3-Blade propeller for MP1 ?

[mnis]

Hello MP1 users.
I recently discovered 3-blade propellers from an eBay dealer (BESTDEALS_EU). Of course, like so much, the stuff comes from China, where it probably has been available for some time, but the offer looks very interesting. And now the goods are already in DE, which promises a short delivery time.

I wonder if anyone has already dared to try these things? Are there perhaps already reviews?

Here is the product description of the dealer:

Description:
This 3-Blade foldable Quick-release Propeller is made of Real Carbon Fiber, super strong and light weight, good endurance and durability, more safe and energy saving for your DJI Mavic pro series drone flying.

Features:
2pair of 8331 CW CCW Carbon fiber 3-blade propellers for DJI Mavic pro drones.

Foldable, ultra strong and light weight, higher tension, smoother, responsive, low noise, quieter flight, more energy saving flight, quick release, easy to install and remove.
... ... ... ...

 

[Porky]

Have a read through this thread, link below. Might be of some interest to you regarding your question.

Dji new accessories for the M2P/Z

I personally I would only use Dji props. Remember how much your drone costs to the price of a set of props. No brainer

 

[mnis]

Thanks for the link...
I probably did not use the right search words. And that's why I assumed that there is no discussion about these propellers.

I think I am ready to buy these things and to test after evaluation.

My MP is almost out of the warranty period and currently there are enough spare parts for this bird...[emoji848]

 

[ciscokid]

let us know how they work.

 

[mnis]

let us know how they work.

... if I find nice weather out there ...
[emoji28]

 

[mnis]

There are probably 1 to 1 copies of the original 8331F for the M1P. The design of a single rotor blade x3 with matching bracket and not much else. I think the props are without further optimization, but I hope they are really carbon props. And with a little luck, you'll get a little more smoothness and stability in flight behavior. I think a longer flight time will not result ...

 

[Meta4]

I think the props are without further optimization, but I hope they are really carbon props. And with a little luck, you'll get a little more smoothness and stability in flight behavior. I think a longer flight time will not result ...

Of course they will.
DJI's propulsion engineers have no idea what they are doing and buying something random of dubious quality is sure to work much better as long as it's carbon fibre.
What could possibly go wrong?

 

[dennyc39]

The only advantage I would expect would be smaller diameter / better finger clearance. Theoretically, three blades is less efficient than two blades if all else is equal.

On big airplanes the primary reason for adding blades is to provide better ground clearance for more powerful engines. A secondary reason might be noise reduction.

Also, three blades is sometimes seen as rather sexy, even though sex with a drone is usually disappointing.

 

[FoxhallGH]

The only advantage I would expect would be smaller diameter / better finger clearance. Theoretically, three blades is less efficient than two blades if all else is equal.
On big airplanes the primary reason for adding blades is to provide better ground clearance for more powerful engines. A secondary reason might be noise reduction.

Actually, 3-bladed prop's ARE more efficient than 2-bladed as more air is pushed back for each rotation of the propeller. Correct however, in that the overall diameter of the propeller can be reduced, to get the same effect as a larger diameter 2-bladed prop'. Since you already have the clearance for the stock 2-bladed prop on your Mavic, putting a lesser diameter 3-bladed prop' on the Mavic is really not going to give you any advantages (it may actually slow the roll rate!). If you had a 3-blade prop' that was the same diameter and pitch as the stock 2-blade, then you may get into issues about overworking the motors etc. A 3-bladed prop with a lesser pitch would spin faster, and its that rotational speed through the air that generates the prop noise! So - its hard to see where the advantages are for us in 3-blade props for the Mavic Pro range.

 

[Meta4]

In all the alternative propeller threads, there seems to be an underlying assumption that the standard props must be deficient in some way and improvements may be found by swapping them for alternative props.
Has anyone ever been able to demonstrate the assumed problem with original props?
Or any improvement provided by replacing them?
If the answers are No and No, it would seem that all the prop swapping is chasing a fantasy.

