is there a reason that you never see 3 wheel swerve? It seems like it would free up a CIM for whatever shooter/actuator etc you might use. Or just save weight.
Team 16, the bomb squad, is well known for doing 3 wheel swerve.
team 67 did one also in 2005
http://www.chiefdelphi.com/media/photos/21751
Hmm. I guess I just never saw them.
Is there a reason it is not as common?
Mostly its for stability reasons, I know bomb squad is enjoying the recent switch to 4wd swerve, in 2010 they looked like they were going really fast because it rolled around every corner, it was fun to watch.
Didn’t only one of those wheels rotate? Or am I forgetting my FRC history?
I think you’re forgetting. The back two started like 71’s in '02, to allow the robot to slide down the goal, IIRC.
By rotate I mean “swerve.” What you’re describing is unrelated.
I did say that I think you were forgetting. The back wheels started in a given configuration, then rotated to allow a full swerve–similar to 16’s 2008 robot. I also recall there being CD-Media pictures of the robot showing the swerviness, but not clearly.
I’m surprised the discussion has gotten this far without mentioning Tumbleweed, 148’s Championship-winning 2008 robot (and patron saint of robots without much of an active manipulator).
Here’s a picture showing the three modules: http://www.chiefdelphi.com/media/photos/20540
From what I can remember, the drive had multiple modes, from full swerve to a forklift-like drive that could be changed on the fly.