Puncher Shooter
 

Has anyone attempted a pneumatic puncher for a shooter? Do you have plans for one?

Re: Puncher Shooter
 

My team hasn't. When we did the math on how much air we'd have to carry in order to meet our "reload" requirements, it was too much for our liking.

Re: Puncher Shooter
 

Thanks cadandcookies - May I ask how many storage tanks you calculated? We were thinking 4 would be sufficient with the new (slower) compressor.

Re: Puncher Shooter
 

I'm not actually a part of the team that calculated this (that would be our manipulator team), I just asked why they weren't prototyping with pneumatics and that was the answer they gave. I'll check with them next time I'm in the shop.

Re: Puncher Shooter
 

Team 20 has attempted several prototypes of punchers, but at best we could only shoot a few feet. For us, The inspiration for the design came from 1114's 2008 robot, which we later found to actually rely on the release of potential energy, instead of pneumatics.

Re: Puncher Shooter
 

Would it be possible for you to release some data from these tests? This might just be what we need to score in the bottom goal with.

Re: Puncher Shooter
 

Team 178 has had luck with the pneumatic punter. We tested a prototype that gave us a 17" push, divided into 3 stages, with (at least) 50 psi. When tilted (angle currently unknown) it was able to clear the truss and the high goal. Plus, it had enough air stored for two more cycles. Video has been recorded of these tests and I will provide a link when available.

We've got more 8" pistons on the way so the above configuration is not final. If this does become part of our bot the students need to figure two things.

1. Where to mount the completed mechanism on the robot
2. How we can properly seat the ball in place for an optimal shot

EDIT 11:24pm: link to video highlighted above. Go to 10:50 in.

Re: Puncher Shooter
 

Thanks Trevor! That's exactly what I was hoping to hear! One question. What is the diameter of the 8" cylinder you are using?

To answer one of your remaining problems, we have receiver arms that catch the ball and funnel it to a back wall. From that position it is supported in 3 spots and we will shoot it from there.

Re: Puncher Shooter
 

We have actually tried prototyping a slingshot type of idea where a rod is pulled backed to the desired position and is let go to basically punch the ball. We have received satisfactory results launching the ball several feet (Didn't Measure). It is not that reliable though with the hazard of the surgical tubing maybe breaking in a match.

Re: Puncher Shooter
 

We at 5196 tried a puncher with a pneumatic cylinder that's both high velocity and short travel. Even at (over the allowed range) 120psi the puncher did not throw the ball far enough. We attached a weight to the end and it extended the travel distance by a foot.

Re: Puncher Shooter
 

Yesterday our winch-back punch threw the ball 38 feet, with the apex right in the sweet spot for the upper goal. Prototyping matters a lot--at first it looked like an utter failure, now it looks great. (Except that it's heavy, slow, etc, etc. Optimization still needs to be done.)

Note that we're prototyping four different launchers and designing our robot for modularity to accommodate whichever of them we ultimately decide is "best".

Re: Puncher Shooter
 

Thanks Patrick! Can you describe (or share a picture) of "our winch-back punch?"

Re: Puncher Shooter
 

It's a slider carriage with a punch on it, powered by a giant load of surgical tubing, currently pulled back and held (for prototyping purposes) with a screw drive. We're releasing the catch with a hammer at this time.

It's big. It's heavy. It's slower than we want our reload to be. But it achieved the "perfect shot", so we're not ruling it out yet!

I'll see if I can sneak into our supply closet and snap a picture in a few minutes.

Re: Puncher Shooter
 

It seems our teams have ended up with a similar train of thought. At the end of week 2 we had a complete mock-up of one of two designs we felt were feasible. This uses a wide frame orientation with our puncher (mocked using a wooden ramp stopper from 2012 and a frisbee from 2013) with a 'wheels on top' intake/passing system.

It appears at 2:40 in

We've also refined the puncher design with support plates, which are further in the video.

