Lately I’ve been struggling to think of good defensive strategies and mechanisms for the nothing but net competition.
The best defensive robot that I can think of would have a 6-8 motor drivetrain with a transmission and/or a break.
This could be used to stop robots from getting to their starting tiles, or to knock robots around and not let them score.
Any good strategies and mechanisms from other years that I can remember aren’t legal this year.
I don’t imagine that it would be able to score very well after using so much stuff already though.
Any feedback would be appreciated.
Would be a 10 motor drive with transmission coupled with a piston powered drive train similar to a train.
If a robot could really quickly grab stacks and put them back into their own corner, then it would technically be defensive since it’s preventing the opponent from scoring. Basically, an 10 motor drive with a 2 motor intake. Sounds fun 
Other then a few extreme ideas, such as the fan bot idea. Or shooting and catching balls really fast, in front of the opposing alliances net, preventing any of their balls from going in. 
(Don’t think about that too much, it wouldn’t work.) I can’t think of any really really effective defence bots. With a fast high torque drive, you could block any close court bot from scoring by just running back and forth in front of the net really quickly. (You would have to be really fast) However, as has been shown so far, the other robots very quickly improve or develop strategies to counteract you, proving a low scoring defence bot to be no longer useful. Defence bots can be quite useful for now, but by the end of the year, I think those robots that are almost entirely for defence will be needing to score some heavy points as well.
Okay I was too slow… I had other things to say but they have already been said.
Well a big blocking challenge is stopping people from shooting (obviously) and one big capability that seems unatainable is blocking shooters who just meet the top of the 18in cube. These robots can only be stopped by something higher than 18in which is not allpwed unless you are blocking using balls. My theory (probably wont even attempt this) is that a robot that can pick up four balls and hold them fixed in one place at the top of a robot or launch them upward in a sort of bowl shaped collector (think the parachute game you play with dodgeballs) could be used as a very effective defensive robot. Use your preloads for that and then you can use the other 8+ motors for drive.
This is exactly what I was thinking. Unfortunately I think the velocity of the balls coming from the full court bot would be larger then that of the vertically shooting bot, thus the balls would be knocked away from the catching mechanism (funnel) and could accidentally score in the opposing alliances net. Maybe if the balls were shot at the perfect moment and hit the underside of the full court balls it would work.
Here’s another one. Build a super powerful shooter, and sync it to the opposing alliances shooter (using sensors) So you shoot their balls into your net.
I know that there’s no way that it’s legal this year, but I really like what 2W did back in gateway.
I guess that it’s why they won at world.
Something similar happened to me. My robot shot a ball at the same time as the opposing alliances’ robot did. Our was going to go in and theirs wasn’t, but they collided in mid air and theirs went in and ours didn’t. I don’t think that it was on purpose.
This happened to us at the south island qualifier, fortunately we were already winning the match. I believe you only lost the match you were referring to by 5 points? Thus a incredibly unlikely turn of events in a tiny period of time cost you a match… Maybe the strategy is effective then… Unfortunately I don’t think any Vex sensors are accurate enough to make it work.
We won the match by 6 points.
Sorry, this is getting off topic.
Both of the strategies above are the main viable strategies I can think of.
Just a few tweaks though. I suggest an 8 motor drive with 4 motors on the intake since I don’t think a 2 motor intake can keep up with the maximum speed of a 10 motor drive (you don’t want balls scattering away). An 8 motor holonomic may be something to look into for the second strategy. Both strategies can be easily combined and intertwined depending on your opponent.
When designing a defensive robot with limited capabilities, you don’t want to think of a match as a 2 vs 2, but rather a 1 vs 1 or something to give your ally the slight edge like a 1.1 vs 1. Because of this, you may want to consider a PTO or sacrificing 2 motors for a partner lift
What’s PTO? This is all that I could find when I searched for it.
Why don’t you think that 2 motors couldn’t keep up with a high speed drive?
In this video, 2R has a 4.8:1 drive ratio in this video, and 1 motor is keeping up with the first stage of ball collection just fine.
A PTO is a “power take off” system, which is a system that allows you to transfer motor power from one system to another. In real life, you see it mostly in tractors, where they have to power other systems. Probably the most famous example in vex is green eggs from toss up, where they transferred their drivetrain power to their lift system to hang https://www.youtube.com/watch?v=Ox8MIW7khI8
If I remember correctly though, I don’t think green eggs disengaged the drive motors when lifting. That is something you’ll need this year (just imagine trying to elevate while moving)
It doesn’t. it doesn’t collect all balls without scattering while driving at full speed.
In 0:42, they grab 2 of the 4 stacked balls, and you see them slow down.
in 0:44, they aim for 8 balls and they only collect 2, also note they aren’t driving at full speed
in 1:03, they grab against the wall, so there was no chance of balls to roll away
in 1:11, they aim for 3 balls, only grabs 1
There’s probably more instances, but I think you get the point. Adding more motors allows you to gear up for more speed in hopes of grabbing more balls. Or you can apply a passive system which prevents balls from rolling away
I see what you mean, I was being a bit hasty by saying that. It will require testing, but at the speed that the robot is driving at, I don’t think that it’s possible to run into a pyramid and not have at least one of the balls fly off, no matter how fast the intake is rotating. At least with that design. A pyramid capturing design like this one would be needed.
@DracoTheDragon Gael Force has a PTO to their flywheel that disengages the drive…