My team typically uses mecanum, and we are starting an off-season drivetrain. We understand most but can't see / make sense of some of the omni based drivetrains.
http://www.vexrobotics.com/vexpro/examples-guides
What are the pros and cons of this 2+2 drivetrain? Why only go two omnis vs 4? I could imagine some scrub reduction, but why not all 4 wheels? And if you are using 4 independent gearboxes, why couple each side with belts/chains? Are they trying to mechanically couple and equalize wheel speed per side?
Then we were looking at 1114's 2014 robot, and it looks like 4 wheel traction, but two wheels have butterfly like modules where you can drop omnis on one side (not sure if it was the front or back). Similar to the above, is temporarily reducing scrub important enough to add that weight?
Are we missing some understanding from these designs?