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Weight problem... help

Discussion in 'General Discussion' started by Grazman, Dec 8, 2013.

  1. Grazman

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    Hello, I have the problem of excessive weight on my Dji Phantom.

    - Phantom 1.1.1
    - Tarot gimbal
    - GoPro Hero 3
    - Fpv
    - 2 original 2200 mAh batteries with carbon support
    - Original motors
    - Original self tightening propellers

    Total weight of 1450 grams. Flight Time: 3.5 / 4 minutes, really too low.
    I do not understand where this weight comes from: it is the same configuration many use, but they have weights of 1150/1200 grams.

    Will you help me figure out how to lighten the Dji Phantom and how to get more flight time?
    Has anyone ever used powerful batteries, such as 2 battery 3000/3500 mAh?
    Thank you.

    Tom

    ps: I'm looking for a GoPro 3 protection case for Tarot Gimbal: who can help me?
     
  2. ElGuano

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    That is a bit on the heavy side, but you won't find many people running dual-batteries, gimbal and FPV under 1200g. I think I have one the lighter modded Phantoms out there, and with gimbal, gopro, fpv, 4400mah, and 9" CF props I tip the scales at 1210g. I haven't seen anyone with a similar setup be any lighter. Without gimbal or FPV, my naked Phantom with dual batteries is 937g and flies for over 22 minutes. You can't add a Tarot and gopro to that (250g combined) and stay under 1150g. I think most people you see with that gear under 1200g are running single batteries.

    There are a few ways to save a lot of weight. Are you running prop guards? Those weigh a ton. How is stuff like your Tarot and FPV bolted to your Phantom? For your dual batteries, the carbon plates + hardware + parallel cable probably add over 70-80g over the weight of the second battery alone. If you're going that route, it may be worth looking at running a single 2700-2800mah battery instead. How are the batteries mounted (are they exposed to the downdraft of the props)? Are you using the standard landing gear? If you have a Tarot gimbal, you are probably using some kind of landing gear extensions (even more weight). There are replacement landing gear available that are taller and still less than half the weight of the stock gear.

    From there you can get into all kinds of more extreme ways to save weight, but the returns start diminishing.
     
  3. rotorhead42

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    Do away with dual batteries and use a single 2800 mAh one, you`ll get 8 solid minutes.
     
  4. ElGuano

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    That might be optimistic given he's currently getting ~3-4 minutes. It really depends on how inefficient his dual-battery setup is, though I agree that most likely he'll be better off with a larger single battery.
     
  5. Peter Patricelli

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    If the original self-tightening props are not 9"....then you can do much better with a prop change.

    The basic IN-efficiency of your battery set-up aside as mentioned by El Guano, there are two problems. 1) how much "stuff" you keep adding to the bird, and 2) how much the individual components of that "stuff" weighs. There are lighter cameras and heavier cameras. There are lighter landing gear and heavier landing gear, etc., etc.. Assume each GRAM of weight costs you one second of flight time. if you save 30 grams....you GAIN 30 seconds of flight time.

    the FIRST thing I look at at ANY addition is the WEIGHT! I weight nuts and bolts and screws, antenna, wires....EVERYTHING. 4 grams her, 5 there, pretty soon you have gained a minute.

    The Zen-muse gimbal and GP3B combo weighs 230 gms. The Tarot (or any OTHER gimbal) + camera are 275 gms. there is 40 seconds.

    Fancy landing gear can weigh 100 gms. Stock is about 46 (I think). You can get sticks for 35 or so. There is ten seconds.

    Basically, did you look CAREFULLY at the weight of each thing you added and consider the price versus necessity. Maybe you bought an FPV TX that was 600 or 1000 mW wanting "more than enough" when 250 mW (physically lighter) might do for your purposes. With 4 minutes of flight time you aren't going far....are you?

    Seems to me most who get great flight time have upgraded motors, carefully test their props, and carefully research the components rather than buying the first, fanciest mod they see.

    Getting a battery voltage tester and carefully monitoring when your low battery sequences (changeable in Assistant) are set and when they start might reveal something "off" on your setup. Remember, the red lights begin when voltage drops to a set point....initially only when the motors are really under load, then continually when even hovering pulls the voltage down to that set level. With a REALLY HEAVY bird, the load of CLIMBING or maneuvering is severe and you will get temporary red lights much EARLIER so the TIME BETWEEN first warning level and second warning level gets MUCH LONGER than with a light bird. it is hard (and dangerous) to keep flying when you are seeing lots of red lights but there are ways of taking advantage of that. But you really have to understand your bird and batteries, so a lot of testing and timing. Not for the faint-hearted.

