pic: Swerve^2 Prototype

[WizardOfAz]

Originally Posted by FotoPlasma

Do you think you might be able to post a CAD or two of the wheel modules? I am very interested in how you implemented the coaxial swerve system.

Here's a photo of a pre-season prototype wheel, #0 as it were. Though the new ones have minor improvements (e.g. better spacers), they are essentially like this one.

http://crush1011.wookus.net/pix/2003...lPrototype.jpg

The motive drive comes down the center shaft, through the miter gear pair, then by chain to the wheel. The ratio is 1-1 all the way from the S-B motor up to the last sprocket, where it gets geared down by 1-2.8 (10 to 28 tooth sprocket). The vertical shaft is spinning in and supported by a half inch bore in the large teflon bushing.

The steering drive comes in the big sprocket on top. That sprocket is bolted through the large teflon bushing to the top plate of the yoke. Steering is accomplished by turning the teflon bushing in the top plate. The top plate mounts to the robot frame. The steering drive is also a 1-2.8 geardown, using the globe motor.

For size reference, the top plate is 6"x6". The large teflon bushing is 3" OD with a 3/8" groove where it rides in the top plate. The teflon splits in two pieces within this groove in order to make assembly possible.

We have some CAD drawings, but a few changes were made to the design post-CAD. Hopefully this picture makes it all reasonably clear. If not, please ask.

This system is not without its challenges, but we're working through them. First, it's a lot of gears and chain, and resulting end-to-end losses. Second, there is some coupling from the motive drive to the steering drive, which makes good steering tracking code more important.

It's very fun working on it though [;-)

Bill