Jitter on tilt when conrtrolling with Spektrum

Discussion in 'Radian' started by Thijm, Oct 9, 2012.

  1. Howard Dapp

    Howard Dapp Active Member

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    I see you're investing loads of time and effort into producing an ULTRA smooth flying heavy lifting rig rather than focusing solely on a rig that can lift a heavy load. Faster spinning smaller diameter props will certainly produce a smoother flying rig, it's finding the perfect prop size/motor kv/lipo voltage combo that makes it grueling. It's also exciting to hear that there are so many prop size options for a big lift rig running 6s with the kw10s...13"-15" props can be used depending on payload. I'd never guess that 13" props would be enough to lift a rig hauling a full Epic setup.

    As for your previous setup, it takes a brave soul to build an octo with 830kv motors on 6s! Sounds terrifying!!!
     
  2. Thijm

    Thijm Member

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    The 13" props only work well at Sea level. But in conditions like last week > 28-45km/h. I really miss the xtra power. So 14" is the correct route for me.
    Previous setup was a bit stupid but Fun! however i had great control over throttle with a fully loaded rig while doing driving shoots at speed!
     
  3. Josh Lambeth

    Josh Lambeth Well-Known Member

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    I am having vibration issues on my setup now... Thought I had gotten things balanced correctly prop wise... but I was wrong... so now I need to go back and do it again!

    Any good tips to make sure they are all balanced correctly? Thanks!

    Josh
     
  4. Howard Dapp

    Howard Dapp Active Member

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    Josh, I've learned some time ago that having a perfectly balanced prop isn't always enough. Sometimes you also have to balance the motor and prop as one system. I'll find the link that explains how to do it.

    I think higher higher kv motors will give you better results overall. If you were flying a heavier camera like an Epic then I believe maybe you would have smoother results with your current setup.
     
  5. Josh Lambeth

    Josh Lambeth Well-Known Member

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    That would be great to see. Thanks!

    Josh
     
  6. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Howard: Did you have OMM (Old Man Mike's) method in mind?
    I got the following from http://www.rcgroups.com/forums/showthread.php?t=1560414


    Balancing props and motors first separately and then together dynamically is important for reducing vibrations which can interfere with gyros and accelerometers and cause fuzzy photos and video. Magnetic balancers are best for static balancing props. There are various techniques for dynamic balancing of the prop and motor combination, such as the procedure suggested by OMM here:http://www.rcgroups.com/forums/showp...&postcount=228.
    **Laser motor balancing is recommended and can also be used to assist in the dynamic motor and prop balancing using OMM's method: How to balance a brushless motor using a Laser
    Prop balancing video tutorials: Prop balancing video tutorial and HorizonHobby.com How To - Prop Balancing and Motor balancing by sound by Alllbe and Balancing 3-bladed props.

    I've not checked all the links, but they looked promising.
    Andy.
     
  7. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    There's also this technique using an iPhone (or Android) with a vibration measuring app.


    I wonder if you could do this one motor/prop at a time if you hold down the boom on a CS6/8 and use the MK Tool's Motor Test?
    I hate having props spinning on my workbench....

    Andy.
     
  8. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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  9. Howard Dapp

    Howard Dapp Active Member

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    Yes, the OMM method. thanks for locating that Andy! Josh, as a test try hard mounting your gimbal, no o-rings or any dampening. Maybe you can use some zip ties to tightly fix the gimbal to the frame. As crazy as it sounds sometimes hard mounting produce better results.
     
  10. Thijm

    Thijm Member

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    indeed an daunting task. But it will pay of for flight characteristic and stable image when hard mounting. It has to be 100%

    Edit;Typo
     
  11. Thijm

    Thijm Member

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    Btw Recheck your gain setting's while test flying the hard mounting setup. Otherwise your FC can also ad some vibrations!
     
