What does a defense robot NEED?
 

My team and I are just putting ideas together. does anyone have any tips? Ideas? strategies?

so far, we have come up with a robot design that can hypothetically push another robot the direction that their wheels are facing and change the angle to make it harder to shoot. any advice?

Re: What does a defense robot NEED?
 

:D Thanks! The limit height while deployed is 84" though. We'll see what we could do :p

Re: What does a defense robot NEED?
 

Before you go nuts on torque for pushing, just make sure you can catch the people you are supposed to be defending.

Re: What does a defense robot NEED?
 

Good Point! :yikes:

Re: What does a defense robot NEED?
 

Honestly, if you make custom gearboxes that deliver enough torque, you don't even need to make sure the robot you are pushing is moving in the same direction as its wheels. Easier said than done, however. :p

For most teams without reliable vision tracking, ramming into them should be enough.

Re: What does a defense robot NEED?
 

why not just make a huge curved wall that extends up to block the robots view and have a ramming tool of some sorts

Re: What does a defense robot NEED?
 

Consider putting all 6 CIMS on the drive or using the Vex Pro transmissions. This will let you be fast and pushy. Also, a 10 point hang is easy to make happen.

Re: What does a defense robot NEED?
 

If you are on the side that you will be defending from, you are actually limited to 60 inches per G22 B.

Re: What does a defense robot NEED?
 

a defensive bot needs the beefiest drivetrain and frame possible. it also needs to be quick, able to accelerate to its top speed in 1-2 robot lengths and traction. lots of traction.

Re: What does a defense robot NEED?
 

Why build a defense bot when you can, with little effort, make a 10pt hanging, 1 point low goal scoring robot?

If you guys are planning to only play a defensive role in this year's game, I urge you to reconsider. Scoring the smaller objectives, while not as glamorous as the larger ones, will still help your alliances win matches. Your season will be far more fulfilling as a result.

If you're planning on doing all of this already and are just trying to find out about good ways to play defense, then don't mind me.

Re: What does a defense robot NEED?
 

An ideal defensive bot, besides playing good defense, should be able to score 2 discs (in the low goal) in auto (4 points). It should also be able to hang on the bottom rung for 10 points.

A defensive robot has two choices for playing defense, defending the opponents robots, or defending the discs. I believe that going after the discs is a much better option. To do this, a defensive robot should have a large shield that extends all the way to the height limit. Have this robot sit near your opponents feeder stations blocking both robots and discs from getting past. If a team can only get discs from the feeder station, you could be a great hindrance in their navigating the field.

You could also decide to go onto your opponents side of the field and sit in front of their goals to prevent teams from dumping. I like this a little less because some robots might shoot while touching the tower, making it difficult for you to slow them from shooting.

Honestly, I would just try to have a tall robot that can stop robots that can only get discs from the feeder stations. Blocking the transfer of discs from their feeder station to their goals is a good way to slow/stop an opposing alliance from scoring. With a defensive robot that can score 14 points too, you would be a strong 2nd pick at most, if not all regionals.

Re: What does a defense robot NEED?
 

A good defense robot should be able to push opposing robots, but not be pushed itself.
A good defender should be able to take discs on its opponents side and shoot them to its team's side of the field.
A good defender must have drivers that are aware of the penalties in the game, and they must be sure that they do not violate any rules.

This year, we were toying with the idea of using a high-airflow fan to deflect opposing shots, but we decided against playing defense. Due to the lower height limit while defending, some defenders might not be able to block shots, so a way to block the shots without being really tall may prove useful.

It helps for defenders to be able to maneuver quickly to prevent opposing robots to get around them, though having a high power drive base is the higher priority if you can only have one or the other.

Re: What does a defense robot NEED?
 

Avoid at all costs getting penalties. If you're playing defense it's fine to be aggressive to a point but if I see your robot consistently being fouled you're on the don't pick list for us.

Re: What does a defense robot NEED?
 

A robot drive system, a sturdy frame, high traction, and excellent drivers.

Re: What does a defense robot NEED?
 

I strongly advise against a defensive robot for one reason:

Robots that are in contact with their pyramid can not be touched, whether climbing or just shooting

If you defend well, all they have to do is go to their pyramid to shoot

Re: What does a defense robot NEED?
 

