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Question about triple blades...

Discussion in 'Phantom 2 Discussion' started by Ezookiel, Dec 29, 2014.

  1. Ezookiel

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    G'day all,
    I've only been a quad owner a week, and with stormy weather in that week, I've only managed to fly it twice.
    While I was looking for photos of a Carbon Fibre Phantom 2 to show a friend what one looks like, I found some replacement blades for the P2 that are a carbon fibre, folding, 3 blade design.
    What would the advantage/disadvantage be to these having 3 blades on each?
    I'm assuming more lift if you have 3 blades on each corner, but probably less flight time as spinning 3 blades might be more power hungry than spinning 2, but that would only be guessing. Would that be correct?
    I can't work out if they'll spin slower, so make the quad slower, or give more thrust and so make the quad faster? I still have a lot to work out in the dynamics between prop size, spin speed, number of blades, and how those affect flight times, lifting capacity, speed, etc.

    The folding design would be nice for packing away in it's case, possibly without having to remove the blades, but mine won't go in the case with the prop guards on anyway, so until I'm confident to remove them, I don't get to use the case much anyway.
    They might also suffer less damage in an impact if they would fold under the contact, but again that's surmising rather than knowing.

    Would love to know what others think of them.
     
  2. Mako79

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  3. Ezookiel

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    That looks like them.
    What are the advantages or disadvantages to them?
    They'd sure look mean on a carbon fibre one. They look mean on that one, so on a black CF model, they should really look good.
    Are they 9 inch?
     
  4. Mako79

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    These are the STO ones from infinite Hobbies.
    The are NOT carbon fibre. The are the same lengths as DJI once attached to the 3 way hub.
    http://www.infinity-hobby.com/main/prod ... s_id=10955

    Pros:
    You can always keep them on for quick ATTI launches.
    Looks cool.
    Longevity as they fold when obstructed.
    Folds away for storage.
    The props are cheap

    Cons:
    Less flight times from weight.
    Needs inspection before flight to make sure there isn't too tight or too loose as you get imbalance or lose a prop.

    Performance.
    Feels more nimble (placebo maybe).
    I haven't tried increasing cargo weight.
     
  5. Ezookiel

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    The risk of loss of a prop would be a huge con for me.
    Once up in the air away from obstacles, then short of a fly-away, bird strike, or loss of a prop, there's not a lot else that will bring you back down unless you choose to come down. But losing a prop would do it real fast. It's kind of why I love the self-tightening ones so much, there's just that little more confidence when out over water, or over a forest, or going somewhere that you really don't want to come down.
    The ones I saw were definitely carbon fibre, so maybe these are a similar system but without the CF. The CF ones would cut the weight issue a bit.

    I'd love to be able to calculate the actual physics, so I could know if an extra blade, gives enough extra lift, to compensate for the extra power used to spin that extra blade.
     
  6. PhantomFanatic

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    I posted the same thing in the past. I didn't buy them, but I wanted to find out the true pros and cons. About all of the response were negative, though no one had tried them. I finally decided that perhaps DJI didn't put 3 bladed rotors on the Phantom for a reason.

    I'm also curious about drones that have two motors, back to back, with a rotor above and below. It would seem that one rotor would cause an air disturbance for the other.

    About the 3 bladed rotors, why don't you do some tests and let us know the results?
     
  7. PhantomFanatic

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    Is that your bird or a photo that you ran across? If it is yours, spout forth thy knowledge! :)
     
  8. PhantomFanatic

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    I didn't read this until now. I may have to buy some. From what you said, are these not self-tighten versions?
     
  9. Mako79

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    That is my bird.

    the 3 way hub is self tightening, however the fold component is NOT self tightening. There is no manual or a suggested torque setting.

    I did do some tests and posted up on an earlier post that I cannot find. The search on this forum isn't the best.
     
  10. EMCSQUAR

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    I did comparisons last year on the std vs tri props - http://youtu.be/5tccMBb815s?list=UU_2vD ... VSNdmm127A

    Overall tri props were tough to balance and caused alot of turbulence in normal flying and with gimbal. They worked well for speed and were better for lift, but stability was questionable.
     
  11. Meta4

    Meta4 Moderator
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    For some reason new owners are particularly attracted to prop "upgrades" for their Phantoms.
    DJI engineers put a lot of effort into getting the stock props right and all year I haven't heard anyone come up with any improvement in the prop department. There have been quite a few reporting less than satisfactory performance for various reasons.
    For the OP .. you have prop guards on your bird and you are tempted by badass black CF tri-blades!
    You'll get a significant performance boost by taking those sails off your machine (and a better chance it won't crash)
     
  12. SteveMann

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    Here's a NASA study on coaxial rotors: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19970015550.pdf
    More math than I can ever understand, but here's the conclusion:
     
  13. Ezookiel

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    Thanks Meta4 (great name by the way) I fully intend to take the prop guards off. The guards are really only there for while I get the hang of flying these larger quads. They paid off today when she twice tipped over on landing in 18kmh winds that were gusting to 23kmh. I'm told the 30km/h is starting to stretch the friendship with these things, but today seemed manageable, if not just a little more challenging. But that's why I was deliberately flying in winds --- to build my skills up more quickly. It's pretty easy to fly these things in still conditions, and if that's all I ever flew in, I'd not learn much. I sure learned a lot more today flying in higher gusty winds.
    Gotta say that I loved the challenge today. It was bloody awesome actually - I'm still smiling from ear to ear. But today was a mixed lot with the guards - yes they saved it twice when it tipped on landing, but I also suspect that the surface area that you described as a "sail" is exactly that, and really adds to the battle with the winds, and may have contributed to the tip overs. I think rather than PG's, I should probably have gone with the wider angle legs, which stop it tipping so easily. Or just learn to fly better ;)

    I mostly like the idea of CF blades because the body is CF, and so CF blades will really look the part. I like the way my quad looks, and want to improve that look.
    It's not really looking for an upgrade, it's more about "looks" (yes, I know how sad that is)
     
  14. Meta4

    Meta4 Moderator
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    1. Lots of flyers have tried CF blades but the general opinion is you are better off with the original props.
    2. 30 km/hr = 18.5 m/h Your Phantom can handle more than that with ease
    3. Propguards are a good way to crash your Phantom. They significantly handicap its performance and as you observed catch the wind. They cause more problems than they prevent.
     
  15. Ezookiel

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    I'm taking them off as I write this.
    Firstly because I have 3 full sets of spare blades, so even if a blade or two is damaged, I'm not exactly short of them, and secondly the guard stops me packing it away which is sure to end up damaging something just taking it to and from the car, and thirdly I've noticed on several occasions I've had a nice perfect landing, and then it's blown over AFTER the quad is settled enough to have not been caused by the landing itself, but had to have been blown over. So I tend to agree with your assessment of them being more trouble than help.
    The 30km/h wind limit was based on something the guy in the hobby store that put it all together for me had said. I'd asked how susceptible these are to winds, and he said "We've had them out in up to 30km/h winds." The way he said it, it sounded like that was really pushing the limits at that kind of wind speed.
    Even in the 25km/h gusts the other day I noticed I had no trouble flying back against them. Perhaps slower than flying away, but they sure weren't threatening the quad in any way, and that was with the sails on it.
    By the way, thanks for the advice. I really appreciate it.