How to change catapult shot strength?

[christheman200]

Hi all,
Team 854 didn't go with a catapult design this year, but I've wondered: how do pneumatic catapult designs reliably change their shot range/angle? Is it just changing how long the pneumatic valve is opened for?

[lethc]

Originally Posted by christheman200

Hi all,
Team 854 didn't go with a catapult design this year, but I've wondered: how do pneumatic catapult designs reliably change their shot range/angle? Is it just changing how long the pneumatic valve is opened for?

The ones that I've seen with variable shot range have 2 sets of 2 cylinders apiece. For the long shot, the team actuates all four cylinders. For a shorter shot, they'll only actuate one set of two. I believe that this is how Titanium operates their pneumatic catapult

[AWoL]

I've never actually done this, but I would imagine you could easily have a variable release point for the catapult.

[dradel]

In 2014 we did a shorter pulse on the solenoids for our catapult, for passing and for truss.

[Michael 4499]

Also, if you want to change the arc mechanically, you can put the pneumatic cylinders on a separate regulator and adjust that to give it more or less power.

[LCJ]

148 has a pair of hooks that actuate in place to become a variable hard stop for their pneumatapult. Because the ball is released at different times from the arm, they have two different shots.

[BenjiSG]

We used a "rolling" design for our shooter, with the ball moving back along a piece as it shot out, giving the shot more of an arc which we were able to control by adjusting the tips of the shooter using a set of servos which would adjust to the correct angle based on our vision code. It turned out to make for a very effective and highly accurate shooter.

[Matt C]

In 2012, there was robot with a motor attached to a secondary regulator that would adjust the air pressure.

[Daniel_LaFleur]

Originally Posted by christheman200

Hi all,
Team 854 didn't go with a catapult design this year, but I've wondered: how do pneumatic catapult designs reliably change their shot range/angle? Is it just changing how long the pneumatic valve is opened for?

For the range -- you could use an electronic pressure regulator downstream of the main regulator. That would allow you to adjust the pressure from 0 - 60 PSI controlled by tour RoboRio.

For angle -- I'd just make your hard stop adjustable.

[hrench]

Team 1108 has built catapults a few times, but mostly we've decided that changing the strength of the shot this year isn't useful.

We have the shot set up so we can hit from anywhere on the batter to about one-foot out while the shot is on the 'upward' arc of the parabola.
And if we're just off the outer-works, to about five foot in front, it will hit on the downward arc of the parabola.
So there's only about six or eight feet in between that we can't hit. So we don't shoot from there.

In Aerial assist, we had a pneumatic catapult there too and it was useful to have a short-shot for passing and for passing back to the human player. That year, we put the two (left and right) catapult cylinders on separate air solenoid valves and for the short-shot, we only activated one side.

In Rebound Rumble, we actually made a motor-driven sliding mount for the catapult cylinders' fulcrums so that they could have a longer stroke, but in truth, after a few games we learned that the drivers chose to make set-shots from the initial length rather than try to decide how many inches-in could correlate to how long-of-a-shot. If they moved the control, we didn't have good reporting to them how long the shot would be, so they would miss.

But unlike others, we usually hold the catapult with an electro magnet while filling the air cylinders, so we can also change the amount of time we hold-down before release and that can change the shot. But we tried that in practice for Aerial Assist and it just wasn't necessary or helpful. If they shoot from the same areas every time, it was just easier.

[tickspe15]

There are two things that affect a shot the release angle and the release velocity
Ways to change shot:
Firing different number of Pistons
Pulsing pistons(artificial hard stop)
Adjustable hard stop

[Abhishek R]

Originally Posted by tickspe15

There are two things that affect a shot the release angle and the release velocity
Ways to change shot:
Firing different number of Pistons
Pulsing pistons(artificial hard stop)
Adjustable hard stop

And the PSI, but yeah, basically sums up the ways I've seen.

[RoboChair]

You should look at a close up of our 2014 catapult. We had a pair of fingers that we could change the length of in order to adjust the shot(release angle) and a deployable hard stop to change the release point(release velocity). Ours was powered by a bundle of surgical tubing and drawn back via a cam.