pic: New low bar flaps

[Chris is me]

Originally Posted by Jon Stratis

Seeing as FIRST basically had no low bar flaps left after week 1, no matter what they did it would have been "an entirely different obstacle". This seems like the closest they could get to the former behavior on their tight schedule.

I don't know, using bumper fabric for low bars didn't make the obstacle entirely different, except for the part where bumper fabric was far less prone to ripping apart. If anything buying a few yards of fabric seems easier for most events to do than getting strips of vinyl cut and zip tied together. I really don't get why FIRST went this route.

I'm especially troubled by the early reports that this vinyl makes the low bar effectively shorter. Making the biggest design constraint in this game even tougher, long after we're finished with our robots, instead of "just" buying tougher fabric? For once I'm glad I competed Week 1 and not Week 2!

[jlmcmchl]

FWIW, the material is surprisingly heavy as a curtain, and is just as effective as the previous style of low bar for preventing balls from passing.

[Sunshine]

Watching the live feeds, it looks like individual flaps can enter the robot? Can anyone at an event verify this? If true, and if the height has truly been shortened, FIRST has dropped the ball on this one. I can see the need for a remedy but the characteristics need to be identical. This is the best engineers can come up with?

[AmiableVariable]

Originally Posted by Sunshine

Watching the live feeds, it looks like individual flaps can enter the robot? Can anyone at an event verify this?

Can confirm that flaps can fall inside robots, we actually had to e-stop our robot on the low bar because of a combination of this and some partial automation. We mistakenly dropped our arm using "intake" instead of just lowering the arm, and a flap falling inside the robot triggered the beam break to make the arm and shooter both unfold up while we were halfway through. Would never have been an issue with the old flap.

As a quick fix, these worked pretty well. The fact that flaps can fall inside seemed to be the biggest functional difference, the new physics did not seem to be to much of an issue for most of the teams, and beyond a habit adjustment we did not need to make major changes. That being said, a robot with similar design but different quirks to the code could have a rough time with this.

[Mr V]

Originally Posted by Chris is me

I don't know, using bumper fabric for low bars didn't make the obstacle entirely different, except for the part where bumper fabric was far less prone to ripping apart. If anything buying a few yards of fabric seems easier for most events to do than getting strips of vinyl cut and zip tied together. I really don't get why FIRST went this route.

I'm especially troubled by the early reports that this vinyl makes the low bar effectively shorter. Making the biggest design constraint in this game even tougher, long after we're finished with our robots, instead of "just" buying tougher fabric? For once I'm glad I competed Week 1 and not Week 2!

With McMaster's incredible distribution system the events did not have to obtain the vinyl strips, they were drop shipped, presumably to the organizer of the event. They can be implemented with the tools in Case 8 so that they are identical across all events. The availability of fabric locally may be hit or miss and FIRST probably couldn't find a supplier that could ensure that almost all of the 21 events being played this weekend received it in time. It would also require a sewing machine at the event and it really needs to be a heavier duty unit to stand up to sewing the bumper fabric consistently.

Consistency is a huge part of this and having the field supervisor cut the roll into specific lengths and drill a couple of holes at a specific point is something that should be relatively consistent.

Are you basing the thought that it reduced clearance a statistically significant amount on actual match play reports or what has been postulated here? Ditto for the hypothesis that a human player can bowl the boulder through it. Personally I've only seen speculation about that and not verified proof of either. Yes the 4mm thickness of the freezer door is more than the cloth but it is certainly within FIRST standard of tolerance that teams should have designed around. The freezer door material is quite heavy and semi rigid. With two strips I doubt the mass of the boulder is high enough to break completely through properly positioned flaps unless you've got a really really strong bowler.

