[Kevin Kolodziej]

Aren, did you find all three types of rollers?? They weren't just in your main toolbox either...

I'd like to add to this little debate. Just information..do with it as you see fit.

Team 1675 has used Mecanum wheels in four years of competition:

2007: 8" wheel on slightly modified kit chassis (custom pillow blocks). We had a long center mounted arm that could reach in front and behind the robot to pick up and score, and score over opponents between us and the rack if need be. We decided that the strafing ability would be more beneficial to us when lining up away from the rack, even though we could get pushed away more easily. In most cases, the defender between us and the rack would be parallel to our strafing motion, meaning that we weren't going to get pushed away, just blocked, so in this case, advantage went to us. Disadvantage came when climbing partners ramps...or rather, attempting to. We only had success with lifting platforms. We were selected for elims in Cleveland, but not in Milwaukee or Atlanta. By the end of Atlanta though, we were consistently scoring 4-5 tubes per match.

2008: 6" wheels on custom 2x1 chassis. The 6" wheels were new that year and relatively untested. We encountered some initial problems with the plates warping and subsequently digging into the carpet. We solved this problem and newer generations of AndyMark's product have also addressed this issue. We had grand plans for a ball lifting mechanism that never were realized so we became a runner bot. Geared for speed, our bot was one of the fastest in Milwaukee and Chicago. We chose mecanum that year so that we could maintain orientation while going around the field (i.e. always have the robot facing us so we're ready to launch the ball as soon as we cross the lane divider). This became a non-issue when we abandoned the balls. Instead, we used mecanum to "change lanes" and eventually twisting of the frame actually allowed us to "powerslide" around every corner because of the rollers. The advantages we realized were not initially planned for, however, the planned for advantages were never needed, so it worked well anyway. We seeded 8th in Chicago, were picked by #1 in Milwaukee (lost due to mechanical issues), and were not picked in Atlanta or IRI.

2010: 8" wheels on suspension pods on custom chassis. The idea was to be able to manuever around defenders while using our ball magnet and be a top scorer. The ball magnet never worked properly (and was abandoned completely for NorthStar). Mechanical issues in Milwaukee prevented us from doing...anything...but things went well at Northstar and we were picked by #7 alliance. Did not go to Atlanta, were not picked at IRI. Mecanum allowed us to slide into the wall to retrieve missed shots, but otherwise didn't give us much advantage as it was geared to slow to evade. Unfortunately, not geared slow enough and thus was unable to climb bumps either...but this was solely a gearing issue and not a traction issue. This is the only year I would redo without mecanums if I could do it again.

2011: 8" wheels on custom chassis. Our most precisely crafted chassis led to our best functioning mecanum bot yet. The reasoning for using mecanum was simple: its quicker to move sideways to fine adjust with a stationary elevator than it is to back up, turn, and pull forward. We accepted the fact that defense would have their way with us most of the time (which, in reality, we did a pretty good job of evasion this year and there is one match in particular at St. Louis that we were able to spin around the defender while in full contact with them because of the rollers...traction wheels would have just stuck us there...quirky, but I'll take it...if I can find video, I'll post it), but were okay with that as we expected to be rarely leaving the scoring zone. The concept was sound, execution is where we failed. Tubes didn't always get to us, so staying close to the scoring rack didn't always happen, which led to being defended. Even so, we were top 15 in Milwaukee and Chicago, drafted by #8, and were the #8 captain in St. Louis, so I think we did something right. IRI we were usually the feeder/defender, which didn't work out so well for us. If I had to do this year over again, I'd use mecanums again without hesitation.

The biggest difference I see between a team like us (a team that has used mecanum wheels in multiple years, learned from mistakes, and developed designs and software to make proper use of mecanum abilities) and your perennial top tier teams (71, 111, 148, 254, 1114, etc) is practice. We have never built a second robot. We have old robots with mecanum drive still functional, but its not the same. Those teams I've listed, and many more, were extremely good at what they did this year because of the time their drivers put in. Their routes, routines, sitelines, alignments, etc. were nearly flawless by St. Louis (some well before that). Even though our robot this year was the most finished its ever been going into the crate, we still managed to miss all but one practice match this year, including St. Louis. We spent time at each event on the small practice fields, with drivers driving from an unusual viewpoint, and had one session on the practice field in St. Louis. Everything else our drivers learned came from in match experience. I have absolutely no doubt in my mind that if our drivers had a second robot and a rack to practice with at home, we would have been just as quick a scorer as 2826 or 111. We still would have been lacking in the minibot department though

I think I've said quite enough.

Kev