Re: Mecanum drive on Einstein
 

They do neither what?

Re: Mecanum drive on Einstein
 

Oh engineers. Can't even figure it out when someone turns a clever phrase. He meant they can neither push nor shove.

Re: Mecanum drive on Einstein
 

I definitely got that but I thought he forgot to type something because in my previous post I asked him why he didn't think there wouldn't be a competitive mecanum team this year.

Re: Mecanum drive on Einstein
 

Whether we run with it in competition or not, mecanum has been a fantastic tool for us this year in terms of inspiring students and the community. Yay mec!

Re: Mecanum drive on Einstein
 

I think he was confused as to why someone would state a blatantly obvious fact and act as if it were clever.

Regardless, mecanum drive is horrible. You would need a game which is centered around virtually no alliance contact and great maneuverability around game pieces, tea mates, and obstacles. I can't imagine the gdc EVVVER making a game like that.


Oh wait...they did.

Re: Mecanum drive on Einstein
 

All the mecanum hate makes me sad. While I was on a team, we did mecs every year except Lunacy (obviously). What many people don't do with mecs is create a suspension for them. We never had traction issues with the suspension.

We also didn't have fancy field-oriented controls, but as the driver for 2.5 of the 3 years we did mecs, it didn't seem important. To me, it was still easy to drive once you grasped the concept of how it reacted to the controls.

To all the people saying "mecs suck cause they can't defense!!", isn't there a quote about the best defense being a killer offense or something? I can remember playing Rack 'n' Roll (oh god I'm old!) where another robot tried to keep us from scoring, so we just strafed around them when they thought they had us pinned.

Mecs don't work very well for the strategy of "push everyone out of my way so I can do what I want". You have to be a bit more clever about how you want to move and play the game. I think of different drives like kids in middle/high school. You've got the popular kids (WCD), the jocks (tank), theatre kids (omni, cause they're pretty and harmless), nerds (mecs), and then the couple of insanely smart ones (swerve). Just like surviving school, each type has a different strategy for being competitive in a game.

Anyhow, everyone's entitled to their own opinions on mecs and other drives, but please try to back up blanket opinions with facts ;)

Re: Mecanum drive on Einstein
 

If the back wheels have absolutely no traction, and the center of gravity is directly over the front wheels, then the robot is essentially a mecanum-wheeled Segway. Forward and backward will work as expected. Strafe and turn will act identically, doing a sideways arc with a radius that depends on roller friction -- more friction gives more turn, less friction gives more strafe.

Re: Mecanum drive on Einstein
 

Sketch showing approximate center of rotation for frictionless rollers

We messed around with PWMs to disable motors in a sloppy manner. Long story short when we disabled wheels on one side it moved the turning point to the midpoint between the two unpowered wheels. The implications I pulled away from this is that by adjusting the speeds on the motors we can move the turning point of the robot to anywhere within the frame. That being if you can change your turning point you can if pushed off center can roll out of any pim attempt.

Re: Mecanum drive on Einstein
 

...or outside the frame.

Re: Mecanum drive on Einstein
 

Why do mecanum when you can just build an H-drive? :rolleyes:

Re: Mecanum drive on Einstein
 

Why do an H-drive when you can just do mecanum?

Re: Mecanum drive on Einstein
 

Weight, gearboxes, wider drivebase for clearing obstacles, maintenance, frame complexity, etc.

Lots of pros and cons for both drivebases.

Re: Mecanum drive on Einstein
 

Four gear boxes with four wheels and four motors is heavier and more complex than most other drive trains? (And I have no idea what you're on about with clearing obstacles needing a wider wheel base, or frame complexity. Mecanum wheels work fine on a standard frame.)

Re: Mecanum drive on Einstein
 

Like this.