I'd hazard to predict that the best defensive bots will:
Weigh 120 pounds.
Have two speed transmissions.
Six or Eight wheel drive.
Good Drivers.
Four cim's on drive (six cims stalling will throw your main breaker, I think)
Run every match.
WON'T GET PENALTIES.
Under 30 in tall (to fit under the pyramid)

Their defensive strategy would either involve the choke points located between the pyramid and the wall (to slow down traffic), or camping under the opponent's pyramid and then running out to hit/ push them around when they try to score. You could also deny a climb this way.

Re: What does a defense robot NEED?
 

Read Alec's post again. Please consider not building a defensive robot. The low rung on the pyramid and the 1pt goal are there to give teams of all skill levels the ability to play an offensive game.

Re: What does a defense robot NEED?
 

Re: What does a defense robot NEED?
 

What is so wrong with building a defensive robot? Seriously, at the rate some people in FIRST are starting to denigrate defense we might as well go back to 2001. If I was picking partners for a top team (and I never have, so maybe that's why), I would be way more inclined to pick a good defensive robot over one that can maybe score a few points, and in almost any regional any team, regardless of "skill level", can contribute to a strong alliance.

EDIT: This may not fall into the category of "need", but I would consider some of the following non-traditional forms of defense:

1. A very large fan to blow frisbees offline - people keep talking about it, but this year with the extra CIMs and aerodynamically sensitive game pieces, I really think it can work!

2. A robot that quickly picks up and shoots frisbees away (not off the field!) to deny the opposing team from picking them up

3. Keep them from getting into their loading zone - yes, their are rules from touching another robot in its loading zone, but there is no rule preventing you from going in their loading zone, as long as you keep them out!

4. Be as tall as possible to block frisbees - if there are any long shooters at your regional, have some way to get 84" high to block all their shots

Re: What does a defense robot NEED?
 

The robots they recommend building could easily fall back and play defense if necessary. A robot in a random qual with no standout opponents can't play defense.

Also, a defender that can 10 point hang is far more valuable than one that can't.

Re: What does a defense robot NEED?
 

Defense is a strategy, rarely if ever a design. Designs can have features attractive to defensive strategies, but I wouldn't call any truly viable FRC design a "defensive design".

That said, the ideal robot to execute a defensive strategy - high traction drivetrain, shifting is nice but not required, excellent drivers. As you can see, this could be* most FRC robots. This is why everyone is advocating for you to build a simple offensive robot, such as a 1 point dumper or 10 point hanger. You can easily do both.

Plus, offensive features lead to greater defensive strategies. Here's one example - let's say you add a floor pickup mechanism to a robot. You can start to play defense by picking up misses and other frisbees on the floor and then returning them to your side of the field.

Re: What does a defense robot NEED?
 

Get a transmission if you can afford one or make one of your own so that you can catch the other robots and then be able to shift to torque. May I also suggest that you create a mechanism to flip the Frisbees over? Many teams launchers rely on the lift that the dent in the Frisbee creates when it is rotating. If the Frisbee is upside down, the Frisbee will fly differently.

Re: What does a defense robot NEED?
 

A good drive train with a good driver with solid knowledge of the rules and a coach who is an agile thinker who also has a solid knowledge of the rules is a good place to start.

Re: What does a defense robot NEED?
 

Be able to flip disks upside down this could be the biggest pain for a lot of teams. Most teams will make flipping devices but they take longer time flipping disks the right side up.

Re: What does a defense robot NEED?
 

Field trolling. I like!

Re: What does a defense robot NEED?
 

I'm not trying to denigrate defense as a strategy, but I am trying to denigrate a box on wheels robot that can ONLY play defense.

I've been in a lot of scouting meetings and made a lot of pick lists, I can't remember EVER considering to pick a robot with no offensive capability. At the very least we've decided on teams that might score in Auto and then we've instructed them to play defense ETC but we always base decisions on offensive contribution to our strategy.

Obviously teams are well within their right to build a "defensive" robot. The reason I urge against it is because the team will struggle to make eliminations at their events without some offensives capability.

Re: What does a defense robot NEED?
 

