Re: what was the best shooting mechanism for 2016?
 

Definitely agree with this. It is all in the optimization and execution...

Team 230 built a catapult... and we had the 2nd highest OPR at the Championship event. Our catapult was highly optimized (as noted in this post: http://www.chiefdelphi.com/forums/sh...9&postcount=47) ... and it did not suffer from any kind of reliability issues to to springs stretching out, because there were no springs. It is a fully electric catapult, driven by 2 mini-CIMs. The best part about the catapult was that the boulders that were being damaged by the wheeled shooters were not an issue for us as the catapult is unaffected by the size and shape variations.

Re: what was the best shooting mechanism for 2016?
 

I feel that "best" is relative to what you value the most. For our team accuracy is the most important over distance, and speed. If you are going to take a shot make it count otherwise you spend more time chasing it down.

We did a two wheeled shooter in 2012 and actually found it to be much less accurate than the single wheel shooters. We thought that going with high speed motors on both sides of the ball would give us more range and having two wheels would make it more consistent but we were wrong. What we ultimately found out was that there is better energy transfer between the wheel and the ball when you give it a curved track to allow the mass to get up the wheel's spinning velocity. Because of this it was more consistent and seemed to go further even with less powerful motors. Ours just kinda burned out on the ball because we were taking something that is not moving at all and all of a sudden trying to get it up to full speed. This varied based on how well the wheels gripped the ball which changed as the wheels got dirty or the balls varied.

Echoing the previous comments I think execution is key and that any design can be successful as long as the time is put in to remove inefficiencies and variability.

Re: what was the best shooting mechanism for 2016?
 

Regardless of type of shooter, there were patterns of thought process that lead teams to consistent, optimized shooting mechanisms.

Every consistent shooter had an optimized shot trajectory. There were two different camps here. One camp set the peak of their shot's parabola at the top of the goal, taking advantage of the vertical goal to maximize the sweet spot of their shot. In fact, many teams had a single, workable shot from the outworks all the way to right in front of the batter. The other camp, including teams like 971 and 987, were able to adjust their shot angle using vision targeting. This camp then used flat shot trajectories, decreasing the impact of exit velocity consistency on shot accuracy.

Additionally, many teams in both camps maximized their release height in order to circumvent the threat of blockers and further maximize their trajectory's sweet spot.

The next variable that posed a threat to consistency was ball variation. As balls were used on the field they became more compressible. Catapults elegantly avoided this variable by never compressing the ball. For the flywheel shooters, minimizing compression also decreased energy transferred to the ball. Thus, competitive flywheel shooters counteracted this with higher wheel surface velocities, more power, and larger contact patches on their wheels. Flywheel shooters also relied on sensor feedback in order to accurately control their wheel velocity. While my team did not extensively prototype the two wheel shooter design, I would also conjecture that the single wheel designs were more consistent because they had less variables to control.

Catapults on the other hand still had a slew of problems to contend with in order to get consistent exit velocities. Pneumatic catapults had to deal with airflow, limited by their solenoids, regulators, pneumatic tubing, and fittings. From talking with some pneumatic catapult teams, I heard that many used high-flow solenoids in conjunction with air tanks after the regulator. Spring powered catapults had to deal with spring wear and consistent release/pull-back points. My team ended up finding success with high-quality extension springs.

Lastly, alignment time was critical in this game, given that teams could only hold one ball. Both camera and flashlight alignment was proliferate, and some teams used turrets to great success, which could align fast and accurately.

Re: what was the best shooting mechanism for 2016?
 

I liked 125's catapult. It was integrated into their utility arm, so it was able to shoot from very high up. That paired with its ability to shoot from anywhere on the field made it very difficult to defend against.

Re: what was the best shooting mechanism for 2016?
 

Also 148, the robot with the highest opr at champs, had the highest opr. Catapults are good.

Re: what was the best shooting mechanism for 2016?
 

Those are two examples. They certainly don't constitute a proof, especially if you're basing it solely on OPR.