 

[FoxhallGH]

In all the alternative propeller threads, there seems to be an underlying assumption that the standard props must be deficient in some way and improvements may be found by swapping them for alternative props.
Has anyone ever been able to demonstrate the assumed problem with original props?
Or any improvement provided by replacing them?
If the answers are No and No, it would seem that all the prop swapping is chasing a fantasy.

Only if you ignore the improvements that have been mentioned ...

 

[Meta4]

Only if you ignore the improvements that have been mentioned ...

Please enlighten me.
All I'm aware of is a small reduction in the already low noise levels of the Mavic.

 

[SIDEHACK]

Actually, 3-bladed prop's ARE more efficient than 2-bladed as more air is pushed back for each rotation of the propeller. Correct however, in that the overall diameter of the propeller can be reduced, to get the same effect as a larger diameter 2-bladed prop'. Since you already have the clearance for the stock 2-bladed prop on your Mavic, putting a lesser diameter 3-bladed prop' on the Mavic is really not going to give you any advantages (it may actually slow the roll rate!). If you had a 3-blade prop' that was the same diameter and pitch as the stock 2-blade, then you may get into issues about overworking the motors etc. A 3-bladed prop with a lesser pitch would spin faster, and its that rotational speed through the air that generates the prop noise! So - its hard to see where the advantages are for us in 3-blade props for the Mavic Pro range.

I am unsure where you found any data to support 3 blade Propellers being more efficient than 2 blade Propellers. Especially for drones. They are slightly quieter but mostly they offer a solution for clearance problems such as the 210mm racing drones. The 1000mm XDRONE's all use 2 blade props and exceed 100 mph! Take a moment and look at the specs from popular drone motor manufacturers. Rather than pick a specific one for you and to avoid any possible bias you should pick a couple of your own choice. Some of the most popular are; KDE Direct, T-Motor, Cobra, and SunnySky. KDE Direct has the most complete info. I guarantee you will not find a single example of a 3 blade prop out performing a 2 blade prop. Just sayin........

 

[FoxhallGH]

I am unsure where you found any data to support 3 blade Propellers being more efficient than 2 blade Propellers. Especially for drones. They are slightly quieter but mostly they offer a solution for clearance problems such as the 210mm racing drones. The 1000mm XDRONE's all use 2 blade props and exceed 100 mph! Take a moment and look at the specs from popular drone motor manufacturers. Rather than pick a specific one for you and to avoid any possible bias you should pick a couple of your own choice. Some of the most popular are; KDE Direct, T-Motor, Cobra, and SunnySky. KDE Direct has the most complete info. I guarantee you will not find a single example of a 3 blade prop out performing a 2 blade prop. Just sayin........

I wasn't referring to just Drones. The tech' behind aircraft propellers in general is based on multi-bladed prop's being more efficient. It's not just about ground clearance - otherwise aircraft like the C-140 Hercules would have long 2-blade props. All the development you see in aircraft tech' where prop's are involved (and there still are a lot of a/c with prop's out there), is showing us 4 to 6 multi-bladed prop's. For example, the C-130 Hercules went from 4 blade paddles, to 6 blade scimitar type prop's. In helicopters you don't see many 2-rotor machines out there now - especially military copter's - which are more likely to be 4 or 5 rotor machines. The efficiency factor in multi-blade prop's comes from allowing you to push more air backwards for one rotation of the airscrew. Without getting into any aerodynamics, you must agree that a 3 bladed prop must push back 30% more air than a 2 blade prop (assuming the same diameter and pitch of course). Major development of multi-blade prop's and multi-rotor copters have been about reducing the level of noise both for civilian and military reasons. Multi-blades means that you can reduce the rpm of the prop' and get a similar thrust to 2-blades. Reducing the diameter of the multi-blade prop also means that the tips are moving slower through the air, and therefore are quieter. That's why a 4-rotor Apache attack helicopter can get right on top of you before you hear it, but you can hear a 2-rotor Huey wop-wop-wop'ing in from miles away!
There are a lot of reasons for multi-bladed prop's - but the prop is just one part of the propulsion system of an aircraft, and is part of the balance of airframe & motor. In the case of the Drones you mention, quite right - especially if part of your performance relies on rapid roll stat's - because then longer prop' blades are a must-have, because they act as a longer lever to push the drone over. If you were able to have variable pitch prop's on your aerobatic drones though - you'd then see 3-bladed prop's because the roll would be done by putting +'ve pitch on the prop's on one side of the drone, and -'ve pitch on the other. When you can do that, long prop' blades are a disadvantage!

