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2 blade or 3 blade props
4722 28 2018-1-11
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Rene Jensen
First Officer
Denmark
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Hi there
am i right if i say that 3 blade propellers use more power from battery so your flight time reduces??
2018-1-11
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Geebax
Captain
Australia
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I would not think so, the aircraft only commands the motors to run at a speed which will do the job, therefore if the props run slower for a given amount of lift, then that is what would happen. But I would never use non-DJI props.
2018-1-11
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Labroides
Captain
Flight distance : 9991457 ft
Australia
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DJI propulsion engineers have already worked out what props work best for your Phantom.
I have a feeling their design would work better than whatever cheap props you find on ebay.
2018-1-11
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4WDaus
Captain
Flight distance : 1187257 ft
Australia
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Interesting wind turbines use 3 blades as they are better balanced
2018-1-11
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Genghis9
Captain
Flight distance : 961 ft
United States
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Whatever gain you may get in lift will not necessarily translate in to improved battery time...
You will experience some increased induced drag, there is some added weight although likely negligible so at best you would likely get a wash in performance overall.  Depending on the performance demands it could mean reduced batt time versus straight hover which might mean some slight improvement.  
As Labroides indicated DJI has already worked to find the sweet spot of props considering prop count, weight, what materials to use in the mold process, camber, aspect ratio, AoA, etc.
Like anything involved with performance factors there are tradeoffs to any decision in using one design over another.
2018-1-11
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RedHotPoker
Captain
Flight distance : 165105 ft
Canada
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4WDaus Posted at 2018-1-11 22:31
Interesting wind turbines use 3 blades as they are better balanced

I have never seen a wind turbine fly. What about you? Haha


But those are mighty big props, too heavy for lift off... ;-)


RedHotPoker

2018-1-11
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4WDaus
Captain
Flight distance : 1187257 ft
Australia
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RedHotPoker Posted at 2018-1-11 22:53
I have never seen a wind turbine fly. What about you? Haha

Lol you are right, you got me
2018-1-11
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RedHotPoker
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Flight distance : 165105 ft
Canada
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4WDaus Posted at 2018-1-11 23:01
Lol you are right, you got me

I'm happy about that. Lonely never more. Haha

Yes, those wind turbines are huge. But not appropriate for flight.


RedHotPoker
2018-1-11
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4WDaus
Captain
Flight distance : 1187257 ft
Australia
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RedHotPoker Posted at 2018-1-11 23:11
I'm happy about that. Lonely never more. Haha

Yes, those wind turbines are huge. But not appropriate for flight.

If you did would make  very big drone!
2018-1-11
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RedHotPoker
Captain
Flight distance : 165105 ft
Canada
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4WDaus Posted at 2018-1-11 23:13
If you did would make  very big drone!

Sure, majestic even...

I thought this would put some perspective to your thinking.
The world’s 10 biggest wind turbines
http://www.power-technology.com/ ... d-turbines-4154395/

But this was a couple of years ago, already.


RedHotPoker


2018-1-11
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4WDaus
Captain
Flight distance : 1187257 ft
Australia
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RedHotPoker Posted at 2018-1-11 23:15
Sure, majestic even...

I thought this would put some perspective to your thinking.

Really hard to get a feel for how big these turbines are! Thanks for sharing!
2018-1-11
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Labroides
Captain
Flight distance : 9991457 ft
Australia
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4WDaus Posted at 2018-1-11 22:31
Interesting wind turbines use 3 blades as they are better balanced


There are a number of considerations in wind turbine design when it comes to the number of blades but balance is not one of them.
That's because propeller balance isn't affected by the number of blades.

This piece from Wikipedia gives some idea of the factors at play in wind turbine propeller choice:
The number of blades is selected for aerodynamic efficiency, component costs, and system reliability. Noise emissions are affected by the location of the blades upwind or downwind of the tower and the speed of the rotor. Given that the noise emissions from the blades' trailing edges and tips vary by the 5th power of blade speed, a small increase in tip speed can make a large difference.

