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Year Of Creation 2020-2021
Current Version V 2.0
Update Year 2021-2022
Wins/Losses 2/2 Moto 1/2 AVC
Information and Statistics
Weight Class Featherweight
Weapon Class Shell Spinner
Combined Wins/Losses 3/4
Weapon Speed 1200 RPM (67 MPH)
Other Chonk!!!


This robot had a name before a design. It born when Brian thought to himself, "Hey, it would be really funny if we named a robot Chonki and made it really, really big and really really loud..." Throughout the design process the robot lived up to its name. Chonkii is a 45lb shuffling shell spinner competing in the 30lb weight class that serves as an iteration on the original Chonki, which was never fully constructed. It was developed during 2021-2022. The drive system was iterated from that of Apachi and Chonki. The weapon system was a brand new concept for BattleBots. The goal of Chonki was to evaluate the viability of shell spinners while taking advantage of the 1.5 times weight multiplier afforded by using a mechanism other than wheels for movement. Competed at Motorama 2022 and finished with a 2-2 record.


  • Mihir Nagaraj (Lead)
  • Brian Epstein (Mentor)
  • Janie Edgar
  • Sydney Baker
  • Thomas Jackson
  • Cole Sosnowski
  • Christopher Bellflowers
  • Emily Liu

Drive System

Chonki utilizes a shuffler system for drive. It consists of two shuffler modules, each with 4 UHMWPE feet. The feet sit on two parallel, keyed cam shafts. These allowed for the four feet to be positioned 90 degrees from each other, so feet would always be in contact with the ground through the cam shaft's rotation. To fit inside the feet get smaller as they move away from the chassis. The longer feet have fillets to clear the rollers and support which they sit under. The cams have offset keyed holes to accommodate the shafts and sit inside circular cutouts in the feet, which keep them parallel with the ground as it walks. The use of the shuffling system allowed Chonki a weight bonus, bringing the max weight to 45 lbs.



Foot Profile

The shuffler feet are shaped as such for several reasons. The decreasing lengths are such that the module will fit inside the circular profile of the shell. In the future, the lengths could be further shortened so that the modules could have armor plating in front of them in case a weapon is able to penetrate the shell. The downward slopes of the feet are to provide space for the rollers on which the shell rides. The needle roller bearings are placed into the circular cutouts.

Foot.PNG Foot2.PNG

Foot3.PNG Foot4.PNG

Cams and Bearings

The cam profile is updated from Apachi. This version allows for a single cam profile and greatly simplifies shuffler manufacturing. Using a shaft and key that we have a broach for would be better than waterjetting and removing taper with a jank key-turned-broach.

Cam1.PNG Cam2.PNG

Cam3.PNG Cam4.PNG

Drive Gears

The drive gears were offset at around a 45 degree angle. Replacement gears should be purchased as the tended to get worn down after prolonged use.


Weapon System

Design Considerations

Since the weapon on this bot also serves as its armor, it was imperative that the weapon be large enough for the robot to fit inside. An additional constraint was that it must be small enough that a reasonable thickness could be attained while still remaining under the desired percentage of the total weight of the robot (~50%).

Shell Design

Shell was milled out of a 250 lb block of A36 steel. It took forever but was very effective in absorbing damage.


  • Less expensive than the nested ring design
  • Made from one solid piece so it didn't have connection points to fail at
  • Lives up the it's name, super THICCC
  • Its SHINY!


  • Expensive, had to get Speed Machine to have them use a larger machine to mill the shell out.
  • One piece, parts that got damaged on shell were not replaceable - dents needed to be pressed or hammered out.

Weapon Shaft Interface

A tapered roller bearing fits into a housing that is attached to the top of the shell.

Bearing Section View.PNG

Weapon-Drive Mechanism

  • Inspired by Hyperpolarized, it was later decided to drive the weapon by using a single driven wheel at the top of the bot, with rollers along the surface to give additional support. A central shaft was used as a dead axle support.


Chassis System


  • The chassis mostly consisted of aluminum, featuring of a ¼” top and side plates and ⅛” bottom plate.
  • The front and back plates were made of HDPE, which bent to form Chonkii’s robustly round shape.
  • The chassis had multiple rollers spaced out along its top, giving additional support to the shell track above.
  • The central dead axle was constrained by two blocks, mounted to both the top and bottom plates. However, it was later determined that a single longer block with a key would constrain the shaft better than the two block system.
    • While drilling through the blocks into the shaft, a drill bit melted inside, acting as a makeshift pin (that was instantly destroyed in competition).


