Shifting Swerve Drive Question

Hello. I just want to confirm that there is no well known and accepted method for modifying the MK4i swerve modules to have gear shifting capabilities. Thank you in advance, and sorry for wasting your time.


There is not a known / documented way to shift with any COTS swerve module. AFAIK the generally accepted rule of thumb since brushless motors have come out is that shifting is not practical anymore since these motors have enough power to break traction and still be plenty quick.


Arguably shifting has seen a massive decrease in popularity over the last decade predating BLDC motors.


We programmed a “turbo mode” button on the driver controller. All the joys of shifting without the mechanical complexity. :smiley:


I’ll add on to this - 449 used to be a big shifting WCD team since 2017, when it served us well for the long field sprints. We even put together a shifting drive simulator to identify ideal gear shift ratios. It turned out that even pre-BLDC, the reduction in sprint time between ideal SS and ideal DS gearings was only about 7%, and now with BLDC you can already be pretty close to traction limited even with a reasonably fast speed, so the gains from shifting are even less.

The one advantage I can still think of is that shifting drives could achieve greater efficiencies when accelerating, but I’m not sure if that’s really worth it, particularly if you include the power needed to pressurize. 449 has since stopped using shifting drives.


FWIW, differential swerve seems that it could even further reduce the motivation for shifting, since it allows two motors to both power the drive wheel. I’d guess you might see this offered before a shifting swerve…

While there is not mod kit for the MK4i, team 4265 has been using a custom shifting swerve during the 2022 season. While it was not a game breaking invention, it definitely gave us an advantage with maneuverability, we almost never got pinned/could push almost any robot on the field while still having the ability to travel at 18 fps. If you look at 254 on Einstein you’ll notice they got pinned a lot, with the shifting swerve this would almost never happen.


They still won.


But think about how much harder they would have won if they didn’t get pinned.


I feel like a 2767-style dual-wheel module would provide more benefit than shifting gearboxes (or differential swerve for that matter). During our season, we felt very traction limited with our MK3s, and my intuition is that the MK4s are also traction limited with pushing (even with the thicker 1.5-inch wheels) rather than being limited by the gear ratio. The Falcons are crazy strong motors.

For several years 1640 developed and ran a CVT swerve module. It worked very well. Then came brushless motors. We have since abandoned the CVT. Brushless motors are a real game changer.

Brushless I assume?

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Do you have any picture or videos of the module?

Yes! This is our 2022 swerve if you have any questions I’d be happy to answer them. We also have a few videos on our YouTube channel. I forgot to mention this before but we are currently working on an inverted shifting swerve, we hope to make a post about it around the start of build season.


That looks really tall. Does it stick up a foot above the frame rail?

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I’m not completely sure on the dimensions but it sticks about 1-2 inches higher than the MK4 modules. That is one of the reasons we are designing the inverted modules.

I can also vouch for the effectiveness of the shifting. Team 2557 ran a shifting swerve drive during the 2022 season and we found that it gave us a measurable boost to maneuverability while still giving great pushing power.

Shifting swerve release


The shifting swerve sticks up around 6.5 in above the frame. Here is our 2021 cad release
FRC 4265 Secret City Wildbots Shifting Swerve CAD Release

the main reason that 254 was getting pinned so much is that the geared their modules too fast for a full weight robot and never bothered to change them


The reason you don’t see many high performing teams spend time on shifting (or worse, shifting swerve) is that every ounce of effort placed into using shifting swerve is effort that could have been used to get better at something more useful (strategy, scoring, reliability, etc).

If you want to do swerve, you’ll almost certainly be a better performing team if you use COTS swerve and use your remaining “engineering points” on other parts of the robot. Few teams are going to see a net benefit from designing, building, and installing a custom shifting swerve.

For teams in here that used shifting swerve in 2022: I’m sure you liked it, and I’m sure the maneuverability did help in some way, but it almost certainly wasn’t an efficient use of your time.

However, there’s nothing wrong with that. It’s a really cool project that I wish we had the time and expertise to tackle. Using time inefficiently is fine as long as you know that you’re making a choice that benefits your learning and fun at the expense of winning. It just isn’t the most effective use of the time when the goal is “win”.