Thread: Mecanum or 6WD
View Single Post
  #12   Spotlight this post!  
Unread 09-01-2011, 22:59
Siri's Avatar
Siri Siri is offline
Dare greatly
AKA: 1640 coach 2010-2014
no team (Refs & RIs)
Team Role: Coach
 
Join Date: Jan 2008
Rookie Year: 2007
Location: PA
Posts: 1,626
Siri has a reputation beyond reputeSiri has a reputation beyond reputeSiri has a reputation beyond reputeSiri has a reputation beyond reputeSiri has a reputation beyond reputeSiri has a reputation beyond reputeSiri has a reputation beyond reputeSiri has a reputation beyond reputeSiri has a reputation beyond reputeSiri has a reputation beyond reputeSiri has a reputation beyond repute
Send a message via ICQ to Siri
Re: Mecanum or 6WD

Quote:
Originally Posted by Joe Schornak View Post
Process of acquiring and scoring a tube:
6WD:
1. Get tube from feeder.
2. Zip across field to scoring zone, using superior speed and traction to avoid other robots.
3. Advance to hang tube. Miss.
4. Back up, adjust angle, try again. Miss.
5. Repeat. Miss. Waste 20+ seconds on a single tube before finally succeeding
That's interesting reasoning. How did you come up with this assessment? We haven't been able to test it with old bots yet, but by contrast tank drive was the norm for effective hangers in '07. And that was with a free-swinging rack with much larger end caps. The flat scoring grid does highlight lateral motion somewhat, but I wouldn't think it was that much at first estimate. In both cases, a lot of its down to drivers and sensors. Best case: do not let go unless you know it'll hang.

Steve: Good point; motors and frictional coefficients rule the game here. But correct me if I'm wrong, even if 6wd and mecanum tie the motor battle (i.e. a 2 motor 6wd), mecanum still loses on the coefficient front.
- AM Mecanum Wheel values (static forward/reverse, sideways): 0.6 and 0.5 (6"), 0.7 and 0.6 (8"), 0.54 and 0.41 (10").
- AM Traction Belt values: 1.2 (wedgetop), 1.3 (roughtop)
Even dropping the 6wd center, you're still looking at double or more the mu's.
Purely anecdotal: I've never seen a mecanum win a pushing war against a reasonable tank drive, 6 wheel or otherwise. In fact, in 4 years behind the alliance station glass, I can't think of (m)any that tied either.

Charmander: Expect tubes on the ground. There is 1 very important rule in the world of FIRST game pieces: no matter what they are, no matter where they start, no matter where they're going, significant numbers will end up pushed against the wall on the floor. This year, I'd predict lot of that happening from robots dropping and human players throwing. No all-star team is going to show up at competition without very well-exercised human players. Why go all the way to the store when you can get them air-mailed?
__________________
Reply With Quote