Finding the Best Motor/Prop Combo

Hi All,

I am an engineering student at Montgomery County Community College, Blue Bell, PA, US and I am part of a quadrotor research project (website: quadforge.net). We are using a DJI F450 with the APM 2.5 and this site, along with the hardware and firmware, has been invaluable. Thank you. 

We are starting to test various prop and motor combinations to see which one gives us the greatest g/W. There a lot of threads with advice about which combinations are the best but not a lot about how to test which is the best. We have come up with a simple test rig:

3690994014?profile=original

The motor/propeller would be free to move in the notches cut out of the PVC. Everything would be connected to the APM 2.5 (with power monitor), we would set a few specific throttle levels and see which combination generates the most thrust over how much power it is using. After we figure out which one generates the most g/W we're going to fly and see if we are right.

What do you think of the rig?

How do you test out which motor/prop combination is the best (so you know, we are not looking to change frames which limits our prop diameter to 12 inches)?

Do you have any advice as to what motors and propellers to purchase (other than the stock DJI ones we have)?

Thanks again,

Jake

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Replies

  • Moderator

    For props and motors you have to take the common lowest denominator, i.e. which are most commonly used. There is such a massive variation of props but APC slowfly are fairly ubiquitous, others are rare in many regions. Other variations like altitude and temperature can make a difference too.

  • Moderator

    I did a lot of testing a few years ago when I started electric flying. Used a simple L-shaped thrust meter pressing on a digital scale and a Hyperion Emeter connected to a PC running Logview (www.http://logview.info/). Peaks were recorded both by the Logview program and by taking a photo of the Emeter and scale at full throttle.

    The best though is not to use a battery if possible but rather an adjustable power supply, that way variations in measurements can be avoided. (Different LiPo batteries under load can read anywhere between 10.8 and 11.4V which messes up all the measurements.)

    g/w is good for different prop sizes, rpm/w is good for the same prop size.

    These are some of the peaks:

    3692614615?profile=original

  • I assume you are going to incorporate a graphing watt meter into the test stand. That's a critical piece of equipment for prop and motor testing. There are plenty of relatively inexpensive ones out there. 

    Xtrema Charger - TME - Tejera Microsystems Engineering
  • Jake,

    I'd recommend Graupner E-Props or Xoar E-Props for the best efficiency. Also get a quality motor with quality bearings; if you can afford ceramic bearings, get them as they will give you the best efficiency.

    I'd be interested in seeing your results, will you be posting them to the website that you mentioned?

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