Re: Puncher Shooter
 

Our first idea was to use a pneumatic puncher but it just didnt have power or speed to punch the ball very high or far. We have switched over to a spring-powered catapult with a winch system to wind it back up, it works fairly well.

Re: Puncher Shooter
 

we used it on our 2008 ball and its what we are using this year.
link from my old teams 2008 bot
http://www.youtube.com/watch?v=QeQSGmFnKAE

Re: Puncher Shooter
 

Our team tested both a puncher and catapult design (when I was home for break). Last time I checked, I believe that we found the catapult was more accurate and consistent (Someone from my team correct me if I am wrong, as I haven't been at the shop since last Saturday.)

From what I can tell, a puncher has a smaller area of contact than the catapult during the actual shooting process. Since it is applying a lot of force to a small area, it causes much more deformation in the ball than the catapult, which can lead to inconsistency in the shooting (due to even the smallest factors like amount of air in the ball, location of point of contact, etc.) Once again, someone correct me if my observations are wrong.

Re: Puncher Shooter
 

I think our's fits into the description you are calling a "puncher," but we discovered that "punching" was not as effective as "pushing."*

http://youtu.be/UK2f9lvskcQ

This is three 3/4" cylinders with 12" stroke through some fairly high performance solenoids (.75 M^3/s flow) and the return ports left open to allow quick venting. We need to turn the pressure down to about 42 psi to avoid breaking things. (And we'll need to attach some kind of spring to bring the plunger back to the firing position.)

*The difference: we found it most effective to have the ball rest on the plunger of the cylinders before launch (push) rather than have a separation and have the ball struck by an already moving plunger (punch).

Re: Puncher Shooter
 

I'm not sure if this is a "puncher", but we were able to get an air cylinder to push the ball for a ~15 ft shot during our "proof-of-concept" stage. It took more work than you're expecting though:

1) You need a big cylinder. We used a 2" bore, 15" stroke
2) You can't deliver enough power through the FRC legal solenoid valves. Instead, treat the cylinder like a gas spring and pre-charge it.
3) Because you can't exhaust air through the solenoid valves fast enough either, you can't use the same cylinder to retract. Instead, you need a separate cylinder (or winch), and a release mechanism (basically all of the things you would need if you were working with surgical tube instead of a cylinder)
4) The cylinder should have a tank of at least equal volume attached directly to the port with hard pipe (preferably 1/4") *not* tubing. The extra volume of the tank will keep the pressure in the cylinder from dropping to nothing when it expands, but the flow restriction through the port puts an upper limit on power.

So in summary - doable, not much easier than a surgical tube slingshot, although it does let you vary force.

Check out this thread from a few years ago: http://www.chiefdelphi.com/forums/sh...ad.php?t=79952

Re: Puncher Shooter
 

Aw hell, I just re-read the manual after seeing a couple of successful pneumatic catapult. I thought the solenoid valve restriction was 1/8" orifice diameter (another way to limit CV). Turns out it's 1/8" NPT Port Diameter. You can get solenoid valves with 1/8 npt ports and CV's above 1.0 each - more than enough!

/that moment when you realize you've made a wrong assumption, and its too late to change course :(

Re: Puncher Shooter
 

Surgical tubing puncher with pneumatic retraction:
http://www.chiefdelphi.com/forums/sh...highlight=rail



It is all about hitting a good peak ram velocity while it remains in contact with the ball. Having pneumatics pre-pressurized and surgical tubing prestretched with ram in retracted position is important. Rapid acceleration is what is needed, so a low mass ram with high initial force is best,

-Dick Ledford

Re: Puncher Shooter
 

My advice to you and the rest of your team is never have your face anywhere near this beast when pulled back. I still get flashbacks to 2006 when we tested a similar method for launching foam basketballs.

Re: Puncher Shooter
 

I don't mean to call you out, but I don't think 2006 had basketballs. I believe the balls were foam though.

Re: Puncher Shooter
 

It it is a little scary standing next to it while it is loaded. Luckily we don't have to do that during the competition.