Team 4926 Swerve Drive CAD

[NowlingPro]

Here is the link to all of the CAD models and renders: https://grabcad.com/library/frc-team...swerve-drive-1

This is the swerve drive model that I created for my FRC team for future use hopefully. This is our first time working on swerve drive, but our programmers have experience with mecanum.

The model consists of 2 key components; the swerve drive pods and the dual speed gearboxes. The dual speed gearboxes are a bit on the experimental side as they do not use the traditional dog gear to shift. They instead rotate gears to mesh and unmesh on the fly. The gear ratios are 5.33 in high gear and 10.88 in low gear. Two gearboxes are put together to achieve shifting with a cylinder between them. This allows for half the needed cylinders while still having each wheel independently driven. A SRX Mag Encoder is attached to the output shaft. The output shaft then drives the swerve pod via chain and sprocket.

The swerve drive pods use a coaxial drive, with the drive power running inside the pivot shaft. The pivot shaft is a hub that clamps on a 1" x 2" rectangular tubing with thrust bearings to lower the friction. The pivot motor is attached to the 1" x 2" tubing and drives the hub with gears. The drive shaft comes to a bevel gear to rotate the power transmission by 90 degrees. The wheel is driven with a chain and sprocket, allowing for a simple change in gear ratio if needed. An electronics assembly has been added, but is still a work in progress.

Specs:
5.33 high gear and 10.88 low gear ratios
4" High traction wheels
48ish pounds as measured in Inventor (still working on accurate weight calculations)
Using the JVN Motor Calculator, I have 14.13 ft/s in high gear and 6.92 ft/s in low gear

Is there anything missing in my model? Any points of failure? Any suggestions on gear ratios or speeds? Any improvements that you can think of?

Thanks for all the feedback!
-Reed Nowling, GalacTech Robotics Engineering Design Team Leader

[Cothron Theiss]

May want to move this thread to Robot Showcase or Technical Discussion. A lot of people aren't subscribed to the CAD forum, so not many people won't see this.

[Chak]

Looks good. Nice detail on the CAD. At first I thought it was too bulky, and then I realized I've been looking at asid61's swerves for too long and that this is fine.

A lot of the bulkiness comes from the shifter. I'm not sure about shifting speeds by crashing spinning gears into each other. I vaguely remember someone prototyping that awhile back. Did it go well?

The chain run from the shifter to the swerve module goes on shafts from 2 separate parts. Do you have the manufacturing tolerances to make sure that these 2 parts line up? If not, might as well add a tensioner.

On the swerve module, it looks like you're doing a lot screwing into the side of .25" sheet aluminum. You can make the bolt bigger and your life easier by cutting a cross into the side of things and slipping a regular nut in there (no tapping!) like this: http://www.instructables.com/id/How-...tted-Insert-N/
That link is good for other stuff too.

Do you plan on actually making this, or is it a practice thing?

[NowlingPro]

Originally Posted by Cothron Theiss

May want to move this thread to Robot Showcase or Technical Discussion. A lot of people aren't subscribed to the CAD forum, so not many people won't see this.

How would I do that?

Originally Posted by Chak

Looks good. Nice detail on the CAD. At first I thought it was too bulky, and then I realized I've been looking at asid61's swerves for too long and that this is fine.

A lot of the bulkiness comes from the shifter. I'm not sure about shifting speeds by crashing spinning gears into each other. I vaguely remember someone prototyping that awhile back. Did it go well?

The chain run from the shifter to the swerve module goes on shafts from 2 separate parts. Do you have the manufacturing tolerances to make sure that these 2 parts line up? If not, might as well add a tensioner.

On the swerve module, it looks like you're doing a lot screwing into the side of .25" sheet aluminum. You can make the bolt bigger and your life easier by cutting a cross into the side of things and slipping a regular nut in there (no tapping!) like this: http://www.instructables.com/id/How-...tted-Insert-N/
That link is good for other stuff too.

Do you plan on actually making this, or is it a practice thing?

I remember seeing an initial prototype that worked well, but not heavy lifting.

I was thinking of ways I could add a tensioner, but I could not find a simple solution. Any suggestions on tensioners? I have never designed with one in my 3 years of FRC experience.

I really like using the nuts like that! I will be doing a redesign and updating the model here soon!

This is intended to be one of two drive drivetrains that we use this coming season. Depending on the game, we will be going with a tank drive or this swerve drive.

Thanks for the feedback!

[Peyton Yeung]

Originally Posted by NowlingPro

This is intended to be one of two drive drivetrains that we use this coming season. Depending on the game, we will be going with a tank drive or this swerve drive.

Thanks for the feedback!

I'd highly suggest not selecting a drivetrain during the build season that you haven't physically prototyped in the offseason. This is my opinion for all drivetrains not just swerve. While CAD is great for getting the feel of a design, the build and software for a swerve drive can be taxing.