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  1. #1
    RC Racer
    Join Date
    Apr 2017

    How hot should my motors get?

    Hello everyone,

    I noticed that when I run my vxl 380 brushless motor, it seems to get quite warm on 2s. I've always been able to hold my finger on it for 5 seconds, or longer, but I'm wondering if it will become much worse on 3s. I also wonder if the finger test is even viable.

    I also have a Castle Creations 1406 4600kv motor in a 2wd vehicle, and I geared it up to try and get 60mph for a few passes. A few passes turned into about ten, and by the end of those runs the motor was quite, quite warm. I would say that I could only hold my finger on the motor for about 2-3 seconds. After that, it just felt too hot. I let it cool down, and ran out the packs the rest of the way once I got home, and after that, the heat wasn't that bad. Performance hasn't degraded or anything, so I'd assume that the 4600kv is perfectly fine.

    From what I've read online, Castle motors seem to handle heat well, and numerous people have reached extremely high temps without ruining their motors. I'm not very concered about the 4600kv, but I am about the velineon 380. Will it fry just by running 3s? (also, gearing on the 380 is 25/55 with the traxxas with the 1/16th summit tires)

    One last thing. I read that 140 degrees Fahrenheit is the limit to what humans can touch. I'm think this might prove the finger test wrong, as 140 is well within the safe standards for running a brushless motor.

    Thank you!

  2. #2
    RC Turnbuckle Jr. Petertje60's Avatar
    Join Date
    Jan 2011
    Rotterdam, Netherlands
    Finger test is not reliable. Everyone has a different level of which heat they can handle. If you want the best care for your motors, get a decent temp gun. In the end it will cost you less than you save with it.
    Brushless motors can reach temps which cause blisters on your fingers. Another reason to use a temp gun
    Nobody is born with experience

  3. #3
    RC Champion zedorda's Avatar
    Join Date
    Sep 2015
    S.E. Michigan
    You want your motor from the outside to not exceed 165F. This temperature is a safe distance from the 180F-200F range when a magnet will start to lose it's magnetism depending on quality level. Why the 15 degrees? Because the inside temperature is always higher than what you can detect from the outside with a temp gun. There are other parts of the motor that can fail from excess heat but the most consistent and sensitive are the magnets.

    As for the finger test. It is very subjective but generally the avg adult can hold their finger on a 150F-160F metal surface for 2-3 secs without damage, pain is another subject. Once you get to about 165F the majority of adults will not last more than a second. So basically if it is too hot to hold a finger on for more than 2 second it is time for a break.

    If you can take your own pain tolerance into account with experience you will know if it is getting close to being too hot and stop early enough. But no it is not a good idea to start with finger tests. Buy a temp gun! It will save you way more than the $20-$30 they start at.
    Last edited by zedorda; 07-20-2020 at 12:33 AM.

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