Broken gear in RobotZone 3rpm motor

Robotics
1

I’ve been running one of these 3RPM motors for a couple of months now and it is great. So, I fired up my 2nd one last week, and once it encountered resistance there was a snap and the motor stopped. I opened it up and saw that a tooth had broken off on one of the internal plastic gears. I’ve enclosed two pictures:

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Is there any way to get a replacement gear? The motor started running again after I opened it (probably when the broken off tooth unjammed).

Is there a warranty? Thank you.

Just for a little context - I’m using these motors to make my own walking machine… Bill

2

Hi wmspears,

Sorry to hear you have a gear that broke on your Gearmotor. When it failed, was it unloaded or did it have a load on it? If it was loaded, did you stall the motor by chance? Similarly, was this the first time you powered it up or was this after running for a while? Unfortunately, we do not have replacement gears available for these motors so we would need to replace the entire motor if necessary.

3

Great questions, and let me tell you the process I use with these motors.

  1. I have a 3-12V adjustable power supply.

  2. I start around 3V. If the walker linkage works I’m all happy because I

know I’ve built it well (low friction and well balanced).

  1. If it stalls I increase the voltage to increase speed.

  2. I don’t go above 12V.

I thought this would be a good safe way to test everything.

In this case I had run this new motor for a several minutes on a partial linkage at

low voltage and everything was fine. I connected the full linkage together

and started my normal process. It was sometimes stalling, so I slowly increased the voltage

to almost 12V. Then it snapped. Before I could power it off.

It never had occurred to me that any gears could snap when below the max voltage, even when

stalled.

If this is normal behavior, well, I’ve learned a lesson.

My other 3 rpm identical motor has been running off and on for a couple of months

and a few times the machine has physically jammed and I’ve always had

time to shut the power off before any damage occurred. Hence my surprise.

So, in short, this motor had only been run for several minutes and once it hit

a stall near 12V a gear tooth snapped. You guys are the experts - if you feel this

is reasonable, I’ll accept that and be even more cautious in the future.

If you know of even sturdier motor/gear assemblies, that would also be useful.

Best regards, Bill

4

Hi again Bill,

Thanks so much for that detailed description of the issue. Stalling this motor (at any voltage/speed) can damage the gears and it sounds like that is what happened here. These low RPM motors produce a lot of torque and that can damage the gearbox when stalled. It’s less common with higher RPM gear motors of the same type since they produce less torque but it still is possible.

We are going to add notes on the product pages for these motors to clarify that since the manufacturer has a similar note on their pages. Now, for your case specifically, since we did not have that notice when you purchased them, we can probably help you out with some form of compensation for the damaged motor. If you purchased them directly from SparkFun, please fill out the form on [this page and in the “Why do you want an RMA?” box, fill in a brief description and link to this post and we will follow up with further instructions.

As for a higher power option, we do not really have any but the manufacturer of these gear motors, [ServoCity, does offer some heavy duty gear motors with a planetary gearbox but the lowest speed they have is 12 RPM.](https://www.servocity.com/)](Return Policy - SparkFun Electronics)

5

Mark, I’m sorry for the delay in responding. Thanks very much for your response - this was all really useful information. Both w/r the stalling and the ServoCity motor.

I went to the returns link and noticed it mentions items being returned w/n 90 days. I’m way past that - I ordered all the motors from SparkFun at the end of Nov in 2018. I’ve run the other three without problem, but didn’t get to this motor until a couple of weeks ago. If I’m too late, ok. If you still think I should fill out the form, I will. I actually do want to replace this motor with the same unit, since I want to test two identical “legs” (of my linkage) at the same time, and my other 3 rpm motor is working fine. Now that I’ve been forewarned about stalling I’ll test even more carefully.

Thank you, Bill

6

Hi again Bill,

When it comes to returns beyond the 90-day period, we deal with them on a case-by-case basis so I would go ahead and fill out that form just in case and we may still be able to help you out here.

7

OK, thank you! I’ve just done so. Cheers, Bill