3-Blade propeller for MP1 ?

[Meta4]

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 ...

Propeller design is very complex with many factors involved. Much more than a simplistic more blades is "better" approach.
The evolution of propellers for Spitfires and Hercules aircraft is dealing with huge increases in engine power - something we aren't concerned with on Mavics.
For helicopters, more blades makes for a smaller diameter which makes the helicopter easier to fit into tight spaces too as well as handling bigger power plants, reducing tip speed etc.

That reference I gave is very interesting and informative and will give some idea of what's involved in the small props our drones use.
It also defines efficiency.
http://aerotrash.over-blog.com/2015/02/2-blade-vs-3-blade-and-4-blade-propellers.html
It shows some results of testing that don't go the way you'd expect.
For example, this plane, equipped with an APC 9x6 thin electric, 9x6 sport or the 4-blade 9x6. The simulation shows that the 4-blade can't even reach the performance of the 2-blade propellers because the high power consumption reduce considerably the rpm !

But after all of that, since the flight controller is going to vary motor speed to control flight in accordance with the specs, you aren't going to see any improvement in speed and probably not in flight time either.

 

[tcope]

I think this has been beat to death in prior threads and it looks like it is going that route in this one as well.

If 3 blade props were better in _any_ way, why would DJI not be selling them? They have hundreds if engineers working on their drones. You don't think they tried 3 blade props? Of course they did... and they are not any better... nor are carbon fiber props (another topic that has been beat to death).

3 blade props and/or CF props are not any better than original props from DJI.

But people continue to spend their money on these things. Some have issues with flight, most get lucky and don't have any issues but get nothing in return.

 

[FoxhallGH]

I think this has been beat to death in prior threads and it looks like it is going that route in this one as well.

If 3 blade props were better in _any_ way, why would DJI not be selling them? They have hundreds if engineers working on their drones. You don't think they tried 3 blade props? Of course they did... and they are not any better... nor are carbon fiber props (another topic that has been beat to death).

3 blade props and/or CF props are not any better than original props from DJI.

But people continue to spend their money on these things. Some have issues with flight, most get lucky and don't have any issues but get nothing in return.

Hi @tcope - if you look back at my post #9 you'll see I agree with you. We are having a very interesting discussion regarding propeller design for drones and aircraft in general. Feel free to join in if you want ... It's something I'm interested in because without the tech' that's behind prop's we wouldn't get off the ground. This is a forum for people to share ideas and discuss things about Drones. You have a choice to be part of a post or not ... that's up to you. Don't beat us up because we want to use the Forum for what its here for ...

 

[tcope]

Hi @tcope - if you look back at my post #9 you'll see I agree with you. We are having a very interesting discussion regarding propeller design for drones and aircraft in general. Feel free to join in if you want ... It's something I'm interested in because without the tech' that's behind prop's we wouldn't get off the ground. This is a forum for people to share ideas and discuss things about Drones. You have a choice to be part of a post or not ... that's up to you. Don't beat us up because we want to use the Forum for what its here for ...

I have no issue with the discussion (nor would my opinion on that matter). I'm just putting in my 2 cents on the initial post about using 3 bladed/CF props. Discuss on.

 

[FoxhallGH]

Propeller design is very complex with many factors involved. Much more than a simplistic more blades is "better" approach.
The evolution of propellers for Spitfires and Hercules aircraft is dealing with huge increases in engine power - something we aren't concerned with on Mavics.
For helicopters, more blades makes for a smaller diameter which makes the helicopter easier to fit into tight spaces too as well as handling bigger power plants, reducing tip speed etc.

That reference I gave is very interesting and informative and will give some idea of what's involved in the small props our drones use.
It also defines efficiency.
http://aerotrash.over-blog.com/2015/02/2-blade-vs-3-blade-and-4-blade-propellers.html
It shows some results of testing that don't go the way you'd expect.
For example, this plane, equipped with an APC 9x6 thin electric, 9x6 sport or the 4-blade 9x6. The simulation shows that the 4-blade can't even reach the performance of the 2-blade propellers because the high power consumption reduce considerably the rpm !

But after all of that, since the flight controller is going to vary motor speed to control flight in accordance with the specs, you aren't going to see any improvement in speed and probably not in flight time either.

