Using a Plunger System to Launch Balls

[JamesCH95]

Whatever you wind up doing I would incorporate a way to induce a controlled amount of spin. I think the last thing you'd want is a knuckling flight path.

[pilum40]

We're considering using a straight up system almost like a paintball marker. The loader would be simple-a laundry basket with a hole in the bottom that has a sliding door attached. The inbounders for our team will pitch or place the basketballs into the basket. the breech would be a 90 degree angled piece of 12" diameter pvc tubing. The "barrel" would be a length of 12" pvc or heavy duty cardboardtubing. We would use a Medium sized Bimba pneumatic piston with the acutating arm moving through a piece of pvc drilled and glued into the center in the 90 degree piece.Inside, the piston end would have a small piece of ply or pine covered in bumper fabric to keep it from ripping the game basketballs. We will use the adjustable inlets to regulate pressures between matches The trigger would be acutated via button on controller or via programming in hybrid. The piston would be moved back into the ready position by a second button/refilled with air. As the arm moved back into place, a line would pull the "shutter" open to load another ball into the breech almost like a paintball marker uses vertical feed. The barrel itself will be raised and lowered by a second pneumatic piston. This is rough...very rough at this point. The other option is a baseball thrower. We're deciding how much time we really want to spend on shooting versus getting to the ramps, staying on the ramps, blocking and getting coop points. Which is more important and will help us advance to the alliance phase? All good questions, we're kicking them around as we build and program the other components of the bot.

[JamesCH95]

If I understand you correctly you're using a piston to directly launch the ball? If you want to go this route I would strongly suggest using either multiple small-diameter cylinders with one solenoid valve per piston, or multiple solenoid valves per piston if they are larger. These are the only way to get enough air flow for an effective pneumatic shooter that I know of

[pfreivald]

If a punch-launcher is what you're after, you might want to consider other activation methods as well (like a spring with a cam) as pneumatics.

[Siri]

Originally Posted by JamesCH95

If I understand you correctly you're using a piston to directly launch the ball? If you want to go this route I would strongly suggest using either multiple small-diameter cylinders with one solenoid valve per piston, or multiple solenoid valves per piston if they are larger. These are the only way to get enough air flow for an effective pneumatic shooter that I know of

<R78> The outputs from multiple valves may not be plumbed together into the same input on a pneumatic cylinder.

Correct me if I'm wrong, but I think this precludes your second alternative. You are correct though, with the CVs we're allowed, large pneumatic cylinders are quite slow for this application. Small ones likely are too, depending on the range you're looking at. I won't say it's impossible, and there are ways to speed things up. Any team looking at this should do the math and test thoroughly, or you may be sorely disappointed painfully late in the season.

In the past, teams have used pneumatics (and cams, and countless other systems) to [edit]arm[/edit] such linear punches, but used springs/surgical tubing/etc to transfer the actual force, as they're so much faster.

[JamesCH95]

Good catch on the rule. IIRC it was legal up through 2010 when I last looked. Always pays to double check

[HFCHS-NASA]

We are trying to avoid pneumatics because we want to have the precise control of electric motors. How does a spring and cam system work? That sounds what we want to do.

[EricH]

Originally Posted by HFCHS-NASA

We are trying to avoid pneumatics because we want to have the precise control of electric motors. How does a spring and cam system work? That sounds what we want to do.

http://www.chiefdelphi.com/media/photos/31538
http://www.chiefdelphi.com/media/photos/31539

That should get you started on some things of that nature.

[pfreivald]

Originally Posted by HFCHS-NASA

How does a spring and cam system work? That sounds what we want to do.

A cam is just a plate or something of the sort with an irregular shape. You attach it to an output shaft (geared up/down as necessary) and use it to stretch a spring or other elastic material (surgical tubing, for example). As it goes around, the object slips off of the cam and slams to equilibrium position. You can stop the cam each revolution using a sensor of some kind, so it doesn't fire continuously.

This video, http://www.youtube.com/watch?v=_hTyXQUgYLE at 1:49 shows a cam-powered kicker running.

[Brandon Zalinsky]

we messed with a pneumatic/spring plunger mechanism and we couldn't figure out how to make the ball fly farther than 10 feet without dumping our entire tank. If you find a way to do it well, please share!