Warning - Do not use aftermarket props

Discussion in 'ALTA' started by Tabb Firchau, Jan 4, 2016.

  1. Tabb Firchau

    Tabb Firchau Administrator
    Staff Member

    Joined:
    Jun 28, 2012
    Messages:
    910
    Likes Received:
    472
    I made a post about this a while back, but wanted to make sure everyone got the message.

    http://forum.freeflysystems.com/index.php?threads/alta-after-market-props.7137/page-2#post-65213

    The motor drives on the ALTA are not like standard off the shelf ESC's you are all used to using. The drives are tuned specifically for the combination of the F45 motor and the ALTA prop. The weight and inertia of every prop is different, and thus requires new tuning of the motor drive to function reliably.

    Using a prop other then the stock ALTA prop can (and has) caused a crash. The failure mode is that the motor drive can lose sync with the motor and then cause all kinds of problems including stopping the motor.

    So long story short, only use the stock ALTA props.

    Thanks

    Tabb
     
  2. Cam Batten

    Cam Batten Member

    Joined:
    Jun 10, 2013
    Messages:
    103
    Likes Received:
    4
    Tabb, what are the chances of FF selling individual prop blades? I think a lot of users would see value in being able to purchase just the individual blades rather then an entire assembly, which is rather price inhibitive to keeping a set of spares.

    Having to purchase an entire assembly if you only had a chip from a single blade is a costly endeavour.

    I understand there may be a reason behind this strategy, such as blades are balanced in pairs, but if not, is this going to become an option?
     
  3. Tabb Firchau

    Tabb Firchau Administrator
    Staff Member

    Joined:
    Jun 28, 2012
    Messages:
    910
    Likes Received:
    472
    Cam, the blades are balanced pairs, so we cannot sell single blades and ensure adequate balance. Improper balance can cause vibration levels that are unacceptable for the ALTA.
     
    Cam Batten likes this.
  4. Cam Batten

    Cam Batten Member

    Joined:
    Jun 10, 2013
    Messages:
    103
    Likes Received:
    4

    No worries, thanks for the response
     
  5. Steve Maller

    Steve Maller UAV Grief Counselor

    Joined:
    Oct 30, 2012
    Messages:
    3,979
    Likes Received:
    807
    Tabb,
    How about selling matched pairs of blades?
    Or maybe you could do an exchange program where we can send in expired :rolleyes: ALTA props and pay for you to replace just the blades and rebalance them? $129 is not an unfair price for a new prop, but it feels wasteful to throw away the hub/bumpers, etc.
     
    Michael McVay likes this.
  6. Josh Lambeth

    Josh Lambeth Well-Known Member

    Joined:
    Jun 29, 2012
    Messages:
    1,312
    Likes Received:
    213

    What is an acceptable level of vibration? Still haven't received an answer on this.

    Thanks

    Josh
     
  7. Steve Maller

    Steve Maller UAV Grief Counselor

    Joined:
    Oct 30, 2012
    Messages:
    3,979
    Likes Received:
    807
    This brings up a related question: if I have a nick or some other blemish on a prop and I continue to use it, how can I check to see if it's causing any stress or anxiety to the Motor/ESC/Synapse?
     
  8. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
    Staff Member

    Joined:
    Jul 31, 2012
    Messages:
    10,347
    Likes Received:
    1,159
    If you look at the Synapse flight logs, Steve, you'll see that there Motor Acceleration values in columns DK to DP.
    Have a look at pre-nick/blemish flights and compare the vibrations with the post-nick/blemish. I'm not quite sure what the units are, but I'd go with the "teeny numbers good, big numbers bad" approach.

    If you run the Synapse Flight Log Converter, you'll also see a summary in the flight metrics file:

    Maximum ESC Acceleration (check for excessive vibration):
    1 = 32.10 at IMUTime 475.0043 seconds
    2 = 22.30 at IMUTime 480.2814 seconds
    3 = 35.90 at IMUTime 376.1493 seconds
    4 = 24.60 at IMUTime 481.0870 seconds
    5 = 25.00 at IMUTime 433.9960 seconds
    6 = 20.80 at IMUTime 542.9217 seconds
    Average = 26.78, Odd/CW = 31.00, Even/CCW = 22.57, Difference = 8.43


    Andy.
     
    Dimitar Krustev likes this.
  9. Steve Maller

    Steve Maller UAV Grief Counselor

    Joined:
    Oct 30, 2012
    Messages:
    3,979
    Likes Received:
    807
    Thank you, Andy! I'll look and see (if I...ahem...ever nick a prop). :)
     
  10. Tabb Firchau

    Tabb Firchau Administrator
    Staff Member

    Joined:
    Jun 28, 2012
    Messages:
    910
    Likes Received:
    472


    Hey Josh,

    If you see anything above +- .3 G deviation on the X Y or Z accelerometer on the Synapse I would investigate (I mainly worry about the Z axis!)
     
  11. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
    Staff Member

    Joined:
    Jul 31, 2012
    Messages:
    10,347
    Likes Received:
    1,159
    Tabb: The values in the Synapse log appear to be just numbers (the units are shown as "#") -- they may even be dimensionless.
    How do we convert them to G accelerations, please?

    Thanks
    Andy
     
  12. Tabb Firchau

    Tabb Firchau Administrator
    Staff Member

    Joined:
    Jun 28, 2012
    Messages:
    910
    Likes Received:
    472
    Hey Andy,

    I am talking about the Accel X Y and Z readings in the "IMU Basic Readings" Those are the ones I was talking about. I think you are looking at the Accel 1-6 for the motors. I dont typically use those motor acceleration readings as they are more difficult to set a proper threshold.

    Hope that helps clarify (slightly)
     
  13. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
    Staff Member

    Joined:
    Jul 31, 2012
    Messages:
    10,347
    Likes Received:
    1,159
    Gotcha. You're right. I was looking at specific motors in the context of Steve's hypothetical (cough, cough :rolleyes:) nick in one prop. Should that ever happen to him...

    The IMU Basic Readings are for the ALTA as a whole, so I can see why that would be a good "tell tale" for a problem -- and the odds are that there would be an "outlier" reading for Accel 1 - 6 that would point the finger at which ESC was experiencing unusual vibration caused by the hypothetical nick. :)

    Andy.
     
  14. Steve Maller

    Steve Maller UAV Grief Counselor

    Joined:
    Oct 30, 2012
    Messages:
    3,979
    Likes Received:
    807
    "Hypothetical Nick" is what I call my pretend camera operator when I'm flying solo. :)
     
    Mateusz Hajdziony and alex ryan like this.

Share This Page