Creating a Tiny Three-Motor Swerve Drive

So, do you actually increase the performance with 2 motors? Same wheel setup, same carpet, same FRC environment, how fast can you accelerate with this without slipping?

For a while, there was an option like the Vexpro “CIM-ile”. https://www.vexrobotics.com/cimile.html

It’s since been discontinued, but I’m sure there are likely some floating around somewhere.

Otherwise, as you said, nearly any legal motor can be adapted to “Look like” a CIM (.750" Mounting Boss, Mounting Holes on a 2" Dia Circle) using some flavor of planetary, VersaPlanetaries being the easiest, but there are other options out there as well.

Excluding the Mechanical Interfaces - if you wanted to use a Brushed Motor for Steering, now you may need to mix and match motor controllers. This in itself is a non-issue as you could use a Victor/Talon speed Controller with a Falcon on the Drive and stay exclusively CTRE or use SparkMax’s and Neos and Stay exclusively Rev.

The problem I was alluding to comes around when someone wants to run Falcons as the Drive (Propulsion) motor and a Neo550 / Not a Falcon Brushless Motor as the Steering. Now you’re mixing CTRE and Rev Products on the Same Sub-System which does create some complexities in software that would not exist otherwise. It’s mostly related to libraries and the availability of a “Pre-Canned” Solution, so depending on other resources, this may or may not be a problem.

This is a complicated question - with no single answer as your propulsive force (Thrust, Tractive Force, Etc) is a Function of the available Traction, which in itself is a function of Mass and Effective Coefficient of Friction. Technically speaking, a lower overall mass with the same propulsive force will accelerate faster than a higher mass, however the lower mass will also have less traction which will limit the rate at which force can be applied to the wheels. Odds are, doing a back to back test with the only change being the addition of power will actually decrease acceleration as you will likely encounter more wheelspin than initially.

That said, as an example.

Assuming a robot is geared for roughly 17fps free (6:1), using neos, with a 4" Wheel, CoF of 1.3 and a “Competition Weight” of 140lbs and a Sprint Distance of 30ft

  • 8 Neos: 16ft Acceleration Distance
  • 4 Neos: 22.2ft Acceleration Distance

As a point of reference, a decrease in “Competition Weight” by about 30-40lbs will also provide a similar improvement in acceleration.

Again, there’s a lot more to the conversation than the raw numbers, but there is some amount to be gained with respect to Acceleration when increasing the motor count.

With the above being said, odds are, the limit will very quickly become either available current (From the Battery) and/or effective traction. Nearly all modern FRC Drivetrains are always traction limited at well below their current limit (assuming sane current limit of <80A and Brushless Motors) so the probability for wheelslip is going to be incredibly high without proper planning.

Beyond that, the odds of system resting voltage dropping into the brownout range is… Very, very Fun. There are ways around this too, but they’re not as easy as just “Throwing Power at the Problem”.

@jjsessa what have you done

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Keep up boomer

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I’m deleting fabworks off the AFT approved vendor’s list.

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This thread is getting volatile and I am here for it.

I love the concept and documentation that accompanies it. I also respect the use of the Neo to turn rather then the Falcon but would love a motor that doesn’t use up 12 ports.

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Such a boomer move to pay more elsewhere over words on the internet

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One unique application of 2 drive motors per swerve module is to sum their outputs at different gear ratios, allowing you to have a bit of an e-cvt depending on which motor you direct more current to. Team 2609 Beaverworx (also on the Einstein winning alliance) used this approach to build the fastest swerve in Ontario:



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4414 swerve and its consequences have been disastrous for tryhard cad nerds

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I’ve updated the GrabCAD link to include the native SOLIDWORKS version as well. Hopefully this will make it easier to adapt to your needs (and to increase the free speed).

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You can’t CAD your swerve and have it too

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swerve

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No one asked but I answered, here is a non-inverted 3 motor swerve that fits in a 6" x 6" footprint that is entirely plagiarizing SDS my own work



And yes I hate electrical :+1:

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Beautiful, now make it a differential system so even the programmers hate you :sunglasses:

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TSIMFD

Really slick way to do it if you’re not married to inverted like us.

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Acronym explanation please?

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Adam’s Fruit Trunk

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Looks good! Here is the 3 motor MK4 module I designed a couple years ago. Very similar concept.


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Just start selling these, you’ll get at least a couple of buyers

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image
i too hate packaging things well… lol

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