Spin Reaper

Difficulty

Advanced

BYOB Kit

$105

Build Time

4-8 Weekends

Arena

Combat · Freestyle

Overview

Dead washing machines contain beefy brushless DC motors capable of 1000+ RPM with serious torque. Harvest one, mount a hardened steel bar or disc, and you've got the heart of a spinning-weapon combat bot that hits like a freight train. This is the heavyweight arena build — not for the faint of heart.

This build requires metalworking skills, respect for kinetic energy, and serious safety awareness. A spinning weapon stores enough energy to shatter plywood and bend steel. Build it right or don't build it at all.

The Build

This is a real combat robot build. You're working with high-RPM rotating mass, high-current LiPo batteries, and steel construction. Every safety measure exists because someone learned the hard way.

Remove the back panel of the washing machine. Front-loader direct-drive motors are bolted to the drum shaft — typically 3-4 bolts and a wiring connector. The motor is a large pancake-style BLDC with a stator and rotor. Remove both as a unit. Cut the wiring harness with 12 inches of lead.

Test the motor with the VESC: connect the three phase wires, run detection, and spin it up slowly. These motors produce serious torque at low RPM and terrifying speed at full throttle. Start at 10% power.

Mount the weapon shaft through the chassis with the included bearings. The hub mount connects the motor to the shaft. Attach your steel bar or disc to the hub with the grade 8 bolts. Balance the weapon: spin it at low speed and check for vibration. An unbalanced weapon will shake the entire bot apart.

Weld or bolt the chassis from steel plate or aluminum box section. The project files include plans for a 30-pound class wedge bot with top-mounted horizontal spinner. Key design points: low center of gravity, weapon motor protected by armor on all sides, battery compartment with foam padding, and accessible master switch.

Mount the drive motors with wheel hubs on the rear of the chassis. Wire to a dual ESC controlled by the RC receiver. Tank-style steering: each drive motor runs independently. Keep drive wiring separate from weapon wiring — the weapon motor pulls 60+ amps at full spin and will brownout the drive system if they share a battery.

// RC channel mapping
CH1 → Drive left motor
CH2 → Drive right motor  
CH3 → Weapon speed
CH5 → Weapon enable (safety)
// ... full wiring in project files
  

The master power switch with lock-out key disconnects ALL power — drive and weapon. The weapon ESC requires a two-step arming sequence: CH5 switch ON, then CH3 throttle up. If CH5 goes OFF at any time, the weapon brakes immediately. Test this sequence 20 times before your first spin-up. Your life depends on it working every time.