Swerve/Crab

Hey,
It is too close to season to probably get a swerve drive working, but I wanted to have some more info on it (most likely for next year).
I’ve looked through CD-media and was wondering if anyone has any CAD designs my team could look at (ideally in Inventor, but I’ll take anything)?
Also does anyone have any specific advice? I’ve found a lot of designs, but have they been successful or did you end up reverting back to your old drive train?
Finally how would you compare mecanum to swerve?
Any help would be greatly appreciated! Thanks!!

Mecanum is rather iffy. First, you’ll never get the full power of the motors because it’s vector based. Also, it’s somewhat difficult to keep your robot from turning in circles when going sideways. I’m guessing this is due to not all motors having the exact same specs as all the other motors. That’s another thing with mecanum, you have to have a motor per wheel with no chain. When we tried out a mecanum drive base, there were some issues with use going around in circles.

Mecanum and swerve are two entirely different animals. Mecanum drives are vector based, and result in less efficiency (and therefor less power from your motors). But mecanums can change direction almost instantly.
Swerves get roughly the same power output from their motors as a differential (Scrub) steered robot would, with the exception that their “steering” motor(s) give no output power to the drivetrain. Swerves take more motors than any other drivetrains and are often the heaviest wheeled drivetrain. They cannot change direction instantly, as it takes time for their motors to re-position.

Crab steering (this is the term used for swerve since it emulates the way a crab walks.) is not needed for every game. For this reason, we do not decide which drive train we will use until after the game has been analyzed. This year’s game did not require crab steering. When maneuverability is an absolute must or when the robot is required to move sideways to pick up or retrieve then crab is a possibility. The design of the drive modules will determine the weight and individual transmissions can double the weight if similarly sized gears as tank designs are used. Since each tranny carries less load, the components can be lighter.
Of prime importance is the ability to control the steering. Therefore a good feedback system and software are needed. The operator control is another factor that needs thought to make driving easy. Designs can have other problems that vary with the design. How will you get wiring down into the module, will the module contain the motor or will all the drive components be outside the rotating device. What is the game going to require as to the base dimension and what is needed for retrieval of game objects. You may find that a design that requires 8 or 10 in. sq. will not allow space between the modules for other robot components. Finally, How do you get to Carnegie Hall? Practice, Practice, Practice. Even the best crab drive system won’t get you anywhere if your drivers can’t control the robot well enough to play the game.

I have a few cad drawings of a crab drive (partially inspired by Hammond, Wildstang, Hot Bot, and Rage.) ’

http://www.chiefdelphi.com/media/photos/25248
http://www.chiefdelphi.com/media/photos/25250
http://www.chiefdelphi.com/media/photos/25228
http://www.chiefdelphi.com/media/photos/25227

If you wanted to make them available for download I will host the files for you. Email me gneedel(at)gmail(dot)com