Could a suddenly-detached motor wire cause a prop to fly off?

[SteveMann]

Just for the record though, our p2 motors ARE 100% true AC synchronous motors, not something different.

Nope. I have built enough drones to know a brushless 3-phase motor when I see one. Why would DJI use anything else when the motors and ESC are used in virtually every drone, model airplane and R/C car?

The centrifugal force would keep it spinning clockwise.
But, I've been wrong many times before. Is it possible that the wire detached and somehow the prop then flew off?

To the OP - Yes, losing a lead will instantly stop the motor and the prop will fly off.

if the prop came off, it is your fault: you did not use your wrench to tighten it.

The wrench is supplied with the P2 to assist prop removal. The manual specifically says to hand-tighten the props. Besides, if the motor stops, what difference does it make if the prop stays on or flies off? You will crash either way.

 

[yorlik]

Nope. I have built enough drones to know a brushless 3-phase motor when I see one. Why would DJI use anything else when the motors and ESC are used in virtually every drone, model airplane and R/C car?

Steve, stick to playing lawyer. As such, you give entertaining replies, and actually often really good comments. You obviously have no clue that an AC synchronous motor and a brushless motor are two names for the same device. You must have been REALLY bored tonight to respond here with such drivel.

The wrench is supplied with the P2 to assist prop removal. The manual specifically says to hand-tighten the props.

Steve, I previously did scientific documented tests proving the P2 do produce more torque than any human could apply without a wrench and as such the props CAN fly off due to a simple momentary glitch. Sometimes manuals state incorrect data - THIS hand tighten section in P2 manual was scientifically proven to be wrong. But according to you, since it is in writing, and posted on the internet, it must be correct? Stick to your lawyer talk my friend.

Besides, if the motor stops, what difference does it make if the prop stays on or flies off? You will crash either way.

Steve, it can make a difference between a destroyed phantom or not. Who told you that
the motor will stop and not restart instantly? Scientific documented engineering has shown that a simple GLITCH can stop the motor for 50-100 milliseconds, then continue as if nothing ever happened; yet a hand tightened prop would easily unscrew in that time. Some folks may want to NOT crash their drone simply because you, without any scientific study, say so.

 

[SteveMann]

Steve, stick to playing lawyer. As such, you give entertaining replies, and actually often really good comments. You obviously have no clue that an AC synchronous motor and a brushless motor are two names for the same device. You must have been REALLY bored tonight to respond here with such drivel.



Steve, I previously did scientific documented tests proving the P2 do produce more torque than any human could apply without a wrench and as such the props CAN fly off due to a simple momentary glitch. Sometimes manuals state incorrect data - THIS hand tighten section in P2 manual was scientifically proven to be wrong. But according to you, since it is in writing, and posted on the internet, it must be correct? Stick to your lawyer talk my friend.



Steve, it can make a difference between a destroyed phantom or not. Who told you that
the motor will stop and not restart instantly? Scientific documented engineering has shown that a simple GLITCH can stop the motor for 50-100 milliseconds, then continue as if nothing ever happened; yet a hand tightened prop would easily unscrew in that time. Some folks may want to NOT crash their drone simply because you, without any scientific study, say so.

OK, I'll grant you that the motor could restart making a secured prop more desirable. I am curious, however if it has ever happened to a Phantom pilot.

But

An Asynchronous AC motor is not the same as the DC Brushless motors that we use in the drones, though the DC brushless motor can resemble a 3-phase motor in construction. An Asynchronous AC motor simply chases its own rotating magnetic field and the speed is determined by the frequency of the AC supply. A DC Brushless motor speed is controlled by the pulse width applied to successive windings in the stator. The rotor is a set of magnets that follow the magnetic field generated by the DC pulse. If you applied AC to a DC Brushless motor, it would just sit there and hum. An AC asynchronous motor also suffers from lower torque at lower speeds, and being asynchronous, speed control is slow and the response time would not be good for the drones which need a near-instantaneous speed response from the controller. DC brushless motors have the same torque at any speed.

An Asynchronous AC motor and a DC Brushless motor are completely different.

 

[yorlik]

OK, I'll grant you that the motor could restart making a secured prop more desirable. I am curious, however if it has ever happened to a Phantom pilot.

But

An Asynchronous AC motor is not the same as the DC Brushless motor....

Steve, PLEASE stick to lawyerisms! You are posting nonsense that will confuse others.

I never said phantom motors are Asynchronous motors: I consistently said they are synchronous motors. You have no clue there is a difference, and therefore should not be posting crap. Yes, our motors are indeed AC synchronous motors. Google is your friend.

As for your other comment, help me with legalese thinking on it: how do you PROVE someone did NOT crash because they had a glitch with props tight enough to NOT fly off and thus crash their drone? You of all people should realize you cannot PROVE something didn't happen because of a negative....

 

[Monkeyleg]

Here's what I know: the prop came off when I was flying in a straight line, and had been flying in a straight line for several hundred feet. I wasn't turning or banking or decelerating or anything else that would change the centrifugal force.

If the prop had been put on loose, why would it come off when the centrifugal force was such that it would be tightening the prop?

 

[syotr]

Differentiate Synchronous and Asynchronous Motors :: Groschopp Blog

 

[syotr]

Here's what I know: the prop came off when I was flying in a straight line, and had been flying in a straight line for several hundred feet. I wasn't turning or banking or decelerating or anything else that would change the centrifugal force.

If the prop had been put on loose, why would it come off when the centrifugal force was such that it would be tightening the prop?

Actually, it isn't centrifugal force that holds the prop on. It is friction (if tightened enough) and the motor forcing it to rotate against the air resistance. If the motor stops suddenly, the prop will try to keep spinning from inertia. If there is enough friction between the prop and shaft threads, it will stop with the motor, if not, it will keep spinning and unscrew.

 

[Isaac Garcia]

Here's what I know: the prop came off when I was flying in a straight line, and had been flying in a straight line for several hundred feet. I wasn't turning or banking or decelerating or anything else that would change the centrifugal force.

If the prop had been put on loose, why would it come off when the centrifugal force was such that it would be tightening the prop?

The same exact thing just happened to me today! were you able to send it in to DJI and get a new one from warranty?

 

[Monkeyleg]

Mine wasn't covered by warranty, as I bought it used. I sold what parts I could on Ebay, and almost covered the cost of a new used P2V+. I'm now convinced that the thin wire broke at the solder joint, causing the crasch, so I immediately cut the wires on the motors up to about 1/2" away from the motors, and then used 18 gauge stranded wire from there to the ESC's. The 18 gauge wire/23 gauge wire solder joints I covered with heat shrink tubing. I doubt those joints will flex enough to break, and the stranded wire won't break.