Wind turbines developed over the last 50 years have almost universally used either two or three blades. However, there are patents that present designs with additional blades, such as Chan Shin's Multi-unit rotor blade system integrated wind turbine.[27] Aerodynamic efficiency increases with number of blades but with diminishing return. Increasing the number of blades from one to two yields a six percent increase in aerodynamic efficiency, whereas increasing the blade count from two to three yields only an additional three percent in efficiency.[28] Further increasing the blade count yields minimal improvements in aerodynamic efficiency and sacrifices too much in blade stiffness as the blades become thinner.[citation needed]

Theoretically, an infinite number of blades of zero width is the most efficient, operating at a high value of the tip speed ratio. But other considerations lead to a compromise of only a few blades.[29]

Component costs that are affected by blade count are primarily for materials and manufacturing of the turbine rotor and drive train. Generally, the lower the number of blades, the lower the material and manufacturing costs will be. In addition, the lower the number of blades, the higher the rotational speed can be. This is because blade stiffness requirements to avoid interference with the tower limit how thin the blades can be manufactured, but only for upwind machines; deflection of blades in a downwind machine results in increased tower clearance. Fewer blades with higher rotational speeds reduce peak torques in the drive train, resulting in lower gearbox and generator costs.

System reliability is affected by blade count primarily through the dynamic loading of the rotor into the drive train and tower systems. While aligning the wind turbine to changes in wind direction (yawing), each blade experiences a cyclic load at its root end depending on blade position. This is true of one, two, three blades or more. However, these cyclic loads when combined together at the drive train shaft are symmetrically balanced for three blades, yielding smoother operation during turbine yaw.

Turbines with one or two blades can use a pivoting teetered hub to also nearly eliminate the cyclic loads into the drive shaft and system during yawing. A Chinese 3.6 MW two-blade is being tested in Denmark. Mingyang won a bid for 87 MW (29 * 3 MW) two-bladed offshore wind turbines near Zhuhai in 2013.
Finally, aesthetics can be considered a factor in that some people find that the three-bladed rotor is more pleasing to look at than a one- or two-bladed rotor.
2018-1-11
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RedHotPoker
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Flight distance : 165105 ft
Canada
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4WDaus Posted at 2018-1-11 23:19
Really hard to get a feel for how big these turbines are! Thanks for sharing!

Yes, much bigger than you probably ever would have imagined.

Even an intelligent guess would have difficulty realizing their actual measurements.


RedHotPoker
2018-1-11
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4WDaus
Captain
Flight distance : 1187257 ft
Australia
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RedHotPoker Posted at 2018-1-11 23:27
Yes, much bigger than you probably ever would have imagined.

Even an intelligent guess would have difficulty realizing their actual measurements.

Passed one on the back of a semitrailer a couple of months ago, awesome to see.
2018-1-11
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DJI Susan
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Rene, it is recommended to use the OEM propellers. As Labroides mentioned, this has been fully tested and works best for the drone.
2018-1-11
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RedHotPoker
Captain
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Canada
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4WDaus Posted at 2018-1-11 23:34
Passed one on the back of a semitrailer a couple of months ago, awesome to see.

Is there anything a transport truck won't bring for delivery?
image.png

That would be an extra long and wide load, flat bed.



RedHotPoker
2018-1-12
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4WDaus
Captain
Flight distance : 1187257 ft
Australia
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RedHotPoker Posted at 2018-1-12 00:38
Is there anything a transport truck won't bring for delivery?
[view_image]

Yep that’s huge
2018-1-12
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Nebuchadnezzar
Captain
Flight distance : 2489482 ft
Spain
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RedHotPoker Posted at 2018-1-12 00:38
Is there anything a transport truck won't bring for delivery?
[view_image]

divide it in 3 parts and you can transport it
2018-1-12
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RedHotPoker
Captain
Flight distance : 165105 ft
Canada
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DJI Susan Posted at 2018-1-11 23:49
Rene, it is recommended to use the OEM propellers. As Labroides mentioned, this has been fully tested and works best for the drone.

DJI Susan,

There hasn't been much explained, that I have read, with regard to the efficiency or benefit of using the OEM DJI carbon fiber reinforced rotor blades?

Do you have any experience or personal thoughts about them?
I wondered about their abilities, Aside from aesthetically.
Aesthetics (/ ɛ s ˈ θ ɛ t ɪ k s / or / iː s ˈ θ ɛ t ɪ k s /; also spelled esthetics)


RedHotPoker
2018-1-12
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RedHotPoker
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Canada
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Nebuchadnezzar Posted at 2018-1-12 00:50
[view_image] divide it in 3 parts and you can transport it

That's neat to see. I wouldn't wish to be his coworker, who drives the follow vehicle. ;-)



RedHotPoker
2018-1-12
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*onecooltech*
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United States
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RedHotPoker Posted at 2018-1-12 00:52
DJI Susan,

There hasn't been much explained, that I have read, with regard to the efficiency or benefit of using the OEM DJI carbon fiber reinforced rotor blades?

