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Is it harmful to run motors without props?
3758 24 2017-12-4
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dorbot
Second Officer
Flight distance : 844770 ft
France
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If you run the motors without props is it harmful to them in any way?
I think that it is bad for car engines to run at high RPM without load but I dont know about these PWM motors where the only moving part is the motor casing carying the permanent magnets. Its not reciprocating, just going round.

Any thoughts?
2017-12-4
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Punchbuggy
Captain
Flight distance : 395551 ft
Australia
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I wouldn't have thought so for short periods. Indeed, one of my pre-flight checks is to start the motors prior to putting the props on to check that there are no questionable sounds from the motors. I'd rather find out on the ground that one of the motors is grabbing, rather than finding out when it's a hundred metres into the air...
2017-12-4
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RedHotPoker
Captain
Flight distance : 165105 ft
Canada
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Yes, a preflight check list may include turning on the drone, and checking motors, without props, to see there are no interference.


Shouldn't be a problem what so ever...


RedHotPoker


2017-12-4
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sSkyPilot
First Officer
Flight distance : 290856 ft
United States
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Hmmm... Myself no, I took props off when I first set my P3S up. For safety concerns. I'm settings up a Spark now... without the props. Keeping safe while numbers and passwords are entered. Hopefully nothing spins-up. ya never know...  Cheers
2017-12-4
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sSkyPilot
First Officer
Flight distance : 290856 ft
United States
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Oh sorry, I got side tracked, I would say no to your question. For me, I wouldn't let that happen for more than 5 seconds. Cheers
2017-12-4
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DJI Susan
Administrator

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Hey Dorbot, it is one of the pre-flight checklist, no worries. If anything goes wrong, please stop the motor asap.
2017-12-4
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CraigR
lvl.4
Australia
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DJI Susan Posted at 2017-12-4 23:59
Hey Dorbot, it is one of the pre-flight checklist, no worries. If anything goes wrong, please stop the motor asap.

I've searched but cannot find it. Where's the link for the official pre-flight checklist (I'd like to print a copy)
2017-12-5
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Nebuchadnezzar
Captain
Flight distance : 1806824 ft
Spain
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Before Fly ,i like hear the motors without props , to check every motor sound (anything could get inside)
2017-12-5
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Rigger73
First Officer
Flight distance : 378478 ft
United Kingdom
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We test our Seaeye ROV thrusters, at work without props sometimes.  They are industrial 250Vdc Pulse Width Modulated thrusters - and they are fine.

They are designed to run a nominal load of 4.5A in water. Pulling less current in air does them no harm whatsoever.  It's part of our pre-dive and post dive checks.

I would imagine the principle for the DJI thruster motors will be the same.


Happy to be corrected.


2017-12-5
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KedDK
Captain
Flight distance : 1133038 ft
Denmark
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I have tried on the 4P, it popped an error within a few seconds and shut the motors off by itself.
Some have reported that it is not advisable to have the AC turned on for longer time indoor as things might heat up too much. On the other side from reading here it actuay sounds like some have been using the sim and that require ac to be on ...
2017-12-5
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solentlife
Captain
Flight distance : 1087530 ft
Latvia
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Brushless motors by design are freer running than brushed and can easily exceed max rating rpm.

Even so called high quality BL motors can throw magnets if run up too fast.

BUT - running BL motors without props is fine - BUT a) do not run for more than necessary to do the check, b) try not to run full throttle because without load - they can overspeed very easily.

You can lose magnets, you can overspeed bearings ....

I have a couple of motors that have donated magnets as hatch closers etc. through being oversped.

Summary answer - Yes no problem to run without props - just take it easy and no high speed long runs ...  

Nigel
2017-12-5
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dorbot
Second Officer
Flight distance : 844770 ft
France
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Good spread of responses.
Thanks all.

2017-12-5
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Kuya Kano
First Officer
Flight distance : 791086 ft
United States
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Were you thinking about using the rotors to power your car's engine?  There are some inspections that require such testing, however don't see the benefit of doing so for a long period of time unless you are strapping the rotors to something brilliant
2017-12-5
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GaryDZ
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United States
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solentlife Posted at 2017-12-5 07:11
Brushless motors by design are freer running than brushed and can easily exceed max rating rpm.

Even so called high quality BL motors can throw magnets if run up too fast.

I thought these are stepper motors. If so, the ESC sends pulses to the fields of the motor. So it can't exceed max rpm unless the ESC let it do so.
2017-12-5
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Punchbuggy
Captain
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Australia
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KedDK Posted at 2017-12-5 06:24
I have tried on the 4P, it popped an error within a few seconds and shut the motors off by itself.
Some have reported that it is not advisable to have the AC turned on for longer time indoor as things might heat up too much. On the other side from reading here it actuay sounds like some have been using the sim and that require ac to be on ...

