Discs Bounce Out of Goals

[Alpha Beta]

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.

http://www.chiefdelphi.com/forums/showpost.php?p=1227216&postcount=13
http://www.chiefdelphi.com/forums/showpost.php?p=1226811&postcount=6
http://www.chiefdelphi.com/forums/showpost.php?p=1226077&postcount=2

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.
(http://www.chiefdelphi.com/forums/showthread.php?t=84091)

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.

[Andrew Schreiber]

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.

http://www.chiefdelphi.com/forums/showpost.php?p=1227216&postcount=13
http://www.chiefdelphi.com/forums/showpost.php?p=1226811&postcount=6
http://www.chiefdelphi.com/forums/showpost.php?p=1226077&postcount=2

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.
(http://www.chiefdelphi.com/forums/showthread.php?t=84091)

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.

[Mr. 1033]

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.

[Willyspu]

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

[mwmac]

Sounds like an argument in favor of floor pickup:)

[jspatz1]

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

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.

[avanboekel]

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?

[Mr. 1033]

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.

[waialua359]

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

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.

[Andrew Schreiber]

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.

[avanboekel]

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.
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.

[capnslow]

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?

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.

[djdaugherty]

The game rules say (3.1.5.1) 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.

[Johnbot]

The game rules say (3.1.5.1) 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. :(

[djdaugherty]

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?

[Johnbot]

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.

[djdaugherty]

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.

[Retired Starman]

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.

[Alpha Beta]

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.

http://www.youtube.com/watch?v=sWF3hHrAwxg
http://www.youtube.com/watch?v=xN9IUKN0PBs&feature=youtu.be

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.

[dtengineering]

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.

Jason

[Gregor]

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.

Jason

Many teams, mine included, didn't include chains in our goals. We just had a hole.

[Andrew Schreiber]

Many teams, mine included, didn't include chains in our goals. We just had a hole.

Seems like a great lesson on the importance of emulating the actual environment as closely as possible while testing.

[Mark McLeod]

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.

http://www.youtube.com/watch?v=sWF3hHrAwxg
http://www.youtube.com/watch?v=xN9IUKN0PBs&feature=youtu.be

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.
I don't see what you mean.
The chains appear to be swinging quite freely.

[Alpha Beta]

I don't see what you mean.
The chains appear to be swinging quite freely.

Between 6 and 14 seconds on this video (http://www.youtube.com/watch?v=xN9IUKN0PBs) it sure seems like something is connecting the bottom edge of the chains to each other. They move together like a curtain. If they were not connected at the bottom I would expect the strands to fly in opposite directions from the initial point of contact with the disc. The bottom edge is free from the box, but has limited freedom from the neighboring strands.

At 1:31 I can see that the strands separate enough for a disc to pass bewteen them, but the bottom of the chains do not whip apart as they should if they were truly free from each other.

Of course if no one at the scrimmage can confirm this set-up it must be my own imagination run a muck.

[Cory]

Between 6 and 14 seconds on this video (http://www.youtube.com/watch?v=xN9IUKN0PBs) it sure seems like something is connecting the bottom edge of the chains to each other. They move together like a curtain. If they were not connected at the bottom I would expect the strands to fly in opposite directions from the initial point of contact with the disc. The bottom edge is free from the box, but has limited freedom from the neighboring strands.

At 1:31 I can see that the strands separate enough for a disc to pass bewteen them, but the bottom of the chains do not whip apart as they should if they were truly free from each other.

Of course if no one at the scrimmage can confirm this set-up it must be my own imagination run a muck.

I do not know if they have made the change you are pointing out, but our FTA told us that they have made multiple revisions to the field. I know one of them is that some kind of angled bars are being placed at the top of the goals to keep discs from being shot out the back of the goal when they enter at a high angle of attack.

[JB987]

The actual field drawings, referenced in recent update, actually show a cable connecting the chains across the bottoms.

[Grim Tuesday]

The actual field drawings, referenced in recent update, actually show a cable connecting the chains across the bottoms.

See the updatehere (http://frc-manual.usfirst.org/Updates/0#term 93).


Game Manual


The following field drawings have been updated to reflect current designs:

Goal Bottoms
Goal Chains
Pyramid Cap Locking Mechanism
Updated drawings can be found on the Manual Homepage

2-22-13 team update

[Alpha Beta]

See the here (http://frc-manual.usfirst.org/Updates/0#term 93).

2-22-13 team update

Part GE-13809 Cable Assembly was what I was looking for in the updated drawings. Thanks for helping me locate it. Completely overlooked that they had changed the drawing last night.