Anxieti

Chonki
Year Of Creation	2020-2021
Versions
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!!!

Introduction

Anxieti is a classic undercutter with a modern twist. A heavy emphasis was placed upon serviceability and reliability, resulting in a design with easily swappable armor plates, drive modules, and a removable weapon block. Most of Anxieti’s design is relatively straightforward, with the main unique aspect being the slanted armor, meant to deflect direct hits to the robot and mitigate some of the absorbed energy. Anxieti competed at NHRL's March Qualifier, winning 3 matches and losing 1. The team qualified for the NHRL World Championship.

Members:

• Lucas McCarty (Lead)
• Todd Hayes (Mentor)
• Keaton Sadoski (Weapon Lead)
• Paul Matesevac (Chassis Lead)
• Evan Strakes
• Daniel Johnson
• Xiang Li
• Lucy Bricker

Chassis Subsystem

Anxieti has a rectangular footprint measuring roughly 12x18 inches at its widest. Side Plating in vertical planes was avoided, instead opting for smooth slanted sheets of Titanium (0.125 inches thick in all directions except for the front plate which is 0.25 inches). These smooth angled plates were meant to help deflect the energy from hits to the robot during combat and prevent Anxieti from absorbing the full force of other weapons. Furthermore, the chassis features a “skirt”, metal plating covering some of the distance between the bottom plate and the ground, helping to defend against Vertical Spinners or Beater Bars by preventing their access to a biteable ledge on the bottom of the robot.

The drive system features four inch Coulson wheels directly mounted to 1:16 gearboxes which are mounted to the chassis. Given the ½ inch shaft diameter for the gearboxes, concerns about lack of dual sided wheel support were minimal. Furthermore, the gearboxes are driven by two Turnigy Aerodrive SK3 - 4240-740KV Brushless Outrunner Motors. These gearbox+wheel+motor modules are easily swappable between rounds. In terms of electronics, two 5500 mAh 3s batteries were selected to run in series to get 6S voltage in a divided form factor. A closer view of the drive system and electronics is displayed below.

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.

Pros:

• 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!

Cons:

• 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.

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).

Electronics

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

Competitions

Motorama 2022

• Results: 2-2
  • Bracket Style: Double Elimination
    • [Chonkii (winner) V.S. Marathon (loser): YouTube Link]
      • This match saw Chonkii head to head with a drum spinner driven by this dude: https://www.reddit.com/r/battlebots/comments/twk4da/if_anyone_needs_an_angry_reaction_gif_for_after/
      • Chonkii got a bunch of good hits in, sparks flew multiple times.
      • Shove, wall, stay
    • [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"

Issues

• 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