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Bigger propellers?

mfc

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I've been musing about the noise issues with drones and noting that several people have commented that the Mavis Air is 'more annoying' that the Mavic Pro. It seems the Mavic Air is spinning its props about twice as fast as the P3P (and perhaps faster than the Mavic Pro, too -- I haven't been able to find any numbers). This shifts the noise power spectrum up and makes it more annoying.

It occurs to me, therefore, that larger and slower-spinning folding props would be a good way to go for DJI on future Mavic models.

Indeed, third-party larger props for the Mavic Pro could be interesting -- the firmware should spin them more slowly as they'd provide more lift. They could be up to 270mm across (as opposed to the current 210mm) before there's a risk of collision with another prop (although there would be some slight interference in airflow between front and rear props). That size would not affect the folded size of the Mavic Pro, either.
 
Indeed, third-party larger props for the Mavic Pro could be interesting
The current rear props come very, very close to the body of the Mavic as it is. You're not going to be able to retrofit larger props on it.
 
The current rear props come very, very close to the body of the Mavic as it is. You're not going to be able to retrofit larger props on it.

Good point; probably not worth adding 5mm there.

The front props, though, have quite a bit of clearance -- so if they were larger (and keeping the standard rear props) just having the fronts spinning slower should even out the noise profile.
 
Maybe it's just me, but haven't the 50-pound brains probably already run and crunched all the numbers on this issue by now? I would think that's what they're getting paid the big bucks for?
 
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Maybe it's just me, but haven't the 50-pound brains probably already run and crunched all the numbers on this issue by now? I would think that's what they're getting paid the big bucks for?

Apparently they haven't, which is why I'm asking the question (and yes, my brain is 55-pound and I still get big bucks for my ideas :)).
 
Longer propellors are not necessarily quieter. The linear tip speed would increase with length, but the lower angular speed may cancel this out. But if you add more propellor blades you can lower both the angular and linear tip velocity without the problem of the the blades hitting the drone. Four blade props would be quieter, but I don't think you could get folding ones.
 
Longer propellors are not necessarily quieter. The linear tip speed would increase with length, but the lower angular speed may cancel this out. But if you add more propellor blades you can lower both the angular and linear tip velocity without the problem of the the blades hitting the drone. Four blade props would be quieter, but I don't think you could get folding ones.

Yes .. longer propellers at the same rotation sped will certainly be noisier. [Aside: folding three-blade props could be interesting, too.].

Another thought occurred to me: if the front and rear props were spinning at different speeds, there would be a lower beat frequency generated .. that actually might make the drone sound more like a hum than a screech?
 
It will also effect the ESC's and the battery life. The loading of props to ESC/motor characteristics is quite "a balancing act". Change one thing, and the formula goes a bit wacky.
Just changing to a differet type/length of prop will change things for the AC. Motors and ESCs could run hotter etc.
It is a balancing act....
 
It will also effect the ESC's and the battery life. The loading of props to ESC/motor characteristics is quite "a balancing act". Change one thing, and the formula goes a bit wacky.
Just changing to a differet type/length of prop will change things for the AC. Motors and ESCs could run hotter etc.
It is a balancing act....

Absolutely. Equally, the software can/must adjust for that (consider a damaged propeller). But, surely, putting longer props on the front .. properly tested and tuned .. should not be ruled out just because no-one had tried that?
 
Another thought occurred to me: if the front and rear props were spinning at different speeds, there would be a lower beat frequency generated .. that actually might make the drone sound more like a hum than a screech?

I used to have a part share in a Turbo Discus glider with a retactable self-sustaining engine. The prop on that was an amazing piece of engineering. Seven blades, each a different length, different pitch, and different spaces between them. Oh, and it folded too. The blades all resonated at a different frequency, but the whole thing was still in balance. Much quieter and less annoying than an ordinary propeller. Still bloody loud though with a 2-stroke engine a foot behind your head. Not that you needed to run the engine for very long. A quick climb to get out of trouble, then put the engine away and enjoy the 43:1 glide angle.
 
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