pic: 1675's REAL IRI Upgrade

[Hawiian Cadder]

that is a pretty excellent prank.

IMO, if the bumpers were made out of a fabric that was slippery, mechanum drives would have (maybe) a significant advantage as they could slide around the higher traction drives, however, because the bumpers sort of stick to each other, I think that most omni directional robots fall prey to the faster accelerating, more grippy tank drives.

we have built 2 mechanums and 2 tank drives since i have been on the team, and i would have to say that the mechanum prototype, weighing less than 40 lbs fully loaded (with battery), could probably drive circles around one of the tank drives (geared slower than it) and maybe the other (geared faster than it). However the full 120 lbs mechanum suffers too much loss of acceleration to out maneuver either of the tank drives.

[Taylor]

Originally Posted by Duke461

I see your point, but i think mecanum can play defense.

Depends on the game and the strategies in place. In a year like this one, getting in the way constituted most of the defense, not pushing people around. Mecanum does well with that. In a game like Aim High, defense was pushing people around, and mecanum drive would be arguably a poor choice.

[Duke461]

Originally Posted by Taylor

Depends on the game and the strategies in place. In a year like this one, getting in the way constituted most of the defense, not pushing people around. Mecanum does well with that. In a game like Aim High, defense was pushing people around, and mecanum drive would be arguably a poor choice.

Agree completely. You've basically said what i was trying to say, i just couldnt think of the right way to say it.
thanks,
-duke

[ratdude747]

Originally Posted by XaulZan11

I think Ratdude actually shows an advantage of tank over mecanum. One of the reasons I want my team to use the same strong 6/8 wheel tank drive (or something similar) is that we can always play defense if we need to. Obviously, we always go into the year thinking we are going to be one of the best scorers at our events, things don't always go to plan and you need to adjust. Things break mid match or your scoring isn't quite as good as you expected, so you may be better served playing defense in some matches. This year at the Championship and IRI we played defense around half of the matches (depending on matchups), and got picked at both events because of our ability to play defense. I think there is no way we would have gotten picked if we had a mecanum drive. I don't recall seeing any mecanum drive play better than just 'ok' defense as they are just too easy to push around.

two different bots, two different games, two different goals, and two different teams.

the mecanum was meant to be an offensive machine. the tank was meant to be a bump hopping defensive machine.

if you use your interpretation, then all it really proves is if your manipulator design is crap, then you will be stuck in defense.

may I ask how mnay defensive bots do you see on einstien? winning regionals? note that the tank bot lost in the semifinals. why:

1. 1018 was in the far back zone, we were middle, and 1501 was by the goal. this was so 1018 could use their 3 ball auto.
2. then 1018 and ourselves would switch places by crossing the bump. we would play defense and 1018 would feed balls to 1501 and score mid zone goals directly.
3. the failure was in the switch... the alliancein the semi picked up that if they blocked the bump, 1018 would be stuck as they were too tall for the tunnel. we were tied up getting them off the bump to let 1018 cross, so their goals were undefended, hence why we lost.

the fact that we were only good in one zone (defensive) was the kiss of death...

also, the reason why both designs in my last post failed was they same for both. we spent so much time screwing around with perfecting designs, trying to do everything, and over-complicating things that there was no time to troubleshoot and find practical bugs. both times the drivers only got 1 day of practice before competition.

so if you plan to have a manipulator that doesn't work, yeah, go tank since being able to score won't be on your agenda.

If you give your design a serious effort and get something for the drivers to play with with plenty of time to spare, then mecanum may be helpful.

[AlecMataloni]

Originally Posted by Duke461

P.P.S. You guys may disagree completely with me, and i'm not looking to make this an argument; however, i believe 100% that 254, 111, and 973 still would have won it all if they all had Mecanum drive trains.

I don't think so. 973's defensive prowess definitely kept us ahead of the competition due to their awesome drivetrain (and drivers, of course). I remember many instances where all 3 of us had to weave through traffic and probably would've been out of luck if we had mecanums.

[XaulZan11]

Originally Posted by ratdude747

may I ask how mnay defensive bots do you see on einstien?

I believe there were 3 or 4 (not sure about 25) teams on Einstien who did not score a logo piece.

I think your idea that you only play defense if you plan to have a bad manipulator is very flawed. I'm pretty sure teams like 469, 71, 1625, 25, 973, 968, and 217 (all of which played defense more than once) thought they would have a good manipulator (and all did).

[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

[BigJ]

Something not mentioned: These treads were eventually used to make Greg Rupnick's Traction Hands to help him on his way to winning the IRI Mentor Minibot tournament!

[XaulZan11]

Originally Posted by Kevin Kolodziej

I think I've said quite enough.

