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Toroidal Propellers
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Lost Somewhere
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Has anyone ever made or used toroidal propellers? I was going to print some to try them out. Any suggestions?
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2023-1-29
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The Saint
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why? to what end?  im asking what benefit are we looking for with these?  more flight time, less maintenance, more durable, more maneuverability, quieter?
2023-1-29
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Lost Somewhere
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The Saint Posted at 1-29 18:12
why? to what end?  im asking what benefit are we looking for with these?  more flight time, less maintenance, more durable, more maneuverability, quieter?

Noise is the main reason. There has been extra talk about it recently so I thought I'd try some.
2023-1-29
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DJI Paladin
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Hi there. Thank you for reaching out. We do not recommend using a 3rd party accessories especially propellers as we cannot guarantee the stability of the aircraft when in used with the said 3rd party propellers. Should you have other inquiries, please don't hesitate to reach us. Thank you.
2023-1-29
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Lost Somewhere
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DJI Paladin Posted at 1-29 18:51
Hi there. Thank you for reaching out. We do not recommend using a 3rd party accessories especially propellers as we cannot guarantee the stability of the aircraft when in used with the said 3rd party propellers. Should you have other inquiries, please don't hesitate to reach us. Thank you.

Thanks for the advice, duly noted.
Do you know if DJI R&D has experimented with this type of propeller?
2023-1-29
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TonyPHX
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Why are you doing this?
2023-1-29
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Lost Somewhere
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TonyPHX Posted at 1-29 19:07
Why are you doing this?

Engineers at MIT seem to think it's a good idea to try.
https://hackaday.com/2023/01/28/ ... ones-less-annoying/
2023-1-29
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The Saint
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Lost Somewhere Posted at 1-29 18:30
Noise is the main reason. There has been extra talk about it recently so I thought I'd try some.

the m3p is already very quiet; however, may i suggest: https://www.masterairscrew.com/p ... e-propellers-x4-red
2023-1-29
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Lost Somewhere
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The Saint Posted at 1-29 19:45
the m3p is already very quiet; however, may i suggest: https://www.masterairscrew.com/products/dji-mini-3-pro-stealth-upgrade-propellers-x4-red

It is quiet. I was mostly curious to design and try something really unique. I like the bright color, and the quieter the better, I'll keep these in mind. Thanks

I do also like that the toroidal ones don't have a sharp tip. Not as good as a prop guard, but still a lot better than nothing and they don't add hardly any weight compared to a prop guard.
2023-1-29
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DJI Paladin
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Lost Somewhere Posted at 1-29 18:57
Thanks for the advice, duly noted.
Do you know if DJI R&D has experimented with this type of propeller?

You're welcome and we appreciate your understanding. We don't have any information regarding this accessory however, I will take this as suggestion of yours and will forward to our designated team for attention. Thank you for your valued support.
2023-1-30
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LV_Forestry
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They are not really toroidal propellers on your screenshot. You're more likely to knead bread dough with it than hope to fly a drone.

A toroidal propeller is more of a 4-blade propeller on which 2 ends are joined to try to eliminate or reduce the turbulence that forms at the end of the blade and generates a lot of noise.

But hey, who knows! send a video if you try. I'm curious to see the result.
2023-1-30
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LV_Forestry
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Lost Somewhere Posted at 1-29 19:12
Engineers at MIT seem to think it's a good idea to try.
https://hackaday.com/2023/01/28/toroidal-propellers-make-drones-less-annoying/

Here we are. This is toroidal.
2023-1-30
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Lost Somewhere
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LV_Forestry Posted at 1-30 03:53
They are not really toroidal propellers on your screenshot. You're more likely to knead bread dough with it than hope to fly a drone.

A toroidal propeller is more of a 4-blade propeller on which 2 ends are joined to try to eliminate or reduce the turbulence that forms at the end of the blade and generates a lot of noise.

