Dual wheel per axle set crab-steer concept

[Revolverx7]

For a few years my team (358) has used a crab drive system. It was somewhat crude, but got the job done. We had two seperate drive trains facing 90degrees from one another, one inside the other. the center drive train would be forced down with a pnuematic cylindar thus lifting the other drive train off the ground.

Pros: crab steering, easy programming, good manuevering.
Cons: heavy, and a little less powerful.

Dual wheel wouldn't give you too much advantage for the added weight and complexity. However, if you did want to go with it, you don't need a differential. All you would need is a miter gear at a 90 degree angle from the axel of the dual wheels. This would effectively give you perfect transmission of power (with only a slight loss of efficiency).

[Veselin Kolev]

I have pondered the though for quite a while as well. I see the following pros with the design i came up with: you can use small wheels (about 2" diameter) with a differential in between. Also, you can have a CIM mounted vertically, feeding power straight into the differential. This lets you have a VERY small module turning radius. If you think about it, having bevel gears on a single wheel swerve to have the motor vertical is pretty close in size to having two smaller wheels and a differential, with a vertical motor. Sure, a few more gears, but worth a serious thought.

[Andrew Schuetze]

Here is an image found in a FIRST mechanism library posted in another thread on off-season crab-steer projects.

[Ben Piecuch]

Dating back to 2001, Penn Robotics (Team 135) used a dual-wheel per axle, crab-style drive system. It was extremely fast, and very maneuverable. Those kids obviously had some stick time behind it, as it was a blast to watch.

Here's a pic I dug up from the 2001 KSC regional. Maybe someone from the team can tell us a little more about it?

FRC135, 2001