Home Forums Everything about everything else Impossible Tail Duct (With .STL)

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  • #58897
    Kevin_Erik
    Moderator

    Did a quick test flight and thus far everything works!

    A bit of vibration can be heard at lower RPM’s signifying the propellers coming into contact with one of the ducts. Will need to adjust the placement of the propellers before a full out FPV flight.

    #58915
    Kevin_Erik
    Moderator

    Acro Flight

    Note: Copter has not yet been tail / auto-tuned for use with the Ducts. Odds are that some of the resonance encountered may be reduced with proper tuning.

    First impression: Was that the throttle was wrong somehow cause is wasn’t even using 15% to achieve a stable hover. Furthermore the forward flight shown in the video was slower. Please be aware, that ‘m deliberately keeping the throttle < 50% and speed down to avoid oscillations during testing. Even still there’s a noticeable decrease in forward speed. (maybe 1/4th or 1/3rd slower)

    Resonance: Just above idle, there is a strong vibration as the ducts achieve resonance but as throttle is increased this quickly goes away. I suspect that changing the print material or method would help reduce the likelihood of resonance. Maybe thickening some parts of the wall would also help.

    Wall Tolerance: After some effort I was able to get the propellers centered within the Ducts. ( < 1 mm ) However at resonance it’s still possible for the propellers to briefly contact the walls. This can be heard at the very start of the video, then stops as the throttle increases.

    Maneuverability and Stability: Other than a slight amount of Tail-wag the copter was very stable and had no issues flying under / around trees.

    #58976
    Kevin_Erik
    Moderator

    I think I’ve discovered whats caising the resonance and will test fly tomorrow to see if its gone.

    #58993
    Kevin_Erik
    Moderator

    Performed the dRonin Tail Calibration and Autotune while the ducts ware installed.

    Motor Thrust Factor: 12.95762730
    Servo Speed: 243.61677551
    Max Angle: 35 (Manually limited due to Baby-Tri’s frame coming in contact with Duct wall)

    It was a pretty windy day but all things considered, the results were pretty good.

    #59006
    Kevin_Erik
    Moderator

    I’ve completed what testing I’ve wanted to conduct. If there are any bi-copter builders out there interested in trying a pair of ducts, i can send you some. I’ve two pair currently, 3 in-use and a spare.

    Side note: Can effectively hover at 5 Amps or 84 watts.

    #59226
    aaron.neill
    Participant

    Has anyone tried these ducts on a Bicopter yet?? If not i will print these and test them on the bicopter frame.

    #59232
    Kevin_Erik
    Moderator

    @aaron

    I’ve sent Litterbug 3 Ducts to test out pending the weather / time to be able to do so.
    He’ll magage the test when he feels his chances of succsess are greatest and not before.

    Edit: The while point of the tests is to verify that Ducting the props, shields the Bicopter from its own wash. Thus helping to reduce oscillations and stabilize controlled flight. While I’ve tested it on a Tricopter and “feel”it works. The proof as they say, is in the results. Once everything is confirmed i can begin making structural changes based upon his feedback and video from the flights.

    Beyond that, your welcome to print out your own so long as you understand that these are not easy prints. If printing using ABS they’ll require hand finishing and vapor-smoothing to achive the strenght and polished finish needed. Keep in mind that your propellers will be spinning inside at over 20,000 RPM’s so any print mistakes will quickly become very apparent as your copter implodes. (Sounds like fun huh?)

    Side Note: Do not use PLA as its garbage and will quickly come apart at the layering. ABS is good but Nylon is far far superior. Thats assuming you have the hardware capable of accurately printing Nylon. Personally, i use a contracted 3rd party to print Nylon Ducts for the simple reason, that if they mess up they have to redo it for free.

    My Bench Test: https://m.youtube.com/watch?v=KYfMw9gPbCE

    Maiden Flight: https://m.youtube.com/watch?v=2uCiyu11BtY

    #59233
    aaron.neill
    Participant

    Kevin

    Thanks for the reply. I would greatly appreciate if you could send me the files as I should be able to print this on my own printer. I totally agree with printing these in nylon. Wish me luck!

    #59234
    Kevin_Erik
    Moderator

    @aaron

    The links are on the earlier posts in this thread. Look for the V2, Simple Duct.

    And oh, Good Luck!

    Kevin

    #59479
    Kevin_Erik
    Moderator

    Made the following Changes to the simple Duct to “Beef” it up. (See image)
    Note shown in 1st image is that 1 set of mount holes were removed and the rest were enlarged slightly.
    Total prop area increased from 128mm to 129mm.

    Look for “Beefy” version of Simple Duct on : https://www.thingiverse.com/thing:3032817

    #59576
    Kevin_Erik
    Moderator

    The Beefy Simple-Duct has been printed and is in route.

    #60065
    Frederoo
    Participant

    This is very interesting, I always wanted to try ducts! Still, the precision required and additional aerodynamic issues kind of cooled me down. I think the speed decrease you noticed is due to this effect:

    Or it might be just drag, as you don’t seem to have a lip on yours right now. Does the tail motor work harder than usual? Ie. is it warmer than without the ducts? I will try to print the liped ones out for the BiCopter (on Prusa i3 Mk2 from PLA) when I have the time. PLA is significantly lighter and I never had any layer separation issues, strange…

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