Long vs. Wide Drivebase

[meebee]

Originally Posted by BrendanB

Three wides will fit with 11inches of overhang. If one of those is long you are never balancing.

Doesn't this mean that if the outer bots are 4wd, just the slightest error in driving will send one of the robots toppling over the edge?
This 3 robot balancing act seems to be getting harder and harder...

[GBilletdeaux930]

They don't necessarily have to go single file remember.

Bridge is 48" wide, two relatively thin robots could squeeze next to each other. Or overlap could occur to squeeze a third on.

[Djur]

Originally Posted by GBilletdeaux930

I think you are overestimating how tippy the bridge is. You can be pretty offset and the bridge will still stay "balanced"

http://youtu.be/-AMaqqmoLgQ?t=1m27s

The offset isn't the problem; the amount of space available for turning is. With 2 other robots, even if they're sideways, you'll only have 20 inches or so in which to turn.

[Ninja_Bait]

You'll literally have no space to turn once the other two robots are on. 3 wide robots, with bumpers, will take up 28X3 inches + 4X3 inches, or 96 inches. The bridge is 88 inches. You get a few extra inches if the wheels of the end bots are right at the edge, but not enough. Someone has to hang off or be way smaller than the max dimensions.

[AlecMataloni]

Originally Posted by BrendanB

If you want to be picked for elims then go wide. No long robot will get on that bridge with two other robots and balance.

Three wides will fit with 11inches of overhang. If one of those is long you are never balancing.

Those are some very bold statements. Have you already tested your bridge theory?

Coming from a team that has been Wide Base more often than not, I've learned that controlling a wide base robot on a field with terrain without tipping over is a considerable challenge. According to one of our mentors, our Aim High robot was driven very carefully (on a field with no terrain besides the ramp) to avoid tipping. Rapid acceleration and deceleration while driving a wide base robot is a recipe for disaster. Drivers used to a standard drop center 6 wheel drive will find that driving wide base is quite different than what they're used to. It obviously can be done, but it's just tougher.

Despite the drawbacks, wide bases do have certain advantages that might be pivotal. The increased area for an accumulator allows drivers a lot more leeway during pickup, regardless of ball control. I can see this reason, coupled with the attractiveness of having a smaller profile on the bridge, driving many teams to build wide base robots; however, I'm expecting that the disparity between Elimination-worthy wide and long bases will favor the latter, due to more teams sticking with what they're comfortable with.

[Joe Schornak]

My team was initially favoring a wide base over a long base, for the reasons mentioned above. This changed when our prototype shooter bot almost tipped backwards when I lifted its front wheels onto the barrier. Our current design is now a long base with a hybrid mecanum/traction drive to aid in climbing the barrier.

I think that teams are underestimating the difficulty of crossing the barrier. It will be very difficult or impossible to do with 8 inch wheels or smaller, unless you have a way to change your wheel's initial contact point on the barrier. The necessity of large wheels or other chassis shenanigans will reduce the length of the wheelbase and make a wide configuration less advantageous.

[samholladay]

Our team was wondering if we could climb over the bump/barrier with 6 8" wheels. We were thinking of making a robot that is slightly wide, maybe 28 x 32. In that case we would have some of the advantages of a wide chassis (and would fit on the bridge better), but hopefully it wouldn't be as tippy as a robot that was, say, 28 x 38. Of course, 8" wheels may not be able to get over the barrier, and that will become a big issue for a lot of teams as the build season goes by. If 8" wheels don't work we may have to try something weirder, like 8 6" wheels or something.

[MrForbes]

The reason a wide robot is tippy is because it's only 28" long (maximum), not because it is wide. With 8" wheels you have a 20" long wheelbase maximum, probably considerably less since you probably need some frame to be outside the wheels. It's the short wheelbase that is the issue.

[davidthefat]

Originally Posted by squirrel

The reason a wide robot is tippy is because it's only 28" long (maximum), not because it is wide. With 8" wheels you have a 20" long wheelbase maximum, probably considerably less since you probably need some frame to be outside the wheels. It's the short wheelbase that is the issue.

Not unless you use a 20 inch wheel.

[KennyLives]

Well, longways seems to be much easier to control, especially over the bump. If you want the best of both, you could go with a mechanum drive, if you don't mind being pushed around.

[rifkinni]

Our team is still debating the issue. One of the advantages that hasn't been mentioned is that a wide robot can pivot better than a narrow one. It might make things easier for fine-tuning your aim.

[B-Bot]

Just make a long robot with mecanum drive so you can get on the ramp the head on way during qualifications and then sideways during finals.

[jblay]

The Dean Kamen segway wheelchair (Don't know the actual name off hand) would be ideal for this game

[J.Warsoff]

As I type this, my team is testing a wide chassis prototype. I just watched the thing fly a full 4-5 inches into the air after hitting the hump. Besides for that, it is very unstable and top-heavy. We are all leaning towards the fact that the narrow chassis is a much better choice.

[Bruceb]

How far off the ground was your shooter and how heavy was it?
Bruce