Check out the link on the MIT research.
This is for a Mini 3 so of course each prop uses 2 of these, hence the toroid.
2023-1-30
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LV_Forestry
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Lost Somewhere Posted at 1-30 03:57
Check out the link on the MIT research.
This is for a Mini 3 so of course each prop uses 2 of these, hence the toroid.

That's exactly what I'm telling you. Look at the propellers on the link you posted. There is a phase shift on the blade root. they are not at 180.
2023-1-30
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Lost Somewhere
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LV_Forestry Posted at 1-30 04:01
That's exactly what I'm telling you. Look at the propellers on the link you posted. There is a phase shift on the blade root. they are not at 180.

I know, I show the right and left. Then you print 4 sets.
2023-1-30
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LV_Forestry
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Lost Somewhere Posted at 1-30 04:04
I know, I show the right and left. Then you print 4 sets.

Experiment with the design you made.
I predict there is going to be a vibration problem. Maybe not !
If so, make a mono hub:

toro.JPG

And the propellers in 3D print I have already tried. I can only recommend that you make a wooden or aluminum mold with a CNC, then you put your 3D print on it and put everything in the oven a little below the melting temperature of the plastic. This will join the layers. Otherwise it is guaranteed explosion as soon as the propeller is loaded.
2023-1-30
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Lost Somewhere
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LV_Forestry Posted at 1-30 04:13
Experiment with the design you made.
I predict there is going to be a vibration problem. Maybe not !
If so, make a mono hub:
[Image]

Yeah, who knows, it's very possible it doesn't work well, especially the first version.
I'll print it with a resin SLA printer not FDM, so it won't have as many issues I hope.

I like the 2 piece rotors, that fold and provide softer acceleration, so I'll start that way. I can always spin the model I have 180 on the motor axis and add a rigid support between the hubs.
2023-1-30
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LV_Forestry
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Lost Somewhere Posted at 1-30 04:25
Yeah, who knows, it's very possible it doesn't work well, especially the first version.
I'll print it with a resin SLA printer not FDM, so it won't have as many issues I hope.

I have never tried to make SLA propellers. Is it flexible enough?
2023-1-30
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Lost Somewhere
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LV_Forestry Posted at 1-30 04:36
I have never tried to make SLA propellers. Is it flexible enough?

Yeah, the Tough 1500 is very strong and just a bit flexible. I can go more rigid from there even up to Rigid 4000 with glass fill, but that will shatter if impacted.
2023-1-30
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Lost Somewhere
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LV_Forestry Posted at 1-30 04:36
I have never tried to make SLA propellers. Is it flexible enough?

I posted a picture of some Tough 1500 landing legs I made, on a different post.
2023-1-30
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LV_Forestry
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Lost Somewhere Posted at 1-30 04:50
Yeah, the Tough 1500 is very strong and just a bit flexible. I can go more rigid from there even up to Rigid 4000 with glass fill, but that will shatter if impacted.

Flexibility is the whole point with propellers. On Pixhawk you can modify the PIDs with custom propellers. On the latest generation of DJI we can not. This is a big problem for anyone who wants to experiment.
2023-1-30
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WernerD
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(I have a degree in aeronautics. Just saying.)
These are very interesting, indeed. Would love for somebody to try them out with the Mini3 but I fear simply creating some and bolting them onto the Mini 3 will not work. As somebody said before, these propellers should be seen as 4 blade props with extra long blades (wing tips increase the effective wing span). Hence I would expect that the rpms must be approx half of what the Mini 3 operates normally.
If I am right, that would require adjusting the motor control software.

I would start we a non-stock drone where you have 100% control about all parameters.
2023-1-30
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Lost Somewhere
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WernerD Posted at 1-30 08:49
(I have a degree in aeronautics. Just saying.)
These are very interesting, indeed. Would love for somebody to try them out with the Mini3 but I fear simply creating some and bolting them onto the Mini 3 will not work. As somebody said before, these propellers should be seen as 4 blade props with extra long blades (wing tips increase the effective wing span). Hence I would expect that the rpms must be approx half of what the Mini 3 operates normally.
If I am right, that would require adjusting the motor control software.

