Solo specs and ecalc

Hi all,

I am interested in purchasing a Solo and decided to have a closer look at the Solo specs. Apart from all smart things the most interesting values are:

  • Motors: 880 kV
  • Propellers: 10″ diameter 4.5″ pitch
  • Flight battery: Lithium polymer 5200 mAh 14.8 Vdc
  • Flight time: 25 minutes; 20 minutes with payload*
  • Max speed: 55 mph (89 km/h)
  • Weight: 3.3 lbs. (1.5 kg) / 3.9 lbs. (1.8 kg) with GoPro® and Solo Gimbal

I tried to replicate this setup in ecalc. But no matter what motor I selected, I always end up with around 15 min of hover flight time (at 1.8 kg) and a max speed of around 60km/h. I don’t believe in magic and I am pretty sure the 3DR specs are correct.
But even if ecalc is relatively conservative these are big differences. I am wondering where this discrepancy (+-25% in flight time and 40% in max speed) comes from. Any idea?

Best regards,

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  • Has anyone tried to roll their own batteries for this?  5200 mAh seems pretty small compared to what's available on the market.

  • In normal Fly mode you will not get 55MPH. I believe it is around 30 MPH. In Acro mode you might get that speed. I can get around 20 minutes of flight time leaving the battery at around 25%.

    • 3D Robotics

      Fly mode is governed in software. 55 mph is possible in Fly Manual or Stabilize in absolutely ideal conditions (perhaps with a bit of a tailwind) with this stock PixHawk params, but can be achieved more consistently by increasing current limit, lean angles, and perhaps a few others. I had a lot of fun playing around with these while minimizing time to complete an autonomous course I set up.

      Due to the lift generated by the rotors and body, flight time is maximized at 6 m/s. With the hard mount, our flight ops team has seen just over 20 minutes flight time at hover, just under 25 minutes at 6 m/s, and just over 20 minutes at 12 m/s. I don't have the data for flight time with the gimbal, but it is highly likely that the 20 minute figure came at 6 m/s in calm conditions at sea level on a cold day.

    • Daniel,

      Do you have a representation on the speed slider that equates to those settings?

      Or was 6m/s programmed as a limit somehow to get those ratings?

    • 3D Robotics

      Good question. I don't, but I should. If I were forced to spit out some numbers, I would say turtle is 2.5 m/s and rabbit is 15 m/s.

      To do these experiments yourself, you can change WP_NAV_SPEED and/or LOIT_SPEED in Tower and see how that affects your fight time. I would love to see some independent results up here so we can learn about flight times in different conditions.

  • T3

    Thanks for all your replies!

    In summary 20min seem to be possible under optimal conditions. This is good! 45mph (72km/h) as reported by Kelly is pretty fast as well.

    Maybe 15min of flight time is more realistic to have some buffer. I had a look at the last T3 challenge results and the average max speed seems to be around 50km/h. This is closer to what ecalc is guesstimating. This for sure all depends pretty much on the wind conditions. 

  • I haven't gotten anywhere close to 55mph with my Solo. The highest speed I've seen is 45mph, and it was having a hard time maintaining altitude at that speed. The flight time I'm getting (with camera, no gimbal) is closer to 15 minutes hover.

  • I believe that 3DR will say that their claims are based on virtually perfect conditions such as "at sea level", "temperature 70 degrees", "standard atmospheric pressure", "zero winds", etc.  Wouldn't surprise me if their testing were in a wind tunnel or some such location where all these factors could be controlled.  And I don't see that as being "cheating".  Any test should be under controlled conditions such that it could be replicated by anyone else, anywhere else...and with the expectation of obtaining the same results.  

    Additionally, eCalc is based on an algorithm some human has produced (in essence, a model).  Any model is ONLY as good or accurate as the algorithm and any algorithm is inherently imperfect.  Just as 3DR makes its claims based on perfect conditions, a model, such as eCalc, is based on its algorithms being perfect...in neither case is the reality, "perfect".  Has anyone EVER flown in the conditions used by 3DR? (unlikely).  Is eCalc algorithm "perfect"?  (unlikely).  

  • 15 minutes seems to be about what everyone is experiencing for a normal flight.

  • I have gotten 20 minutes of flight time but the only way for it to get up to 55 is by falling out of the sky.  I would guess the fastest I can get mine to fly horizontally is about 40mph.  That's just a guess though I haven't measured it.

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