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Thread: Broken gets a Stingray

  1. #1
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    Broken gets a Stingray

    I flew 3D helis for years, got burned out, took 10 years off, and recently got excited about RC again after seeing all of the cool FPV stuff people have been doing. Conventional quadcopters had limited appeal due to their limited aerobatic potential, so I was planning to get another 700ish helicopter... but as soon as I heard about Curtis Youngblood's Stingray, I signed up for the waiting list. It's just such a neat idea. Light weight, fully aerobatic, cheap rotor blades, no more boom strikes... what's not to like?*

    It arrived late last week, and I finally opened it up today. What's in the box?

    Click image for larger version. 

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    There was a surprising amount of pre-assembly. The front and rear booms were attached to CNC'd bulkheads, gearboxes were attached, and the pitch mechanisms and blade grips were attached.

    I just realized that I forgot to include the body in that picture. I'll add that tomorrow... It's pre-painted. I'm very happy to get airborne without painting (I hate painting) but just slightly bummed that I won't have my familiar color scheme. I'll order a new canopy at some point, and find someone else to paint it. (Did I mention I hate painting?)

    Tonight I got the drivetrain put together, and mounted the servos:

    Click image for larger version. 

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    The drivetrain in pretty slick - one motor drives a shaft that runs front-to-back, and the rotor at each corner is driven by it's own belt from the central drive shaft. Each corner is essentially equivalent to a conventional helicopter's tail rotor gearbox, but the pitch mechanism allows equal pitch in both directions.

    The only trouble I ran into was with the central drive shaft. One end was just a little too big for the pulleys, and the other end was too big for the pulleys, bearings, or washers. I had to use some sandpaper to turn it down enough to fit properly through the various bearings, washers, and pulleys that it passes through. The fix only took a minute, but it took me a few failed assembly attempts before I realized I was going to need sandpaper.

    But, so far, everything else has dropped into place.

    The instructions called for the servo output shafts to be vertical, but I opted to put them in the same plane as the pitch arms for the rotors:

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    Tomorrow I'll put the pushrods together and mount them, and hopefully get the electronics done as well.

    In the meantime, Curtis has a nice series of videos on his site, showing how to build one of these:

    http://www.youtube.com/embed/videose...RpPkbLg4YICDJU

    * There won't be any autorotations with this. The belts create some drag, and there's no one-way clutch, and the rotors are so light they probably couldn't store much energy anyhow. But then again, the drivetrain is so simple that I expect very few in-flight failures.
    Last edited by Broken; 15th November 2013 at 03:09 AM.

  2. #2
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    I was considering doing a pictorial of how it goes together, but the youtube playlist above does a much better job than I ever could. So I'll skip that.

    Here it is, assembled, with no FPV gear yet - just the Rx, ESC, and flight controller:

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    The Rx came with my Spektrum DX8, and the ESC, motor, servos, and FC all came with the kit. It's available without electronics if you want, but I figure I'm not likely to outsmart Curtis Youngblood when it comes to component selection.

    There is a little bit of free space under the hood for FPV gear, but unfortunately that free space is right next to my receiver... not the best place for a video transmitter. I'm going to build brackets to mount the VTx and the camera closer to the front of the chassis, and I'll probably just leave the body off for FPV flights. Or maybe cut a hole in it to let the camera poke through... but that doesn't sound pretty either. We'll see.

    ---

    After snapping the front and rear landing gear in my first flight, I decided to try TRex 450 landing gear because they seemed to be about the right size and they're relatively flexible. After mounting them, I realized I did this wrong, but you can learn from my mistake. A fragment of the old gear is also shown for comparison:

    Click image for larger version. 

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    The stock gear has a hole in the center that leaves space for the head of the center screw. After drilling the new gear similarly, it occurred to me that it would probably be stronger to just a bolt-sized hole in the middle, and use a washer to add strength. But I'd already drilled a bold-head-sized hole, hence the stack of washers you see here. That's also a longer-than-stock bolt, to keep the same penetration depth, since the bolt also pins the center boom (another bolt also clamps it, but the pinning helps too).

    And here it is from a distance... Again, this is T-Rex 450 gear, cut into two and drilled to fit:

    Click image for larger version. 

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    Last edited by Broken; 19th November 2013 at 01:19 AM.

  3. #3
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    This post reserved for the initial line-of-sight flight tests.

  4. #4
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    This post reserved for FPV electronics.

  5. #5
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    This post reserved for the initial FPV flights.

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    This post reserved for stuff I haven't thought of yet.

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    And one more post, just in case. (Crash-worthiness, perhaps?)

    I'm hoping to get the first LOS flights on Wednesday, and FPV a few days later (next weekend if I'm really lucky).
    Last edited by Broken; 4th November 2013 at 06:06 AM.

  8. #8
    Is working on 12 projects Sicarius's Avatar
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    Oh my.. I must make one of these. Is there a way to get my grubby hands on those CP mounts?
    Youtube username: SicariusMortus
    FPV NL

  9. #9
    Defeating gravity FPVsam's Avatar
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    Broken gets a Stingray

    Funny that he markets his product as the first 3d quad with CP, while I have seen a quad already do this a couple of years ago at a university.
    Team T&B

  10. #10
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    How much was the university selling their models for?

    And how long was his in development? I know its been at least a year, but I wasn't even involved in RC two years back.

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