Oh awesome, you're the guy I need!
I'm a mechanical nuclear pharmaceutical engineer so I make no claim to know aeronautics.
Like you said, the toroidal design is sort of like having 4 blades at each motor instead of 2. So if they have the same pitch and length and width, then the lift will be a lot more and it will spin slower but take more power. However, if I make the pitch a little less and the blade a little narrower, it might be closer to the original. If it doesn't work well, and I don't expect the first set to be perfect, then I can adjust any of the 3 parameters so that I can get back to the same RPM and lift. The idea is that it will be quieter, but I don't know if it will end up more or less efficient in the end, the losses are likely higher, and some noise reduction might just be from spinning slower. But they claim this design reduces noise, so I assume that should be at the same RPM, but who knows. It's fun to try.

Here's an image with the standard props just for comparison. And one with the whole set programmed for the SLA.

If you have any suggestions or websites that I should use to calculate the optimal pitch, let me know.

2023-1-30
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WernerD
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The motor controller is a fine tuned PID control loop. It must match the drone movement requirements and and hardware. Yes, making your prop a bit smaller would increase the chances to get into a range where it is more likely to work but smaller, faster turning props will also be louder and less efficient. At the end, all the advantages of this design are lost.
I stick to my suggestion of using a custom drone with a fully programmable ESC and flight controller.

Best would be to join forces with some drone enthusiast that has such a drone already, else you will spend lots of time in learning that as well. Do you have any FPV racers in your network of people?
2023-1-30
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WernerD
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One more thing, again, like somebody else said before me. I do not understand the geometry of your props given the screenshots. To me they look like a ring. No increased pitch closer to the axis, the wing depth seems to be constant, no wing-shaped profile. It looks like a cement mixer, not a propulsion device on the pictures.
I am not sure a proper and efficient form can even be designed without a fluid dynamics software. As approximation I would take the existing Mini 3 props and "bend" the tips 90° up. Then take the same pair with wingtips bent down. Then connect the two pairs in the CAD software so they merge at the wing tips and at the axis via parallel transformations and without changing the pitch.

2023-1-31
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fansb4f50ec1
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WernerD Posted at 1-30 08:49
(I have a degree in aeronautics. Just saying.)
These are very interesting, indeed. Would love for somebody to try them out with the Mini3 but I fear simply creating some and bolting them onto the Mini 3 will not work. As somebody said before, these propellers should be seen as 4 blade props with extra long blades (wing tips increase the effective wing span). Hence I would expect that the rpms must be approx half of what the Mini 3 operates normally.
If I am right, that would require adjusting the motor control software.

Instead of reducing RPMs (which is out of user control), could another approach be to adjust the pitch (and reduce lift)?
2023-1-31
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WernerD
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True. But noise = rpm². Since the entire goal is noise, I ruled that out. But yes.
2023-1-31
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Mobilehomer
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Check the link in the OP - https://mavicpilots.com/threads/ ... prop-design.134694/
2023-2-1
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Lost Somewhere
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WernerD Posted at 1-31 01:27
One more thing, again, like somebody else said before me. I do not understand the geometry of your props given the screenshots. To me they look like a ring. No increased pitch closer to the axis, the wing depth seems to be constant, no wing-shaped profile. It looks like a cement mixer, not a propulsion device on the pictures.
I am not sure a proper and efficient form can even be designed without a fluid dynamics software. As approximation I would take the existing Mini 3 props and "bend" the tips 90° up. Then take the same pair with wingtips bent down. Then connect the two pairs in the CAD software so they merge at the wing tips and at the axis via parallel transformations and without changing the pitch.
[view_image]

I was trying to maintain a similar profile and angle as the original prop. But to reduce the noise I was trying to also round the profile. I start with around 40 degrees and it's about 25 degrees in the middle, dropping lower at the tips. But I'm also a little narrower than the original so that I'm not adding 2X the lift surface. If you know that the idea angles are or there's an online calculator you use, just let me know.