Why don't we do something similar and look at all the captain and first selections that made Einstein- not necessarily representative of the best, but pretty close.

• Newton 217, 3476
• Curie 694, 3339
• Archimedes 1501, 1986
• Galileo 195, 987
• Carson 2122, 2052
• Tesla 2056, 1690
• Carver 330, 2481
• Hopper 148, 1678

Hooded Single Flywheel Shooters:

• 217, 3476, 694, 3339, 1501, 2056, 2481, 1678

Catapults:

• 1986, 195, 2122, 2052, 148

Double Flywheel:

• 987 (horizontal), 1690 (vertical)

Linear Punch:

• 330

This data could be the way it is for multiple reasons.

1. These are the best kinds of shooters
2. These are the most common types of shooters
3. These are the shooters that happened to make Einstein

But if you look closer at how they got there, you'll start to notice trends.
9/16 of these teams had inarguably high release points. 5/16 couldn't go under the low bar as a result of that.

These teams prioritized certain objectives, and met them 100%. It's obvious when looking at 1678 and 1690's designs that they anticipated needed a high release point, but also needed to be able to get a solo breach. They have the resources to execute that at 100%, so they did.

Other awesome teams on Einstein had other priorities above high release point.

2122 showed up at their first regional just making low goals. They then improved by adding a climber and then eventually their extremely accurate high goal shot. They did, however, shoot from almost the ground.

1986 had a catapult, which allowed for a relatively high release point that would get over most blockers while still going under the low bar.

217, 3476, and 1501 eschewed the low bar in favor of a harder to block shot and a climber.

The type of shooter you choose isn't about which is objectively "the best", but rather which one fits your priorities and resources the best.

Re: what was the best shooting mechanism for 2016?
 

To the extent of my knowledge, 2481 didn't have a climber.

Re: what was the best shooting mechanism for 2016?
 

You're correct. I edited my post to reflect that. The rest stands.

Re: what was the best shooting mechanism for 2016?
 

Thank you for this great data! I understand that we cant deifne what is the "best" type of shooter. My main goal was to see what mechanism the teams that were successful at shooting this year used. I can say about my team(3339) that we used one wheel shooter and it worked well, we've reached the consistency we were looking for but our main problem, like most of the wheeled shooters was the damaged boulders.
Again, it is obvious that we can't define what is the "best" type of shooter, this disscusion was ment mostly for sharing data and experience about the types that were used by different teams.

Re: what was the best shooting mechanism for 2016?
 

when we were looking at shoots we looked at wheels but the problem with that is ramp up time. Catapults are wishy washy. So a liner punch seemed like the best design for consistent shots. But most teams had wheels.

Re: what was the best shooting mechanism for 2016?
 

We didn't worry about ramp-up time as much because of the fact that robots can only carry one boulder. With only one boulder to shoot, you only need to make sure that your shooter gets turned on sufficiently ahead of time (for us we turned it on right after crossing the outer works). Another neat trick I've heard of is that some teams leave their shooter running at half speed or quarter speed for most of the match so it takes them less time to spin up.

Re: what was the best shooting mechanism for 2016?
 

I'm curious about how you came to this conclusion. Our catapult could shoot from any legal spot on the field.

Re: what was the best shooting mechanism for 2016?
 

I'd love to know how your catapult was powered. One of the bigger advantages to a catapult in my opinion is that you can make it have a consistent amount of power with relatively little programming by using springs, pneumatics, and hard stops.

Now there are ways to make each of these methods shoot from multiple positions, and also ways to make your trajectory flat enough to shoot from a ton of different locations with the same shot.

I'd love to hear about how some of the best catapult teams made their catapults work this year.

Re: what was the best shooting mechanism for 2016?
 

Ditto, I would love to see some more details of your catapult. I loved watching your robot put shot after shot in the high goal. I figured it was spring or pnuematic powered.

Re: what was the best shooting mechanism for 2016?
 

No springs or pneumatics. It is a fully electric catapult powered by 2 mini-CIMs. Steve describes it here:

http://www.chiefdelphi.com/forums/sh...9&postcount=47