Pneumatic Ball Puncher

[Ed Sparks]

Look at the pneumatic rules very closely. There are deliberate specs in these rules to slow down the transfer of energy from the holding tank to the actuators (small valves, small id tubing, 60 PSI working pressure). At some point, given the mass of whatever were tossing, the physics just doesn't work out. If we were allowed to use 1" actuated ball valves and 1" tubing ...... well ...... we could be having some chunk'n fun.

[czeke]

Keep in mind, that using a punch, similar to Team 1114 from 2008, also allows you to shoot straight ( towards an alliance partner for an assist ) &
tilting forward ( to harvest a ball from the field ). Plus, if designed with some reinforcement, could make somewhat of a mitt, for catching.

[PANTHERPROJECT]

Team 2064 made prototypes for a pneumatic catapult instead of the ball puncher because we had absolutely no luck with the puncher, however the catapult is making progress. We're trying out different solenoids to see which one works best and I suggest that you do the same.

[DRH2o]

We have tested with four 3/4" X 10" stroke cylinders with a festo solenoid valve per cylinder and an accumulator feeding each valve at 60psi and have been able to get about 7 feet straight up from the ball resting on top of the cylinders that are spaced evenly around a 4" diameter tube. We were getting 4' with three. We plan to use 6 and hold with vacuum next test. Will let you know how it works... Not a punch -- more of a put (like shot put).

[DELurker]

Originally Posted by theCADguy

Team 20 has prototyped pneumatic system to propel the ball. We had absolutely no luck. The system barely got the ball in the air.

1370 did some testing last night. the 1-1/2" cylinder (1.7 factor) moved too slowly to launch and the 9/16" cylinder (0.2 factor) didn't have enough thrust. The students are interested in splitting the difference and going for a 1-1/16" bore cylinder (0.9 factor), but we would have to get one.

Right now, we're putting air punches on a back burner pending the outcomes of other ideas.

[Sarakiro]

If you are looking at a linear "punch" (actuation), your best bet (if you intend to use pneumatics) will likely be to use a wide bore piston to reset a highly tensioned plunger mechanism on guide or track. Just a thought.

[Al Skierkiewicz]

Brandon et al,
During inspection, launchers may have to demonstrated for "dry firing" to see if they are in fact safe with no ball present. Having no external hard limit for cylinders quite frankly scares me. While the working pressure is only 60 psi, a cylinder can impart quite a bit of force on the piston and the end assy with no system resistance. I have seen enough catastrophic failures to worry about this design choice. Please prototype with extreme safety in mind.

[PVCMike]

Originally Posted by Al Skierkiewicz

Brandon et al,
During inspection, launchers may have to demonstrated for "dry firing" to see if they are in fact safe with no ball present. Having no external hard limit for cylinders quite frankly scares me. While the working pressure is only 60 psi, a cylinder can impart quite a bit of force on the piston and the end assy with no system resistance. I have seen enough catastrophic failures to worry about this design choice. Please prototype with extreme safety in mind.

While a 3/4" cylinder with good flow to it moves pretty quick, and we always make strong efforts to work and design safely, I would be amazed if an unmodified COTS piston operated at less than 50% max psi recommended by the manufacturer (125psi max, operated at 60psi per FIRST rules) failed due to dry firing. This would be a major design flaw by the manufacturer. Now if we dry fired it at 125+ psi many times and it failed that's another thing. We will of course exercise caution but a failure of this type with no other damage or modification seems implausible especially given the reliability of our product manufacturers.

[Al Skierkiewicz]

Originally Posted by PVCMike

While a 3/4" cylinder with good flow to it moves pretty quick, and we always make strong efforts to work and design safely, I would be amazed if an unmodified COTS piston operated at less than 50% max psi recommended by the manufacturer (125psi max, operated at 60psi per FIRST rules) failed due to dry firing.

Mike,
125 psi is the working pressure at which integrity with pressure is guaranteed. It does not relate to mechanical failure of the device with no load.

[PVCMike]

Originally Posted by Al Skierkiewicz

Mike,
125 psi is the working pressure at which integrity with pressure is guaranteed. It does not relate to mechanical failure of the device with no load.

Hi Al, i understand that

Originally Posted by Al Skierkiewicz

125 psi is the working pressure at which integrity with pressure is guaranteed.

I have never seen any documentation from the manufacturer or anyone else for that matter suggesting that this guarantee is under the condition that there is a minimum load applied to the cylinders. A mechanical failure of the cylinder, operated as intended and within the specified psi, unmodified and undamaged/not worn, would be a product or design failure by the manufacturer. These cylinders are designed to be operated under the specified pressure and are not subject to the condition of a minimum load to be safe. Yes they will actuate very fast (especially smaller diameter cylinders) but especially when restricted to 60psi (again less than 50% working pressure) we are well within the scope of intended and safe use specified by the manufacturer.

[Animal Control]

If you punch it too hard with too much pressure and not enough padding between the cylinder and ball you will puncture the ball.

[Dr.Gusta]

Okay would something like the rough drawing below work? A ram is pulled back by a pneumatic piston, the surgical tubing wants to pull the ram back. To fire it the pressure in the pneumatic piston would be released allowing the surgical tubing to pull the ram out and hit the ball. The only thing I am really kind of worried about is the sergical tubing will loose a lot of force trying to pull the piston out even though there is no pressure. Thoughts? Ideas?https://docs.google.com/file/d/0B7jE...p=docslist_api

[Dr.Gusta]

There it should be fixed now. Sorry I forgot to make it public.https://drive.google.com/file/d/0B7j...it?usp=sharing

[Steven Smith]

If I understand the drawing correctly, you would essentially have an outer tube to contain both a pneumatic cylinder and a firing pin. The firing pin is mounted to both the end of the pneumatic cylinder, and a bolt that travels in a slotted groove in the outer cylinder. The pneumatic cylinder compressed, extending the latex, and then is "triggered" by allowing the pneumatic cylinder to extend again (possibly driving it back into the firing pin, but with the assist of the latex tubing). This essentially looks like a pinball launcher to me.


As noted before, two issues you may struggle with are:
-Insufficient speed on your ramming arm, as larger cylinders can often move more slowly
- Too much speed on a relatively small ramming head, which at best will lead to lower accuracy, or at worst could damage the ball.

I'd mock up something simple and see where it gets you (prototype). If you like the idea of the pinball tube, I think you may get more "oomph" from actuating it from the outside, with a mechanism that can run the bolt connected to the latex tubing backwards until it reaches a breaking point... slip off to allow the shot, then catch it back at the starting point.

I do think you would be wise to consider a few other designs that might be simpler (backup plan), but it might still be worth prototyping your original design to see what comes of it.

Steven

[Dr.Gusta]

I think you slightly miss understand but you have the basics down. The piston will pull the surgical tubing tight and the ram into the arm. In order to fire both sides of the piston will be opened thus causing the sergical tubing to actually pull the piston open. So all of the firing power comes from the tubing and none from the piston. Hope that makes more sense.