Swerve Module Mounting Bearing

Originally Posted by ajlapp

Bushings are more than sufficient for the application.



Though frc118 did deploy silverthin bearings successfully for many seasons they would be the first to tell you that these bearings are often the weak point in their setup.

Fee free to review our co-axial swerve design or our Wildstang clone. www.team221.com

Good luck!

The 221 Wildswerve is an excellent example of Bushings only. All my my later designs revolved around only bushings mounted inside of either a block, or two plates. I usually use a 1-2" pivot shave that has the coaxial drive shaft running inside. That pivot shaft sits in two bronze bushings. We built a non-coaxial with the same setup on 114 (here), and that system still runs to this day. In fact, it was strong enough that we've had two of the modules on a little person cart for the last two or so years, and it has yet to fail.

Originally Posted by Nathan Streeter

I am pursuing designing a new coaxial swerve/crab/swivel drive train for my team. If possible, could those who have designed and used similar swerve modules please leave your feedback? I know Craig Hickman has designed several coaxial swerve modules, which seem to use similar mounting types. Also, I know the 118 swerve modules use similar bearings, so I'd particularly appreciate hearing from these two groups; however, many others have similar designs/insights!

As Anthony Lapp said above, Bushings will be more than sufficient for this use. Bearings may seem tempting, but the cost is not worth the advantage for a FIRST system.

I'll invite you to check out this latest CAD of a crab system (and by latest I mean early 20008...): http://picasaweb.google.com/ironspork/CrabDrive#

The system uses two bushings inside of a milled block that anchors to a bar of 2x1. This is the system we used in 2005 on our crab, and it never broke. Still hasn't to this day. Keep in mind the chassis I linked isn't legal anymore due to the constraints of the newer bumper rules. It would take some creativity to use that style of frame legally.

I've also done a crab out of punched sheet that was supported by bronze bushings. It wasn't coaxial, and didn't allow full rotation... But it was on a production robot that weighs ~200 lbs. If I had the rights to, I would post an image.

Basically, bushings are fine.

Feel free and email me at craig AT hickmanfamily DOT com if you have any other Crab questions.

[AdamHeard]

The key difference between bushings and bearings is cost as everyone has said, and then efficiency.

Efficiency might matter for your design, it might not, it depends on what motors you're using to steer.

We had two globes steering 4 modules on bushings, and it worked fine; with such an overpowered system we actually ADDED friction to help tune the control loops.

If we were trying to do a crab steered by window motors, I'm unsure what we'd do, I imagine bushings would still work depending on your reduction.

[Aren_Hill]

We did giant needle bearings, largely because we needed to steer 6 modules with 2 window motors, bushings would've killed us.

Some people switched their 4wd swerves away from windows on steering because the windows were overheating quickly.

[artdutra04]

228 used large Delrin bushings for both the lower and upper supports on our 4WD independently steered GUSwerve this year.

Since each pod was steered by a single Denso motor, we had some initial issues with them overheating. Once we correctly shimmed the Delrin plates using .010" Delrin shims and set the Jaguars to coast instead of brake, we haven't really had any issues with the motors overheating.