Re: Mecanum or 6WD
 

Mecanums strafing ability allows for added maneuverability.
6WD allows for more traction.
Neither is inherently better than the other in a 1v1 match up.
The aspect that pushes that match up towards one side is going to be the amount of practice the drivers get with their robots, and robots with similar drive bases. If a defensive bot has experienced drivers that have had a couple years and a practice bot, and the mecanum offensive drivers have never touched a holonomic drive in their lives, the mecanum drive will be completely dominated. However, if the mecanum drivers have spent a hundred or more hours with the 3-axis joystick in their hands and the 6WD drivers are taking their first turn behind the drivers' station, a juke and a spin is all it will take to get into the scoring zone.

Re: Mecanum or 6WD
 

Can you point to a video of a mecanum drive that's ever done that?

Re: Mecanum or 6WD
 

We are going to test both. We have a team working on each type. We have found our past mecanum systems to be plenty fast. I also think that they are advantageous this year with the narrow feeder chute. It might be easier to make lateral corrections to our position with the crabbing ability. Rather than having to back up and turn, we can make small moves sideways if our tubes are a bit off.

As for dealing with defenders, our drivers have been able to use crabbing to outmaneuver less agile robots. We are sometimes a bit slower in a straightaway than 6 wheeled robots, but haven't been significantly disadvantaged by that.

We are interested in whether the rocking motion of the CA drive will make use vulnerable to tipping when extended. Jury is still out, of course.

Re: Mecanum or 6WD
 

I sure hope to see a spin move this year. Very cool.

Re: Mecanum or 6WD
 

Not exactly, I do have a couple of pictures of 2337's mecanum drive shoving HOT up the bump though.

The key to either system is having a skilled driver who communicates effectively with the coach and his other driver. There are benefits and drawbacks to everything and we must be able to effectively figure out which downsides we can live with and which we can't.

I personally am doing either 6wd or 8wd this year, we talked about mecanums (3450/314) but we are building multiple bots and doing that makes cost highly prohibitive. (4 gearboxes + 4 mecanum wheels for each bot) I am also an alumni from the Martian "defense" era. The best defense is having more traction than your opponent. For the record we also considered doing a swerve drive but buying 3 Revolution modules or 3 WildSwerve modules was out of the question price wise.

Re: Mecanum or 6WD
 

Quick question (I hope you read it...):

For your 6WD in '08, were the center wheels dropped, and if so, how much?

Re: Mecanum or 6WD
 

Our team is going with mecanum because it is obviously superior to 6wd in every way. There is really no debate

Re: Mecanum or 6WD
 

As with all decisions made in the engineering world, there are pros and cons of everything. I'm not trying to say mecanum isn't great, but if you open your mind up a bit you just might learn something.

Re: Mecanum or 6WD
 

Remind me to just cite you as a source for anything I need in the future since you seem to have no problem making stuff up and presenting it as facts.

Dangit Jim, we are engineers not politicians.

Re: Mecanum or 6WD
 

As long as you have built both systems and worked with them extensively, then good for your team for making a decision, but in engineering there is always pros and cons because nothing is perfect.

We will have fun pushing you around if we ever meet! ;)

Re: Mecanum or 6WD
 

I think he forgot his [kidding][/kidding] tags!

Re: Mecanum or 6WD
 

In the end, our team is going with 6WD. The choice came down to this: A 6WD has two advantages over mecanum:

It is faster. We used mecanum in 2010, and noticed that as we accelerated, we lost power from the slipping of the rollers; however, to me, this didn't seem like a significant loss.

Secondly, it gets better traction. (I was talking with someone from 330 at one of the regionals, and they had put a mecanum drive bot in a pushing match with the 6WD. Mecanum lost consistently, even with the same gearing).

The Mecanum Drive has one advantage: its ability to drive sideways.

Here's the rub: Driving sideways would be a solution to the problem of scoring accurately, reliably and quickly. We could also solve that problem by having the driver practice with the alternative drive option. We decided on 6WD, and our plan is to give him weeks of practice on tank after ship and before regionals with the kit bot.

Re: Mecanum or 6WD
 

IIRC, it was a 4WD (2003 drill motor drivetrain). Same principle, though. We also put those two through the block/get around block routine. Mecanum still lost! Because mecanum lost both pushing and block evasion, the 6WD stayed on our competition robot. Results of that were good; this was in 2005.

If 330 ever saw that mecanum would be an advantage, they could do it. The mecanum that lost to the tank drive systems had two years of development behind it. Knowledge doesn't disappear very well...

Re: Mecanum or 6WD
 

The debate between Mecanum and 6WD is very subjective to the game itself. However each team analyzes and decides on which drive system is "better" for the suited game differs from team to team. According to the poll, 6WD is favored this year. THAT is a fact.

Re: Mecanum or 6WD
 

this isn't a very defensive game, so i don't think you need to worry about traction and pushing power. no other robot will play heavy defense.

Re: Mecanum or 6WD
 

That sir is where you are wrong, this game is a very defensive game. The robot that cannot pick up a tube, either by design or failure of strategy and prototyping, or breaking is not going to spend 2 minutes letting you put tubes on the rack. There will be defense. Every robot on that field can drive faster than you can strafe (presumably unless I am missing a strategy to move slow and relentlessly), and I expect to see a 6wd will be able to bulldoze (of course not at ramming speed) through a robot that is trying to block their path, especially if the robot isn't on tractioned wheels.

As long as the robots are allowed to contact each other, traction will be important.

Its not that hard to find a way to slow down another robot, and pinning is not the only way to slow down or stop another robot from scoring. ask all the robots that sat in front of a goal last year, or all the robots that are going to turn sideways and mirror your attempts to pass them. I think I would be able to teach my alliance partners to play pestering defense in under 30 seconds.