I'm not sure I feel like going to the level of running it all through ANSYS to simulate lift, but I probably could. I figured it was so easy to just print some and find out how close I am in the real world.

The standard prop is in the middle, but I'm not sure exactly how accurate it is, just being the online model that was available.
2023-2-1
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LV_Forestry
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Lost Somewhere Posted at 2-1 11:04
I was trying to maintain a similar profile and angle as the original prop. But to reduce the noise I was trying to also round the profile. I start with around 40 degrees and it's about 25 degrees in the middle, dropping lower at the tips. But I'm also a little narrower than the original so that I'm not adding 2X the lift surface. If you know that the idea angles are or there's an online calculator you use, just let me know.

I'm not sure I feel like going to the level of running it all through ANSYS to simulate lift, but I probably could. I figured it was so easy to just print some and find out how close I am in the real world.

Looks like you're using solidworks.  Your initial sketch looks pretty good.
You can import a .DAT file with the coordinates of a NACA profile.  
I'll try if I find the time.
On the hubs I would start with 65°, at 1/3 45°, at 2/3 20°, and at the end finish with 5°.

To join the two blades I would bend the junction like a winglet on a wing.  In order to break the turbulence.

The challenge will be to find the right distance between two consecutive blades to avoid cavitation of the next blade in the flow of the previous one.

I don't know if it's worth bothering with calculations.  The best would be perhaps to make the part in parametric so as not to have to redraw everything with each modification.
2023-2-1
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Lost Somewhere
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LV_Forestry Posted at 2-1 11:39
Looks like you're using solidworks.  Your initial sketch looks pretty good.
You can import a .DAT file with the coordinates of a NACA profile.  
I'll try if I find the time.

This is what the wing tip looks like.

2023-2-1
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WernerD
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That looks good!
2023-2-1
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PixelPro
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Just stick with the propellers you have. I wouldn't risk it for the price.
2023-2-2
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Lost Somewhere
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PixelPro Posted at 2-2 13:19
Just stick with the propellers you have. I wouldn't risk it for the price.

I think it's easy enough to put some mitigations in place.
Plus, as an engineer, half the reason to have a drone is to experiment with it. If this doesn't break it, something else will.
No sacrifice, no victory
2023-2-2
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The Saint Posted at 1-29 18:12
why? to what end?  im asking what benefit are we looking for with these?  more flight time, less maintenance, more durable, more maneuverability, quieter?

Noise reduction
2023-2-2
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Justgerald
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DJI Paladin Posted at 1-29 18:51
Hi there. Thank you for reaching out. We do not recommend using a 3rd party accessories especially propellers as we cannot guarantee the stability of the aircraft when in used with the said 3rd party propellers. Should you have other inquiries, please don't hesitate to reach us. Thank you.

Please consider offering toroidal propellers as they are very quiet and less of a nuisance.
2023-2-2
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Lost Somewhere Posted at 1-29 19:12
Engineers at MIT seem to think it's a good idea to try.
https://hackaday.com/2023/01/28/toroidal-propellers-make-drones-less-annoying/

Works for boats as well.
2023-2-2
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Dontevenworryabootit
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Lost Somewhere Posted at 2-2 15:16
I think it's easy enough to put some mitigations in place.
Plus, as an engineer, half the reason to have a drone is to experiment with it. If this doesn't break it, something else will.
No sacrifice, no victory

Hey agree 100%, drones are ment to be used.
2023-2-2
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Lost Somewhere Posted at 2-2 15:16
I think it's easy enough to put some mitigations in place.
Plus, as an engineer, half the reason to have a drone is to experiment with it. If this doesn't break it, something else will.
No sacrifice, no victory

Happy to sacrifice my mini pro 3 for testing
2023-2-2
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The Saint Posted at 1-29 19:45
the m3p is already very quiet; however, may i suggest: https://www.masterairscrew.com/products/dji-mini-3-pro-stealth-upgrade-propellers-x4-red

You've tried these?
Are they reliable?
2023-2-3
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