QAV400 Mods to Increase Flight Time

I built a QAV400 that flies well and records smooth video. I'm getting 10 minute flights using 5200mAh LiPo batteries.

I want longer flight times.

My Plan:

  • Create a baseline using a standard battery.
  • Reduce the weight of the "dirty" frame by 200g, maintaining strength and rigidity.
  • Design the new, lighter frame to allow for 10" props (current limit is 8").
  • Reduce the weight of the "clean" frame by 50g or more.
  • Replace the original 1100kv motors with more efficient, lower kv motors.
  • Document the performance of various prop/motor combinations.
  • Find other ways to reduce overall weight/increase flight time.

Goal: To achieve 30 minute flight times while maintaining good flight performance.

I've been following posts by Forrest Frantz who currently holds the Guinness record for Longest Electric RC Multicopter Flight at 97 minutes!! He has some great threads with tons of info, especially this one on Building Copters with Round Tubes...

I'll be posting detailed notes and photos of each step...

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  • 3702068338?profile=original3702068258?profile=originalHere are some detail shots of the nylon bolts and the ejected motors. Initially, I used shorter nylon bolts just running through the balsa/carbon fiber motor mounts. For my new frame, I added carbon fiber plates under the arms and ran longer nylon bolts through both. I think its much stronger this way and the weight penalty was only 4g total. Thanks to Jim Frantz for the double plate idea.

  • 3702068302?profile=originalHere's my quad right after the crash. (This is not the crash site- I took this picture after we got back to the house). Notice the smashed GPS mast, the missing receiver masts, and the bent video transmitter antenna. Three of the motors ejected on impact but none of the wires broke. Not a single prop was damaged.

    Also, my Styrofoam pontoons were perfectly intact. This could be because the quad was upside down when it hit the ground but its also because I wrapped each pontoon with this fiberglass drywall joint tape. The joint tape is a white, open fiberglass mesh that is super strong and light. I used blue duct tape to attach the pontoons to the frame. Each pontoon weighs 32g (including the blue tape) and will float 2+ pounds. 

  • So, I went to Virginia to visit my friend Jenna Kellen and we went to go fly my new frame. Everything was going well, until something caused my quad to literally fall out of the sky. I've edited the video down to less than 2 minutes so you can get and idea of my flight before the crash.

    The good news is there was minimal damage. As planned, three of the motors were ejected from the frame on impact. This is because I'm using nylon bolts to attach the motors to the frame. Thanks to Forrest Frantz for that idea! I was happy there was no damage to the gimbal. Also, NO PROPS were broken!! Here's a complete damage report:

    - (2) Broken receiver antenna masts
    - (1) Broken GPS mast
    - (1) Broken video transmitter antenna mount
    - (12) stripped 3mm nylon motor mount bolts

    Now the big question- what the hell happened? The battery was fine (I think). GPS appears fine (I was in Alt-hold mode when I crashed). If you listen carefully, it sounds like motors shut off, even though my throttle was up.
    When we got back to the house, I attached the motors with some extra nylon bolts I brought with me. powered it up to see if there was an ESC failure or a wiring problem. The quad armed as usual and ALL FOUR motors started normally. I couldn't fly yet because I had no antennas or GPS mast. I repaired those a few days later.

    I've been talking with Forrest and Hugues about the crash and while they have given me a lot of great information, no one is sure what happened exactly. If anyone would like to study the log from this flight, PLEASE go ahead! I'll attach the log to this post...

    2015-07-28 17-36-55.log

  • 3702068134?profile=originalHere's the completed ship with battery and GoPro, powered and ready to fly, with an AUW of 1749g.

    The Lumenier 5200mAh 4S battery weighs 505g.
    The GoPro HERO 3 camera weighs 75g.

    I won't have much time for flight tests before my trip to Virginia, so we'll see what it does when I'm up there.

    • Great :) , waiting amazing videos ;)

      • Unfortunately, I crashed and I haven't figured out why. See my next post...

  • 3702068540?profile=originalHere's the stock QAV400 upper frame with receiver, flight controller, video transmitter, OSD, 3DR GPS/compass, and Lumenier 2-axis gimbal. A small flight camera is mounted under the gimbal. One of my next projects will be trying to reduce the weight here. While I can't really do much to make the individual components lighter, I definitely think I can reduce the weight of the upper frame itself.

  • 3702068107?profile=originalHere's the lower frame, ready to fly at 634g. This includes 4 motors, 4 propellers, 4 ESCs, QAV400 vibration dampers, landing gear, 3DR power module, and all ESC/motor wiring. At this point, if you added a flight controller, receiver, and battery, you could be in the air.

  • 3702068232?profile=originalHere's the finished frame with the QAV400 vibration dampers and landing gear, weighing in at 121g. The landing gear is in two parts. Four small sections of braided tubing have been permanently glued to the arms. Next, I made some lightweight, 3 inch landing gear from clear tubing fitted with plastic end caps. The landing gear is flexible to absorb impacts. It can also be easily replaced.

    Finally, I cut holes near the center of the frame to feed the ESC control cables and accessory power wires through. Since the carbon fiber skins on the frame are only 0.008" thick, I added some 0.020" reinforcement around each hole. 

  • 3702068432?profile=originalThe completed frame with the arms and motor mounts weighs a total of 94g

    3702068511?profile=originalCompare my V3 frame, which is stiffer and can take up to 10" props, to the original QAV400 frame at a hefty 267 grams. You might be thinking, "Oh but the original QAV400 frame is stronger, etc." But is it? We'll see. Because my frame is a lot lighter and diagonally braced, it should withstand impacts more effectively. Also, I'm using nylon bolts to attach the motors. This should eject the motors on impact and drastically reduce the G forces acting on the frame.

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