 

[FoxhallGH]

Please enlighten me.
All I'm aware of is a small reduction in the already low noise levels of the Mavic.

That can be a big advantage if your job or hobby involves filming wildlife ... for example.

 

[SIDEHACK]

I wasn't referring to just Drones. The tech' behind aircraft propellers in general is based on multi-bladed prop's being more efficient. It's not just about ground clearance - otherwise aircraft like the C-140 Hercules would have long 2-blade props. All the development you see in aircraft tech' where prop's are involved (and there still are a lot of a/c with prop's out there), is showing us 4 to 6 multi-bladed prop's. For example, the C-130 Hercules went from 4 blade paddles, to 6 blade scimitar type prop's. In helicopters you don't see many 2-rotor machines out there now - especially military copter's - which are more likely to be 4 or 5 rotor machines. The efficiency factor in multi-blade prop's comes from allowing you to push more air backwards for one rotation of the airscrew. Without getting into any aerodynamics, you must agree that a 3 bladed prop must push back 30% more air than a 2 blade prop (assuming the same diameter and pitch of course). Major development of multi-blade prop's and multi-rotor copters have been about reducing the level of noise both for civilian and military reasons. Multi-blades means that you can reduce the rpm of the prop' and get a similar thrust to 2-blades. Reducing the diameter of the multi-blade prop also means that the tips are moving slower through the air, and therefore are quieter. That's why a 4-rotor Apache attack helicopter can get right on top of you before you hear it, but you can hear a 2-rotor Huey wop-wop-wop'ing in from miles away!
There are a lot of reasons for multi-bladed prop's - but the prop is just one part of the propulsion system of an aircraft, and is part of the balance of airframe & motor. In the case of the Drones you mention, quite right - especially if part of your performance relies on rapid roll stat's - because then longer prop' blades are a must-have, because they act as a longer lever to push the drone over. If you were able to have variable pitch prop's on your aerobatic drones though - you'd then see 3-bladed prop's because the roll would be done by putting +'ve pitch on the prop's on one side of the drone, and -'ve pitch on the other. When you can do that, long prop' blades are a disadvantage!

Understood. Since this is a drone forum I limited my thoughts to them. Full size aircraft use slower turning, constant speed propellers so the tips don't break the sound barrier and possibly destroy themselves. 3 blade drone props turn so fast that the prop vortices created often interfere with the following blade. Wide, squared off tips (hogs head) seems to help stave off flutter at higher speed but are incredibly noisy! For the majority of the DJI drones we fly 2 bladed props with a shallow pitch and longer length are a great compromise. IMHO

 

[Meta4]

That can be a big advantage if your job or hobby involves filming wildlife ... for example.

Like I said, I was already aware of that.
But I haven't seen any evidence of any other "improvements that have been mentioned".

