Motor running slow?

[lewis_1988]

hi guys

A new pilot here with a phantom 3 standard which is less than 2 months old. I've done about 4 hours flying with it and had no major issues at all and no crashes. I noticed the other day that one of my motors appears to be running slower than the others. It has looked slightly less stable in the air recently and wondered if this could be the reason?

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If this is not normal behaviour, any suggestions on how to fix?

thanks very much

 

[Mark The Droner]

Welcome to the site!

First - the image is skewed because you're watching the props at X frames per second. So the one that appears to be running slow might actually be running fast. In fact, from the video it looks like all the props are moving clockwise which is impossible. So regarding speed, you can't really tell.

If you study it, it appears all four motors are running at different speeds - not just one. But it doesn't matter what speed it appears to be moving on video. What you know for sure is they're not spinning at the same speed.

I think you're fine. I don't know what the RPM speed is in that situation, but given it's a pretty high number, you can't expect the motors to be exactly synced.

If you're concerned, you could test them by giving them a twist when the system is powered down. Try to find some resistance. You could also touch them after flight to feel for over heating. You could also smell them after flight to test for burning.

I think you're likely just fine.

 

[OrlyP]

Even at idle, the motors will individually change speeds to maintain stability. For example, if the ground is sloped or if the aircraft is not perfectly level on the ground, the rotor or rotors that are lower than the others will tend to spin faster as it tries to level the aircraft to prevent it from toppling over.

 

[Techcop50]

Check for play at the tips of the props, gently move the tips up and down. You should feel the spring in the blade, but not any noticeable play or looseness. Compare them to one another, as this could be a motor bearing issue. I've had this twice, replaced the motor the first time. I have not dealt with the second time, as I found pressing firmly down on the center of the prop (while supporting the motor from below) seemed a temporary fix. A bearing issue will definitely affect stability, and should create some increased noise.
And of course, welcome, Lewis!