A great Defense robot will need to be able to do everything that the other two offensive robots on the alliance can't do, or can do them so they don't have to.

This includes but not limited to:
1: Hanging for 30 points
2: Handle and score 4 of the colored alliance discs in the pyramid goal.
3: Push around opponent's robots from their most effective scoring locations.
4: Push around other defending robots so your alliance's offense can go off without a hitch.
5: Travel fast around the field to bog down locations of high traffic for your opponents.
6: Maneuver around discs on the floor and under both pyramids easily and quickly.
7: Score in autonomous.
8: Have great drivers, coach, and communication skills with the rest of the alliance.
9: Have a great Feeder who can follow instructions and feed alliance robots correctly.

Re: What does a defense robot NEED?
 

Are people forgetting that touching the opponents pyramid is a technical foul? If I were a drive coach I would have the robot steer clear of the pyramid, let alone have them drive under it to play aggressive defense on another robot.

Also, I would tend to agree that an robot with mild offensive capabilities playing defense fits this years game better than a pure defensive robot. If I were a top end team, I would love my second pick to have a shooter, that simply gets the frisbees across the field from the feeder station and can hang for 10. No floor pickup, not even an accurate shooter, no 30 point hang and dumps. Just something to feed the disk hungry teams. After shooting a few, you can play defense on teams on your end of the field, come back and feed them more, etc. and then a 10 point climb at the end game. Also this strategy allows for a decent attempt at autonomous, even if it's in the middle or low goal.

Re: What does a defense robot NEED?
 

Inconsequential contact will not be penalized - therefore I find it perfectly fine to utilize the space under the opponent's pyramid to drive around in for getaways or other fast travel. The real problem is avoiding robots that are touching their pyramid for sure.

Re: What does a defense robot NEED?
 

I think I'm going to see if I can Q&A what they mean by inconsequential in this rule. I've been trying to use my best judgement, and still struggling with it. My gut tells me that if you're playing defense on a robot underneath the pyramid (one that is not touching the pyramid) and you hit the pyramid, that would be a consequential contact, as something that you're doing at the time had a consequence on the outcome of the match.

On a slightly related note, if I have a Q&A account, how do I submit a question, do I need permission from my team or something?

Re: What does a defense robot NEED?
 

I've really wanted to see a robot with a powerful fan or air cannon system, so they can just stand under the goals and blow air vertically, and the gust of air modifies the flight paths of the discs enough so that they hit the top of the goal, and fall to the ground. My team did some prototyping, and we had to eventually get a leaf blower to get the effect we needed, but we did notice differences with the smaller machines we used to blow air. The leaf blower just provided the needed scale of power. We looked at the rating on the motor of the leaf blower, and it would be very hard to recreate it with the motors we have provided, but then we did come up with the idea of an air cannon. We thought about having 2 aircannons fire one at a time, and it would be like an anti aircraft base style mechanism. My team ultimately chose to go with an disc shooting robot, and to some degree tabled the possibility of having fans on our robot, but I would really like to see another team test it further.

If I was the #1 seed, I would definantly pick a robot with a large fan as my #1 pick, because I want to have that advantage, and I really don't want to end up going against a robot that can do that!

Just my 2 cents, thoughts?

Re: What does a defense robot NEED?
 

Nearly any bot can play defense, although I don't recommend holomonic drive. Strong drive trains are always good but in this game I'd take speed over power. You need to be infront of them before you can worry about them pushing you away.

The most important thing for a defensive bot is good drivers. Make sure your drivers are practicing with a driving bot ASAP.

The second most important thing is a drive coach and drivers who know how to play offense. The best way to think about stopping an offender if from the perspective of an offender.

As far as specific features some sort of mechanical breaks could be very advantageous for a defensive bot whose drivers know how to use them.

Re: What does a defense robot NEED?
 

Why stand next to the goals, though? Since a disc flies in a nearly straight line, if you impact the disc's flight closer to the start of its flight, that impact grows as it flies along its path.

Assuming a disc is shot, on average, at the centre of the high goal, you need to change its height at the end of its path by 6" vertically. Let's also assume that the shooter is shooting from the auto line, 216" out from the alliance wall they are scoring on, and the disc leaves their shooter 50" above the floor. This means that the disc flies at about a 15.5 degree angle.