I think you forgot a year, Kevin. The year you didn't have a mecanum drive and won a regional playing great defense.

[ratdude747]

Originally Posted by XaulZan11

I believe there were 3 or 4 (not sure about 25) teams on Einstien who did not score a logo piece.

I think your idea that you only play defense if you plan to have a bad manipulator is very flawed. I'm pretty sure teams like 469, 71, 1625, 25, 973, 968, and 217 (all of which played defense more than once) thought they would have a good manipulator (and all did).

thats not what I was meaning. my point was if one wants offense and screws up the design, you will be stuck playing defense like it or not.

playing defense beacuse you elect to and playing defense because thats all you have left are not the same. all of your examples are elective defense moments, not forced (you said so).

I might also point out that not every bot on Einstein played defense at one point either. defense is not necessarily a "must have" to be successful. It all comes down to how one wishes to play the game.

bottom line: add defense if you want, just be aware that if you want more, design your manipulator carefully and remember Karthik's golden rules: don't bite off more than you can chew and its better to be good at one thing and poor at the rest than so-so at everything.

[BigJ]

Originally Posted by XaulZan11

I think you forgot a year, Kevin. The year you didn't have a mecanum drive and won a regional playing great defense.

shhh Kevin hates defense

(the kids threaten to want to build a solely defensive bot every year to mess with him)

[Laaba 80]

Originally Posted by XaulZan11

I think Ratdude actually shows an advantage of tank over mecanum. One of the reasons I want my team to use the same strong 6/8 wheel tank drive (or something similar) is that we can always play defense if we need to. Obviously, we always go into the year thinking we are going to be one of the best scorers at our events, things don't always go to plan and you need to adjust. Things break mid match or your scoring isn't quite as good as you expected, so you may be better served playing defense in some matches. This year at the Championship and IRI we played defense around half of the matches (depending on matchups), and got picked at both events because of our ability to play defense. I think there is no way we would have gotten picked if we had a mecanum drive. I don't recall seeing any mecanum drive play better than just 'ok' defense as they are just too easy to push around.

in 2010, 525 was able to defend me with mecanum drive. Its a little weird though, because in the entire match, they did not appear to strafe once. They were pushing the corner of our robot, and had me essentially pinned in the center of the field for around 10 seconds. In the end I realized our 6wd was faster, and used that to my advantage, but they put up a very good fight. They held me to 3 balls scored in the first match, and 4 in the second, compared to the ~6-7 i was averaging.

[Duke461]

Originally Posted by AlecMataloni

I don't think so. 973's defensive prowess definitely kept us ahead of the competition due to their awesome drivetrain (and drivers, of course). I remember many instances where all 3 of us had to weave through traffic and probably would've been out of luck if we had mecanums.

So you're saying mecanum's limit your ability to weave through defenses???

[Katie_UPS]

I don't go on CD for a day, and you guys have interesting conversation without me..

Originally Posted by XaulZan11

I think you forgot a year, Kevin. The year you didn't have a mecanum drive and won a regional playing great defense.

During heated traction vs. Mecanum debate, this argument does not go over well (trust me, I know).

Originally Posted by Duke461

So you're saying mecanum's limit your ability to weave through defenses???

Speaking from experience as a spectator and one-event coach, most defensive motion is perpendicular to the motion of robot being defended (so if scoring robot is trying to move north, then the defensive robot is orientated to move east-west)*. Strafing is slower than typical forward/backward motion. A lot of robots are typically geared 12 fps**, our robot (this year) included. If my math is correct (basic geometry/trig)(someone feel free to correct me), a mecanum geared like ours (~12 fps) can only strafe at ~8.5 fps. Therefor, "weaving through defense" isn't as plausible as one would think.

Not to mention pushing, to which mecanums have little resistance to (the whole "non-powered rollers" thing).

However, a good driver can play fancy, and do some moves to mess with the defending driver... but that isn't the machine beating a machine, that's the driver beating a driver (although, as many of the greats will tell you, good drivers are just as -if not more- important than a good robot when it comes to winning matches).


EDIT: Also, Traction-Upgrades also make for some pretty spiffy belts



*Applying this defense to games such as Logomotion and Breakaway. This strategy was not as applicable in Overdrive/Lunacy, and I haven't focused on the defensive strategies in games before my time.
**excluding two speeds, but a lot of teams using two speeds are also not playing defense

[Chris is me]

Originally Posted by Duke461

So you're saying mecanum's limit your ability to weave through defenses???

Absolutely. That's part of why no one has been able to ever produce a video of mecanum running circles around 6 wheel drives. People just seem to assume that sliding sideways is some kind of magic defender stunning motion.