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I own a brushed micro quadcopter, more commonly known as a tiny whoop. I've read that brushed motors in general, and especially those used in such quadcopters, have a limited lifetime and that you should replace them when they near the end of that lifetime.

However, as far as I can tell, there are no obvious signs that the motors have become too old to fly, as they don't break but instead their performance decreases over time. There's a maximum total runtime in hours listed for the motors, but I can't imagine any way to track how many hours the current set has been flown for besides writing down the length of each flight, which would be extremely tedious.

So how do I figure out whether my motors are worn out and should be replaced, or are still okay to fly with?

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As someone who loves collecting data for analysis, I do track all of my flights. I have found that, under normal conditions, brushed motors should last for at least a few hundred flights. You can get higher if you don't fly hard or get things caught in the props or motor shaft that will make the motor heat up more than normal.

How to determine whether a brushed motor needs to be replaced is a tough question and it really depends on your willingness to fly with a drone that isn't operating perfectly. With mine, the telltale indicator is that I notice less power than usual and yaw is off a bit (twitchy or lethargic). This makes sense since all motors perform to the level of the least capable motor. If you experience less performance, first, ensure that it's not just the battery. This is easy to do - just use a newer battery, or one that you know is still providing good power. The next thing to do, if the battery checks out, is to replace the motors. I recommend replacing all of the motors at once for brushed motors since they are all getting some form of wear while in use. Replacing them all ensures that you are starting with peak performance.

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  • $\begingroup$ Thanks for your answer! Can you tell more about how you track the flights? Do you just record the number, or something else? $\endgroup$ – FlashCactus Apr 19 at 16:54
  • $\begingroup$ I have a spreadsheet and I just mark down the number of flights on any given day. When I replace motors, I add a note so I can track the number of flights since the last motor change. I also do this for batteries so I know how many uses each has and have a better understanding of when/why they start to hold less current. $\endgroup$ – Schome1 Apr 19 at 17:01
  • $\begingroup$ Just wondering, is there a chance that one of the motors just suddenly stops, with absolutely no warning? Or is there always some sort of sign to tell you, "get this thing on the ground NOW"? $\endgroup$ – Galaxy Jul 22 at 17:52
  • $\begingroup$ Typically, the signs are subtle at first and more apparent the longer you wait to replace the motors. Also, if your motors are hot to the touch, it might be time to replace them, or take the props off and clear out any fuzz that is building up around the motor shafts, which could also bind or maybe even stop the motors if it is compacted enough around the shaft. $\endgroup$ – Schome1 Jul 24 at 2:29
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Look for performance issues. A lot of signs of failing motors are visible, such as if the drone falls out of the air or the motors sometimes foal so start.

If none of these signs are present, most likely the motors don’t need replacing.

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