Upgraded Kit of Parts Drivetrain · Project X001
An 8-wheel upgrade to FRC's standard Kit of Parts drivetrain.
Overview
X001, nicknamed "Kitbot on Crack," was a heavily modified version of the standard FRC Kit of Parts drivetrain. The goal was not to redesign the drivetrain from scratch, but to improve a proven base platform around the problems Team 4079 had repeatedly experienced in past seasons.
The design replaced the default 6-wheel drop-center layout with an 8-wheel drivetrain, added more secure bumper mounts, improved wheel serviceability, and used a flipped custom gearbox to open up more space in the center of the robot. It was still designed to stay compatible with the default Kit of Parts drivetrain configurations, including long, square, and wide.
Outcome
X001 produced a fully modeled upgraded Kit of Parts drivetrain that improved stability, serviceability, bumper mounting, and mechanism packaging space while staying grounded in the parts and manufacturing resources available to the team.
The project was later used as a design base for the Backlash and Overhang robot concepts. It also gave the team a reusable drivetrain idea that could be adapted across multiple seasons instead of starting from the default Kit of Parts drivetrain every year.
Problem & Goal
The standard Kit of Parts drivetrain is reliable and accessible, but the team had run into several quality-of-life issues with it over multiple seasons.
The 6-wheel drop-center layout caused the robot to sit slightly tilted, which could affect camera angles and vision consistency. Wheel replacements could also be frustrating because the middle wheel was harder to service. The default bumper mounting approach was another pain point because bumpers were slow to install, difficult to align, or prone to shifting and lifting during matches.
The goal of X001 was to keep the strengths of the Kit of Parts drivetrain while fixing the issues that made it harder to use in a real competition environment.
Design Requirements
- Improve drivetrain stability compared to the default 6-wheel drop-center setup
- Keep the robot flat to improve vision consistency and reduce angle fluctuation
- Make all 8 wheels easy to replace without removing side plates or gearboxes
- Create bumper mounts that are fast to install but still hard-mounted
- Prevent bumpers from falling off, lifting, or shifting during a match
- Add more center clearance for mechanisms
- Protect Falcon 500 motors from impact using aluminum plates
- Stay compatible with long, square, and wide Kit of Parts drivetrain configurations
- Reuse parts the team already had or parts included in the Kit of Parts where possible
- Minimize extra purchases and fabrication needs
Process
- 1Reviewed recurring drivetrain issues from previous Team 4079 robots
- 2Compared the default 6-wheel Kit of Parts drivetrain against the upgraded 8-wheel concept
- 3Modeled the 8-wheel layout in SolidWorks
- 4Designed the flipped gearbox for better center clearance
- 5Added motor protection plates around the Falcon 500s
- 6Designed new bumper mounts using standoffs, L brackets, and wing nuts
- 7Checked compatibility with the default Kit of Parts drivetrain configurations
- 8Created a pricing breakdown to understand what parts needed to be purchased, reused, or fabricated
Technical Decisions
- Used 8 wheels instead of 6 to keep the robot flatter and more stable
- Removed the default drop-center behavior to improve vision consistency
- Used dead axle wheel mounting so wheels could be replaced more easily
- Designed hard-mounted bumpers to prevent lifting or falling off during matches
- Used wing nuts for faster bumper removal and installation
- Flipped the gearbox to create more usable center space
- Added aluminum motor protection plates around the Falcon 500s
- Pocketed gearbox plates to reduce weight
- Kept the drivetrain compatible with long, wide, and square Kit of Parts layouts
- Prioritized parts the team already owned to reduce cost
Drivetrain Layout
The largest change was switching from the default 6-wheel drop-center drivetrain to an 8-wheel layout.
This helped keep the robot flat instead of naturally rocking on the center wheels. A flatter robot was useful for vision because the camera angle stayed more consistent while driving and aiming. It also made the robot feel more stable overall. This also decreased the effective wheelbase size, as the 2 center wheels are the effective wheelbase for any wheel scrub.
The 8-wheel design also improved maintenance. Instead of needing to remove a side plate or gearbox to access a difficult middle wheel, each wheel could be replaced by removing a dead axle bolt and nut.
Flipped Gearbox
The main mechanical feature of X001 was the custom flipped gearbox. By changing the gearbox layout, the design created more open space in the center of the drivetrain. This still utilized the Kitbot gears from the Toughbox Mini gearbox, but repackaged it for more clearance in the drivetrain.
That extra center clearance gave future mechanisms more room to package intakes, indexers, elevators, shooters, or other robot-specific systems. The gearbox also used aluminum plates to protect the Falcon 500 motors from impact and damage.
The gearbox plates were pocketed to reduce weight while still keeping the structure strong enough for drivetrain use.
Bumper Mounts
X001 also redesigned the bumper mounting system. The new bumper mounts used standoffs, L brackets, and wing nuts to make bumper installation faster while still keeping the bumpers hard-mounted.
The goal was to avoid bumpers falling off, lifting up, or shifting during a match or while the robot was being picked up. In the CAD, the nuts and bolts were also oriented for easier tool access because the team had struggled with tight hardware access on past drivetrains.
Kit of Parts Compatibility
X001 was designed to remain compatible with the default Kit of Parts drivetrain configurations.
The CAD showed the long configuration because that was the setup Team 4079 used most often, but the design was intended to work with:
- Long configuration
- Wide configuration
- Square configuration
This made the project more useful because the upgrade was not locked to one drivetrain shape.
Cost and Manufacturing
The design was planned around parts the team already owned, parts included in the Kit of Parts, and a small number of fabricated plates and purchased belts.
The pricing breakdown explored two different paths:
| Option | Notes |
|---|---|
| $450 voucher path | Reused older hardware such as churros, bolts, and nuts, with about $35.72 out of pocket |
| Opt-in drivetrain path | Included a new AM14U5 drivetrain with new hardware, with about $67.72 out of pocket |
The cost plan also noted that pulley extensions could potentially be 3D printed. This helped keep the upgrade realistic for an FRC team budget instead of becoming a fully custom drivetrain that required buying every part new.
What I Learned
- How to improve an existing COTS-based product instead of designing completely from scratch
- How small quality-of-life changes can make a drivetrain much easier to use at competition
- How wheel layout affects robot stability and vision consistency
- How to design a custom gearbox with pocketed plates
- How to package motors, belts, wheels, and structure inside a tight drivetrain
- How to design bumper mounts around real field and pit problems
- How to balance performance improvements with cost, part reuse, and fabrication limits
