VEXIQ Swerve Drive

[Foster]

Last week when I was on vacation there was this post about swerve drive in VIQ

Vex iq 2025-2026 mix and match

Hey - Yeah, this robot uses differential swerve drive on the front. The robot was made for a trade show demonstration, and we decided that swerve might be a cool thing to show off. It was subsequently modified to demonstrate IQ Pneumatics for that video. I can’t find this robot in the office right now (it might still be packed away with trade show stuff in the warehouse…), but I have another robot that uses similar differential modules. Its modeled after the 2023 FRC 148 Robot that a few of th…

I’ve always been a swerve fan, even in the early days:

4-Wheel Pivot Drive - DEW Robotics

There was this post a few years ago about V5 version:

Coaxial Swerve Drive Reveal

[VEX Swerve Drive Reveal] I posted this in a different older thread and was told to make a new one, so here goes: As part of a summer job, I was tasked with making a complex robot for middle schoolers to learn to code on. I chose to make a basic swerve, and while I wanted to make a full differential swerve, thought that would be too complex for them to code. That said, the normal swerve and funky spring-loaded intake rollers were still quite fun to build! Even without any lubricant…

At one point I built a coaxial swerve drive in VIQ. One of the issues with a coaxial drive is that the shaft that goes down to drive the wheels has to pass through the gears at the top that spin the wheel around. I didn’t have gears like that, so I drilled holes in mine.) There is a 36 tooth idler gear, no idea what kit they are in.

It worked pretty well, but as noted it’s impractical for VIQ since it needs 8 motors, and the current rules limit is 6 motors. (I’m still pitching VIQ-University to Dan, so there is hope)

@bkahl in the second picture. I think what I’m seeing is the yellow gear is driving the two blue 12 tooth gears that use the shaft going down through the turntable to the two 45 degree miter gears to drive the wheels. The two grey gears make the turntable spin. What I’m missing is how they are attached to the turntable. Can you help me out?

Check out this channel for more VIQ swerve.

robotics shenanigans with nick

Nick builds a swerve drive module, then makes a robot 4 of the modules. He then makes another robot with just one swerve module in the center. (I love how he says “I was bored and decided to make …” So much better than doom scrolling. Also check out his 1 moto drive base)

[bkahl]

Here is an unannotated section view of that module:

This isn’t a co-axial module, it uses a differential between the two motors to either use both motors to power the wheel, or to steer the module, depending on which way the motors are spinning.

Here is powertrain 1:

Here is powertrain 2:

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Here are a few clips of the module running:

In this first clip, I demonstrate that when the two motors spin opposite directions, the differential drives the wheel. The two motors spinning opposite directions cancel eachother’s steering power, holding the heading of the module, and as a result work together to power the wheel.

Pay close attention to the stacked grey gear and the yellow gear in the middle of the module. When the wheel is spinning, these are spinning opposite of eachohter.

In this second clip, you can see that when the module turns, the gears are spinning the same direction. When the module steers, the grey gear and the yellow gear spin the same direction until the robot reaches its desired heading, and can resume driving.

Differential swerves are cool because you can steer and drive at the same time, without sacrificing that extra motor power. Depending on the difference in RPMs and direction of spins, the module can drive and steer in any direction at any time.

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Bonus clip of the robot driving around – the code definitely needs some work. The control loops are not tuned well at all. If I remember right, I think this version of code might have even been rudimentarily done in Blocks.

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There are many better clips that contain animations or video clips that better demonstrate Differential Swerve Drive on YouTube. I encourage you to check those out if you’re interested! They’re better at explaining these mechanisms than I am

[bkahl]

Found another module revision from before this version that actually better demonstrates the differential. This version of the module uses custom 3D printed parts and packages very differently, but accomplishes the same mechanism. The design was further revised to the latest version, shown above, which doesn’t require any custom parts (at least that I remember…)

You can much more easily see on this module how the direction the motors spin affect what the module does.

[BananaPi]

That is… something else…

Do you have a CAD of the robot?

[bkahl]

Just the module, but no plans on releasing it.

If you’re REALLY interested, you should be able to get really darn close with the images I posted above.

[BananaPi]

@bkahl

Just the module, but no plans on releasing it.

Aww, no fair.

I probably could figure out the modual from the pictures, but I just wanted to be able to see it from multiple angles.

[Foster]

I’ve seen FRC robots with those gears with teeth on the edges and the face. It was a nice move to get to the final robot. I’ve got a packed next few days but I’ll give it a shot to see if I can reproduce it. Thanks for taking the time out to make these extra videos.

[bkahl]

Crown Gears stink, wouldn’t recommend.

There was a good reason that they were designed out of the module. They’re very inefficient and not conducive at all to misalignment. Crown gears also typically require custom driving pinions, unless in 1:1 applications. When driven by a normal gear, there can be interferences on the teeth that increase friction and bog the mechanism down. The crown gear tooth profile can be adjusted to account for these interferences, but it will increase backlash.

Stick to bevel gears when trying to turn 90* wherever possible…

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Aside:

Crown gears ARE great in super small applications. Small bevel gears can be painfully challenging to machine, as the teeth are incredibly small and weak. Additionally, the manufacturing costs for bevel gears is astronomically larger than that of a crown gear. In small gear applications, like the old HEXBUG transmissions in various toys, crown gears are the go-to for turning 90 degrees.

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@Foster

Thanks for taking the time out to make these extra videos.

Sure thing! Happy to kill some time on my lunch break helping out!

[Foster]

@bkahl

Crown Gears

Help me with the right term. Crown gears are where the teeth stick up like little points from the face. Spur gears have the teeth on the outer edge.

The gears you 3D printed are a merge of both types. At :34 seconds of the video you can see the blue gears on the spur part of the gear and the green gear riding on the points of the crown gear.

So the correct name for this Frankenstein gear is a … ? I’ve never seen them anyplace other than an FRC robot.

[bkahl]

@Foster

Crown gears are where the teeth stick up like little points from the face. Spur gears have the teeth on the outer edge

Yup!

Crown Gear:

Spur Gear:

@Foster

The gears you 3D printed are a merge of both types.

Yup!

@Foster

So the correct name for this Frankenstein gear is a … ?

Some kind of compound gear, it might have a fancy name, but I don’t know what it is.