Discs Bounce Out of Goals

Several teams have noted that goals with a back and chains behave quite a bit differently than the open holes suggested in the low cost field diagrams.


We can confirm those concerns. We have observed that a direct hit on a chain will drop a disc into the goal, but as the chains start to swing on successive shots (or if a shot hits between two strands of chain) it is quite easy to get them to bounce back out. By suggesting in the low cost field diagrams that teams build goals without chains and a hard backstop to test with many teams have been set-up for an unpleasant surprise when nearly 50% of their shots are rejected.

Is this just part of the design challenge or will FIRST modify the field set-up to help discs be retained in the goals? It reminds me of the surprise last year (2012) that led FIRST to flipping the polycarbonate over under the bridges. It also reminds me of 2010 when FIRST modified the penalties associated with a design constraint after it proved detrimental to game play. Looking forward to our week one event in Lubbock to see how the real goals behave.

In 2010 FIRST removed the penalties for having a soccer ball go under the robot after week 1 events when penalties dominated many mid-level teams’ performances. Appears to be a case where the design challenge was clearly given but enforcing it proved detrimental to the overall event.

2012 is the first time I remember FIRST changing the field design after a week 1 event to help out the teams who couldn’t work with the polycarbonate under the Bridge. Part of the problem was the polycarbonate was not part of the low cost field suggested by FIRST and while some teams designed a mechanism to reach under the bridge to get the balls, having the majority of the balls stuck out of play and disabling the bridges was a big deal for teams who didn’t plan for it.

In 2006 this was also an issue. FIRST did not modify anything and instead said that it was just part of the game challenge.

I agree this is an issue and also agree we wont see anything change on it.

I’d recommend lowering the speed of your shooter and going for closer shots.

Good post to bring to everyone’s attention though.

Hmmm, now we have to spend more $ to buy chains for testing.

Sounds like an argument in favor of floor pickup:)

We are experiencing this issue with relatively close shots, in and around the pyramid. We have found closer shots at a higher angle are even more of a problem.

We were finding the same problem when testing shooting into the pyramid goal. The disks don’t fall down into the goal, but rather bounce straight back. We were shooting at about 90% speed of our shooter when trying to do this.

Has anyone else tested shooting into the pyramid goals?

Are you going straight on towards the goals or at an angle?

We found the more speed and spin on the disc increased this issue.

If a linear shooter:
Try adding a flywheel or motorized wheel to the opposite side of your shooter wheels.

We did this and got a repeatable shot with less spin.

That’s true.
At least some teams could have it go right back into their hopper and cycle it back in 2006.

Kind of hard this year to do. We didnt make our goals with the chain, and I hope we dont have the same issues as well.

When we saw the speed the frisbees were attaining we had our field build crew make us at least one goal that is as close to field spec as possible. The chains do help but I have a feeling a lot of the longer range shooters are going to bounce back out.

We were shooting at a pretty straight angle. If we are going to try to shoot them in match, we’ll probably have to move closer to the goal, and decrease the speed.

Yes, we have tried shooting at the pyramids and think that in order to do so the Frisbee must really land in the goal and you can’t rely on the chains to stop the Frisbees because Frisbees do bounce and or spin off of the a lot.

The game rules say ( that if any part of the disc has crossed through the opening, it will be considered scored. I assume that means it doesn’t matter if it bounces back out.

Did you read the very next phrase:
“is in the GOAL at the end of the MATCH”?
I took that as they have to be in the goal after the match to count.

Our team just built the team field, so some of us are worried that our discs will bounce out, and we currently don’t plan on pickup up discs. Because of this, we might be in for a surprise like last year, where all of our shots went clean over the baskets at our first competition because the balls weren’t the same density as the ones we used to practice. :frowning:

But it also says that it “is not in contact with any robot on the alliance.” How could it possibly be in contact with a robot and also in the goal?

If you dump in the 5-point goal of a pyramid, there is a chance for them to cross the goal opening, but still touch your dumping mechanism.

You’re right. I was thinking only of the other goals. According to the game questions clarifications (#71), if the discs bounce out, they do not count.

As in every year, the field IS the field. It is the same field for every team. I hate to see scored Frisbees bounce out, but it will probably happen to every team, unless someone has a shooter that floats the disks in to a soft landing.

I suspect that most teams have been designing for longer, faster, harder shots. Makes me think my original idea of a robot to scoop them up off the floor and dump them in the low goal might not have been such a bad idea after all!

Dr. Bob
Chairman’s Award is not about building the robot. Every team builds a robot.

Has FIRST published an official change to the chain structure of the goals? I don’t remember seeing it in an update, but the week zero scrimmages clearly had the chain strands connected at the bottom.

Surprised no one has brought this up on CD to my knowledge. Am I just seeing things?

Seeing all of the unconnected strands in the reveal videos last night brought it to mind again.

Balls bounced out of the goal in 2006.

The playing field characteristics were clearly documented.

I think teams could have reasonably predicted that having discs “stop” inside the goal would be a factor.