Re: 2012 drivetrain
 

48/3193 ran with a 6WD with 8" AndyMark pneumatics (work flawlessly - great product - now offer a 6" version!), no center drop, angled frame with riveted delrin skids.

We easily cross the barrier and possess good maneuverability in both high and low gear. The lack of a center drop permits more stable shooting with no rock.

Re: 2012 drivetrain
 

Did you guys have any problems turning without a dropped center?

Re: 2012 drivetrain
 

6wd long, with supershifters, and a wedge integrated into the frame. If we were going to do it again, I would have gone with 8wd, smaller wheels, and drop down wheels, just so we could get over the barrier slightly quicker. It still wouldn't have made much of a difference, a couple of seconds per match at most.

Re: 2012 drivetrain
 

We ran 4 8" plaction wheels with toughboxes. For another game where we drive into a steel bar like the bump we might look at different wheels, though two regional events and the championship with just one broken wheel the way we abused them isn't that bad.

We are planning to build a prototype geared drivetrain this fall, much like 25s, because the chain is what gave us the most trouble.

Wetzel

Re: 2012 drivetrain
 

They most likely de-inflated the front/back pairs of tires a bit so they turn easier, and can get over the bump easier.

Re: 2012 drivetrain
 

No. Our driver had no issues slinging the bot around. The distance between our front and back tire contact points is 24". Distance between contact points left/right is about 25". We used a West Coast style setup, so that helped us widen the wheel gap.

We also did very slightly lower the pressure of the front and rear tires relative to the center, which we kept near max pressure. There is no noticeable rock on the robot at all.

Here is a link to a pic of the underside of 48's robot:

https://docs.google.com/open?id=0B5w...3RiTkV6SmlyVXc

Re: 2012 drivetrain
 

We used an octocanum drive base this year -- 4 traction wheels and 4 articulated mecanum wheels, so we could switch between traction and mecanum drive. This was our "best of both worlds" drive train. 6 inch traction and 6 inch mecanum, but the mecanums were sped up 1.5x the traction wheels speed.

6 6" colson wheels with a center drop in a wide orientation. I liked how it drove but would have preferred a system which takes it over the bump.

Re: 2012 drivetrain
 

There is a very basic paper that explains why a drop-center wheel (or set of wheels) is totally unnecessary for wide-drive robots at or near the max robot base dimensions.

http://www.chiefdelphi.com/media/papers/1443

Orientation is just as critical in these responses as # of wheels. :rolleyes:.

4WD Tank, Wide Drive.

Re: 2012 drivetrain
 

We only did 6 so we could be wide and hang off the bridge.

Re: 2012 drivetrain
 

Long-orientation octocanum.
9:1 reduction p80 CIMs direct driving fixed AndyMark HD 6" mecanum, in turn driving articulated 4" performance wheels with roughtop tread via gates sprockets and belting. The performance wheels were at an additional 5:1 reduction, for a total of 45:1.

We love the drive -- it's robust and (relatively) elegant, fast and maneuverable, has monstrous pushing power, and I love that it's chain-free. We're looking at doing something similar with smaller traction wheels -- perhaps 2" colsons -- in the off-season.

Re: 2012 drivetrain
 

Wide 6 wheel drive with modified AM shifters. Plenty of speed and power.

We used the KOP wheels in a live axle hex driven setup and were thrilled with their performance, especially on the bridge.

Re: 2012 drivetrain
 

True, It's not important for turning. That doesn't means it has no use. In fact extra wheels can provide many useful benefits, especially in non-flat field years.

We went with 4-wheel swerve (fully independent drive and steering). It's a great drivetrain, but you do have to compensate for things like hanging off the bridge/even close to the edge and managing ball control while maintaining workable geometry for the Barrier. Definitely doable (we did, though all our official triple balances have been as the middle robot), but extra axles definitely have their benefit.

Re: 2012 drivetrain
 

You don't want to deflate any pneumatic wheels if your objective is to turn easier. In fact, you want to do the exact opposite, inflate them to their maximum pressure.

Lower pressure pneumatic tires have a lot more surface area, and have a lot more opportunity to "interlock" with the carpet fibers (think of it almost like Velcro). When this happens, the drive train will draw significant current while trying to turn, potentially even enough to trip the main 120amp breaker if other subsystems are in use at the same time.

Re: 2012 drivetrain
 

Our method is passive. We just angled the front and back edges of drivetrain, and riveted on strips of Teflon along the entire base to slide over the the barrier. This has allowed us to drive full speed into the barrier and get over. On 1114, we like the Dukes of Hazzard method of getting over obstacles.

The drivetrain is a 6WD using the AndyMark 8" pneumatic wheels (long configuration).