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gadgeter
01-15-2015, 07:07 PM
I learned my motor has a break function that can be activated to stop the motor spinning quite quickly.
It's on a phoenix evolution 2.6m power glider and I'm looking for suggestions on whether or not to use it. It seems it uses up some degree of battery power to activate so I'm leaning towards not using it.

Al_M
01-15-2015, 07:17 PM
use it.

fhhuber
01-15-2015, 07:48 PM
Motor brake is required for proper operation of the folding prop.

The way to adjust it if your radio has sliding trim levers (I hate digital trim for throttle) is such that break on is throttle stick at 0 and trim all the way down too. Trim appx half to all the way up should release the brake. You can turn off the brake once prop is folded.

With digital trim you need to program a mix to a switch to change the value of 0 throttle stick to enable or disable the brake in flight.

There are times you want the prop to windmill with the throttle at 0, to act as an air brake, so you need that throttle position easy to lock in.

For endurance gliding you want the prop to fold.

It will not fold without brake unless you stall the aircraft, holding nose up.
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It will not unfold if you return the throttle to the 0 power, brake off setting, which should be minimal ESC power demand.

Power demand to activate the shorting transistor for brake (that's how it works... it shorts the motor so it acts as a dynamic brake) is just a few miliamp... maybe 0.5 seconds worth of motor run per 10 min of brake on.

Wildflyer
01-15-2015, 07:57 PM
I don't believe it uses any battery power to stop the motor.
I have not seen any increase in power drawn from battery when the motor is shut off, using or not using a motor brake function. There might be a quick pulse of power in a way to stop, but I don't think so.

If any permanent magnet motor has it's leads shorted out, it will stop as fast as possible.
That is exactly how we applied a brake function to the slot cars, I raced in the 60's, the controller shorted the strip conductors on the track together, the motor acting as a over loaded generator slowed down much faster than using a controller without brake.

fhhuber
01-15-2015, 08:18 PM
The ESC brake function does use some power... Depending on the ESC is is normally very tiny but a poorly designed one could be significant.
You are powering a transistor (or similar component) to short the motor windings.

The actual power stopping the prop is generated by the prop.

You can set up an experiment to see how it works. Mount a motor with prop... No ESC and set it so the wind can spin it. It'll spin pretty well in mild to moderate wind.
Now short any 2 of the motor leads together. and the prop will rapidly slow down and should fold. The brake action won't stop a non-folding prop, but it will turn a LOT slower..

solentlife
01-15-2015, 08:45 PM
I keep mine simple .... BRAKE on when throttle is idle - no need for trim use.

As soon as throttle clicks a notch - the motor just gets that kick to try to start, prop unfolds - (just because BRAKE is off ... the prop will often NOT unfold without a kick or blip of motor from throttle ...)

I fly ASK 21 with folding prop and I need to give a blip of throttle to get it to unfold and spin ... otherwise it just lays back still.

Many guys I know with powered gliders and folders actually don't even put motor on the throttle stick ... they put motor on a ON - OFF switch ...

Nigel

gadgeter
01-16-2015, 02:26 AM
Thanks for the replies.
My motor has enough natural magnetic resistance to keep it from windmilling hence my question. The prop fols back without any breaking function activated. Im wondering if I should leave it alone. Perhaps I'll try it and see what the diff is.

fhhuber
01-16-2015, 02:35 AM
The difference is it will fold the prop at a higher airspeed.

Yes, there are some cases where high cogging and low speed can fold the prop without brake but its not common.

If your prop folds without having to stall the plane then brake is going to be a relatively minor help.

gadgeter
01-16-2015, 03:33 AM
Yea, I turned it on and I'll fly like that for a while. On seems to be general consensus and higher airspeed may windmill prop.
Thanks,
Did you see my landing gear post?

kyleservicetech
01-16-2015, 06:17 AM
Yea, I turned it on and I'll fly like that for a while. On seems to be general consensus and higher airspeed may windmill prop.
Thanks,
Did you see my landing gear post?

If your prop doesn't continue to windmill, don't really see any need to activate the prop brake.

If you do turn it on, look to see if your ESC has a "Soft Brake" function. I had one ESC that stopped the prop so suddenly, it unscrewed the prop nut. No matter how tight I'd made it.

solentlife
01-16-2015, 06:55 AM
Thanks for the replies.
My motor has enough natural magnetic resistance to keep it from windmilling hence my question. The prop fols back without any breaking function activated. Im wondering if I should leave it alone. Perhaps I'll try it and see what the diff is.

My opinion ... turn it on. In gentle flight just cruising and hunting thermals - your prop as you say will usually fold. That's really good.

What happens when you put nose down and build up some speed to do a loop for example ?

For me it's like a car sitting on level flat ground. It needs no hand-brake to stay where it is. But a slight change and that lack of hand-brake can have that car moving off ... Bit over-dramatic example .. but I think you see my point.

I flew my ASK 21 withouty Brake when I first got it ... and prop would fold when gently circling ... but as soons as she started to speed up or if she stalled into a nose down ... prop would fall back out again giving its own brake effect. I soon activated brake and that stopped.

Now here's something ... There are times when STILL the prop will unfold even though brake is on .. OK it doesn't windmill as easily but there's nothing to stop the blades extending. BUT at least you do not get the braking effect of the prop windmilling. THAT is what you are trying to avoid.

Nigel

carpetbagger
01-16-2015, 10:54 AM
your ESC may be set at default brake. Mine are - set to brake prop default setting, needs a program cards to change them.

gadgeter
01-16-2015, 11:17 PM
Bagger, I get what your saying but when I turned brake on there was a big difference in stopping and holding and I do have soft brake on for less violent stop.