Shooting Multiple Balls At Once

Technical Technical Discussion
,
#1

This year’s game was designed around cycling balls as quickly as possible (as seen by the 4th ranking point criteria) and I just so happened to be looking through 254’s 2017 Technical Binder and noticed that they had two shooting channels to shoot multiple balls at once. image I figured that that might be possible in this year’s game.

The first pros that comes to mind is that you can potentially shoot your 5 balls in less time and potentially easier to package two linear shooter feed mechanisms than a spindexer or wrapping linear feed.
The first cons that come to mind are that it may be much harder to shoot for the inner goal (if not near impossible), added weight, and can’t be used with a turret.

I’m wondering what you guys think. Is this a viable strategy? Pros/Cons?

2 Likes
#2

You could still use a turret, you would just need to be clever with your feeding system. A couple teams did use a double shooter, including 1758 who were part of the winning alliance at Palmetto.

2 Likes
#3

I don’t think that it really quite makes sense to do a dual shooter for 2020 for several reasons.

Shooting wasn’t the major challenge teams had to solve of 2020, serializing and intaking more or less was. You couldn’t do the former without the latter in some form. The balls were not the easiest to work with, and teams had packaging problems abundant anyways. To serialize into two vertical systems or other mechanisms is not specifically easier than a single well designed one. And there are good , examples of singulators and spindexers to gain inspiration from on teams, or vertical-linear style from teams and Ri3D Capital.

Secondly, volume was the name of the game in 2017, and that doesn’t really hold here when bounce-backs don’t have a decent chance of landing in an area you can easily grab.

You’re right in that cycling time is important for the 2020 game, but I don’t think more throughput is the best optimization to achieve it. That said, I will openly admit I didn’t consider a dual-feeder in my personal analysis of the 2020 game and the though is definitely interesting. it’s just not worth (imho) the tradeoffs compared to other more tested, or visibly more viable designs.

18 Likes
#4

I suppose the value of a double-shooter depends on your game strategy and resources. My team didn’t attempt it, but another team local to mine did and pulled it off pretty well. Made it onto the regional winning alliance and won the creativity award at Arkansas: https://www.thebluealliance.com/team/4576

#5

This is a pretty big con – we didn’t see it matter as much in weeks 1 & 2 this year, but if we had continued to champs, I guarantee that optimizing utilization of power cells would have been important at higher levels of play (especially since your opponent gets the balls after you score them).

1 Like
#6

I agree completely, except that I think this point should be first. In 2017, multiple fuel were needed to score a single point. In 2020, the time to unload a volley of five PC in one stream was usually significantly shorter than the time to collect them and get in position, even if you were firing from the far side of the field.

Additionally, in 2017, the goal face was horizontal, facing upward. This means that fuel had to pass thorough a much slower portion of their arc (at the peak) than when they entered the goal. You could only feed fuel through a single arc at a certain fairly slow speed without having them hit each other. For 2020, the goal was vertical and while many teams had the ball descending slightly as it was scored, it wasn’t going significantly faster than at the peak of its arc (and sometimes slower due to air resistance).

2 Likes
#7

My team opted to shoot two balls at once to make storage and pickup easier because we could pickup two at once and store in two rows allowing us to go under the trench without a complex storage solution. We also knew we likely woudn’t hit the inner port so we prioritized spamming the outer port and still hit the inner occasionally.

unnamed (1)
unnamed (1)2033×2046 547 KB

1 Like
#8

Looks like you guys didnt really have any trouble with a win at Palmetto (i didnt watch any matches, the data says that).

#9

I haven’t seen a single design where the limiting factor was ability to shove balls through the shooter. The limiting factor is how quickly your wheels can recover between shots, and the simpler solution to that isn’t more chambers- it’s just more motors (and gearing them so they’re at peak power).

4 Likes
#10

Except you can use firing multiple balls at once to sidestep the indexing problem all together. :wink:

1 Like
#11

MORE CHAMBERS
image

10 Likes
#12

Yeah (problem was more the lack of a climb) and I think it is a lot better in early weeks due to simplicity and others not hitting the inner

#13

You haven’t seen our robot

2 Likes
#14

Do yourselves a favor and don’t do a double barrel shooter unless you really think it’s necessary. I’m still scarred from 2017.

#15

The idea isn’t without merit, certainly - particularly for short range 2 point shots where you don’t need as much consistency in the shooter to make this work. But you should learn about what issues teams had with this in 2017.

By far the biggest reason to do this in 2020 was to completely dodge the issue of indexing balls. It greatly simplifies the robot design, especially if you do not human load directly.

2 Likes
#16

Why does the linear feed have to be wrapping?

We had a straight linear feed on a short bot and it worked out great. (Sorry 2471)

1 Like
#17

Just some quick math for a straight linear feed. All 5 balls lined end to end is 35 inches long (which is fairly long for an frc robot) That doesn’t leave any room for an intake in front and shooter in back. You could position the shooter right above the feed so you don’t need to go any further back, but there is some concern that the less distance the ball is compressed a hood, the less consistent the shot. That’s why at least one team went with a bicycle wheel as their shooter. And there is an argument to be made about spacing the balls out in a the feeding mechanism to let the flywheel recover, which is makes the robot longer.

Don’t get me wrong, I got the pleasure of seeing 1339 in Utah this year and was amazed by the performance of their straight linear feed.

#18

Team 4516 had a double ball shooter at PCH Dalton District Event this year.

#19

Personally, I don’t think this design is a great idea. It is possible to use 1 shooter and fire out balls just as quickly and with 1 shooter, there is less of a chance of balls missing/hitting each other. I could see some teams being able to pull it off, but I would think that those teams should be using that time to focus on other things.

1 Like
#20

Well out problems this season was both the indexer and the shooter. When our indexer jammed due to having an intake on each side of the robot, the shooting was irrelevant.