How much Bridge Space does your robot need?

[Bjenks548]

We've all seen 179's robot that takes ~3" of space. 118 showed us a side hang that essential takes up no room. Many people built a widebot to take up less of the 88" of the bridge. How much room does your robot need (including bumpers) on the bridge (without falling off)?

[Kellen Hill]

This is an interesting subject, as I feel like many people view 179 and 118 as robots that allow you to easily get 3 robots on a single bridge. The problem here is that while these robots require little to no room on top of the bridge, they still have a large footprint on top of the bridge. While they may not be physically using the space, their weight is still hanging there, meaning that other robots can't use the space. Depending on these robot's weights and where their center of gravity is, they aren't really making the bridge balancing challenge much easier.

In fact, 179 might be making it a little more difficult as all of their weight is out at the edge of the bridge (not sure what 179 weighs, but hopefully it would be somewhere south of 100lbs). If they do weigh the entire 120lbs plus all the goodies, they would have a much larger than average foot print on top of the bridge, forcing their two teammates to drive as far as they can to the other edge of the bridge in order to balance it.

I think I prefer 118's balancing technique due to their ability to have their weight more towards the center of the bridge when it comes to balancing. While I do highly enjoy both of these unique designs, they still have many of the drawbacks that any other robot on top of the bridge would have. I will be interested in seeing if these designs can make the bridge balancing act any easier than 3 'standard' robots trying to do it.

Overall point being that space occupied on the bridge, especially for these two bots, does not always equate to the actual amount of space needed on the bridge. To properly gauge a robot's footprint, you should consider other characteristics such as weight and center of gravity along with actual room required on top of the bridge.

[MrForbes]

26 + 2 (3.25) = 32.5" if between two other robots

With the 18" wheelbase and 6" wheels, we take up a bit less room on an end of the bridge. Three of our robots could fit on the bridge, but I don't know how the balancing would work out...it would be "exciting" Also we could interlock front bumpers with another robot like ours, reducing the total length needed.

[Bjenks548]

I assumed the reason 179 showed their bridge technique so early was to inspire other teams to do something similar. Imagine how easy the triple balance would be with 2 179 type robots on opposite ends.

While I see robots like 179's being successful bridge balancers, they still don't play as much of an offensive role to their team like teams such as 118. With 118, they not only take up less physical room for balancing, but they are also an offensive beast. I think the only robots that will be able to get by later on in the competitions are the ones who score really well, and balance on the bridge, because once you get to the championships, most everyone's going to be balancing.

[pyroslev]

This is gonna be a situation in the Alliance pickings where you're gonna see teams look for two types.

-Ball Manipulator: Shooter/Feeder that can rack points up or keep feeding a shooters
-Odd ball/Small ones: Something I can shove in the middle or that hangs off the edge, or even holds a robot on top in the middle.

I think the #8 seed is gonna have the best pick. They can pick their shooter right off the bat and then grab a 179/118 type or something similar to 701.

Then if you add in the shorter robots (28" frame), easy turning robots, mecanums, etc., That bridge is gonna be very entertaining in that bracket.

[Grim Tuesday]

I find it interesting that Chief Delphi has ruled 118's hanger legal. I wonder if we'll see the same ruling at a regional?

[Aren Siekmeier]

23.5" + 6.5" makes us 30" from bumper to bumper. We'd be able to chop about 8" off one side if we're at the end of the bridge, bringing us to 22". So 3 of ours would have 14" of breathing room.

[PayneTrain]

We built our bumpers high and drive base wide to negate as much bridge space as possible. I fully intend on balancing 3 as much as possible if we are lucky enough to be playing in elims. The bumper locking should help us only take up <30 inches of space on the bridge.

[n1ckd2012]

We, 2587 DiscoBots, can balance with ~1/3 of the robot hanging off the edge. This allows another robot to drive up next to us. We are still figuring out how to get up the bridge with only half of our drivetrain. See image:

https://picasaweb.google.com/lh/phot...e mbedwebsite

Our release video:
https://vimeo.com/37359670

Our daily build log:
http://2012.discobots.org/node/31

[RRLedford]

We take up only 13"+ of bridge width as we cantilever the other 20" of our width, hanging off the center-of-field side of the bridge, extending most of our bot into the air well beyond the guide rail (which we do not grip). We are a six wheel "kitbot on steroids" size with severe weight concentration right forward. Our plan is to facilitate three bots on the bridge by allowing a pair of 34+" max width bots to drive right past us while we hold bridge down for them with us parked on side edge and overhanging toward center of field, just past tipping (toward them) point of the bridge. Since we can all three stay nearer the center of the bridge with this scheme, this makes balancing much easier and faster. We are thinking only 10-15 seconds for all three to balance -even with no practice.

We can tip the bridge and drive it end to end along the rail. We can balance it alone in a few seconds after our first wheel goes up. We can pre-tip the bridge downward and hold it there, allowing for our arriving alliance partners to just simply and accurately drive right up and balance (assuming they are not over 34.5" wide). We play defense and shoot returned balls the length of court, but shots go only where robot points (no aiming turret). We are still trying to get a ball pickup scheme working.

If we are partnered with wide bots in qualifying rounds, then we can go for the middle bridge coompertition points . Wide bot alliances will know not to pick us for the elimination round, In the elimination round we hope to be on an alliance with too good shooting offensive minded partners. Our 4-CIM drives lets us play decent defense and/or park at the return slot to fire balls back up the full length of the court - over any defender parked in front of it..

In Autonomous, we can get to the center bridge very fast and, since we have most of our weight up front we are going to win most tipping battles there to get those balls, After which we move over to our bridge bringing those two balls down on our way to the other side to play defense and be an up the court ball passer.

We think we will be a good alliance match fro the right capability partners.

-Dick Ledford

[Swampdude]

Good points made. We are currently just under 100lbs, and around 123 with bumpers and battery. So we figured a nominal 145 lb bot needed to have it's CG less than 19" from the other end of the bridge. Which should be easy and should only require a driver to move as far as they can out to the end. I'm hoping and in theory this should be quick and easy. If there were still a weight issue there's a few pounds to play with but I think we're good as long as we balance with 115+ lb bots.

I agree 118's method is better but we'll have to wait and see what the head ref thinks first.

I will say that the reason the bridge balancing became a priority over scoring balls was the realization of different strategies to defend shooting and starve balls etc. I think the great shooters may be in for a surprise when up against good defense, feeders and ?!?! etc. So I think the 3 bot balance will usually be key to winning in the finals.

[PayneTrain]

I don't want to diverge, but it will be intriguing to see how defense will play out against every shooter on the planet.

I also want to go back and add that we can get by with having 7 inches of our robot hang off the back of the bridge before we get into a hairy situation. We moved most of our weight towards the front because we don't plan on being first on the bridge, unless we are the only team on it.

[Bertman]

maybe a question should be "how much bridge space does your driver need>"

[Alpha Beta]

If in the middle: 3.25 + 28 + 3.25 = 34.5" That leaves (88-34.5)/2 = 26.75" for each end.

As an end robot we take up 25.25 inches.

So, we could fit 3 of ourselves on the bridge, but not alot of room to play around.

I shudder to think what will happen when the last robot on shoves the first robot off the other edge. At least this should only be a serious problem in the elimination rounds.