Self-engaging dc motor

[kahlenberg]

Hi,
Is there a DC motor that can automatically engage and disengage? I couldn't find any, so it seems it's not a standard feature.
The idea is that when current is applied, the motor will "connect" to a shaft or gearwheel and start spinning. When no current is applied, the motor will "disengage" from the gearbox mechanism or shaft, allowing the shaft to turn freely without the friction of the motor.
How is it called?
Thanks.

 

[barry]

It most certainly isn't a 'standard feature'. You will need some kind of mechanical "inertial clutch" (I made that term up, I think) such that when the motor starts spinning, it will force some mechanical engagement. I envision something like a flyball gizmo. (Disclaimer: I am not a mechanical engineer).

You could also think about an electric clutch, so that when power is applied to the motor, it is also applied to the clutch.

 

[BradtheRad]

An automobile starting motor is like that. You turn the key to 'ignition', it revs up, its small attached gear jumps to engage a large gear on the chief engine.

Then you let the key set to 'running' as soon as you hear the engine running. The starter motor shuts off and disengages.