Overall, the drive and weapon were both undervotled and over capacity. The drive performed fine, but was a bit on the slower side. The weapon did not reach a high enough top speed (~1200 RPM max) to deal enough damage. Drive battery was approximately 60% depleted after each fight, and weapon battery was approximately 5% depleted.

Drive Motors Turnigy Aerodrive SK3 - 5055-280KV Brushless Outrunner Motor

Drive Motor Controllers Flipsky Dual FSESC6.6 Based upon VESC6 with Aluminum Heatsink Mini Size (was too big)
Weapon Motor Scorpion SII-4035-250KV
Weapon Motor Controllers Tribunus 06-120A (6S) Brushless ESC
Receiver Hobby King 2.4Ghz Receiver 6Ch V2
Remote Control Hobby King 2.4Ghz 6Ch Tx and Rx V2
Battery Turnigy Heavy Duty 5000mAh 6S 60C LiPo Pack w/XT90
Turnigy Graphene Panther 3000mAh 3S 75C Battery Pack w/XT90


Motorama 2022

  • Results: 2-2
    • Bracket Style: Double Elimination
      • [Chonkii (winner) V.S. Marathon (loser): YouTube Link]
      • [Chonkii (loser) V.S. Yahoo (winner): YouTube Link]
        • Really good fight. Chonkii caught maybe 4 feet of air several times. Shuffles kept working, demonstrating robust design.
        • turtle
      • [Chonkii (winner) V.S. Pigeon (loser): YouTube Link]
        • Wedge plated in titanium. Weapon was at about 50 percent speed and sent a bunch of sparks.
        • Trick shots, smacked off titanium front plate
      • [Chonkii (loser) V.S. Lockout (winner): YouTube Link]
        • Forfeit (5 thou)
        • Over-tightened a single screw mounting the drive motors, causing the chassis to become grounded and lots of sparks when turning on the bot. This took 25 minutes to diagnose, and we only had 20. We subsequently removed the screw and everything worked fine.
    • Robojacket Rumble
      • [Chonkii vs Everyone: YouTube Link]
        • Cost RJ much money.
        • Probably won't do this again.

AVC 2022

  • Results: 1-2
    • Bracket Style: Double Elimination
      • [Chonkii (winner) V.S. Boost (loser): YouTube Link]
        • Expecting to get immediately bum-rushed by the flipper, Chonkii took evasive action directly into the wall
        • After a little shuffling, we bent their front and they tapped out
      • [Chonkii (loser) V.S. Wedgeham (winner): YouTube Link]
        • So we kind ajust got pushed around for a bit without having enough not to spin up the shell
        • After being pushed around, we got launched onto the wall where we stayed for the remainder of the match
      • [Chonkii (loser) V.S. Yahoo (winner): YouTube Link]
        • The rematch of the century was cut short by a wire that was: too short
        • This was caused by us removing our 3D printed esc enclosure because we "didn't want to put it back in"


  • Weapon
    • Weapon speed is too slow to inflict a ton of damage
    • PAIN to manufacture (for someone else)
      • When you turn a 250lb block of steel into a 22.5lb shell, the other 227.5lb becomes chips that someone (Ben) has to deal with
    • Weapon wheel drive does not maintain consistent contact with track
    • Shell is too high off the ground, undercutters = scary
    • Once one hurricane deforms it is the only one that is hit
  • Drive
    • Not enough traction to win in a pushing match
    • Needs more protection, if it got hit it would likely be destroyed
  • Chassis
    • Too big and not dense enough
    • No self righting mechanism

Changes to make

  • Weapon
    • Spring load weapon drive wheel
    • Add another weapon motor to increase reliability and top speed
    • Smaller weapon motor to decrease bot height
    • Switch to angled shell to deflect hits instead of absorbing them??
    • Increase number of hurricanes/teeth
    • Make hurricanes/teeth one part
    • Make hurricanes/teeth replaceable
  • Drive
    • Improve traction
      • Wooden arenas: join blade meta
      • Magnets on shufflers
  • Chassis
    • Optimize wiring and make everything more compact
    • Reduce overall diameter and add extra weight to weapon
    • Self righting mechanism
      • Active: piston with a spike on it?
      • Gigabyte bar


  • The Vectrax was rendered inoperable twice by Chonki members (mainly Brian) during its construction.
  • At AVC people recognized Chonkii, likely because it is so loud and obnoxious. The noise from Chonkii was both a blessing and a curse. Everyone would come watch our matches because the sound of the shufflers on the steel floor summoned them, but they had to grab hearing protection first.
  • During its fight with marathon, Chonkii shattered their S7 weapon hubs by being XTRa thicc.