Low Bar

[Joe G.]

Originally Posted by wireties

Why are folks assuming a robot that can limbo cannot cross other defenses as well? I understand, a little, why a low-rider may have trouble opening doors, lowering bridges or raising the portcullis but why would a low-rider have trouble with the other defenses? The low bar is not so low that it impacts wheel size choices. drive train choices etc.

I agree (being low actually makes many of these easier). But many people are justifying their choice to do the low bar by saying "you don't even have to do anything special to the drivetrain!" Either you haven't done anything special to your drive, in which case you're going to have a hard time with the other defenses, or you have, in which case the point is moot, you've taken the time/effort to cross other defenses anyways.

Why?

I would assume for many reasons in my earlier post. There are going to be a lot of teams that will fail to meet their potential in other aspects of the game in pursuit of the low bar, and as a result, won't be able to gain enough from doing the low bar for it to be worth the design tradeoffs.

Originally Posted by MrForbes

Why? We have room for a nice size electronics board, mounted near the top of the robot...easy access, etc. It took our electronics team about an hour to mount the parts and do the preliminary wiring.

This was not our experience, and I know of many teams sharing in our pain. There are factors that don't apply to all teams (in our case, significant amounts of space dedicated to boulder pathways, and being unable to afford to do the whole robot on Talon SRXs). I've seen worse, but there will be a lot of cramped boards this year.

[Anupam Goli]

Originally Posted by mrnoble

Why?

I'm not Karthik, but from my experience in FIRST:

1. Teams often have trouble doing basic game piece manipulation. Throw in the low bar, and you'll have teams be even worse because now they add in the design constraint of going under the low bar.

2. Doing the low bar means you'll likely have to compromise on some other game objectives.

[mrnoble]

I've just seen it as a design challenge so far: how do we fit all the stuff into a compact package? It's been challenging for our team but the process has been positive and productive. Having a low height constraint has the side benefit of preventing other problems (high COG). Hm.

[Joe Johnson]

Originally Posted by Billfred

We built for 15 7/8", and we were just scraping; 15 1/2" probably would've done it for that robot. Your mileage may vary based on wheel placement and angle of attack. (I drove the robot for the reveal video, and I had better luck coming in at a slight angle than straight on.)

The shape that you need to be able to get under to limbo is surprisingly complicated. If you are not using CAD or some sort of to scale drawings, you are going to be one of those teams I discussed above, that THOUGHT they would go under the bar but don't in the end.

First of all you have to ask if you need to go under the bar in FWD and REV and from which side. The envelope changes significantly if you face your robot toward the opponent's tower or toward your own because (thanks FIRST) the bar is not in the middle of the outer works.

A lot depends on your wheel base and wheel diameters and such but (SPOILERS) there is a V out in front of (and behind of) your robot that is not even close to 14 inches from the "ground plane" (i.e. the plane that your robot drives on if it were a flat floor). I don't have the CAD pulled up but I think for our particular chassis parameters, the base of the V shaped "keep out zones" comes close to the top of our bumper.

SO... really if you have some boulder collector device you plan on folding out in front of your robot while it's doing the limbo, you really really really need to be sure that you can limbo in the real world not just in your minds.

Word to the wise.

Dr. Joe J.

P.S. Getting your boulder mechanism hooked on the limbo bar counts as a Tortuga. I'm just saying...

[Anthony Galea]

Originally Posted by mrnoble

Why?

Something people are forgetting is that if you have a low shooter, due to the nature of virtually no safe zones besides the outer works, all that a team has to do to block you is strap pool noodles onto a kit bot and your shooter is rendered useless. Even with the outer works safe zone, your shooter better be getting the ball to 54" tall before it leaves your frame perimeter or its getting blocked. My team was considering the low bar for the first week of build season and we ruled it out for that reason along with the difficulty of compacting all components of the robots in that small of footprint, because a team with my team's level of resources (3 mentors, two that are technical), building a good shooter that can do tasks other than the low bar is a much better option than forcing a design contstraint that causes more problems than it fixes.

[laplacier]

This is what I see the advantages and disadvantages of being against a defender.

Cons:
1. Your cycle time when shooting is increased. depending on the robot matchup (faster vs slower, taller vs shorter) this could be significant.
2. Your potential to challenge the tower for the extra point at the end of the match could be at risk.
3. You can have your boulder stolen from you in a race to pick up a deflected ball. This would be a significant time loss.

Pros:
1. Unless the defender leaves to accomplish tasks periodically it isn't contributing to its team's ability to meet the requirements to gain ranking points (barring W-L points).
2. A defender is scoring 0 boulders while defending. Assuming all robots have equal offensive scoring capabilities (a stretch, I know but for the sake of argument) a 3 robot offensive is still going to push out more points through goals unless said defender can impede the progress of more than one robot simultaneously and do it well. 2 unimpeded robots on the enemy alliance are not going to outscore 2 unimpeded robots on your alliance plus one impeded robot.

On that note, if anyone has some good footage of defensive robots impeding multiple robots during an FRC game where multiple robots can score at the same time (much like this year's challenge) I'm looking for them! I do think there will be some strong defenders and I need to convince the rest of my team they exist.

Now on the topic of "low robots will always be shut down by tall robots" I don't think that will be the case because:

1. You can close the distance between yourself and the tower where a robot can't maneuver in between yourself and the goal. Stopping you from getting to that point is difficult since the defender would need to give you enough space to start in their courtyard to not incur a foul when you are traversing the outer works.
2. Trajectory is key. If you arc your shot you can shoot over a tall robot. As long as you're not shooting from the front edge of your robot you have wiggle room to arc it.

