Running motor by itself: bad?

[FFF_Ferret]

So I'm building my first TRex 450, and I have a newb question: is it bad to spool up the motor, mounted in the heli, but with either no blades attached, or without even the main gear in place? Does it hurt the motor at all to run it with so little (or no) load against it?

I'm not saying I need to do this frequently: I just wanted to make sure the throttle was actually responding to stick input. Just wanted to make sure I didn't harm the motor doing it.

[ahahn]

This seems to be another "urban" legend that running a motor unloaded is bad for it.

As long as you are using the same voltage pack that it was designed to be used with, everything will be fine. After all, if you are running a 100% throttle curve, the motor rpm is probably around 80% of that unloaded rpm.

Now with that being said, the motor is making some heat, just the no-load current times the pack voltage. In a normal flying heli there will be some airflow from the rotor wash for cooling purposes. So don't run it for a really long time without some airflow over the motor (although an out runner shell is constantly rotating which provides some cooling and airflow in the motor).

[FFF_Ferret]

Thanks, that's exactly what I wanted to know.

Makes sense about the heat. I didn't run it long enough to even get warm. But it's good to know this isn't intrinsically bad for the motor.

[desertstalker]

Heat wont be an issue, the motor has its own fan (even the scorps but less effective) rotor wash for a motor is practically nothing as you are so close to the hub.

Just keep in mind if you are using a governor, it may not peform very well without the inertia of the drive train so the esc may hesitate or RPM may oscillate. Wont hurt anything but it can be a bit weird.