slowgo wants to know what is the purpose of the brake on an ESC ?

It keeps the propeller for free-wheeling in the wind when you cut the power.

Ken

The brake is simply a "reverse" current applied to the motor which slows it or 'brakes' (as in brakes in a car) the propellor shaft rotation.

I am currious why you douldn't want the motor to freewheel during flight, I hear that can help extend flight times.... since i do reember that on those rubberband windup planes, the props freewheled, and that worked good at slowing them down[8D], am I correct or wrong or what??

Some ESC equipped gliders also have folding props. That's actually the way to really cut down the drag, which is why gliders have folding props. With a folder, the brake will stop the rotation with some authority which helps the folding action.

Also, it's to your advantage with any airplane that doesn't have gear to get the prop to stop horizontally. Lots of park flyers have no gear. Landing that kind of model can be a problem with the prop windmilling. It's guaranteed the prop will hit the ground with whatever blade is coming around the down side as the plane is about to settle in softly. And you can forget about the softly when that happens. With a brake you have a 50-50 chance of the blade stopping out of the way. If it doesn't, you blip the throttle and you got another chance.

That would be great if it would actually work. But you can't get something for nothing. To extend the flight time the prop has to actually be pulling the plane, and that requires that power be applied to the motor which will spin the prop which will pull the plane. When the prop is freewheeling it is just obeying Newton's third law!!!

Ken

Whether a prop has less drag freewheeling or braked has a lot to do with its pitch to diameter ratio. A plane gliding at 30 mph with a 3.75x12 3-D prop would have the prop windmilling at about 8400 rpm with the tip speeds at about 300 mph. At 300 mph, there is a lot of air drag, even if the tip is lined up with the airflow. If the prop is stationary, it sees an airspeed of 30 mph. Prop blades that see 30 mph wind have a lot less drag than at 300 mph, even with the prop's blade broadside to the airflow.

Rubberband powered freeflight planes have slow turning props with a very coarse pitch. Such a prop might only be windmilling at 1000 rpm at 30 mph. On this kind of prop, there may be less drag if the prop is allowed to freewheel.

I was thinking of using like a OWB to let the prop "freewheel" and thus create less resistace...???

OWB?

one way bearing, to let it "overide the motor", it is a car tem, sorry I did't explain what it was[8D]

As RCKen noted, a freewheeling prop probably won't create less resistance.

Freewheeling props almost always create more drag than stationary ones.

BTW, you don't need a OWB for the prop to freewheel. They freewheel the same direction the motor turns them.

The brake function on most esc's can be programed to be on hard, on delayed (factory default setting), or completely off. I have it completely off on my plane. With a APC 15X10e prop up front, the prop braking seems to be minimal.
Direct drive outrunner brushless motors don't offer much more turning resistance than a set of bearings would.

As a glider pilot I am very very concerned about drag. The amount of drag created by a prop that is spinning free is huge. It is acting like an air brake on the plane.

Stop the prop and the prop will create a LOT less drag.