Letting the motors run without props is one thing, but trying to take off without them is another. I suspect that's why you got the error.
2017-12-5
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dorbot
Second Officer
Flight distance : 844770 ft
France
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I'm sure i saw a "motor has reached max speed" warning at one point but not an overspeed warning. Not really wanting to do any more experiments though, lol.Its a shame coz they sound so good!
2017-12-5
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repairman
lvl.4
Flight distance : 3894 ft
United States
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i would not run them at high rpm with no props .really no reason to .just run them at low rpm with no props for the motor test.over speed can damage motors.
2017-12-5
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DJI Susan
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CraigR Posted at 2017-12-5 01:38
I've searched but cannot find it. Where's the link for the official pre-flight checklist (I'd like to print a copy)

Hello, CraigR, I do not have the list at my hand now, but there is one tutorial video of Mavic, which includes the check of motors, you can take it as reference. If the motors do not spin smoothly or there is any irregular noise, you can start the motors without propellers to check.

2017-12-5
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CraigR
lvl.4
Australia
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DJI Susan Posted at 2017-12-5 23:10
Hello, CraigR, I do not have the list at my hand now, but there is one tutorial video of Mavic, which includes the check of motors, you can take it as reference. If the motors do not spin smoothly or there is any irregular noise, you can start the motors without propellers to check.

https://youtu.be/CaFikz4GrL4

Cheers, I'll give it a look
2017-12-5
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solentlife
Captain
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Latvia
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GaryDZ Posted at 2017-12-5 13:12
I thought these are stepper motors. If so, the ESC sends pulses to the fields of the motor. So it can't exceed max rpm unless the ESC let it do so.

The motors are designed to provide x rpm per volt. Generally regarded as the KV value. This is the theoretical value the motor will spin at for 1V excitation.

But it never works that way because props / drive shafts provide load. This reduces the actual RPM achieved.

If you run the motor without load - yes it will reach its designed max and because of production limitations and theoretical - it will 99.9999% be certain it will overspeed.

BL Outrunner motors such as the P3's construction relies on 'glued' magnets on the inside of the motor bell. Spin that bell up to max or just over and you are quite likely to throw a magnet or two.... if you run for significant time. Short test bursts should be OK.

Best is to not give full power without load.

Nigel
2017-12-6
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KedDK
Captain
Flight distance : 1133038 ft
Denmark
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Punchbuggy Posted at 2017-12-5 13:42
Letting the motors run without props is one thing, but trying to take off without them is another. I suspect that's why you got the error.

All i did was start the motors with CSC (sticks down/in). When doing that motors get like a shot series of variable bursts and i believe it just sensed that something was wrong (no props) throw an error and shut down again.
Only tried once and don't remember what the error message was but concluded it don't like to start motors w/o props.
2017-12-6
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dorbot
Second Officer
Flight distance : 844770 ft
France
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Tried running my props without motors. Didn't get very far and didn't sound as good.
2018-1-11
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JamesWhenman
Second Officer
Flight distance : 426375 ft
United States
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I wouldn't run the motors without props. My last check in my preflight is to take off to the hover position , about 3-4 ft AGL , as part of the automatic take off routine in the RC.
This is where I listen, verify forward / backward, left / right , and spin (yaw) L / R . Then I descend a foot to confirm the down part of Up / Down.
Any unusual noises would become evident during this procedure.
This is just my own , everyone else's is their own choice.
2018-1-12
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Inferno-Videos
Second Officer
Flight distance : 838107 ft
United Kingdom
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Try these tutorial videos if using a Phantom 4, apart from the type of fiting of the props it would be the same as a Phantom 3 preflight checklist. Video 2 of 3 talks about testing the aircraft without the propellers.





2018-3-18
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Inferno-Videos
Second Officer
Flight distance : 838107 ft
United Kingdom
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Short answer is No, long answer is: the motors have far more being drawn on then when in flight, being used as a sports drone, rapid direction changes, flying against the wind, flying at full speed/ up to the maximum angle of attack etc... I've read the phantom 3 and 4s  have protected circuits on the mainboard to protect both the drivers and the motors, not so sure about the older Phantoms though.

If you're only running for a short test without the props no harm done, if you're  planning on running for say 20 minutes without props, why? Surely you'd have more fun doing 20 minutes in the air with it, lol.

2018-3-19
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