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Estimate torque and efficiency from Kv

Posted by Charles Blouin on February 15, 2016 at 9:30am

How do you estimate motor torque and efficiency from basic measurements? It is useful to know this information to improve flight time and performance. The video explains the fundamental relationship between Kt and Kv. It turns out you can get a lot of information from the motor Kv.

This video is part of a series. There are more tutorials on the tutorial page of our website. I transcribed the full video, so you can turn on the subtitles.

The following videos are written and will discuss experimental Kv measurement and brushless motor construction. They may take a bit more time to make because I am working on animated graphics. I think those will really help, especially to explain the relationship between Kv and motor/esc timing.

If you have any question about motors, I can answer here, and I will try to include the asnwers in the following videos.

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Comments

  • Charles Blouin February 15, 2016 at 4:51pm

    Glad you like it! There are more pictures coming.

    @Jerry: There are a few universities using our tool in wind tunnels. They should eventually publish results.

  • Xon Xoff February 15, 2016 at 11:27am

    THAT IS IT! Thanks! 1520 on the shopping list for a purchase down the road.

  • Charles Blouin February 15, 2016 at 11:18am

    @Xon Xoff: That is exactly what my colleague and I designed! Both connect to a computer and can perform manual or automated (scripted) test through our our open source software. The 1580 also measures torque, motor resistance, temperature... The 1580 is available now, and will announce and ship the 1520 before the end of the month (probably next week).

    RCbenchmark | Tools for Drone and Robot Designers
    Motion capture and thrust/torque measurement tools for robot and drone designers. Increase stability, improve the lift capacity and flight-time.
  • Jerry Giant February 15, 2016 at 11:09am
    id like to buy a setup and setting a low speed wind tunnel. i want to know how air speed will affect the the result in real use case.
  • Xon Xoff February 15, 2016 at 10:59am

    I am still blown away that no one has come up with a full blown motor/prop testing station on the cheap. I have an idea to take this:

    http://www.hobbyking.com/hobbyking/store/__66623__Turnigy_Thrust_St...

    Add a few parts, and have it run through full tests on the prop, so it can measure amps vs. rpm vs. thrust (etc) through the whole "servo" ESC curve. It would be handled as a one time run through the menu, or can be hooked to a PC to run a series of tests for cataloging and later comparison. It would also enable testing various battery packs and their draw. The ultimate would be to have four measurement systems (or more for hex, etc.) that you can add to simulate the full setup and see how performance is affected when the battery has to feed all 4 motors at once (and how similar/dissimilar the motors are performing)

    Anyone interested in discussing?

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