4 CIM motors vs 4 Neo motors for drive train

Is it better to buy 4 motor encoders for the four CIM motors we already have, or is it better to buy four neo motors (we already have nine unused spark maxes)?

Last year, we used four CIM motors with no encoders and our robot veered slightly to the left.

Thanks!

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One thing you can do that not many people mention is mix similar motors. You can do 1 neo/falcon & 1 CIM on each side if budget is tight.

Veering slightly (depends on how slightly) to a side is usually caused by something with the mechanical construction of the bot. Most often I have seen: a wheel, not greasing a gearbox properly, or something similar.

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You have Spark or Spark MAX controllers? They are not the same. The Neo Motors require Spark MAX controllers.

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I’d recommend buying the 4 NEOs if your budget allows for it. You will get a performance gain and can use the built-in encoders in the NEOs with the Spark Max controllers.

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A few points to make here. First, for a drivetrain you only need one encoder per side since the two motors per side are mechanically linked. Second, are the motor controllers in question standard Sparks or Spark MAX? Only the Spark MAX will work with Neos. From there it’s just a matter of whether or not you can shell out the extra money for more powerful motors.

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Just an fyi, you only need to have one encoder on each side of the robot, not one per motor.

spark Maxes

What is the performance gain? More power?

If I had 9 Spark Max’s laying around, I would throw 4 of them at my drivetrain, I think you would enjoy the reduced weight, built in encoders, and extra power. But it’s up to you. Our team uses almost entirely Neos/Neo 550s on our robots.

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I would encourage you to use this calculator to decide for yourself. It is going to give lots of great information:

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Yes for the same gearing your robot will accelerate faster and have a slightly faster top speed. Your drivetrain will also be more efficient as the NEOs are brushless and not brushed so they generate less heat than the CIMs and their performance is maintained throughout the match better.

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And NEOs are 1 lb lighter than Mini-CIM. I’ll take the 4 lbs!

MiniCIM = 2.19 lb
NEO = 0.938 lb

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Boom! Question answered!

A couple of notes:
If you have the spark maxes and can get buy the Neos in your budget, I definitely recommend that.

I’m pretty strongly still in the camp that if you don’t have the experience to utilize the integrated encoders on a brushless motor, that a brushed motor that you already have (ie is free) is perfectly fine to us. Just don’t buy any new brushed motors (ie, I’d only purchase Neos or Falcons at this point).

However, in the drivetrain I definitely think it’s a big enough advantage that it’s worth buying brushless motors over using a free motor…assuming you have the budget. The weight, efficiency, and power bonus is all multiplied (having at least 4 motors in your drivetrain) and even if you can’t utilize encoders for an auton I think there’s a reasonable chance that someone at your competition can help you make that work. The motors are being used the entire match, so the better thermals are a bigger deal too.

I also think that to match a 4 NEO/Falcon drivetrain in power/ability to handle back to back matches and stay cool, you need a 6 miniCIM drive, so big savings there too.

Lastly I just wanted to point out that in my opinion the reason your robot slightly veered left last year is because of slight mechanical differences in your build (inequal backlash, one side encountering a little bit more friction, a cg that’s off center) rather than because of motor selection. You can use gyro and some software to help reduce that if you’d like.

Would you see an increase on wear on the CIM motor in that configuration with the neo kind of pulling the CIM along? I want to make the switch to neo’s but not sure if we can bear the upfront cost of a total switch and this would make the transition a lot easier.

Also with a mixed configuration can you then mix motor controllers, as in spark max for the neo’s and normal sparks or any other motor controller for the CIMs?

So let me preface this by saying that it is 100% ideal to use 2 of the same motor, but sometimes life isn’t ideal.

See this thread. I have not actually done this for an extended amount of times but have heard of multiple low resource teams doing it.

Motor controllers these days have “solved” the linearity issues you might have heard of in the past. Using two different motor controllers should pose no problems. Just keep in mind it has to be a Spark Max for the neo.

For us, the NEOs give two big advantages (in 2020/21) over CIMs. They are slightly smaller diameter, which allowed for a certain structural element near the gearboxes of the AM14U chassis that the CIMs would have interfered with. And the built-in encoders meant no fussing with sensors and gave great performance with the WPILib trajectory code.

This can be mitigated by using different pinions on the CIM vs NEO. If you’re making your own gearbox, you would move the mount point. Using COTS gearboxes, check out the trick pinions Vex offers. If using a KoP chassis, you can replace the stock pinion on the CIM with the 217-3416 and let the CIM run about 7% slower than the NEO, which gets them MUCH closer to being a match (their difference drops from about 10% to 3%).

Helps a tiny bit with the torque, too.

Take your gearboxes apart and inspect all the gears to ensure that they are the same side-to-side. One year, our chassis consistently pulled to one side going forward and backwards. After the season, I saw some post where someone had a similar problem and found that one of the motors had a pinion gear with a different tooth count from the other motors.

Heard a lot about encoders and motor controllers. Are they the same thing and the NEOS just have built in motor controllers and therefore can be plugged straight into the PDB, or are they more different than I currently understand??