KOP Drivetrain + Falcon 500 = Noise?

We are building our KOP chassis with two Falcon 500s per side, using the AM14U Falcon Hardware Kit from AndyMark. We are noticing what feels like unusual resistance turning the output shaft and hear a pretty rough grinding noise from the gearbox once the motors were installed. One side of the robot is a bit noisy and the other is far worse. Here is a video of a student turning the shaft with the motors unpowered:

Does anyone have any ideas or suggestions?

Did you perform the recommended dry burn-in run per the instructions that came with the toughbox?

We did not. There is no such recommendation in the KOP assembly instructions that includes the ToughBox installation.

Give the burn-in run a try, and possibly contact AndyMark about having it mentioned in the KOP manual. Per the product webpage:

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I cannot listen to the video roght now, but are you certain they are not fighting one another?

We try to always drive each motor first when paired in a gearbox. This year, we forgot for a second and it made a whining noise.

My team ran into the same issue this season. They assembled the gearboxes using the KoP instructions which do not mention the burn-in run. They had already put the grease on the gears by the time I realized.

We also tried pulling off the Falcons and mounting two old drivtrain CIMs from a previous year and it sounded significantly better. The Falcon pinion and CIM pinion are visually indistinguishable (same position on the shaft, same number of teeth, etc.), though, so this didn’t make sense. Hand-spinning the Falcons out of the gearbox there is no noticeable noise or grinding.

Re: the burn-in, I am hesitant to power these Falcons up while it sounds this rough – unless this is normal and it would work itself out, I’m worried about damaging the motor or gearbox if something is mechanically misaligned. If we wanted to do this we would need to remove all of the red tacky grease I guess (solvent)?

Did you use the shorter Falcon Mounting screws that came in the kit? Those were not in the directions, but using screws too long could be problematic as well.

The sound there is within expectation for what I’ve heard from slightly-out-of-tolerance toughbox minis (this isn’t uncommon). Take the grease out and run them dry with only one motor in each. You can clean the grease off with detergent + water.


Yes, we used the ones that came with the kit and only stick 1/4" into the motor.

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OK, we’ll try this on Saturday. When you say run with one motor in each, do you mean one motor powered or only one motor actually attached to the gearbox? Does the mating between the gearbox gears and both motor pinions also need to be broken in, or is this dry run mostly just cleaning up tolerances in the gearbox itself?

Also, would any of this explain why it only sounds this bad with Falcons attached, not old CIMs?

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I meant with only one motor physically attached to the gearbox. If you’re worried about breaking in the geometry for both pinions, you can swap which hole the motor’s in partway through.

It probably sounds worse with Falcons because the Falcon pinions are toleranced slightly differently - even slight differences in surface tolerance can result in substantial differences in friction, especially if the spacing tolerances between the shafts aren’t great.

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It has been a couple years since we put together that gearbox. We once had an issue internally because a gear was flipped. One side had a slight flange(?) And when not correct, we were making metal shavings and messing up a bearing if I recall right. If nothing else works, it might be worth running a quality control check with a fresh set of eyes on the gears inside.

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