What we want to do is find the angle of the flight that will cause a disc to miss the goal for each position of the fan robot on the field. Just set up a couple right triangles to show this.

If you run your fan next to the shooter, your triangle has legs of 66" (the normal 60" of vertical travel plus another 6" to make it miss) and about 190" (about how far the fan might sit from the shooter), such that the tangent of theta (the angle required for the disc to miss) is 60/190. In this case, theta would be equal to about 19 degrees, 3.5 degrees more than the path the disc would take if not interfered with.

If you run your fan next to the wall, the disc begins at about 104" and is still traveling along its 15.5 degree path, so the triangle's legs are 26" (assuming you're as far from the wall as you were from the shooter earlier) and 12" (the 6" of normal vertical travel from 54" plus another 6" to make it miss), and the tangent of theta would be 12/26. That would make theta equal to about 24.8 degrees, about 9.3 degrees more than if you didn't interfere.

What this means is that if you interfere next to the wall, your fan needs to be able to change the path of a disc by nearly 10 degrees, while it only needs about 3.5 if you defend near the shooter.

Note that this doesn't take into account the fact that a disc doesn't fly in a perfect line, as well as the fact that some discs will be closer to the bottom of the goal than the centre, and will need more of an angle change (though this affects both positions equally). Also, it will be a great deal more difficult to keep yourself in position next to a shooter, since they will likely be moving and be near their pyramid when shooting, so you will want to avoid penalties.

Hope this makes sense!

Re: What does a defense robot NEED?
 

Someone did it for me, that explains a lot. Q&A

Re: What does a defense robot NEED?
 

I agree with the vast majority of replies: If you cannot score at all, you will not be a very valuable defensive bot. Even the best defensive bots in previous years often had the ability to score some quick auton or endgame points or to feed their alliance partners (A replica feeder slot on your robot that it could spit disks out of would be cool.....)

Secondly, you need to decide what type of defense that you want to play. If you want to play shot blocking defense, you need a tall bot that can block shots (possibly block the cross-field feeder station shot?).
You could also design a bot that would defend the game pieces themselves. Think Bomb Squad from einstein last year. How could the other alliance have won when they had NO balls to shoot? This would probably require a shorter (<30") robot that can zip around the field and spit the disks out to the other side for your alliance's use.

What you want to do is completely up to your team, but be warned you will need to score some points this year. It doesn't matter if it is in auto or endgame. But I believe that a defensive robot that cannot average 15-20 points by itself (between auto and climbing) will not be worth a pick at any strong regional.

Re: What does a defense robot NEED?
 

They definitely need to be tall this year so they can block any shots by the full court shooting robots, believe me there will be plenty of them this year.

Re: What does a defense robot NEED?
 

What does a defense robot NEED?

Use your vision tracking system to track the opponent's discs and then shoot them out of the air with your discs.

Bonus points if you can calculate their trajectories and only shoot down the ones that are going to score.

Double bonus if you can pick out the opponent's coloured discs, see if they are going to score in the 5 point goal, and then prioritize shooting them down.

Triple extra bonus if you can do it all in auto. Not because the code would be more difficult (it would be the same) but because you'd have to shoot them out of the sky from behind, rather than just get in their way.

Oh, sorry... I thought the question is what does a defense robot need to be more awesome than a good offensive robot!

Jason

Re: What does a defense robot NEED?
 

You'll call me crazy but make sure it has the ability to have something 84" tall on it. Just a sheet on two pieces of wood will do.

Teams are going for the sit-at-the-feeder station and score tons of points strategy. That feeder station happens to be on your side, and therefore you are able to play defense at 84" tall around it.

The opposing team is on your side, so they can only be 60" tall at a max. If you guys can just park infront of them (without getting too close!) they wont be able to make any shots. Period.

Retract your sheet down to 60" when they retreat to their side and follow them. Continue to be in their way at 60" tall. Most teams probably wont build a robot that tall because it isnt good for their climbing, so I feel a robot like this could actually be quite effective.

Im interested in everyone's thoughts on this. At first glance it seems overly simple but why wouldnt this work?