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Low noise home made props
681 13 2018-10-11
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Monk32
lvl.4
Flight distance : 43150 ft
Greece
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Hi all.
Trying to find a lower level noise prop solution, i've modified the stock props in length, cause i believe that the clasic wild bee noise becoming mostly as a result of the aerodynamical reflective flow of the air mass hitting the drone body. The stock props are passing over the body of the drone, so the thrust disk produces a high-speed air flow in a high frequency as a result of the air and surface interaction. So i decide to cut the stock props to the length that just "fits" the arms length, so no air flow from the thrust disk hits the body thus avoiding this high frequency air flow.
I can say i succeed having a much lower frequency noise. Messurment in scale of db's doesn't gave a difference (both stock and modified props) gave an average of 65db but the modified props were produce much quiet noise as final in ears result.
I think worth the try.
As about the drone behavior and performance using the shortened props, i saw no differences cause the system manage to offset the shortened prop thrust disk with a little more motor speed, which was affortable by both props and motors.
Stability and performance tested ok in calm weather.
In first photo you can see the length difference (left modified..right stock one)
I hope gave you a hand in air's noise problem.
2018-10-11
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QuadFunAus
Second Officer
Flight distance : 38832 ft
Australia
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Don't see any photos?
2018-10-11
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devilsBastard
Second Officer
Flight distance : 254370 ft
Germany
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Yep, no photos to see - please add.
2018-10-12
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Bekaru MP UAV
Captain
Flight distance : 14348235 ft
South Africa
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Good experiment - i went on the same trip a while ago with my mavic pro and for the same reason (too much noise).
Cutting the props alters the sound but ultimately the db remains the same - so ultimately not useful.

I cut my props (all 4) first just the tips and then 25%.Even 25% cut off and severly damaged props per image below and my drone flew as well as the stock mavic pro i was flying with on the day.


I did high speed test flights and my drone behaved perfectly throughout.
Ultimately have put proper stock props on because shortened ones did not make a worthwhile improvement to the sound


2018-10-12
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Monk32
lvl.4
Flight distance : 43150 ft
Greece
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The missing photos
IMG_20181011_214611.jpg
IMG_20181011_214445.jpg
2018-10-12
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Monk32
lvl.4
Flight distance : 43150 ft
Greece
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Bekaru...in my case also the db messurment was exactly the same. The difference was in sound frequency. Cutted props create much lower frequency, so the noise was much less wistling in ear feeling.
2018-10-12
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DJI Paladin
Super Moderator
Flight distance : 318 ft

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Hi there, thank you for reaching DJI forum. Just a friendly reminder, we don't suggest any modification on the propellers because we are unable to ensure the performance and compatibility. Thanks for your understanding.
2018-10-12
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djiuser_CEdNxuNmFbIZ
lvl.2

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How do you go about balancing the props as they are so light, to begin with?
2018-10-12
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Bekaru MP UAV
Captain
Flight distance : 14348235 ft
South Africa
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Monk32 Posted at 2018-10-12 01:18
Bekaru...in my case also the db messurment was exactly the same. The difference was in sound frequency. Cutted props create much lower frequency, so the noise was much less wistling in ear feeling.

i agree. i raised this point in a thread before but no one seemed to understand the point i was making.
i thought that if dji could realise that they have not made quieter props but have made better sounding props by altering the frequency then perhaps they can take that a few steps further and maybe in the end develop some props that are more harmonious :-)
2018-10-12
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sky6105
First Officer
Flight distance : 345653 ft
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Just a couple questions on cutting the props down.
Being the drone is all closed in do you think cutting the props would affect the cooling in anyway?
With smaller props do you thing the motors would over rpm to compensate for the shorter props to get lift
causing over heated motors.
































2018-10-12
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Monk32
lvl.4
Flight distance : 43150 ft
Greece
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Sky6105 for sure the motors have to spin a little more to succeed the lift needed but it seems that no problem been raise. System would notify if overspeed occured, and i didn't experience such notification. As about the cooling, there is no matter. All goes ok so far.
2018-10-13
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Monk32
lvl.4
Flight distance : 43150 ft
Greece
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djiuser_CEdNxuNmFbIZ Posted at 2018-10-12 11:29
How do you go about balancing the props as they are so light, to begin with?

Djiuser, balancing such light props is something almost imposible. But be sure the same applied to the inbalance state of them during spin. An almost non traceable inbalance state is a non existed inbalance for the motors.. There is nothing to do further on.
2018-10-15
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Monk32
lvl.4
Flight distance : 43150 ft
Greece
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I finally tried installing Anafi's props and the result was amazing. The noise is now canceled at 50%. Low frequency sound which is not annoying anymore and flying characteristics absolutely normal. The only difference in performance is maybe the little lower final speed in sport mode, but I am not 100% sure about that. I am very satisfied of the result. I urge anyone to try it!!!   
8-27 05:00
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DAFlys
Captain
Flight distance : 428402 ft
United Kingdom
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Master Airscrew make low noise props for the MA.
8-27 05:03
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