Lifespan of motors

I am considering motors to put into a robot that I will sell, and need to know that the expected lifespan of the motors is adequate. How can I get this information? I want a number based on actual tests, not just a general response based on impressions. But if test data don’t exist, it would be very helpful if heavy users could say, e.g., “I’ve run this kind of motor X hours without any failures”. I’m especially interested in the plastic geared motors, , e.g. for motor 1118, and how in general they compare with metal motors.


Unfortunately, we do not have any test data for that specific gearmotor, but from our experience, the first thing to fail in these gearmotors are usually the brushes. The motors on these gearmotors are replaceable, so you could put in your own 130 size motor or replace them as needed. Please note, you can reuse the pinion gear from the original motor, but the pinion gear might get stretched after several swaps.

- Grant

It’s a general question about lifespan data, but let me add my expected usage pattern: I am using two of these motors and a castor wheel on a robot that weighs under 4 pounds and will operate in homes and offices with typical flooring. Mostly the trips will be from one place to another separated by stops. I need to know what is the expected lifespan of various geared motors. I don’t see that in typical datasheets, so who can help?

Sorry, Grant, I didn’t see your response before I just posted again. That’s very useful information–I thought the gears would fail first. It’s great that the motors are replaceable, but I don’t expect that my customers would be capable of replacing the motor alone (though I want to design it so handy users could swap the entire motor+gearbox). So I want the lifetime before the first expected failure to be maybe 500 hours. Under the conditions I’m using them (<4 lb., short trips, typical home flooring), do you believe these plastic gearmotors like the 1120 would last that long? Do the metal motors last longer, since the plastic is not used for moving parts. The plastic motors are going great for me so far.

Unfortunately, we do not have the life of those motor characterized. However, from our experience a 4lb robot sounds kind of heavy for those motor motors.

If you do any lifetime testing on them, we would be interested in hearing the results.

- Grant

I would suggest that if you are considering the lifespan of your motor, remember current draw is very deadly for these motors. So you want to have a safe startup sequence to limit the current impulse. The motors have Ok but not superb gears, which are apt to break with too high a current (Torque = Kt*I). Similarly, the brushes are somewhat low quality (except I understand the HP ones have better brushes), and these, too, can die from current. So don’t just consider your average current, but your impulse current, because these things have fast time constants (the brushes are small and gears break when they’re overloaded not slowly.) Dealing with longevity I moved away from the gearmotors, after busting too many. I may have been asking too much from them. As with most things, they will break outside their intended use margins.

If you can get away with stepper motors, for their price stepper motors have actually some pretty crazy build quality. They’re simpler and harder to kill. But you need more sophisticated control tech, i suppose. And their power density is often less, for many applications (but not all.) But the control tech is not that expensive or difficult when integrated (pololu drv8825 anyone?)