FIRST Robotics Competition

To create a design that would be both extensive enough to reach the highest pegs and shelves and compact enough to rotate approx. 140 degrees into an intake position and maintain a low center of gravity, we chose a telescoping arm. Because the arm had an end load consisting of the end effector and game piece, we opted for a chain-driven design (as opposed to cables or constant force springs that are prone to slipping or inaccuracies). This required is to power the motor in order to both extend and contract. The stages are made from 1/8" thick aluminum square tubing in 2", 1.5", and 1" widths. This creates a perfectly-sized space between the walls of each stage to fit 0.5" hex bore bearings, aluminum hub sprockets, shaft end screws to retain the sprockets and #25 series roller chain. The stages also feature alignment caps made from custom 3D printed housing and 1/2" diameter Olite sleeve bearings. This constrains the stages from moving vertically. Nylon blocks fixed to the bottom of each stage provide additional alignment. Some of the blocks also doubled as chain anchors, as they contained tapped holes for screws to fasten a link of attachment chain to the bottom of each stage, driving the cascading extension. 

Extension and contraction is powered by a Falcon 500 brushless motor on a MAX Planetary gearbox with a 15:1 ratio.

A polycarbonate track for a shaft and pulley were added to create a tensioning system for the Energy Chain cable protectors that house the wires powering the arm and end effector motors. A constant force spring wrapped around the pulley shaft and fixed to the top of the track causes the Energy Chain to form a loop when the arm is retracted, preventing wire tangles or snags when rotating the arm. 

Full Arm CAD Model: https://cad.onshape.com/documents/d48c2bd920206d53d5dc5d57/w/7d4e2be4fa45a6219a88cd23/e/2617f170b44b558e64d12485?renderMode=0&uiState=659c85f100f5b4501dfe69ad 

For the 2023 season, our team had another unique goal: design and build our own custom chassis (in lieu of using the "kit chassis" provided to FRC teams each year). This specific custom chassis was designed to combat issues of tipping and instability that were common to kit chassis robots due to the center wheels being dropped slightly below the four corner wheels. Since the 2023 season game involved reaching high and far out of our frame perimeter and balancing on the tilting dock, we decided that stability was especially important. 

Like the kit chassis, this custom chassis was created using 1/8" aluminum sheet with 90 degree bends in varying directions. This provided us with a lightweight yet sturdy base upon which to build our robot. Sets of mounting holes in 0.5" increments along the frame allows the chassis to be cut to multiple sizes and orientations, permitting re-use for future years. 

Since we wanted out intake design to be inside the frame perimeter, the chassis features a cutout in the front.

The inner rails have mounting holes for a WCP Single-Speed gearbox, upon which we mounted two REV Neo brushless motors. For this specific game, we used a 19:1 overall ratio in the gearbox to balance speed and pushing power. 

To combat issues of turning scrub while maintaining enough traction to drive up on the slippery polycarbonate dock, we used Andy Mark Plaction wheels in the center and on intake side, and VEX omnidirectional wheels on the scoring side. 

We were very fortunate to partner with DJ Fabricators, a local sheet metal shop, to machine our alumnium chassis components.

Full Chassis CAD Model: https://cad.onshape.com/documents/32bcb0ae05544741cc846332/w/e0daef972eebaed4ca1d964c/e/1f97d70a2b3ed4128aab7378?renderMode=0&uiState=65a31bdf6159a84d0c976985 

Aiming to manipulate both cones and cubes, we designed an end effector with the proper geometry to grip cones and cubes in various orientations. The compliant wheels on the ends of the claw are designed to compress the cone between them when the claw is closed. They are attatched via shafts on hex-bore ball bearings, which allow the wheels (and therefore, the cone) to rotate freely. Since the base of the cone is heavier than the tip, and the depth of the claw permits the base of the cone to pass completely through, this results in the cone self-righting into the proper position for placing on the peg while the arm rotates from intake to placing position. Earlier iterations used custom end plates with ball-and-socket mounting in order to form to the angles of the cone, but this was swapped out for higher compression and more flexible "pads" (now wheels) to ensure a firmer grip.

The claw is actuated using a Neo 550 brushless motor on a planetary gearbox with a 125:1 ratio. The motor drives one claw "tooth" via a timing belt and 3D printed pulleys, and the other tooth moves in tandem via an aluminum gear meshed with a matching gear on the driven tooth. The large gear ratio was intended to prevent the claw from opening on its own, thus dropping a game piece. However, we ended up experiencing compression issues due to slack in the timing belt, so we ended up re-designing the motor mount to be directly on one of the tooth gears.

This is a technical drawing (generated from the Onshape CAD model) of the sheet metal for the hood of our ball shooter on our 2022 FRC robot. Two copies were machined out of 1/8" aluminum (one right and one left version). The design includes lightening holes to decrease weight, a hole for a 0.5” hex shaft, and rivet holes to mount the back part of the hood. 

This component of the hood assembly was intended to be attached to a snowblower motor with a hex output shaft so that the hood could be positioned at multiple angles depending on the robot’s distance from the goal. Due to time constraints and changes in strategy, we later opted to fix this component to the other (static) component at one angle.

This is a technical drawing (generated from the Onshape CAD model) of the other sheet metal component for the hood of our ball shooter on our 2022 FRC robot. This is the “static” component that mounts to 2x1 aluminum tube stock which frames our vertical ball conveyor (see full robot CAD). The design features lightning holes to decrease weight, mounting holes for the tube stock, rivet holes for the back part of the hood, mounting holes for the snowblower motor intended to pivot the dynamic hood component, and a 1.125” bearing hole.

Due to the original design including a pivoting dynamic hood component, the hex shaft to hold the flywheel was originally going to be supported by another piece of sheet metal. However, when the pivoting hood was deprioritized and screwed in at a fixed angle to this static component, the bearing hole housed the hex shaft for the flywheel. 

This is a technical drawing (generated from the Onshape CAD model) of the sheet metal plate for the flywheel gearbox on our 2022 FRC robot. Two of these plates were cut, mounted on either side of a piece of 1x1 aluminum tube stock, and fitted with bearings, hex shafts, one central 42T spur gear, and two 14T spur gears for the output shafts of the motors. The output, therefore, has a 3:1 gear reduction for the purpose of decreasing the spin-up time of the 6” diameter flywheels between shots and having enough torque to launch the ball despite 1-inch compression on the ball. The design features lightning holes for weight reduction, two sets of mounting holes in a CIM motor bolt pattern (we used Falcon 500 brushless motors), bottom mounting holes for the 1x1 tube stock, holes for standoffs, and a 1.125” bearing hole.

Physical Assembly of Flywheel Gearbox