12" Propeller on purple stock motors

Hello All,I've got some extra stuff strapped to my quad, and needed a little more throttle with the 10" props to keep her up.I just switched to the 12x4.5, and it made a nice difference. Seems more stable and responsive to flight inputs.I was worried about the temps, and this is what I got with an IR thermometer2650 x 3S battery pack had an external temp of 120F850Kv brushless motors ranged from 140 - 170FDoes anyone see any problems with those temps?Definitely took a little flight time off. Going to try a parallel connection of the 2650mAh batteries, and see what happens.JC

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  • Not an answer to your question, but don't forget to account for the emissivity of the object your are measuring. Shiny surfaces don't play nice with non contact thermal sensors, and will mess with the accuracy of your reading. I have used a piece of black tape in the past to help.
  • Developer

     

    External temp is not the right one because of propeller air flow, even if you are using an infrared thermometer to check.

     

    Internal temp can be higher, specially after motor stopping where the temperature continue to rise.

     

    So after stopping your fly, never stop your motor too fast if you are pushing them to the limit. Wait a couple minutes so that they can cold down.

     

    I've found that 12" propellers are really too big for my 2814/22 motors, at least for 4S powering where full throtle go up to 450W. This is far too high for such a motor. 300W max is a good value i think.

     

     

     

  • Moderator

    LoL I did the opposite.  I have the bigger brother 880KV motors and I switched to 10x4.5 props for 3 reasons.

     

    1.  they are cheaper to replace

    2.  the motors don't have to work as hard to increase RPM, which should equal faster RPM changes and therefore faster response. (in theory)

    3.  I have a hexa, so I'm already getting two extra props providing extra lift.

  • Moderator

    Hi John,
    That's 20-50F over ambient temperature. We, in AZ, don't have much choice if we want to fly  :) . It sure is a double-edged sword here, weather-wise.

    Anyway, looking at some of the temperature limits for various motors online, many recommend staying under 200F. With all of the dust/sand and heat here, we have to face the fact that our batteries and motors just won't last as long. :(  But, we sure get a lot of fly days!

  • are you saying that your motors get up to 80°C ? that's too hot, they won't do long like that (magnets may loose their magnetic force above 80°C permanently!)
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