Re: pic: 1675's REAL IRI Upgrade
 

While I do not think it is right or fair to 1675 that they are signled out in the title and mentioned several times in this thread, debating other team's design decisions is nothing new on CD.

Re: pic: 1675's REAL IRI Upgrade
 

Definitely a funny picture! Hopefully everybody else who has read the mecanum vs 6WD threads enjoys it as much as I did.

I don’ t see too many people making huge generalizations in this thread, which is good.

Here is what I will add:

1) Mecanum is in some ways easier to drive than 6WD. This is because it gives you room for error. If you miss your route to a scoring peg by a bit, you simply correct it in 1-2 seconds by strafing. You don’t need to learn ridiculously complicated drive maneuvers – just drive it like a tank and strafe when appropriate. I’m not advocating sloppy driving– I’m saying that it probably takes more practice time to be a really effective 6WD operator, because it takes longer to adjust if you miss. This is relevant for teams that don’t have a practice robot / practice field or highly experienced FRC drivers. Know of any teams like that?

2) Mecanum is approximately even with 6WD in a few categories that I have seen occasionally cited as advantages for 6WD: complexity, cost, and weight. As a basis for comparison, I’m using “kitbot on steroids” as the 6WD, compared to 6” mecanum drive direct driven with with Toughbox Nanos. The mecanum drive costs about $300 more – not a giant amount when you spend $5000+ on the kit. The weight is about the same, and it’s not really any more difficult to assemble and program than a basic 6WD. The code is provided to everyone. You can bolt a mecanum drive to the kit frame in a week and then focus on the rest of the robot, just as you can with 6WD.

3) This year we had a relatively narrow scoring zone to share with our alliance partners, and the other team was not allowed to drive into it. A mecanum robot can spend most of its time in that protected zone if somebody is feeding tubes, which partially eases the vulnerability to pushing defense. We looked at that situation and went with mecanum, thinking it would help us score faster in tight quarters. One can look back at that reasoning and argue that we made a poor tradeoff, but we did have sane reasoning to go by. It is going a bit too far to generalize to the effect that there can never be a valid reason to select a mecanum drive.

4) At the regional level, mecanum drives held up pretty well. Plenty of teams have brought home regional banners using a mecanum drive along with solid manipulators / driving / etc. There’s nothing wrong with that.
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Overall, I am more of a fan of 6WD after seeing how good the best of them looked on the field this year. I was surprised and impressed by how quickly and easily some of the 6WD drivers were able to hang tubes – essentially, their driving skill gave their 6WD robots the benefits we were looking for out of a mecanum drive. That was an eye opener. We are happy with our robot and our accomplishments from this year, but we’ve been playing with 6WD prototypes this summer and will probably bring some traction next year.

Re: pic: 1675's REAL IRI Upgrade
 

I remember whatching 1675 returning the favor by generously donating 50 or so mecanum rollers to 1625. :yikes:
By the way, did you guys ever find all of those?

Re: pic: 1675's REAL IRI Upgrade
 

Im more curious as to where they got the colored tread :p

Re: pic: 1675's REAL IRI Upgrade
 

Go to Mcmastercarr.com and search for inclined conveyor belting.

Re: pic: 1675's REAL IRI Upgrade
 

***removed***

Re: pic: 1675's REAL IRI Upgrade
 

Im pretty sure that 71 used mecanum this year in logomotion. Cause when i was watching the curie division finals 71 could move side to side, and im pretty sure i saw mecanums on their robot. See in the video how they move side to side. http://www.youtube.com/user/mckinley...49/mVCDScrUCsw

Re: pic: 1675's REAL IRI Upgrade
 

I'm pretty sure they were a crab drive like they have been since 2005.

Re: pic: 1675's REAL IRI Upgrade
 

I am more than pretty sure, I'm certain that they have a crab drive.


@EagleEngineer:
Sideways movement does not indicate mecanum.

Mecanum, kiwi, slide, crab and nonadrives can all move sideways. I personally prefer crab or nona because they sacrifice little forwards power (with nona/slide you still can still put 4 CIMS to the forward direction, and add, say, two banebots to the slide wheel, with crab you can orient all wheels forward for maximum forward power)

(for those who don't known a Nonadrive is a 9-wheel slide drive, with articulating traction wheels. It was named by JVN, who is obsessed with the number 9. It was used by teams 148 and 217 in the 2010 seasons, and almost used by team 148 in the 2011 season (they pulled the slide wheel, but keapt the lifting traction/omni combos)

Re: pic: 1675's REAL IRI Upgrade
 

agreed. i saw the bot up close during pit scouting. motor in pod crab.

Re: pic: 1675's REAL IRI Upgrade
 

I know... The Beast has been crab drive every year that I can recall since 2005. This makes them one of the few top tier teams to have repeatedly used crab. The only ones I can think of other than them are 16, 111, and 1625. Many other top tier teams have experimented with crab and went back to other systems, these included (this isn't definitive, it is only what I can remember off the top of my head)

47 - 1998, 2000 - 0 Championships(to my knowledge they were the first crab in FRC)
67 - 2005 - 3 Championships (2005, 2009, 2010)
217 - 2002, 2003 - 2 Championships (2006,2008)
1114 - 2004 - 1 Championship (2008)
148 - 2008 - 2 Championships (2008 and 1993)
33 - 2005 (switched to 6wd halfway through the year), 2009 - 0 Championships
234 - 2010 - 0 Championships
469 - 2007, 2008 - 1 Championship (2003)
118 - 2005 - 2008 - 0 Championships

Just some extra data for the argument that simplicity is key. Every single one of these teams has since gone back to the tank style drive (6/8wd for most of them)

Re: pic: 1675's REAL IRI Upgrade
 

In 2005, we actually switched after our first competition, and pulled out the whole two crab-modules (two pods and a steering motor on a single removable block), and replaced them with four crab gearboxes mounted fixed (so we had a 4wd with pneumatic wheels, at less weight than the crab drive, and the cg offset of tetras on an arm allowed us to steer without too much bounce.) That non-crabbing robot went on to play on Einstein and win the IRI, but did not get picked at that first competition (the gripper was also partially to blame with that, but with the weight savings of loosing the crab, we could build a much better pneumatic one)


We don't talk about 2009. It sits in the basement and hasn't seen the light of day for about two years.


(47 also had a crab in 2000, FYI)

Re: pic: 1675's REAL IRI Upgrade
 

I know, I remember that 2005 robot. I also remember tipping you guys at West Michigan that year...

I also know about the 2009 robot, I almost borrowed it for a class project but it turned out to be just too large to be safe for me to use for the experiment.

Thanks for reminding me what year 47 ran its second crab. I kept thinking 99 for some reason.

Re: pic: 1675's REAL IRI Upgrade
 

I know, i just though i saw mecanums when i saw their robot on my tv. I must be mistaken, cause i knew mecanums could not be that effectient at moving side to side. So crab drive and swerve drive are the same thing right?

Re: pic: 1675's REAL IRI Upgrade
 

Who initiated the slide drive? I've heard it called Buzz drive because 175 has used it several times, but were they the first?