  12. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Following on from TFCM's comment: I was wondering how many of us have motor wires in hard contact with the FC board? The concern being that those wires might (or will?) feed motor vibration into the FC board -- intuitively this does not seem like a Good Thing.

    I found that, when I braided the motor wires in the boom to reduce the EMI (and possibly RFI), that it shortened them to the point that I had to connect them up to the BL-Ctrls by feeding the wires between the upper surface of the PDB and the lower surface of the FC board....and they form a "bed" on which the FC is in pretty hard contact. I'm wondering whether this might be the cause of some airframe oscillations.

    How are you guys routing the motor wires to the BL-Ctrls? And are they in hard contact with the FC board?

    Andy.
     
  13. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    My pleasure, Mike. I've been quite impressed with what OMM has done.

    I was thinking that just clamping an inspection mirror to a boom out near a motor, and then using the laser technique would allow us to test motor/props in situ so that we don't have to remove'm to balance'm.

    It would require some care, though as you need to orient the prop with the motor casing so that you could return to that position if the prop slips slightly. Also, there's the issue of tethering the bird to the bench during testing, but that's relatively easy (what are woodworker's bench clamps for, eh?)

    Andy.
     
  14. Josh Lambeth

    Josh Lambeth Well-Known Member

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    I just found a nice app for Android. I am going to try this tonight.


    How many people balance using scotch tape? I am not sure I want to sand down my props since it will take the finish off them. Any suggestions? Also do you all use thick CA glue on the hub or something else? Thanks for the help!

    Josh
     
  15. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    I sand the back surface of the outermost part of the APC props -- 180 grit to get close, 320 to smooth back off. The outermost part means the most change for the least amount of material.

    I agree with you that you'll damage the finish, Josh, so all I've seen is Scotch tape -- or PVC tape on a motor housing to balance it.

    As a side note, the Top Flite magnetic balancer doesn't allow for me to put the 14" props vertically, so I was tempted either to (a) hack it to make the side pieces taller, (b) purchase a Du-Bro 499 which allows for "over the shoulder" operation so that the prop dangles off the edge of the table, or (c) something else.

    Once I solve that problem, then I'll go with the Velcro fuzzy material on the hub and adding CA for mass (and sanding it to reduce it).

    One question haunting me: If you're going to dynamically balance the motor and the propeller, why balance the propeller alone? Given the combo is likely to start out being out of balance, could you not use the differential mass of the propeller, rotating it around, to help bring the combination into dynamic balance instead of adding tape?

    I've not graduated to wooden props yet (and my Cinestars have training wheels). I need to stop trimming foliage with the plastic props first.
    Andy.
     
  16. Josh Lambeth

    Josh Lambeth Well-Known Member

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    I too was wondering how possible that would be. Might experiment with it tonight.
     
  17. Josh Lambeth

    Josh Lambeth Well-Known Member

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    This process sucks... Thats all i have to say...

    I guess my next question is... how much vibration is to much vibration? I have reduced the amount of vibration in the motor/prop combo but I don't know if it's enough? Im wondering how with the APC props and motors I was running before I never balanced them and they produced smoother results then these?

    BTW the Xoar props are all out of balance... not a single one has been correct... one was pretty darn close but so far all the others have needed a good amount of balancing done. Some of the hubs were pretty far out too... to the point that I have had to actually glue some small pieces of plastic to the hub to get it to balance... and even then they are still not perfect. Any suggestions? Anyone else run into this with these Xoar props?

    josh
     
  18. Howard Dapp

    Howard Dapp Active Member

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    How rigid is your Cinestar build? Maybe you need to try stiffening it some? Bracing in between the arms possibly.
     
  19. Thijm

    Thijm Member

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    Same here! also used some CA to ad a very small washer or nut to balance the prop
     
  20. Josh Lambeth

    Josh Lambeth Well-Known Member

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    Just went through and re-balanced using washers on some of the hubs. All perfect now! Thanks for the tip!

    Josh
     

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