Don't want to damage gearmotor working it too hard

Robotics and electronics discussion Mechanical design and actuators
1

Hi, everyone.

I have a question about the Pololu Plastic Gearmotor like the 1118 and 1121. In the application I am building, I don’t stall them, but I work them pretty hard for about a second. For instance, the RPM might drop to about 35-50% of the no-load RPM, and the noise from the gears increases. I then will immediately electrically reverse it without stopping it first. The reverse cycle will be no-load, however.

Is this OK for the motors and gears, or am I pushing my luck, and drastically reducing the life of them? This is very intermittent duty, maybe 2x/hour, a second at a time, but 24/7.

Thanks for any help!

David

2

Hello.

We do not have those motors characterized that way, but it generally sounds like what you are trying to do should be okay as long as you don’t have a high-inertia load on the motor output.

  • Grant
3

Thanks for the reply, Grant.

I’m not sure I understand what you say about the high-inertia load. I believe it is a high-inertia load, since that is what is slowing the motor. I am working it close to its torque limit. Forgive me if I have confused the terminology.

When the motor reverses, there is zero load in the reverse direction. Is that reversing what you were referring to as far as the inertia concern?

Thanks!

David

PS: This is my first experience buying from Pololu, and have been very impressed with the products and service.

4

An example of a high-inertia load would be a rotating heavy wheel. A rotating heavy wheel takes more energy to change direction than a smaller wheel rotating at the same speed. This means that more torque must be exerted by the motor to overcome this extra momentum when switching directions to not only slow the wheel down, but ramp it back up to the same speed in the opposite direction. This should be avoided as the additional torque causes more strain on the motor system.

- Grant

5

You didn’t clarify if the load was putting axial or radial forces on the motor. Bear in mind they don’t have thrust bearings and could benefit from radial bearings if you’re doing a radial load with a substantial shaft extension. That I think will be particularly important to protecting the gears.