    The Phantom is NOT a mule pulling a cart. You either need a basically bigger bird, like a 450 or 550, or your bird needs to go on a diet.
     
  6. Peter Patricelli

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    PS....the GoPro protective case for the H3B weighs 100 gms. That takes you down to 2.5 minutes. Sure you WANT that? There is none for the Tarot gimbal without EXTENSIVE modifications....thankully for you. Fly more, better, safer...and ditch the case idea like the rest of us who are pushing the flight time problem hard.
     
  7. ElGuano

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    Simensays makes a (non-waterproof) protective housing for the GP3 that is custom-made for the Tarot gimbal. It weighs exactly the same as the GoPro tray and you have to transfer your gyro/accelerometer circuit to it. It costs quite a bit, but at least it's not going to add to your AUW.

    http://www.shapeways.com/model/1291611/ ... erialId=25
     
  8. TheAirToad

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    I'm running 1070 grams and 8 minutes run times with;

    Phantom
    FPV 1mW boscam
    Zenmuse gimbal
    GoPro 3+
    Gimbal lowering unit with FPV mount
    Extended landing gear
    1 original battery
    Original motors and props.

    I have a Hero3+ but I think it's the same weight as Hero3.
    Extra battery would be 1240 grams. Can't see where your extra weight is coming from. The image shows carbon props but I damaged 1 so I weighed it with original props.
    [​IMG]
    [​IMG]
    Extended landing gear comes in at 25.7 gm.
     
  9. ElGuano

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    Airtoad,

    That's awesome, your landing gear already beats mine by 1.3g, and you're using aluminum tubing to boot! Think you can save a few more grams by using thin-walled carbon fiber legs?

    It looks like your Phantom weight is ~900g without the battery. That puts you at about 1215-1220g if you went to a single 4400mah 3S2P, which is quite impressive; it'd be only 5-10g more than mine. I do see that you have the lighter Zenmuse gimbal, but seeing as your landing gear is lighter to begin with, do you have any other weight saving mods have you made? I'm always looking for opportunities to cut down the weight on mine even further.
     
  10. TheAirToad

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    I had carbon but kept breaking them. Came in at 22.8 gm with carbon fiber. Where are you getting yours?
    No real additional trimming. Changed wire harness for FPV to save 1g.
     
  11. ElGuano

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    Hmm, you may be doing some harder landings or transport than I am! I got some 0.55mm thickness CF legs that are very stiff and much thinner and lighter than the standard 2mm thickness tubing. I cut mine to 4.8 inches, and I've never had a problem with them in dozens of landings, but they're really quite thin.

    Just found my receipt. It was $4 from BPHobbies.

    How much do your 3D-printed parts weigh without the tubing and screws?
     
  12. TheAirToad

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    14.2g without alum. no screws friction fit. Been running with aluminum since Sept. with no problems. I broke them in handling not landing didn't take much when I hit them sideways.
    Mine are 150 mm long for a total just over 6 inches. I needed the extra because I lowered the gimbal about an inch.
     
  13. ElGuano

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    Ah, thanks! My legs weigh about 1.1g each at 4.8" length. My 3D printed parts are 22g (including compass mount, no screws).
     
  14. Peter Patricelli

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    Sorry, but the source of those leg mounts would be???? They do not appear to be the Simensays
     
  15. Dave Pitman

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  16. Peter Patricelli

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    Thanks Dave.

    Since there is new stuff coming out all the time, I just searched again and found these at 12 GMS!!!!! that is the lightest I have ever seen that allows for the gimbal/camera. These are an INSTANT half minute flight over OEM.

    http://www.ebay.com/itm/DJI-Phantom-Lan ... 2a2eb2f356

    BUT...at $60 (shipping included) that is $2270 per POUND!! For a simple molded piece of plastic! Yeah, I know, but I am not THAT desperate...YET

    OP....please note the excruciating obsession with WEIGHT! Changing a wire harness to save 1 gm (above)!
     
  17. ElGuano

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    They say it's "12g lighter than original." My original landing gear are 47g, so these are 35g. That's a middling savings if you're really trying to reduce the weight of the landing gear :)
     
  18. Dave Pitman

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    A gps/compass puck, custom takeoff platform, hand catch (with same custom platform)....no landing gear required at all.
     
  19. Peter Patricelli

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    "12gms lighter than original"

    You are right, I misread it. Sorry. That 0nly reduces it to about $1100 per pound.