I don’t have one to examine just now, but I suspect it at least derives from an off-the-shelf motor.
This is really key to designing a NEO550 mechanism. Similar motor curves are useful for designing with any motor, but NEO550 is comparatively easy to smoke (some brushed motors shared this, really only comparing to other brushless motors…).
You really only want to run these motors so they operate on the right-hand half of this curve – really, the torque should only involve the part of the curve below 40A or so.
Your examples are all with zero forced cooling (only natural circulation). I’m saying adding forced air cooling will significantly extend the time to failure. Let’s take a better example:
The 775 pro is about 50% efficient at its max power point, meaning an amount equaling its 350 W mechanical output is being lost to heat when it is running flat out. It can do that indefinitely because the built-in fan is removing 350W of waste heat (and probably using a good chunk of that power itself in the process).
Now imagine the 775 pro fan ran on a separate motor, instead of on the same shaft as the main motor. When this theoretical fan runs you could keep it pumping out the full 350W of input power (as heat) while the 775 pro was completely stalled.
 - I misread the power curve. The 775 pro is outputting 350W at max power. With 50% efficiency, it is thus inputting 700W (well, not on a 40A breaker it’s not, but whatever) and losing 350W to heat. The general idea is the same though.
For anyone curious discussing the outrunner subject of NEO’s here are some photos of a busted one I have. Falcons are assembled differently but are still an outrunner style. If I had to guess the case on the back may cause less air circulation.
The first image shows the case removed. Motor would still work in this config.
Edit: some helpful advice. Make sure your students understand not to use screws that would be too long. Screws that are too long may press on parts of the motor which can damage and stall the motor hence why this one is broken. It has multiple screw marks inside which stalled it. This goes for any motor not just NEO’s or BLDC motors.
From experience, it does work but not for long. The issue is that the case actually holds the motor leads down. If you take the case off, you need to fasten down the leads some other way (zip tie), or they’ll find their way into the spinning rotor.
This discussion on cooling and current limiting actually makes me wonder why FRC brushless motor controllers for NEOs and Falcons don’t natively support THERMAL limiting, especially considering they all have integrated temperature sensors (I think?). If you know your motor fries at 100C, why not have a feature in the controller that limits it to like 95C? At the very least it could help prevent permanent damage to the motor, even if it turns off a mechanism during a match/test.
Granted, you could probably implement this in code to some extent, but it seems like something that should be simple to do at the controller level.
If this was the only reason to consider vs. all the advantages of 775, I’d still use brushless over the 775s. This has burned us in many situations over the years, including FP, etc. I cant see teams using them at all moving forward.
I’m not blind to this, because goodness knows 1293 lived back of the curve out of cheapskatery for many years. (Heck, we ran OG Talons in 2019 and 6-Mini-CIM drive in 3CIM4U gearboxes in 2020. Would’ve run it in 2021 as well if we hadn’t gotten some outside help.)
But now that SPARK MAX has been in the Kickoff kit for two years (rookies got them in 2021), I don’t think that holds weight anymore. Prices may have changed since, but I ran the numbers shortly before Kickoff this year as part of a presentation. For 200+ watts spinning at 1000ish RPM, a reasonable figure for an intake or conveyor:
RedLine + 20:1 57 Sport = $98
Add SPARK: $148
NEO 550 + UltraPlanetary with 1/2" hex adapter and pinions: $80.50
Add SPARK MAX: $160.50
And that’s before we discuss how current limiting on the SPARK MAX has saved us multiple motors, which saves money and significant amounts of labor.
Would I give a cash-strapped team RedLines and Sports and brushed controllers? Sure. Would I tell them in no uncertain terms it’s a generation behind the state of the art, what the limitations of the setup are, and to budget for brushless in the coming year? Absolutely. The game evolves, and to ignore that evolution willingly off of small sums of money (relative to a five-figure operating budget) is foolish.
Yeah, and thanks (partially) to that, we switched our drivetrain from CIMs to Neos and ran our shooter off Neos this past season. But, our intake and feeding mechanism were 775s, Talons and VersaPlanetaries we acquired in previous seasons. There just wasn’t any good engineering reason to go to the current generation. By your numbers, that’s a $500 savings. Not insignificant and let us make other choices.