For those teams that are complaining that the flaps could damage their camera I have to ask, did you plan for protecting your camera from the missed high goal shot that may land on your robot? For those that the flap causes their ball to be dislodged from its position I have to ask did you design your robot in such a way that the ball is not dislodged from going over the rougher defenses or against rough defense? I have a hard time imaging a situation where the flap sliding across the camera would damage it while a boulder falling from a couple of feet wouldn't. Ditto for dislodging a ball, if a flap can dislodge it what happens when crossing the rock wall, moat, chilli fries or ramparts at speed?

I know for my team I insisted that the camera be located in a manner that it would be protected against a boulder that may land on the robot. Another requirement was that the robot maintain the ball in the ready to shoot position despite an unusually rough defense crossing or a high speed impact. I also insisted that the robot be designed to clear the low bar if for some reason it was 1/2" lower than the dimensions on the official field drawings. So for us I don't see it as an issue but we will find out tomorrow.


For the record our robot was designed with the knowledge that the official fabric was not highly robust. So we tried to minimize any potential damage to the fabric so that we weren't at risk for a penalty for damaging or repeatedly damaging the field.

[Levi Madden]

Robots have no problem with the new low bar, but I have gotten boulders stuck under the flaps, so they doesn't roll back into the neutral zone like it was designed for. I'm sure human players that can bowl better than me could get the ball through the flaps.

[Kevin Sevcik]

Originally Posted by Mr V

I also insisted that the robot be designed to clear the low bar if for some reason it was 1/2" lower than the dimensions on the official field drawings. So for us I don't see it as an issue but we will find out tomorrow.

For the record our robot was designed with the knowledge that the official fabric was not highly robust. So we tried to minimize any potential damage to the fabric so that we weren't at risk for a penalty for damaging or repeatedly damaging the field.

It's nice that you don't have anything to worry about. We designed our robot with many of these things in mind, but under the assumption that there would be that nice solid bar there. We have these dorsal fins that work perfectly well with the normal low bar, but now we have to worry about them dragging excessively on the vinyl, or worse, slipping into one of those slits that are now there. So it's entirely possible to have a reasonably designed robot that's going to have issues with this significantly different obstacle.

[Roger]

After two weekends using them on my fields (WPI and UMass Dartmouth) I can say the plastic flaps held up nicely with no rips and only minor scars along the top. Very few zipties popped. Every few matches in my rounds I'd adjust them back to spec -- "evenly spaced" which ends up around a one inch gap between them. There are two holes for two zip ties either side to keep them on, and a ziptie each flap side around the bar to keep them from sliding too much.

There have been a couple of boulders that managed to roll up to the flap and push the flap a little under the bar, but none (that I saw; I can't be everywhere ya know!) ever got thru. If your robot drives thru fast enough one or more flaps swing up and over, or just roll up, which I guess is where the scars on the top come from.

[Zebra_Fact_Man]

Yeah, honestly I can't remember hearing about any problems regarding the field at our week 2 event, or anything since. I think the fixes to the low bar and Cheval de Frise are holding up. Not bad! Hope they last another 4 weeks of competitions.

[Joe Johnson]

Originally Posted by Kevin Sevcik

<snip>
So it's entirely possible to have a reasonably designed robot that's going to have issues with this significantly different obstacle.

Actually, I am really surprised at the muted response from the Fairness Cult on this point. No matter how you played this your team was impacted by this change. Many teams that designed stuff into their robot that other's didn't have a claim to this being an advantage that the GDC took away from them. Many teams that had perfectly reasonable solutions for the original design have had fits with the new one.

I don't think it is a HUGE deal but I really was expecting a hue and cry from the Fairness Cult corner of the FIRST community.

Am I just getting deaf in my dotage or had the FIRST community matured a little (realizing that FIRST was clearly in the wrong but that they had to do something as not acting was getting more and more impossible as the season progressed)?

Dr. Joe J.

[Roborunner230]

There were times at UMASS Dartmouth this weekend where there were several balls stuck in these flaps, forcing teams to go around the low bar. They would have to go from the courtyard to the neutral zone before attempting to damage the defense so they could knock these boulders out of the way without being penalized. It was a bit of a hassle to say the least.