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Combat Robots Wiki

Drive ESCs

The electronic speed controller converts the receiver’s servo signal into motor power.

Brushed drive ESCs

Section titled “Brushed drive ESCs”
  • Dual-channel combat ESCs drive both sides from one board, take two servo inputs, and often mix onboard. Purpose-built units (e.g. Just ’Cuz WEKA, Repeat Dominion) are the default for brushed beetles and usually include a BEC.1
  • Key ratings: continuous current per channel, peak current, cell count (voltage), BEC output.
  • Features to want: drag brake, direction reversal, a drive calibration routine, and a proper signal-loss failsafe (outputs to neutral).

Brushless drive ESCs

Section titled “Brushless drive ESCs”
  • Drone ESCs running AM32 (preferred) or BLHeli_32 firmware. Beetle-size sensored motors are rare, so this is almost always sensorless with a combat-tuned firmware profile.
  • Dual combat AM32 ESCs (e.g. Repeat Dual AM32) mix onboard and have a BEC and working current limiting; single 35 A drone ESCs (HakRC, Flycolor Raptor5, or the pre-flashed JCR-RC Mini) are the cheap route — most drone ESCs have no BEC, so power the receiver from one that does.1
  • Configure via ESC firmware: bidirectional / 3D mode on (reverses from centre stick), timing medium, startup power max, brake on stop on, stuck-rotor/stall protection off (it trips on hard acceleration), sinusoidal startup off, and a defined signal-loss behaviour.231

Sizing current

Section titled “Sizing current”

Peak drive current per side ≈ stall_current × n_motors_per_side; full-throttle reversals briefly approach it. On a drone ESC the printed rating assumes propeller airflow and won’t be met sealed in a robot — pick a proven ESC for the class rather than trusting the number. Undersized or over-trusted ESCs overheat and cut out mid-match.1

Arming

Section titled “Arming”

A drive ESC set to bidirectional mode only arms when it sees centre stick. If it’s left in unidirectional mode it won’t arm from centre and may drop into throttle-calibration mode instead.1

Failsafe

Section titled “Failsafe”

Every drive ESC path must bring the motors to a safe stop on radio loss. Verify it on the bench: power the robot, arm it, then switch the transmitter off — drive must stop within a fraction of a second. This is a ruleset requirement and is checked at tech inspection.4 See Radio systems & failsafe.

References

Section titled “References”

Footnotes

Section titled “Footnotes”

  1. Ping, L., with L. Skotiniotis, I. Talbert & D. Tran. Beetleweights for Dummies (Fall 2025 revision) — builder-maintained beginner guide distributed via the NHRL Discord. Sections: Brushed Motors & ESCs; Brushless ESCs; Programming ESCs. ↩ ↩2 ↩3 ↩4 ↩5

  2. AM32 ESC firmware and the AM32 wiki. ↩

  3. BLHeli / BLHeli_S firmware; browser config via ESC-Configurator. ↩

  4. SPARC Robot Construction Specifications, v1.4, 2023 — failsafe requirements for drive and weapon systems. ↩