Direct Drive - Slip Clutch Needed?


I’m contemplating a direct drive outrunner project, and I’m wondering if some kind of clutch/mechanical overload prevention device is advisable in this system.

I’m new to the world of ESCs and BLDC Motors, but I do know that ROV thrusters (pretty similar to this application) usually include a magnetic coupler or similar device to prevent damage if something lodges in the propeller.

This provides safety to both man (hand jammed into prop) and machine (slip instead of break).

Do the current overload protections available with an ESC make this unnecessary? Or should we still be looking at using a friction clutch of some kind with systems like this?

I think you’re probably adding unnecessary complication to the setup.
Even the commercial units don’t have this function. Using a duct should be all of the protection you need from hand jam and most types of rope/prop interference. I think it’d be a nice to have rather than a need to have as the likelihood of requiring it is slim. Just my opinion though so if you do decide to proceed with it please put up lots of pics and build info so others can use it if its viable

There is definitely a safety risk involved that could be reduced somewhat with a clutch. Damage to the machine is unlikely i think though. I can’t see any shock loads in the normal use of this thing, and preventing stall (and thus overheating) shouldn’t be needed with a pilot who’s awake, and/or a motor controller with thermistor probe in the motor.

A normal magnetic clutch will need at least a couple more bearings to support the second shaft. Spec’ing the magnets and spacing to get it to slip at a specified torque will be the hard part.

However, as @Foxyirish1987 said, it’s not really mandatory, and the added complexity will lead to added bulk/resistance, increased price, and (likely) lower reliability. Super cool though!

Good luck!

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