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Flight time reduction vrs weight added

Discussion in 'General Discussion' started by Peter Patricelli, Sep 30, 2013.

  1. Peter Patricelli

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    I am surprised there has not been more discussion on here about this issue. We all start with the exact same critter, which, without a camera, will fly 11-13 minutes on a stock battery charge. After adding gimbal, camera, FPV, and maybe recovery beacon, people are getting maybe 4 minutes. The effect of each and every gram of weight is very significant and dramatic.

    In discussion about various gimbals, I was floored to find out, when I checked, that some gimbals weighed 400 gms without camera! My Hero2 weighs 100 gms, the protective case 70. The Hero3 is lighter...dunno the weight. The Zenmuse lists itself as 180 gms WITH camera!! I don't know whether this includes all of the extras necessary to drive the unit, but that is impressively LIGHT.

    In all of the discussions about various FPV units, setups and options regarding power, etc......I have never seen mention about the WEIGHT of the different units.

    As I think about and plan what I want to do with my craft, what to add...or not....then WHICH unit or system....weight will probably have as much or more effect on my flying experience, day after day, than cost.....which is a one time OUCH!

    I would like to generate, for m own interest and purposes, a Reduction in Flight Time (RFT) vesus Weight (gms) graph. The process should be simple, sine I have nothing permanently attached yet.....time a couple of naked, hovering only flights to forced landing.....then add some known weight.....measure flight time......add more weight, etc., etc.

    If that works well, then when they arrive I might generate one with 3 bladed props, etc.

    Has anyone ever done this? Does one already exist?
     
  2. rilot

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  3. Peter Patricelli

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    rilot,
    I assumed something like that existed....didn't know where. Very complete and scientific. Impressive. However, it would take me about as much time to learn WTH and get the figures necessary to get a chart...at +/- 10%....than it will take me to generate one empirically....at I hope better than +/-10%....more specific to the Phantom.
     
  4. Roadkilt

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    That is an interesting spreadsheet for sure although I don't know what half the parameters are, like type of motor, which isn't listed. But I did a good guess at everything and it still doesn't show what the lifting weight efficiency is, or at least I didn't see it. Stock battery, full charge, time out to first level voltage warning. Add 100 grams, repeat. Plot and regress to a curve showing diminishing times. That sounds pretty simple and useful. Next experiment would be with a gimbal and its power draw. And then adding a second battery and how much real time that adds minus the penalty for weight. One thing those graphs wouldn't show is the limited flight handling of so much weight and the stress on the frame and props. The motors themselves can handle more load as the F450 and F550 models use the same motors, just bigger amp ESCs, 30 instead of 18.
     
  5. macbates

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    Another factor would be base altitude. I'm at 7,450 ft MSL (north of Colorado Springs), and with a stock Phantom plus the prop guards, freshly charged stock DJI battery, 52 degrees F, hovering at 6 ft, the time from takeoff to forced landing was 8 minutes, 55 seconds. This seems well below what other people have reported, so I'm guessing that as expected, higher base altitudes can dramatically affect flight times. Temperature is probably another factor, although it may only be a second order effect.

    I've got some carbon fibre blades on order and will see if they make any significant difference in the flight time.

    - Ken
     
  6. BruceTS

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    There has been plenty of discussions about weight affecting flight times on this forum and way to increase it.
     
  7. miskatonic

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    Think of state of the Phantom as a Compaq or HP from the 1990s. It is often times better to build a new system then to keep throwing mod after mod into a stock system. Phantoms are great for the first time user but if you want to do much beyond what is stock in the box you will need to do modifications that push the system to the limit. Often times it is more economical to piece a system together from scratch.

    To give the Phantom have greater endurance people add larger props, motors, and battery packs. Doing so pretty much kills maneuverability and makes the Phantom a brick. Adding a lot of weight also pushes the Phantom to the limits and adds a lot of wear and tear. At the point that you need to strap on so much gear that your Phantom no longer has anything close to the characteristics it originally had, you are better off with a F550.

    I say this because I have had my Phantom for about a month. I have learned a lot and I think that I am ready to ditch my Phantom and build something that has the endurance that I need to do what I want without serious modification.
     
  8. andysydney

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    I'm not sure how much weight a gimbal, gopro, and FPV set up adds to the phantom stock set-up. As a test, I added a 1.5 pound diving weight to the phantom and flew it this weekend. It handled like a brick. I was able to get 2 minutes of flight time until it wouldn't lift anymore. I took the weight off and was able to fly for an additional 8 minutes on same stock DJI battery.
     
  9. Peter Patricelli

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    "There has been plenty of discussions about weight affecting flight times on this forum and way to increase it."

    I am sure. But with a reasonably accurate graph one can not only judge the fligh-time effect of any additions, but calculate the trade-offs wt vrs $, etc.

    "It is often times better to build a new system then to keep throwing mod after mod into a stock system."

    I think you are 100% correct in your whole thought. But, there are k's and k's of Phantoms out there, and I suspect the majority of first time owners are NOT going to build a bigger, better mousetrap. In my case, it was a gift....so I am looking at what kind of lemonade I can make with it. For all those first-time owners....want to hang a camera? take off x minutes of flight time. Tired of jello?...get a gimbal and lose another x minutes of flight time (depending...brand x vrs y). Want to get on-board view....take off another x minutes (depending band x vrs y). Want a recovery beacon.....take off another x minutes. And so on.

    Might as well have a reasonably accurate picture of what is going to happen to flight time BEFORE investing $1K in additional gadgets. Or...I might save $100 on this brand/system....BUT....it's additional weight is going to lose x minutes EVERY flight. Hmmmm!?

    Re-charging the same battery makes me wait between measured flights, but I've got two points already. I will have a preliminary graph by this evening.

    Hey, it is just numbers and information. Everyone should feel free to ignore it if they wish. Making the graph gives me something to do with my birthday present.