 

[FoxhallGH]

Understood. Since this is a drone forum I limited my thoughts to them. Full size aircraft use slower turning, constant speed propellers so the tips don't break the sound barrier and possibly destroy themselves. 3 blade drone props turn so fast that the prop vortices created often interfere with the following blade. Wide, squared off tips (hogs head) seems to help stave off flutter at higher speed but are incredibly noisy! For the majority of the DJI drones we fly 2 bladed props with a shallow pitch and longer length are a great compromise. IMHO

Absolutely ... My thinking was that aerodynamic principles do still apply - but Drone prop's do seem to be designed on the 'spin 'em as fast as you can!' principle. For example, my 8331 prop's on my Mavic Pro Platinum spin at around 510 [indicated] rpm x10 on the controller [5,100 rpm]. If you do the math', that puts the tips of the prop's rotating 85 x a second, and therefore travelling (based on a radius = 105 mm), through the air at a velocity around 560 metres / second. The speed of sound is 343 metres / sec. so that explains why they are so noisy! It also explains why the DJI Engineers are getting efficiency improvements with their prop's by changing the design of the tips. It does make you wonder though, that if you had scimitar shaped blades on the Mavic's (apart from the downside of being really dangerous in regard to cutting a hand off, let alone fingers!), whether that would make a significant difference.
Interesting subject and thanks for discussing this with me.

 

[Meta4]

I wasn't referring to just Drones. The tech' behind aircraft propellers in general is based on multi-bladed prop's being more efficient.

The word efficient is being thrown around a lot here, possibly without concern for it's proper meaning.
Perhaps you mean a multi-blade prop is able to produce more thrust, rather than it is more efficient?
According to the good folks at Hartzell Propellers, in general, 2-blade propellers are slightly more efficient.
They give a short explanation of the various factors affecting the number of blades used in plane design here: Are More Propeller Blades Better? - Hartzell Propeller

You seem to use the word efficient to mean better. But there are many more factors involved in choosing which prop is better.
This article gives some detailed analysis of performance of multi-blade props in model aircraft:
http://aerotrash.over-blog.com/2015/02/2-blade-vs-3-blade-and-4-blade-propellers.html
His results don't confirm the common more must be better hypothesis.
They also give an idea of how much is involved in prop design and why just slapping some cheap thing from ebay on your drone is unlikely to improve its performance beyond what the designers have achieved.

If you were able to have variable pitch prop's on your aerobatic drones though - you'd then see 3-bladed prop's because the roll would be done by putting +'ve pitch on the prop's on one side of the drone, and -'ve pitch on the other. When you can do that, long prop' blades are a disadvantage!

The only controllable pitch drones I've seen use two-bladed props.
But they are seriously cool in what they can do.

 

[FoxhallGH]

Just an observation Meta4, but all the development of propellers for aircraft, and rotors for Helicopters seem to be going along the 'more blades/rotors are better' route. Perhaps I'm using the wrong term with 'efficiency' but that does seem to drive a lot of design ... That and environmental impact of course.
My understanding of 'efficiency' where it applies to propellers, is [to put it very simply] the combination of factors when the prop produces the best thrust for the power put into it. Modern design seems to be all about widening that 'sweet-spot' so it's more a gentle knoll than a peak on a graph. The designs do seem to be multi-blade and improvements that have been made to many aircraft have included an increased number of prop' blades ...
I'm just thinking of a few examples like;
The Spitfire - Mk1 started with 2 blade [wooden] prop, went to 3 blade, then in the last RR Griffon models - 6 bladed props.
Attack helicopters started off with the 2 rotor Bell Cobra, and now we have the 4 rotor Apache, and tho' it may never get to production the 5 rotor Comanche.
Lockeed C130 Hercules started with 3 blade props, then went to 4 and now 6 ...
But - there is of course a huge difference between constant-speed prop's and fixed pitch units ... Fixed pitch are 'efficient' at pretty much only one combination of speed, engine rpm and altitude - so the design is a compromise. Variable pitch - or - constant speed prop's, are able to smooth out that sweet-spot and be better all rounders for most flight conditions.
Although your 'Stingray 500' is a great example, I think we'll be flying fixed pitch props on our drones for a long time yet ...
That Stingray is awesome! - but do you think you could just let the sticks go and it would hover?? Seems pretty hands-on 100% and an Adrenalin rush to fly!