Using a Plunger System to Launch Balls

[HFCHS-NASA]

Our team was thinking of using a plunger system to launch balls. The balls would be loaded into a barrel, which is open at one end and has a plunger-type device on the other. Then, a motor pulls the spring-loaded plunger to a specific distance depending on how far we want to shoot the ball (think of a pinball machine). Anybody else thinking of going this route? We would use linear encoders or an ultrasonic sensor to sense how far back the plunger is pulled.

[krazyman1013]

It would be improbable. First you would have a mechanism to load the barrel, then aim, and finally shoot. There are too many moving parts. Keep it simple.

Good luck on whatever design you decide upon.

[Timekeeper00]

I wouldn't rule it out completely, it would be difficult to do, but if you pulled it off right it would function pretty well.

[DonRotolo]

I can see it as possible. Breech-load from the top (balls just fall into place). Re-cocking the mechanism can't take to much time though - a second is a long time.

Whatever powers the slingshot needs to be highly repeatable - if you pull back X inches, the trajectory needs to be exactly the same, time after time, even if you have to replace whatever it is between matches because it broke or something. That's not an easy problem.

It appears that you are considering being able to "shoot from anywhere" - perhaps you might want to optimize the shot from one or two spots (distances) only. Otherwise this becomes a serious technical challenge - the mechanism must be built very precisely to have that capability.

[EricH]

Originally Posted by krazyman1013

It would be improbable. First you would have a mechanism to load the barrel, then aim, and finally shoot. There are too many moving parts. Keep it simple.

Really... I can think of a couple of mechanisms from 2008 that could be modified to do it well, that are quite simple. Say, Winnovation's punch from that year modified to allow it to latch in any position desired and supplied with a barrel. Then you have to deal with the loading problem, which could be much simpler.

[pfreivald]

Originally Posted by DonRotolo

It appears that you are considering being able to "shoot from anywhere" - perhaps you might want to optimize the shot from one or two spots (distances) only. Otherwise this becomes a serious technical challenge - the mechanism must be built very precisely to have that capability.

A double CAM with two separate draw distances is one possibility for a two-distance shooter, though you'd have to time the breech load properly.

[dtengineering]

Originally Posted by krazyman1013

It would be improbable. First you would have a mechanism to load the barrel, then aim, and finally shoot. There are too many moving parts. Keep it simple.

Good luck on whatever design you decide upon.

Actually 1114 had a not entirely dissimilar mechanism when they won the world championships in 2008.

Different game, different ball, different target... but devastatingly effective in the right application.

Jason

[tetravaal]

Our team actually used a similar mechanism for Breakaway to kick the ball. Our biggest challenge was latching that much force in a spring. We ended up using 2x 2in dia, .5in throw cylinders to do it. That being said we were drunk with power with the fact that we could kick the whole field that we completely forgot to design a decent aiming mechanism.

Lesson for this year for us? Don't focus only on power.. Balance that with a good way of aiming.

[Peter Matteson]

Were you ever on RAGE? They went through a stretch where it seemed like they had plungers on their robot all the time.

Seriously though what you're looking for is the RAGE (173) 2009 robot.

[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