Catapult vs Wheeled Shooter

[backdrive]

I find it interesting how certain shooter designs this year seemed to vary heavily by region- for example, Texas has a bunch of amazing catapult robots (118, 148, 2848, 4587), but California, in contrast had no top-tier catapult bots (correct me if I'm wrong), with nearly all the top teams (254, 1678, 971, 973, etc) opting for flywheel shooters.

[Citrus Dad]

Originally Posted by backdrive

I find it interesting how certain shooter designs this year seemed to be vary by region- for example, Texas has a bunch of amazing catapult robots (118, 148, 2848, 4587), but California, in contrast had no top-tier catapult bots (correct me if I'm wrong), with nearly all the top teams (254, 1678, 971, 973, etc) opting for flywheel shooters.

Yes you are correct about CA. I can't think of any consistent catapult shooters here. I think a big factor is the use of vision tracking (thanks to the assistance of 254 and 971). Wheeled shooters give a more consistent straight line shot that allows varying distance. Catapults appear to be more dependent on a set distance.

[Jared Russell]

Originally Posted by backdrive

I find it interesting how certain shooter designs this year seemed to be vary by region- for example, Texas has a bunch of amazing catapult robots (118, 148, 2848, 4587), but California, in contrast had no top-tier catapult bots (correct me if I'm wrong), with nearly all the top teams (254, 1678, 971, 973, etc) opting for flywheel shooters.

We know how to build, tune, and debug a wheeled shooter, and they've been good to us in the past. We don't know how to build, tune, and debug a catapult. We could probably figure it out, but early prototyping showed that a wheeled shooter could get us the performance we wanted, so why do something else?

I am guessing that many of the Texas teams had the exact opposite experience.

[hank2247]

Our prototype phase took way too long this year parly because we were trying to decide between the two. We ended up using a wheeled shooter because it was more consistent than our catapult prototype and it let us build a 2 axis shooter that fit under the low bar.
Definitely the coolest shooting mechanism our team has ever built!!

[Clayton Summerall]

Originally Posted by Jared Russell

We know how to build, tune, and debug a wheeled shooter, and they've been good to us in the past. We don't know how to build, tune, and debug a catapult. We could probably figure it out, but early prototyping showed that a wheeled shooter could get us the performance we wanted, so why do something else?

I am guessing that many of the Texas teams had the exact opposite experience.

We had tried a wheeled shooter and didn't like the space requirement. Not much experience with either.

[domi]

I agree with Citrus, wheedle shooters are better to track and there is better control of speed and trajectory. Catapults are cool but, they easy to use because you have to think about the speed or rotation of the motor. Then after dealing with that, then you about vision tracking which is a problem because it will be 100 percent so there is a lot to deal with. But, at the end of the day, it's down to which one you are familiar with or comfortable with.

[Mark Sheridan]

Originally Posted by backdrive

I find it interesting how certain shooter designs this year seemed to be vary by region- for example, Texas has a bunch of amazing catapult robots (118, 148, 2848, 4587), but California, in contrast had no top-tier catapult bots (correct me if I'm wrong), with nearly all the top teams (254, 1678, 971, 973, etc) opting for flywheel shooters.

Cause we so fly in Cali


There are two really good catapults going to champs from California: 1836 and 5124.

[backdrive]

Originally Posted by Mark Sheridan

Cause we so fly in Cali


There are two really good catapults going to champs from California: 1836 and 5124.

Oh, awesome! I guess I haven't been paying enough attention to orange county!

[pandamonium]

Originally Posted by Mark Sheridan

There are two really good catapults going to champs from California: 1836 and 5124.

Thanks! Yes the consistency was a major reason for us going catapult. We also liked the appeal of being unblock-able from the outer works while still being low bar capable. Yes several teams have accomplished this other ways with tall arms. The catapult seemed like a more simple approach for our team. The range issue is a bit of a misconception in my opinion. Our catapult has a pretty large sweet spot all the way from outer works to a little before the batter.
We have also added a ball clamp to keep the ball from bouncing out when going over obstacles.

[RoboChair]

How this thread makes me feel



Let's just agree it be shooting season.

[GeeTwo]

Originally Posted by RoboChair

How this thread makes me feel



Let's just agree it be shooting season.

ELMER SEASON!

More seriously, though: most of the posters have said why they went one way or the other, and the reasons appear make sense for where each is coming from. As with nearly any FRC engineering decision, it comes down to two questions:

• What are your priorities? (For us this translates mostly into what is your game strategy?; YMMV)
• What are your capabilities/resources/experiences?

Since every team has the same core values and the same resources , of course we came up with the same solution.

[M217]

Catapults had one big advantage this year that my team discussed in the early build season: typically, the vast majority of a catapult's variance is up-down (largely because of small inaccuracies in distance reading) while they are incredibly consistent left-right. The shape of this years goal allows for a little up-down inconsistency, since that's the longer dimension. I remember a lot of the catapult's I've seen hit a little lower than dead center from the outerworks (for example, 359's balls in tech valley seemed to touch the lower lip of the goal fairly often) but they still went in fine. For this reason, I think catapults were a lot more viable this year than they have been in previous years, and I would applaud any team that built one for making a sound strategic choice.

That being said, the packaging of a wheeled shooter and the flat linear trajectory (at least when you shoot as hard as we do) seemed to offer enough advantages that we decided to go with that. We didn't think defense would be too much of an issue because we planned for a fast release, and we'd already began work on a swerve drive that would make us much harder to pin and block.

The catapult is definitely a good choice this year, more so than I think it was in rebound rumble, but I think there are still advantages to having a wheeled shooter that make the decision nontrivial.

[sspoldi]

At team 230, we were concerned about the variability of the ball as it impacts either a spinning wheel or linear punching style shooter. In addition, we were inspired by the extremely accurate catapult used by our friends at team 177 in 2014, that was not only accurate, but extremely hard to block.

We got around the lack of adaptability of a traditional catapult by going electric, with 2 mini CIMS and a 28:1 reduction (or something like that). We found we could adapt the command profile to get pretty much any trajectory we wanted. If we went spring or bungee powered it would have been far less adaptable.

We had a lot of people comment that they couldn't believe we could shoot with a fully electric catapult. We did a fair amount of simulation to optimize the gear ratio to maximize energy delivered to the ball. A lot of teams don't do this and as a result don't get the most energy out of their device.

We lean pretty heavily on simulation written in Octave (a MATLAB like language) running on a Linux OS. It's all open source, so if anyone want's some more info please stop by our pit in champs and ask for Henry (or the drive team coach if he's off somewhere).

Cheers,
Steve S.

[marccenter]

Originally Posted by sspoldi

. We found we could adapt the command profile to get pretty much any trajectory we wanted. If we went spring or bungee powered it would have been far less adaptable.

We had a lot of people comment that they couldn't believe we could shoot with a fully electric catapult. We did a fair amount of simulation to optimize the gear ratio to maximize energy delivered to the ball. A lot of teams don't do this and as a result don't get the most energy out of their device..

Can you provide a little more information:

1) About your command profile adjustments

2) What your simulation revealed about getting the most energy out of your device (speed?).

[Gdeaver]

Puncher, catapult, or wheels. Many teams had actuate launchers. Auto aim seamed to be what separated the good from the great.