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DJI Mini 3 early test flight with flight inspectors

Discussion in 'Fred's House of Pancakes' started by bwilson4web, Feb 13, 2024.

  1. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Bob Wilson
     
    #1 bwilson4web, Feb 13, 2024
  2. hill

    hill High Fiber Member

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    Looking good!
     
    #2 hill, Feb 13, 2024
  3. ETC(SS)

    ETC(SS) The OTHER One Percenter.....

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    +1

    I have to fly mine outdoors-only because - Boxer.
    I keep waiting patiently for a military base to offer a free Part 107 license exam - and the time to take the test.
     
    #3 ETC(SS), Feb 13, 2024
  4. tochatihu

    tochatihu Senior Member

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    This camera drone gets very favorable reviews. I have seen its predecessor models do amazing things.

    I look to them more for environmental monitoring that has become very advanced for some (not all) sensor types. Not the topic here.

    Another direction is application of agricultural chemicals. Those UAVs are very large in comparison and powered by internal combust engines because ... fuel energy density. One I saw at rest in a remote field station conference room somewhere was an absolute beast. Glad it was sleeping. Not the topic here either.

    But our topic could be said to be that UAVs are still 'young' and what they can accomplish in ~decade is only dimly anticipated. A not-surprising early adopter here is flying in that direction.

    ==
    But I wonder: how well are all their propeller airfoils optimized in important areas of performance envelopes? Do DJI (etc.) just buy any old props, or is somebody actually modeling fluid dynamics? Imagining a secondary industry with 3D printing. Bob or whomever has UAV with props as provided. Buys better designs from somebody. Props themselves must be a very small cost fraction of the complete device. Then our flyers have boxes of options to choose/install for different missions.

    If any here want to do 99% of legwork remaining towards developing this sub industry, you have my blessings.
     
    #4 tochatihu, Feb 14, 2024
  5. bwilson4web

    bwilson4web BMW i3 and Model 3

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    The props have individual blade, lead and lag, horizontal rotation at each blade attachment. This solves a lot of aerodynamic challenges. The real trick is the hubs are fixed. They accomplish rotation and lateral movement by tweaking the power to each hub..

    For manned flight, I would expect tp see at ;east eight, lifting props.

    Bob Wilson
     
    #5 bwilson4web, Feb 14, 2024
    Last edited: Feb 14, 2024
  6. tochatihu

    tochatihu Senior Member

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    You know what cruise and climb props are, but clearly I have not got your thinking here yet. Some UAV missions are local hover, some involve horizontal travel, and others involve a lot of vertical travel. Battery power supply is a constant. Prop pitch will be constant unless someone makes a new (tiny) twister. I assert that a box of different props (to change) could improve mission optimization at low cost.

    But not by Bob, he implies. I'd not go to UAV forums with this. Other options may exist.
     
    #6 tochatihu, Feb 14, 2024
  7. douglasjre

    douglasjre Senior Member

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    I miss my DJI spark. Sunk it in salt water. Be careful with your
     
    #7 douglasjre, Feb 15, 2024
  8. bisco

    bisco cookie crumbler

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    #8 bisco, Feb 15, 2024
  9. bwilson4web

    bwilson4web BMW i3 and Model 3

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    The power output of an ICE engine is a function of air flow through the induction system and strongly impacted by the RPM. So a constant speed prop lets the engine turn at the design power output, a constant RPM, regardless of how torque loaded the prop is. As the incoming air flow increases, the pitch has to increase to keep the ICE running at the desired HP.

    In contrast, motors are affected by the reverse EMI which increases the faster they spin. The lower voltage at high RPM changes how much current they can take and the power they can generate. The peak power and torque are found on the low RPM range of the motor so higher RPMs actually reduce the power absorbed by the motor. The fixed pitch propeller works fine as the maximum power is in the low RPM range and as the prop is 'unloaded' by higher speed airflow, the motor soon reaches a stead state with lower power.

