We’re thinking of building a WCD/Neo drivetrain in the off-season and are trying to guess what products will be available next year. We have limited funds and are trying to avoid investing them in “Betamax” product lines. It seems likely that there will be other brushless motors available. Is this a reasonable assumption? Based on your best guess and past product developments, will the others make them CIM compatible in terms of mounting?
Any advice on a simple, flexible, robust design? COTS gearbox?
I’d bet money that somebody is going to sell a brushless motor with a 775 or BAG mounting profile. Not that that’s relevant for drivetrain design unless you’re going swerve. Hopefully we can get one that’s super small with a bit less power.
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We almost never use “new” products on our drivetrain, simply because it means that we first have to wait for shipping, and with things like electronics, there’s no guarantee you’ll have good libraries or documentation. I would not trust that there is ever going to be a new COTS product, but instead use what’s already available (there’s plenty to use!).
A favorite COTS gearbox of mine is the 2-CIM ball shifter, because it’s simple and durable, and has been tried and tested for many years. I recommend purchasing the 3-stage version and the gears for 4", 6", and 8" wheels, so you can swap them during the season in case it’s a rough terrain game. Integrating this gearbox into a WCD is not the easiest thing, and will likely require that you replace the 3rd stage plate (which can be a helpful design exercise).
The CIM profile is perennial, and any gearbox designed to fit a CIM-style motor (CIM, Mini CIM, NEO, DeCIMate, some VersaPlanetaries…) will work great with them.
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In my opinion you should never use something until other teams have worked out the kinks. This year NEO’s are having a few problems. we programmed our CIMS and haven’t touched them since the beginning of the season while some teams have had to constantly mess with NEO’s to get them to work. I would suggest just using whatever motors you can get to work. you shouldn’t have to spend more than a week on your drive during the season. (unless you need to redesign due to changing designs.
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This is so true, and the reason why my team decided not to invest in the NEO/Spark Max this year. We prefer to use COTS that have been tried and tested by other teams first. Reminds me of when the 775 came out- we didn’t use them until the season after so that we could see how teams fared with them.
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I don’t think that’s next year, two years out seems likely though.
EDIT: On topic, we’ve been very happy with WCP SS gearboxes the last two years. Complicated drivetrains (shifting & power takeoffs) are overrated in the age of unlimited motors.
I’m another new tech luddite when it comes to FRC COTS components, and doubly so on the drivetrain. But NEOs are the product that’s generated the most excitement for me since the roboRio, and 1712 did purchase some to play with (although they aren’t on our competition robot). I eagerly await testing some on a drivetrain in the off-season.
I do believe you’re correct in assessing that a lot more COTS brushless motors are going to be pouring into FRC over the next few years. The CIM has been the “staple” of drivetrains for essentially 15 years, and it’s only in the past few years we’ve seen a flurry of activity to find “better” drivetrain motors than the CIM. I’d expect a mini arms-race among vendors to find a new staple motor in the age of brushless motors (and, in turn, a new brushless speed controller). There’s definitely going to be some turbulence until a specific motor comes out on top of the heap.
That being said, while the Betamax wasn’t the “standard” like VHS was, it was just (actually more) technically capable than VHS. And we’re definitely hitting the point of diminishing returns on drive motor improvements. I don’t think anyone running NEOs are going to be left in the dust by new brushless motors. Heck, CIM and MiniCIM teams will also probably still do just fine. It’s going to be more marginal and incremental improvements than drastic ones. The speed controllers present a bit more opportunity for technical advancement, but you still see teams doing well (and doing fancy autonomous routines) with Victors and Sparks in place of Talons or Spark MAX these days.
Since 2015, 1712 has standardized on a “West Coast Drive” style of drivetrain with a West Coast Products Single Speed (WCP SS) gearbox. This gives us plenty of customization and optimization opportunities in terms of chassis size, wheel selection, and gear ratio options. We have very few complaints about the VersaBlocks or WCP SS. I will say that you should spend some time reviewing the assembly of your WCP SS gearboxes afterwards to ensure the proper pinions and snowman holes have been used. We had our first incident since 2016 of a pinion shifting* to the improper side of the snowman hole during testing this year, but easily remedied the issue by blocking the far side of the snowman hole.
*We also broke our “no new COTS components in the drivetrain” rule by using the new 10tooth pinions from Vex. Something about this particular tooth profile led to the gearbox completely locking as the pinion shifted to the wrong side of the snowman hole. It was an easy fix (we put in back in the correct hole and filled the far side with a small piece of pneumatic tubing). Since then we’ve had no issues.
Stick with as much COTS as you can. There’s such an infrastructure built up around the current motors that new motors, in order to be mainstream quickly, are going to be designed with similar mounting and output profiles as current ones.
Expect to iterate a bit. You’ll build it, find some issues, then come up with a slightly different design to resolve those issues. And then you’ll iterate again 
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