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2-Wire Motor 393

P/N: 276-2177 Make your robot stronger.

The 2 Wire Motor 393 provides 60% more output power than the standard motor, which allows for more powerful mechanisms and drive bases.

  • Strong, steel internal gears.
  • No clutches needed.
  • Shaft coupler (included) replaces the clutch.
  • 2-Wire Motor Ports: Connect directly (Cortex only).
  • 3-Wire Motor Ports: Use with the Motor Controller 29.
  • Can be configured into a “high speed” version.
  • Has 60% more torque than the 3-wire VEX Motor.

The 2-Wire Motor 393 does not have an internal motor controller.

Technical Specifications

Kit Contents

  • (1) VEX 2-Wire Motor 393 Module
  • (1) Inventor's Guide Insert
  • (2) 6-32 x 1/4“ Screws
  • (2) 6-32 x 1/2” Screws
  • (1) Change Gears Set
  • (1) Motor Coupler
  • (1) Motor Post


  • All VEX Microcontrollers (V0.5 requires use of a Motor Controller 29)
  • All VEX Square Shafts 0.125“ (3.2mm)
  • 2-Wire Motor Ports
  • 3-Wire Motor Ports (with a Motor Controller 29)


  • Free Speed: 100 rpm (As Shipped) / 160 rpm (High Speed Option)
  • 1.67 N-m (14.76 in-lbs) (As Shipped)/1.04 N-m (9.2 in-lbs) (High Speed Option)
  • Stall Current: 4.8A
  • Free Current: 0.37A

All motor specifications are at 7.2 volts.


  • Motor: 0.192 lbs (87.1 grams)
  • 6-32×1/4” Screw: 0.0014 lbs (0.617 grams)
  • 6-32×1/2“ Screw: 0.00209 lbs (0.948 grams)
  • Motor Coupler: 0.004 lbs (1.814 grams)
  • Motor Post: 0.002 lbs (0.907 grams)

Actual weight of one item (no packaging)

Motor Internals

The 2-Wire Motor 393 is simple to disassemble and examine. It consists of DC motor, small circuit board, all-metal compound gear reduction train, and plastic housing. The circuit board provides a very simple circuit that attaches the two power wires to the motor through an over-current protection device:

Over-current Protection

The orange component is a PTC which will interrupt the flow of current to the motor if it rises above a certain threshold for long enough. The PTC is marked “HR30-090” which indicates a device rated for continuous use at up to 30V and 0.9A. According to the specifications, the device is guaranteed to trip within 7.1 seconds of continuous exposure to 1.8A, and will trip more quickly when exposed to higher currents or is operated above “room temperature”.

This PTC is primarily a current limiter, but will trip at lower currents the hotter it gets. Since it is in contact with the side of the motor, it is reasonable to assume the device will trip more quickly and/or at a lower current as the motor heats up. This allows the PTC to also serve in a limited capacity as thermal protection for the motor.

Reduction Train

The metal gear reduction train is made up of the motor's drive gear, three compound gears, and the output shaft. The drive gear has 12 teeth, the 1st compound gear is 48t:11t, and the 2nd compound gear is 49t:12t. These are all located under the rear (green) cover and are not intended to be changed. The final reduction gear and the output shaft are accessible by removing the front (black) cover, and can be configured either for high-torque (as shipped from the factory) or high-speed (using the alternate gear set).

  • For the high-torque configuration, as shipped from the factory, the final (3rd) compound gear is 33t:10t which drives the output shaft with 32 teeth. This makes the high-torque reduction train ratio approximately 156.8:1.
  • For the high-speed configuration, using the alternate gear set, the final (3rd) compound gear is 33t:14t which drives the output shaft with 28 teeth. This makes the high-speed reduction train ratio approximately 98:1.

Given these reduction train ratios, the no-load motor speed is approximately 15,680 RPM.1)

vex_robotics_platforms/vex_edr/motors_and_controllers/motors.txt · Last modified: 2017/05/25 00:20 by