FRC488 Pneumatic Catapult
 

Just thought I'd share some video of one of our prototypes.

Variety is the spice of life and maybe other people are also bored with all of the wheeled mechanisms.

http://www.youtube.com/watch?v=Pie_5kIUeIs

Re: FRC488 Pneumatic Catapult
 

Interesting. I like the use of tupperwear on the robot :) Is there a system for changing the distance you can shoot from? Also, is there a cap on the amount of successive shots you can take? You were shooting fairly rapidly from what I saw in the video.

Re: FRC488 Pneumatic Catapult
 

Cool. Looks like it takes up a lot of space though.

Re: FRC488 Pneumatic Catapult
 

While it may appear to take up a lot of space, if this is their game manipulator, might as well allocate as much space as necessary for it.

Re: FRC488 Pneumatic Catapult
 

That's neat! Yeah, it is nice to see something different, especially when it works so well

Re: FRC488 Pneumatic Catapult
 

The tupperware is, I hope, a temporary solution. :)

We plan on varying the flow rate to the actuators. We haven't quite nailed down an implementation yet, but we think we can do it pretty easily.

In our testing, we were able to manually adjust the flow and got similar consistency from the fender out to about 22'. The concept is sound, we just need a mechanical solution that is repeatable.

The robot was on shop air for the video. We'll need to figure out how much stored air we'll need on board for a reasonable firing rate. I don't expect will see 9 balls in 30 seconds during a match, but who knows.

It is very big. We need to rework some of the mounting to make it a smaller package, but we can fit the important parts into a robot with room to spare.

We've found that the compressability of the balls varies greatly and so our wheeled shooters couldn't provide the same sort of consistency. We'd get the same result from the same ball each time, but each ball would travel a different distance.

Re: FRC488 Pneumatic Catapult
 

Great idea:) ! How do you guys plan on keeping the ball stationary when an opponent hits you?

Re: FRC488 Pneumatic Catapult
 

I think they could implement a feeding solution that holds the three balls until they are absolutely ready to be fired, so they aren't in the catapult yet if they get hit. When they want to fire it loads the ball into the catapult. I imagine they'd ideally be shooting from the key, where they won't be in danger of being hit without the other team taking a penalty.

As far as exactly what this would look like, imagine the ball return at a bowling alley. Put this on the back of the robot facing sideways toward the ball holder on the catapult. Balls roll up and drop out into the catapult.

Another option would be to turn the upper surface of the catapult arm into a trough/tube for balls to roll down and into the launcher, where a large enough lip would prevent roll-back. The ball holder/feeder would dump balls into this trough/tube at the fulcrum (or really anywhere on the arm above the launcher) when the arm is in the down and "reloading" position.

I hope those explanations make sense :D . I can clarify if anyone is confused.

Re: FRC488 Pneumatic Catapult
 

The travel of the arm also allows for balls to be loaded at a lower position on the robot and still have a high release point. This means that you could potentially allocate a lot less space for loading mechanisms.

Re: FRC488 Pneumatic Catapult
 

One of the best videos yet...... "Pie" is in the URL.


OT: Did you find that the orientation of the ball mattered for the shots?

We came to similar conclusions about the inconsistency of using wheels as far as the compression and spin of the ball upon release goes, and made a sort of catapult. We were using the same ball over and over for testing, and we found that we were most consistent with the FIRST logo facing up (as opposed to the side) because there was a dent in the ball immediately underneath it.

Re: FRC488 Pneumatic Catapult
 

I remember a whitepaper last year that mentioned using a hi-tech servo on a pressure regulator... that would be my suggestion.

Re: FRC488 Pneumatic Catapult
 

I look forward to seeing this in person at Alamo.

Have you found that the balls are still flying consistently after heavy use? The ball we have played with the most has very little bounce to it anymore and has a very different flight pattern even when we are just shooting by hand. The ball has a few small sections taken out of the covering which accounts for a lot of that.

Re: FRC488 Pneumatic Catapult
 

Shoot from the key. If they hit you and you miss, you still get 3 points. If they hit you and you make it, you get 6 points.

This is the one year where not obeying the rules will really cost you under most circumstances.

Re: FRC488 Pneumatic Catapult
 

the only two problem i see is if you aren't at the perfect distance you will miss and the other problem is how do you intend on reloading. other than tees problems you have amazing accuracy and consistency.

Re: FRC488 Pneumatic Catapult
 

My team is also using a catapult type of launching system. It works pretty efficiently. Balls are gathered from below and then when a second ball is loaded it pushes the other ball into firing position and then compressed air launches a piston which moves at such a good speed and finesse that the final angle achieved causes the ball to perfectly make it into the goal with ease. That's how I see it, but it's not exactly like that. We are still tuning up the shooter and adding final adjustments. Will be testing tomorrow. Hopefully I can post a video or pic soon.

Re: FRC488 Pneumatic Catapult
 

Please look up the first part of JamesCH95 signature. It fits perfectly with your observation. Someday I am going to use that part of the signature myself. I love it. :D