[IronicDeadBird]

Originally Posted by 3175student17

Something people are forgetting is that if you have a low shooter, due to the nature of virtually no safe zones besides the outer works, all that a team has to do to block you is strap pool noodles onto a kit bot and your shooter is rendered useless. Even with the outer works safe zone, your shooter better be getting the ball to 54" tall before it leaves your frame perimeter or its getting blocked. My team was considering the low bar for the first week of build season and we ruled it out for that reason along with the difficulty of compacting all components of the robots in that small of footprint, because a team with my team's level of resources (3 mentors, two that are technical), building a good shooter that can do tasks other than the low bar is a much better option than forcing a design contstraint that causes more problems than it fixes.

With one only defensive robot in your courtyard is hard committing that robot to defend against only one other robot really a good call?

[Anthony Galea]

Originally Posted by IronicDeadBird

With one only defensive robot in your courtyard is hard committing that robot to defend against only one other robot really a good call?

Yes, especially at events where accurate high goal shooters will not be found for second picks, and you can pick a blocking bot who can focus on one shooter on the opposing alliance, forcing them to have one decent/good shooter + one 'okay' shooter while your alliance can be scoring two decent/good bots' worth of shots. At IRI, DCMPs, and Championship, this is different, but you have to get to all of those before you can strategize for those levels of play.

[IronicDeadBird]

Originally Posted by 3175student17

Yes, especially at events where accurate high goal shooters will not be found for second picks

This is taking into account the ranking system this year correct?

[Ryan Dognaux]

Originally Posted by 3175student17

Something people are forgetting is that if you have a low shooter, due to the nature of virtually no safe zones besides the outer works, all that a team has to do to block you is strap pool noodles onto a kit bot and your shooter is rendered useless.

And a lot of people seem to be dismissing the natural 'safe zone' created by the batter and tower itself. Our thought process was 'why shoot from far away when I can drive right up to the tower, wedge ourselves on the ramp and take a close shot?' See 2014 robots that wedged themselves against the low goal and the corner of the field.

We are doing the low bar and so far haven't ran into any major issues. I think it's accessible to a lot of teams with a little planning, but it definitely requires some thought & testing to package everything well.

[Billfred]

Originally Posted by Joe Johnson

The shape that you need to be able to get under to limbo is surprisingly complicated. If you are not using CAD or some sort of to scale drawings, you are going to be one of those teams I discussed above, that THOUGHT they would go under the bar but don't in the end.

...blah blah blah...

Dr. Joe, unsurprisingly, speaks the truth. That measurement was right for us, but it may well not be for you. Plan accordingly!

[MrJohnston]

Originally Posted by wireties

Why are folks assuming a robot that can limbo cannot cross other defenses as well? I understand, a little, why a low-rider may have trouble opening doors, lowering bridges or raising the portcullis but why would a low-rider have trouble with the other defenses? The low bar is not so low that it impacts wheel size choices. drive train choices etc.

I can't speak for everyone, but I don't believe for a moment that being short prevents other options, but it does create some challenges with space and, therefore, potentially the number/type of other mechanisms... For instance, we decided to forgo all pneumatic systems.

I do think that if nearly all robots are short and specialize in going under the bar to retrieve balls from the secret passage that there will be room for robots that specialize in other aspects of the game to excel as they will likely have more complimentary alliances.

[Wayne TenBrink]

Originally Posted by Ryan Dognaux

And a lot of people seem to be dismissing the natural 'safe zone' created by the batter and tower itself. Our thought process was 'why shoot from far away when I can drive right up to the tower, wedge ourselves on the ramp and take a close shot?' See 2014 robots that wedged themselves against the low goal and the corner of the field.

We had decent success with that approach in 2014 and hope to do something similar this year.

I think there are some inherent advantages to being "compact" (generally synonymous with short) this year in addition to getting under the low bar. In fact, the low bar height is just a convenient target value for "compactness". This field is one big fatigue test rig. In order to survive and function the entire season, your robot will need to be robust. The fewer moving parts, deployable mechanisms, lanky appendages, etc., the better you will be after the umpteenth crossing of the Group B & D defenses. A robot that can collect a boulder, cross a defense, and shoot a high goal without moving anything in the shooter assembly is more likely to survive continued contact with this game. Shooting from the batter requires a bit more driving, but it is a semi-protected shot that can be aimed by driving into a couple of fixed field elements (the tower and the driver station wall). Being able to go under the low bar isn't critical to this approach, but it is a good fit.

Scaling the tower is another matter...

[staplemonx]

Originally Posted by Billfred

We built for 15 7/8", and we were just scraping; 15 1/2" probably would've done it for that robot. Your mileage may vary based on wheel placement and angle of attack. (I drove the robot for the reveal video, and I had better luck coming in at a slight angle than straight on.)

Thanks, Did you scrape in both directions or just one direction?

[Rangel]

Originally Posted by Ryan Dognaux

And a lot of people seem to be dismissing the natural 'safe zone' created by the batter and tower itself. Our thought process was 'why shoot from far away when I can drive right up to the tower, wedge ourselves on the ramp and take a close shot?' See 2014 robots that wedged themselves against the low goal and the corner of the field.

We are doing the low bar and so far haven't ran into any major issues. I think it's accessible to a lot of teams with a little planning, but it definitely requires some thought & testing to package everything well.

The difference is that you had squarish robots parkng in a squarish space. This year the park and shoot area is a trapezoid which will make it easier for defenders to turn you so you miss. That said, there are ways to minimize the defenders defense. Such as a turret shooter or a trapezoidal robot.

Speaking of which, has any team ever made a trapezoid robot?