my team needs crab/swerve pod cad files

[JVN]

Hi Will,

Good idea taking a crack at a Swerve drive during the off-season, there is a lot of development involved in something like this.

I don't have Inventor, we do our modeling in SolidWorks. Check the attached ZIP file for a STEP assembly of the Robowranglers 148 - 2008 Coaxial Swerve Module. (The STEP file should import cleanly into Inventor.)

This module was heavily inspired by the Thunderchicken 217 - 2002 & 2003 designs. (Thanks Foof!)

Let me know if you have any questions.
I'm happy to help, and always sympathetic toward a college FIRST team!

Regards,
John

PS - All the dimensions are valid; this is exactly as we built her.

PPS - Don't do a swerve drive for a competition robot.

[s_forbes]

Great files, John! Quick question about that module: What type of bearing are you using for the large turntable? (and where does it come from?) I would have thought that a design with a single bearing like that would put enormous side loads on the bearing that it couldn't handle. Did you have any problems with it at all?

Originally Posted by JVN

PPS - Don't do a swerve drive for a competition robot.

I think we'll take that advice!

[James Tonthat]

Thanks John!

I was trying to figure out how one of the bearing sections worked and what kind of bearing was used (thrust or ball.)

Edit: Err, nevermind

[JVN]

Originally Posted by s_forbes

Great files, John! Quick question about that module: What type of bearing are you using for the large turntable? (and where does it come from?) I would have thought that a design with a single bearing like that would put enormous side loads on the bearing that it couldn't handle. Did you have any problems with it at all?

Yes there are enormous side loads on the bearing, but it handled it fine. The practice chassis deformed but the bearings are fine.

The swerve bearing is a 2" ID, 2.5" OD, 0.25" THK bearing.

It is a KAYDON bearing P/N KA020XP0. You can buy it from any KAYDON distributor. (We got ours from Motion Industries.) If you say you are a FIRST team you can get a discount.

Paul Copioli was the one who recommended it to me, as it is used commonly on the real robots he works with.

After we started production on the swerve parts, I got cold feet. I have never done something like this before, and I am a pessimist by nature. I called Paul up and asked him if this bearing would be able to survive the heavy shock loads caused by our application or if we needed to support the base of the swerve module. He just laughed at me.

These bearings held up great; they were perfect for our application.

It was important to make sure that both the inner race and outer race of the bearing are WELL captivated. You can see in our cross section how we hold the bearing in place. (See above post.)

This may not be the best way to do things, it just happens to be the way we did it.

Hope this helps!

Regards,
John

[James Tonthat]

Wait, so that's a 200 dollar bearing?

[Matt C]

Being able to use a single bearing to mount the swerve module to the robot was probably deemed worth the expense. I believe a normal application would be to have a pair of bearings one to take axial and radial loads, and one to take radial only. This would deal with the moment generated at the mounts. Please correct me if I'm wrong.