That’s great that you’re budget concious. But I don’t think anyone is suggesting throwing out your old stuff just to change for change’s sake.
We shifted to brushless for power (drivetrain) and the integral encoders on other mechanisms. Indeed, several years later (we were a falcon beta test team) we are still in the process of changing over as we retire components and find funds to buy more falcons.
My team is keeping all of our old (mostly fresh) 775 style motors and CTRE controllers so that we have access to them for fun or educational non-FRC projects. We purchased Hero boards from CTRE and will use them rather than RoboRios for such projects.
On competition robots, however, I don’t think we will be using them anymore. We have enough stock of brushless stuff now to make them the practical choice for the foreseeable future.
We used 775s to prototype a shooter, but we ended up using falcons for the actual shooter, we did use 775s for the feeding wheels, but I’m not sure why and we could have probably used Neos for that also. We are transitioning to falcons and we ordered 10 falcons for a swerve drive and other mechanisms for next year. We like the falcons internal pid controller and the increased power over neos and 775s. And we will probably use them for a few mechanisms next season. It is unlikely that we will use 775s or other brushed motors in the future.
We used a couple 775pros this past season because we have a bunch of them + versaplanetaries laying around, and we wanted to use them up if we could & decided they’d be fine on a low torque ball conveyor, and they were. That said, as most have indicated, we’re shifting to brushless (& max or ultra-planetaries).
Bolt to a fat enough metal plate and you’ll be fine–the heat is all in the nose of the motor near the output shaft. Our Championship drive setup was six NEOs with the Thrifty Bot 6-motor conversion kit that Ryan sent us. We were heavier and drove harder there than at Electric City, and our motors barely got warm. Ditto this weekend at SCRAP where we played 12 matches in the span of about eight hours.
For practice, we did use our favorite USB clip-on fans (like these, but it’s a generic design from a bunch of Amazon sellers) blowing on our practice chassis’ 4-NEO (and aggressively-geared Toughbox Mini) setup to help keep it in check for these longer runs. A conveniently-placed bracket let us leave them clipped on while driving.
The brushless motors are very nice, but does anyone else think the Spark Max seems somewhat fragile compared to ‘other’ motor controllers? We pinched an encoder cable this weekend and it seemed to toast to the Max.
If it wasn’t for the Brushless Revolution, we would use a 775Pro with our homegrown gearbox (looks like a CIM-ile) over a CIM. IMO using a 775Pro to 110% isn’t for the faint of heart and this commitment comes with a price in the form of reliability.
775s are fragile and you need to be able to know how to not hurt them (current limit, don’t stall them) and also be able to test their health between matches. Some interesting trivia if you wonder what we found that failed, it’s the brushes. During an unlimited current inrush, the area circled blue turns red hot. At one time, we had video of this happening.
This happens a couple of times and the copper deforms and the motor timing changes. Timing change shows up in a health test. If it happens a couple more times and the carbon button falls off and becomes debris in the motor, typically breaking the fan before the motor comes to a stop.
So why use the 775Pro? We can’t ignore the weight savings compared to the other Brush motors. Simple as that.
I’d say the rather fragile encoder cable is the single largest “issue” with the NEO/SparkMax setup (and think a fair number of others would agree). Would love to see a fix/revision there eventually.
This isnt to say the SparkMax and NEO’s are bad by any means though. My team has been using them since 2019 and have always been cautious when working around/with the encoder cables. We’ve yet to have an issue (but fully recognize others have and it’s a definite potential point of failure).
When working with mechanisms that stick of of the frame perimeter, we do try and stick to a brushed motor just to avoid dealing with the flimsy encoder cables, but otherwise, have clearly made the decision that the benefits of brushless far exceed the downside that comes with the fragile encoder connection for us. I fully believe there are others that lean the other direction, and to that, it becomes personal choice.
We’ve killed a NEO because of the encoder cables before. Not very fun.
If you’ve ever read the NASA robotics alliance project design paper, the description for JST connectors (the connector the encoder cable uses) says “Not recommended for applications that require frequent connection and disconnection cycles.”