How do you know when a brushed motor is going bad?

[Mullet]

This has been on my mind lately.

How can you tell when a motor is going bad? Do they just flat out die? or do they die a slow painful death? Over time I've noticed the performance of my Ladybird M4 with Quatos go down hill. It could be due to a number of things -- batteries losing their mojo, props getting bent around too much (then bent back), or finally... motors (maybe) slowly dying. It could be all things combined. Anyways... just food for thought.

[LPR]

Mull


For the standard Ladybird or the Hubsan quads I find only last for under 20 hour of flight time. The more you crash the shorter their life. If just one motor has some damaged brushes or there are carpet fibers wrapped around the motors shafts under the propeller the little quads will uses a lot more power and it looses the ability to climb rapidly.

When a motor gets week enough to see it's bad because of performance or clipping, it usually doesn't take too long till it dies.

One hard hit on the motor shaft and the end plate with the brushes can be loosened and the some of the six small brushes can be damaged.

Larry

[Mullet]

So are you saying in your experience... the motor completely dies at around 20 hours of use or are you suggesting at around 20 hours things start to go down hill?

I did buy 4 new motors as well as a bunch of sets of props. I'll start with the props first. In another thread I mention I'm having bad clipping with my LB, especially motors A and C or 0 and 2 in the log viewer.

[LPR]

I'm saying that I crash enough times that motors usually fail because the motor shaft hits causes the brushes be pushed a little out of place and then the motor starts to fail. If you take them apart you'll see that one or more of the three fingers on the each brush is gone.

If your very careful while flying they may last much longer. I guess my experience with cheap brushed motors is that they often don't last very long.

Larry

[kinderkram]

The life time of a brushed motor depends on several factors like quality, max. RPMs and personal abuse.
Some manufacturers tell the life span of their motors under normal conditions.

As a rule of thumb: the higher the RPMs, the lower the life expectancy. There are motors with 10-12k RPM that last 10-15 hours while others with 15-17k are tagged 5-6 hours.

Bearings and of course the brushes are prone to wear&tear - the more you crash the faster they will go down the drain.
High pitch or crackling noise are an indicator for this and you can feel the play or scratching when you move the shaft.
Also a loss of power compared to fresh motors points at the beginning of the end.

Cheap motors with cheap bearings will be worn out much faster than quality motors which often cost double or 3 times the amount of the cheap ones.

So in summary: look out for untypical noise, play and loss of power bf swapping them. If 1 motor starts to act up it´ll only be a matter of time when the others will follow. It´s better to change all 4 motors then and keep the others as spares for upcoming crash events.

Norbert