Motor Selection

This is really important knowledge for any new mechanical project that you are starting. Generally you go for Brushless DC Motor.


For every new project you start, you need to write out the specifications for what kinds of motors you are looking for. Then, you can go to

Default choice: Turnigy Sk3 6374

Example of specs (found from HobbyKing) Turns: 18T
Voltage: 12S Lipoly
RPM/V: 149KV
Internal resistance: 0.021 Ohm
Max Loading: 70A
Max Power: 2250W
Shaft Dia: 8.0mm
Bolt holes: 32mm
Bolt thread: M4
Weight: 840g
Motor Plug: 4.0mm Bullet Connector Here are the things that I see Voltage (V) Amperage (A) power

Nm (static torque?)




  • Bus voltage
  • Max modulation
  • Load mass Rotor inertia Pulley circumference or screw pitch Radius Reflected inertia Peak brake power Brake resistor resistance

Conversion constants I by kv to Nm

Encoder Encoder resolution Linear resolution Max speed

And then where does this gearbox equation fit in?

Motor Vendors

I saw James Bruton use Torqueboard motor 6374 from turnigy I saw questionable reviews.

Next Steps

Once you have selected the motor, you need the right Electronic Speed Controller (ESC) if it’s not built into the motor?

  • And then you need the right battery

Just buy a