Driving long?

So now that a lot of previews, teasers, and partial reveals are coming out, I’m noticing a substantial number of robots with a ~38" long drive base. I’m curious what motivated these decisions. You’re almost completely removing any chance of balancing 3 robots, but perhaps there are other benefits? (crossing the bump, getting into corners, etc.)

So why did you decide to drive long?

We’re going long mostly to counter center of gravity and tipping issues while crossing the bump and climbing the bridge. Our ball collection and storage system takes up a significant area between the wheels, so lots of components have shifted upward on the robot. A long base will keep the center of gravity over the wheelbase when the robot tilts. It also lets us put the shooter higher on the robot for the same reason.

Also, mecanum wheels work just fine for taking the robot up the bridge sideways. I forsee on problems in getting three long robots on the bridge, as long as you designate one team to balance and the other two teams to hold very still.

Long bots with a low, centered CoG should still be able to balance three at a time, if the end robots hang off their front wheels.

We intend to drive on, rotate (zero turn radius), and then either slide sideways as necessary or drop our traction wheels so that we won’t move while our partner(s) get into position in order to achieve balance.

This is only the second year since I’ve been on 816 that we had the Wide vs. Long debate, the first being 2009 where building a long base was almost like handing a victory to a capable opponent that could drive reasonably well.

We ended up assessing a few parameters and came to the conclusion that we could build either a long or wide robot without too much hassle and have them both be about equally competitive. These discussions finally culminated in the decision to build a ‘Short Long’ of sorts. For all intents and purposes, our foot print is ~32"x27.75" - It’s only about a bumper’s length longer than a wide robot, which shouldn’t cause too many issues with bridge balancing. If all goes well, when it’s on the bridge, due to some creative weight positioning, it should effectively be smaller than most wide robots.

I’d imagine that the primary reason that many teams have gone long this year is for ease of traversing the field at speed. Having driven both Long and Wide Bots at ~12-13 fps on flat fields, I can say that a wide bot requires the driver to be much more aware of the robots size than with a long.

We came to a similar conclusion. After last year we talked to our drivers about what they would like to see moving forward. They loved the 2-speeds we ran last year but wanted the robot to be more stable and have a more predictable center of turning. When this years game was released we determined that stablity while tranversing the bridge/barrier was going to be critical to our design. We finalized on an 8wd (5" Colsons), with dropped center wheels (1/8"). Our overall chassis size is smaller than your average “long” robot at ~34" x 26".

We decided to go for wide for two reasons: Firstly, it makes balancing easier with three robots. Sure, you can go for long and rotate on the bridge, but that takes time. What if you could have scored 6 extra points in that time? Our second conclusion was that balls would be a tough commodity in this game, so it was essential that we were able to collect them easily. Thus, a larger surface for the collector was necessary, and we put it on our wide side. We’re keeping our CoG low, so we can still go over the barrier.

Less than a second for us, and we can drive sideways afterward. I wouldn’t recommend it without a zero-turn-radius robot.

Do I hear an octocanum drive from 1551?

We figure balancing 3 robots is going to be a lot harder than some people think - especially since no one is going to be trying it until the elimination matches. You’ll see a lot of teams try for 3 and not get any bonus points because of it, being beaten by people going for two who get it because they’ve had a lot of practice doing that.

I don’t know what would make you think that… http://www.youtube.com/watch?v=7GbrprUtC4o


I am not too surprised by the number of teams driving in a long configuration, but I am surprised by the number of them using a <=12" opening for ball collection.

Don’t you expect that most of them will have some kind of deployable appendage for collection?

I am sure lots of folks will, but I’ve come across a number of pictures here that show narrow ball collection openings. Perhaps that’ll feature an additional system that funnels balls into that narrow opening, but that hasn’t been clearly the case so far.

True that. It hasn’t been clear on our videos so far, but we’ve got a deployable collector. I’ve just assumed that everyone else driving longways does, too… (Except perhaps some inexperienced teams that don’t realize how critical it is.) I think in this game that even if we were driving wide, we’d still have a deployable collector!

One of the primary reasons for driving with the long orientation for us was barrier crossing; another is center of gravity driving up the bridge.

FIRST Team 1296 went long so going over the bump will be easier and mounting a ramp lower device seemed easier (given the geometry of our gatherer). Madison is right about the small aperture gatherer mechanisms on long chassis, thus ours gathers from all 4 sides.

Our mecanum drive alignment and software seems really good this year and we can spin in place once on the bridge in a couple of seconds. But is it worth it to try? I agree that 3 (traditional) robot balancing is problematic w/o time to practice the maneuver - hopefully we make it far enough for it to be feasible.

Or use 2 long robots, one wide robot. 256 is going wide this year for a few reasons, mainly because of our awesome offense, and ability to traverse the field without tipping over.

Most of all, I want to see the wide:long ratio of robots on the field vs. the wide:long ratio of robots who make it to the championships.

I like a long bot for greater field mobility which in my mind means moving over the barrier quickly with little risk of getting stuck or tipping. Like most I believe there are designs that will allow you to collect balls quickly as a long bot, so that shouldn’t be too much of a disadvantage. As for the bridge balancing, I think it is far to difficult to assume you will be able to balance the bridge with 3 long bots, I think teams will design for this problem.

EDIT: I assume you meant “no problems”

With 3 true long bots (44 " long with bumpers) you have either two robots halfway off the bridge or an entire robot not taking up and bridge space at all. So in the scenario where you have two robots hanging of either end of the bridge, assuming they have a centered CG the robot in the middle cant move at all without tipping the bridge. Sounds a tad bit difficult to pull something like this off, unless you have designed your robot to do this and have had practice doing it. But this would be my last resort to bridge balancing, I would try and find another way for a long bot to accommodate bridge balancing like others have mentioned.

Agreed - perhaps an automagical (eg s/w assisted) maneuver that enters the ramp in a long orientation but pivots as it balances - hmmm

For all intents and purposes, our foot print is ~32" x 27.5"

Wow, came to the same exact size! Nice.