RedHotPoker,

(Not to go too far off topic) I've used the carbon blade for a while now and they work great in windy situations. A couple months back, my wife and I were on a planned vacation on the California coast and I wanted to fly my drone along the beach and rocks, but I had to plan for windy conditions. Mostly 15-25 mile winds, so I purchased the carbon blades and they worked great on keeping the bird level and controlling the sways.
DJI Susan may be able to clear up a question that I have with the carbon blades, with them needing to be balanced?

( Scott) onecooltech
2018-1-19
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Labroides
Captain
Flight distance : 9991457 ft
Australia
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*onecooltech* Posted at 2018-1-19 20:30
RedHotPoker,

(Not to go too far off topic) I've used the carbon blade for a while now and they work great in windy situations. A couple months back, my wife and I were on a planned vacation on the California coast and I wanted to fly my drone along the beach and rocks, but I had to plan for windy conditions. Mostly 15-25 mile winds, so I purchased the carbon blades and they worked great on keeping the bird level and controlling the sways.

I had to plan for windy conditions. Mostly 15-25 mile winds, so I purchased the carbon blades and they worked great on keeping the bird level and controlling the sways.
What makes you think that the original props wouldn't have been up to the task?
What feature of the CF props would have made any difference?
What differences have you observed?
DJI Susan may be able to clear up a question that I have with the carbon blades, with them needing to be balanced?
Probably not but I'll have a go.
Out of balance props need to be balanced.

But why the fascination for CF props?
I still haven't seen anyone show that they did anything better than original DJI props.
2018-1-19
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RedHotPoker
Captain
Flight distance : 165105 ft
Canada
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Carbon fiber, the dream material.

Do they even look any better than the white blades? ;-)


RedHotPoker
2018-1-19
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P4PCommander
lvl.4
Flight distance : 1153681 ft
United States
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4WDaus Posted at 1-11 22:31
Interesting wind turbines use 3 blades as they are better balanced

Good Point!!
2018-11-25
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P4PCommander
lvl.4
Flight distance : 1153681 ft
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RedHotPoker Posted at 1-12 00:38
Is there anything a transport truck won't bring for delivery?
[view_image]


Mary Jane!!
2018-11-25
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RedHotPoker
Captain
Flight distance : 165105 ft
Canada
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You need to cross the North border, bro... haha
4EBCB305-684B-417A-A35B-09B5A96606BA.jpeg

Run, don’t walk. We’ll be waiting for you...
No loafers allowed, thanks. Chuckles


RedHotPoker

2018-11-25
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solentlife
Captain
Flight distance : 1087530 ft
Czechia
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Geebax Posted at 1-11 20:46
I would not think so, the aircraft only commands the motors to run at a speed which will do the job, therefore if the props run slower for a given amount of lift, then that is what would happen. But I would never use non-DJI props.

As Geebax says ... there shouldn't really be any change.

The Flight Controller interprets the command you give into RPM of each motor. The Accelerometers and other functions such as Barometer, GPS etc. then determine if the AC is acting as requested.
The Flight Controller is adjusted to compensate in its motor control.

The only way a power requirement to hover for example will change - is if the weight of the AC alters (assuming same weather conditions). Therefore you can see that if the lift factor of the prop improves - the FC will reduce its RPM so that it balances the command requested.

Its a different ball game with a fixed wing airplane - as we are not looking to hover in same manner as a Multi Rotor.  A 3 blade prop is often for cosmetic appearance (my Lancaster bomber as example)  and or ground clearance. The 3 blader will give a slight increase with same diameter / pitch ... but not as much as one would imagine.

On the subject of Wind Turbine blades .......... on the Isle of Wight (UK) ... going upriver from Cowes to Newport - is a blade factory. They have special barges built to carry the blades downriver to marshalling yard.

https://www.iwcp.co.uk/news/1669 ... -farm-in-the-world/

Nigel
2018-11-26
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P3KoYoT
Captain
Flight distance : 1567241 ft
Poland
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RedHotPoker Posted at 1-11 22:53
I have never seen a wind turbine fly. What about you? Haha

if any of these huge wind turbine starts spinnig so fast as our drone blades they will FLY OFF for sure
2018-11-28
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RedHotPoker
Captain
Flight distance : 165105 ft
Canada
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P3KoYoT Posted at 11-28 01:20
if any of these huge wind turbine starts spinnig so fast as our drone blades they will FLY OFF for sure

They sometimes get struck by UFOs too. Haha


RedHotPoker



2018-11-28
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