    It is in the HP vs RPM range that gives motors an advantage with a simpler fixed pitch prop. In contrast, the air flow through the ICE engine drive how much power they can deliver before mechanical stress 'rapidly disassembles' the engine. A constant speed propeller is best for an ICE engine.

    It is late so please forgive my word salad. After a night's sleep, I can share graphs showing what happens. If it weren't for weight, an ICE could drive a generator-motor to optimize propeller performance. But generator-motors have a generator efficiency and motor efficient and the product of the two is the energy lost. In contrast, a mechanical, variable pitch propeller doesn't have similar efficiency losses.

    Bob Wilson

    ps. Now I'll dream about it.
     
    #9 bwilson4web, Feb 15, 2024
  10. tochatihu

    tochatihu Senior Member

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    I like salad
     
    #10 tochatihu, Feb 15, 2024
  11. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Here is what I mumble-posted about:
    [​IMG]
    The variable pitch (called constant speed) prop adjusts the blade angle of attack to keep the engine in the peak power range at a fairly high rpm. Higher rpms are associated with spontaneous engine disassembly. Lower speeds are associated with less power.

    [​IMG]
    In contrast, and electric motor HP is a nearly linear increase on the low rpm. Then above a critical point, the power 'flat lines' as the torque, a function of current, falls off because of the reverse EMI. In effect, the faster an electric motor turns, it begins to act like a reverse coupled, generator. Just the nature of the beast. But with a fixed pitch prop, it will automatically change the rpm as the prop unloads with no risk of unplanned disassembly.

    A good source: Fixed-pitch Props
    [​IMG]

    Bob Wilson
     
    #11 bwilson4web, Feb 16, 2024
    douglasjre likes this.
  12. ETC(SS)

    ETC(SS) The OTHER One Percenter.....

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    "Fly-aways" are a thing too.
    If you can't afford to lose it, don't send it aloft.

    Some humans learn to sharpen sticks so that they can collaborate with other humans to kill the woolly mammoth and feed their families.
    OTHER humans use this knowledge to take the mammoth from the really tired humans resting next to the carcass. If they're really clever, they will not even injure the victims - because people have to eat, and so they WILL kill other mammoths.

    MOST of the 'legwork' in drone tech has been taking place in labs where the bosses wear military uniforms.
    The Ukies and the Persians have made excellent use of UAVs in the last few years, and DJI is a CHICOMM company, and the Middle Kingdom is no slouch in the UAV world.

    Nothing much wrong with that.
    My last drone purchase was a DJI, and my next one 'probably' will be as well so I'm not a 'purist' where 'blood tech' is concerned.
    Just remember which flag they salute at the end of the day....

    Besides....
    I'm a devout optimist.
    The CCP may run the prison today, but only as long as the prisoners themselves allow it.
     
    #12 ETC(SS), Feb 16, 2024
    Last edited: Feb 16, 2024
  13. tochatihu

    tochatihu Senior Member

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    Few would doubt that militaries optimize their UAV props for their missions. More might doubt that everything useful for other users' space becomes available.

    I have seen since posting first on this that an abundance of aftermarket props are offered to civilians. Those may or not be derived from CFD across civilian user space.. But since we're talking about Bob here, some links:

    https://journals.sagepub.com/doi/10.1177/16878132231206330
    Energies | Free Full-Text | Variable Pitch Propeller for UAV-Experimental Tests
    Design and analysis of passive variable-pitch propeller for VTOL UAVs - ScienceDirect
     
    #13 tochatihu, Feb 16, 2024
  14. fuzzy1

    fuzzy1 Senior Member

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    That is how the family farm acquired its first and only quad-copter drone, a Star Wars X-Wing Fighter. Found in cow pasture while checking fenceline just before herd was to be turned in and trample it. Sans controller, so it is now just a fireplace mantelpiece. Still has its training wheels propeller bumper guards attached.
     
    #14 fuzzy1, Feb 16, 2024
  15. John321

    John321 Senior Member

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    #15 John321, Feb 22, 2024
    Last edited: Feb 22, 2024
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