that simple designs are some of the best. I tried making the beavertail design because it was new to our team. The design is very niche and overcomplicated, and it did not work well. Altering a simple and familiar design took much less time to make and worked way better than the beavertail.

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When working on my future projects, I will remember how simple designs can be some of the most effective and conserve the most resources.

Relevant Skills

Onshape

Used for custom side plate design and assembly creation

CNC Mill

Used to manufacture custom lexan plates

Lathe

Used to cut down hex shafts and spacers to exact size

Manual Mill

Used to manufacture metal brackets

3D Printing

Manufactured mecanum wheels, ramp, and pulley wheels

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