NEO Motor Problems

Hello All!

At our last competition are team arrived with a robot that had 4 mecanum wheels attached to 4 CIMple gearboxes with NEO motors. Before we had arrived at the competition we had our robot driving forwards, backwards, and turning. As some of you may know mecanum wheels are often chosen because they can strafe (move side to side). Before we left our robot could barely strafe one way and not the other. When we arrived at the competition we had decided that the strafing problem was not due to our programming as we had previously used the same mecanum programming.

For our first quarterfinals match we decided to change our our wheels for pneumatic wheels and here is where our problem gets worse. Our robot barely moved that match at all and when we brought our robot over to the practice field you could hear the motors whining and clicking as we “drove” it around. We are looking into changing out our chassis and are wondering if anyone has had a problem like this with the NEO motors before.

Edit: we have also previously had problems with the NEO motors clicking as we are driving

Clicking: check that your motor mounting screws aren’t too long!

Mecanum not strafing: make sure the rollers on the wheels are spinning freely.

Also, changing mecanum for pneumatic may have too long an aspect ratio for you to be able to turn. If the track isn’t a fair bit wider than the wheelbase is long, you’ll need 6 wheels and a drop center (or fully inflated tires in the center and underinflated on the corners).

There’s almost no way that anyone can help without a lot more detail and some pictures of the robot and drivetrain. To start, from a mechanical perspective:

  1. If you put the robot up on blocks, can you spin all four wheels by hand?
  2. With the robot still on blocks, try to drive it. Do all of the wheels spin? Are there any worrying noises from anywhere?
  3. What size wheels, and what gear reduction do you have?

So the screws being to long was our original problem. W were wondering if this may have caused any long term damage?

I would like to second this question. It sounds like you might not have enough torque to move your robot. In other words, your gear ratio may be too small and you are stalling your NEOs.

That is definitely a possibility. Without taking apart the motors, it will be hard to determine what, if any, long-term damage happened. One scenario includes heat damage to the motor windings due to the extra load on the motor from the screws.

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Yes, that. The CIMple is a single stage gearbox, 2.67:1 IIRC 4.67:1. You probably don’t want to run this with wheels any larger than 4" unless your robot is significantly under the maximum weight.

  1. Yes, when we put our robot up on blocks we can spin all four of the wheels.

  2. When the robot is up on blocks all for of the motors spin and after replacing the screws they no longer made the clicking noise that they make when they drive on the field.

  3. We have 8in mecanum wheels and I believe that our reduction is 3:1 but I will double check.

We have a similar (toughbox micro) setup, and while we have not had the same problem with the motors, we had similar issues with the gearboxes.

Make sure each box has the right gears (one of ours had the wrong gear connecting the 3/8 inch shaft to the output.

Make sure the flat side of the gears are the side that is touching.

Make sure you use the bearing on the inside of the back plate for the 3/8 inch shaft.

Make sure the spring clip is firmly seated on the output shaft.

We had all these issues in our gear boxes.

Edit: I agree that the gear reduction may not be enough. We have 10.75 :1. Also, are the wheels on correctly? They should make an x. If not, they may be fighting one another.

If this is true, not enough reduction is absolutely your problem.

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I have found your problem. That is nowhere near enough reduction for wheels that large. A few seconds in the JVN calculator tells me that you are geared for 68 feet per second. For perspective, 20 feet per second is almost uncontrollably fast, and we are currently geared for 12.

So, what’s happening is that whenever you try to drive your robot, all of your motors are stalling badly because they don’t have enough torque to move the robot. You are going to want a final reduction around 15:1 for 8" wheels on NEOs.

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Alright so we will most define toy be changing out our gearboxes then.

How would we go about checking for damage to the motors though?

Unless they swapped gears, the CIMple is 4.67:1*, not 3:1, so it’s “only” 44 ft/s. Still way too fast.

* 12t pinion, 56t bull gear

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They should never have invented the CIMple.

Or they should put a warning on the web page, so teams can know explicitly that it’s not going to work for driving a robot, without some more reduction. It works fine if you use a small sprocket on it’s output shaft, and a chain driving a large sprocket on the wheel, as it was originally designed.

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Checking for motor damage is tricky, and I don’t know that I would recommend doing it.Once you have a gearbox with an appropriate gear ratio, try driving around to see if everything works. If you’re still having problems then you might want to swap out your motors. If you never saw smoke and don’t smell anything, they might be okay. That said, if you’re in a good financial situation I might just change them all to be safe anyways.

At a guess, the “clicking” you were hearing while driving was from your breakers tripping (the breakers are rated for 40A and NEOs draw about 160A when they are stalling). The more times those breakers trip, the easier it gets to trip them in the future. If you just went a whole event tripping the breakers repeatedly, I would swap all of those out.

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New motors will probably cost significantly less than changing the gearboxes, unfortunately.

Sure, but changing the gearboxes is the necessary change here, and changing out the motors because they might not be good is just a good precaution.

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You certainly will need to change your gearboxes, as many people have said.

If you decide to stay with a 4 wheel setup, I would stay away from pneumatic tires in only 4 corners. 4-wheel setups generally have a difficult time turning, and the grip of pneumatic tires will only make that worse.

4 wheel mecanum drives generally work fine. If you are set on getting rid of the mecanum setup I would either run a 6 or 8 wheel drive with a dropped center. You could also keep with the 4 wheel drive but put 2 traction wheels in the back, and two omni wheels in the front.

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