I'd seen that reference doc' and it is quite interesting. It does show how the prop' is an integrated part of the aircraft. But at the end of the day, I'm not going to be an advocate for 3-bladed prop's on the Mavic - I can assure you ... I'm still waiting for a bit of good weather to do flight-duration testing to compare my 8331 CF prop's to the DJI stock versions however! [I can hear your groan @Meta4 ...] I'm interested in seeing if the CF blades work the motors harder and therefore drain the batteries quicker ... Will let you know how that goes.

 

[FoxhallGH]

I have no issue with the discussion (nor would my opinion on that matter). I'm just putting in my 2 cents on the initial post about using 3 bladed/CF props. Discuss on.

Thanks buddy - sorry if I took that wrong ...

 

[mnis]

Many thanks for your numerous opinions, I really appreciate that.

I understand all the concerns about these replicas. It helps to better understand things and their context. Nevertheless, sometimes I dare to give the replicas a fair chance, provided they meet certain conditions.

I think ... there must be such crazy people in the world. Where else would we get all the negative examples?

In fact, I do not understand much of aerodynamics. But I knew a few things before this interesting policy discussion started. Did I want a policy discussion? ... NO ... I would not be able to keep up.

But still, it's interesting to see how strong the loyalty to DJI and its original props is.

Hundreds of engineers from DJI will probably not be, and if there are so many, then they cook just like everyone else with water. The boys will fall back on existing profiles, here and there to optimize a bit, but still can not reinvent the wheel. They'll think, "Hey, we could do even better, but we'll keep it for the next product line." Or they drill a bit in the nose and after a while discard interesting optimizations, because otherwise the product might not be safe enough for ordinary users to use.

Anyway, I do not criticize it. And so it's just a speculation from me.

So I think, for example, DJI does not produce the propellers in their own factories, but assigns time-limited orders. After expiry of the deadlines production lines are not immediately buried, it comes the time of the varied replicas without brand, caused by former contractors. I think that's what's actually possible in China's factories and everyday normality.

Well speculated enough, and I explain why I want to try the 3-blade things:

Yes, in fact I find these 3-blade propeller sexy ...

Three blades would spin slower, but require more energy than two to the same amount of air move. From this I could deduce a probably shorter flight time, because the small MP batteries will reach the discharge end faster under higher currents.

A slightly lower flight noise is generally desirable.

The most important thing for me is the expectation of a higher stiffness of the rotor blades. I've ever had interesting replicas of the 8331F, which were generally less flexible than the originals, and felt the flight behavior as much more stable.

But from the quality concerns expressed over and over here and there, I rarely used the propellers.

Now it's time for a new venture.

 

[mnis]

And here's what I got yesterday:

 

[Rnl]

Be brave you'll be alright, curious to see what you think

 

[mnis]

- It is actually carbon.
The rotor blades are so stiff, a blade tip can probably hold the whole MP without bending.

- Each rotor blade is held by a real screw in a brass threaded sleeve.

- The workmanship seems perfect.
The edges of the rotor blades are very sharp, and the surfaces smooth.

- The flexibility of the joints is a touch heavier compared to the original.

- The profile of the rotor blades apparently corresponds exactly to 8331F.

I honestly can not wait to test these props ...

 

[Rnl]

I'm using Master air screw and they do just fine.

 

[Rnl]

I would check how tight the screws are as they set them, and check them every so often just to be safe.

 

[mnis]

Good tip ... I will check the screws regularly.

 

[mnis]

I'm using Master air screw and they do just fine.

I read a little bit about it, but I think these things are not available here.

 

[Meta4]

I'm using Master air screw and they do just fine.

That's great. But the important questions are still unanswered.
Do they provide any advantage over the stock props?
Is there anything about the stock props that needs improvement?

 

[mnis]

That's great. But the important questions are still unanswered.
Do they provide any advantage over the stock props?
Is there anything about the stock props that needs improvement?

Until I come to the test I stay with the statement: Seeexyyy

 

[Rnl]

Just flat out are noticeable less noise

 

[Meta4]

Until I come to the test I stay with the statement: Seeexyyy

I guess that's the most important thing for a propeller?

 

[mnis]

And yes ... Are there reviews of the Master Airscrews?

 

[Rnl]

Wildlife is mainly what i video, and get a lot closer without disturbing them, even over the platinum propeller i was using.