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Maiden Flight of Ranger EX 757-3

Posted by Marc Halcomb on February 10, 2017 at 7:30pm

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I completed the maiden flight of my Ranger EX 757-3 today, with mixed results.  The flying weight today was 6lbs, using a standard rule of thumb, the power requirements would be 450 - 600W.  The supplied 3715/1000KV outrunner brushless motor only provides 300W.

The GOOD:

  • Initial parameter selection flew the aircraft safely and successfully in Manual and FBWA! 
  • The build was good (no bits flew off)!
  • All the systems checked out
    • Pixhawk
    • GPS/Compass
    • Power monitor
    • LIDARlite V3
    • Airspeed sensor
  • Modes checked
    • FBWA
    • Manual - now have a good trim

The Mediocre:

  • Under powered, with the current motor and 6lbs flying weight takeoff and climb out were sluggish
    • Batteries 2 x 5100mah 3S 8C batteries in parallel - which should deliver 40A each 
    • 40A ESC
    • 25A motor (~300W)
    • Looking to upgraded the motor to 450W plus and may need 60A ESC for 600W motor
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Comments

  • mary May 11, 2020 at 1:16am

    dear Marc Halcomb would you please help me on something i wanna find telemetry madule 

    and i have holybro 500 Mw i want to  know is it good for ranger or not?i saw ppl used 3DR and X8R,

  • Marc Halcomb March 31, 2017 at 12:02pm

    I did both, I changed the motor first (E-flite Power 15) and flew with a 3S power pack, the performance was better but not great.  Then I changed from 3S 5100mah to 4S 5500mah and the performance is good, lots of power to climb and at 8-10A cruise I get 30min from one 5500mah battery.

    Takeoff weight of my 757-3 = 2700g

    Original Motor 3S battery:  20A full throttle  950g static thrust (10X5 prop) 

    E-flite Motor 3S battery:  22A full throttle 1325g static thrust (10X7 prop) 

    E-flite Motor 4S battery:  33A full throttle 2150g static thrust (10X6 prop)

    E-flite Motor 4S battery:  30A full throttle 1900g static thrust (10X5 prop)  

    The 10X6 prop runs the motor near the motors recommend maximum, but I only use full throttle for takeoff and have not encountered any thermal issues (yet).  I did not go back and try the original motor with the 4S battery, that may be more than enough to get good performance from the airframe!

    Second flight E-flite motor 3S battery:  https://youtu.be/UFxnw4ubSEs

    third flight E-flite motor 4S battery: https://youtu.be/J7a-_8eF0wY

  • Ben Owen March 31, 2017 at 10:01am

    Can you send me a link to the video? I cant seem to find it. Also did you switch to motor or just upgrade to 4s?

  • Marc Halcomb March 31, 2017 at 8:44am

    I just posted and update from my 3rd flight (with video clip of takeoff/landing), switching to a 4S power pack with the new motor have solved the underpowered problem!

  • Ben Owen February 24, 2017 at 7:02am

    Make sure you post some videos so i can see what a good flying ranger looks like. I'm one click from buying this replacement motor. I just don't know if 3s will work.

  • Marc Halcomb February 23, 2017 at 9:27pm

    Thanks for the input Ben.  After much searching, and some simulation I am switching to 4S batteries.  A static thrust test using 3s batteries and various propeller pitches produced results in the 1375g range for a 2700g aircraft.  The 4S batteries produced 2350g of static thrust.  I plan to fly again soon, the local weather has been wet, so maybe a week or so before the 3rd flight.  I hope to get much of the tuning complete on the next outing.

  • Ben Owen February 22, 2017 at 12:30pm

    I tried stability takeoff with the higher max throttle and it worked well. I don't think I have enough stick time to use the word usually. I mainly keep it in stability to ensure when it crashes it crashes gear down. Because of the under powered motor I never have ventured to the fbwa, b, rth, loiter or any other mode where I surrender throttle control.

  • Marc Halcomb February 20, 2017 at 8:46pm

    Ben, besides the "stable mode" takeoff attempt with the 75% throttle limit, do you usually use one of the stability modes for takeoff? eg FBWA, FBWB, STABILIZE ... 

  • Ben Owen February 18, 2017 at 2:34pm
    Once I tried to take off in stable mode with throttle limited to 75 percent. She never made out off the ground. It's easy to miss a parameter when there are so many to look at.
  • Marc Halcomb February 17, 2017 at 5:35pm

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    I was finally able to complete the 2nd flight of my Ranger EX 757-3.  My expectations were high, the results were less than impressive.  After installation of a 450W motor, I expected to the current in the 40A range (Burst) for takeoff, followed by 34A (Continuous)  at full throttle.  I expected a considerable boost in performance from the maiden flight, but as you can see I am running at 25A full throttle, and from the right-hand plot only 12A in FBWA.

    As a result, I only had slightly better performance for the 2nd flight.  Fortunately, my dodgy takeoff was followed by very stable albeit underpowered FBWA circuits around the field, followed by a nice landing.

    1. The underpowered FBWA mode, was an oversight on my part "THR_MAX" was set to 75% (the default)
    2. Still have not figured out why the new motor is limited to 25A, same as the 300W motor.
      1. I did reset the throttle input settings for the ESC with the new motor, no change?
      2. The battery pack is 2 @ 5100mah 8C's in parallel.  I expect the pack to deliver 40A each battery for a total of 80A's from the pack.
      3. I am tempted to try another ESC, maybe 60A's but that's just a shot in the dark!
    3. Airspeed and rate of climb were ok, but I really expect more from the 450W motor, really need to sort out the power issue before the next flight
    4. Also need to sort out the "roll trim", still has a steady starboard roll in manual mode with the trim full port.
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