Consistent shooter

[Ether]

Is there a consensus forming concerning what type of shooter design provides the most consistent shot from beyond 15 feet?

I'm thinking near the top of the list would be a) metal-spring-loaded catapult or pusher whose springs are stressed well below their yield strength and b) pneumatic firing catapults and pushers,

and near the bottom of the list would be a) motor-powered kickers and b) motor-powered wheel shooters.

[dodar]

I would say almost any spring loaded device to launch the ball would be more consistent than a motorized launcher.

[IronicDeadBird]

It would be interesting to see actual data comparing the autonomous score of different shooter mechanisms.

[Ether]

Originally Posted by IronicDeadBird

It would be interesting to see actual data comparing the autonomous score of different shooter mechanisms.

That would be interesting, but it does not take into account battery drain toward the end of the match.

[IronicDeadBird]

I am totally out of it but how is battery drain going to effect the score of auto?

[Ether]

Originally Posted by IronicDeadBird

I am totally out of it but how is battery drain going to effect the score of auto?

In autonomous, it's not. That's the point.

[Lil' Lavery]

Originally Posted by IronicDeadBird

I am totally out of it but how is battery drain going to effect the score of auto?

He wants to consider battery drain as one of the factors impacting shooter design. It would have a much larger impact on systems which use energy provided from a DC motor (wheeled shooters, motorized catapults, etc) than it would on systems where the energy is obtained by compressed fluids or material deformation.

[IronicDeadBird]

Sugar and caffeine are wonderful things ill check in later on this form to see if things change when I am more awake...

[Pretzel]

Our robot uses a type of composite springs most frequently found in bow limbs from Gordon Composites. It's a fairly unique feature of our robot (I haven't seen another one using this technique) and we've found it to be excellent in terms of repeatability and power.

[MikeE]

I agree with most of Ether's OP.
Catapult-like devices (i.e. those that start in contact with the ball and accelerate with it) should be more consistent than shooters relying on impulsive contact such as kickers or punching devices.
The trajectory of the latter depends on more variables than the former, for example ball air pressure and exact contact point.

Beyond that it depends at what level we measure consistency: shots from a single location or ability to shoot accurately from a larger area of the field (i.e. robot scoring consistency). In other words we can argue that there is a balance between consistency of the energy source (where springs & pneumatics win) vs controllability where motors have an edge.

[DampRobot]

Linear punches have consistency limited by two things (as we've found). Besides all the obvious stuff (same pull back same distance, same release, ball in same place, reasonably speced springs, etc) you'll see consistency deteriorate when you don't have a large enough pusher plate and from knuckle.

We found in prototyping and from talking to other teams that large pusher plates give more consistent shots. We had a tennis ball contact the ball in early prototypes and quickly saw that a large plate improved consistency a ton. There's probably a good reason that 118 has a puncher plate the size of a frying pan. The teams with smaller plates generally only go for closer shots, because there consistency doesn't matter as much.

The other thing is knuckle. We aren't putting any spin on these balls, and as they have weird surfaces, they're sensitive to aerodynamic effects. Linear punchers also get the balls going quite fast at first, where they're more subject to aerodynamic effects. We've seen variations of +/- 1.5 ft up and down from knuckle alone. Perhaps someone has come up with a good solution for this, but we haven't.

But all around, I'd say that from what I've seen, high pivot catapults are killer at close range shots, but aren't that great long range shots. Low pivot (team JVN) catapults are quite good at long shots, but are bad at close range. Linear punches (especially at high release points) are pretty good at both types of shots. Strategically, I'd say high pivot and release (think team Boom Done) will continue to dominate the game.

[Duncan Macdonald]

I realize that 1 robot is not a sufficient counter point but 1114's wheeled shooter has been nice to watch today.

From what I've seen I would separate sprung shooter category into "surgical tubing" and "non surgical tubing"

[dodar]

Originally Posted by Duncan Macdonald

I realize that 1 robot is not a sufficient counter point but 1114's wheeled shooter has been nice to watch today.

From what I've seen I would separate sprung shooter category into "surgical tubing" and "non surgical tubing"

I dont think 1114 is a wheeled shooter.

[s_forbes]

We've found that most of the variations in our shots come from ball placement on the mechanism. The balls are only sphere-ish; the fabric stitching has an impact on their shape. If your main contact point on the ball is in the middle of a square patch, vs the vertex of three square patches, the ball seems to react differently (and predictably).

A launching mechanism that is resistant to ball placement would likely fair best. I would expect the large flat-disc linear punchers to be more consistent.

[MysterE]

So, how would one add consistency in ball placement to a catapult based system?