pneumatics or motors?

[tetravaal]

I dont think that will work very well Daniel.. We tried something like that on the 1st day, and the output port limits the speed at which the cilinder will react.. Very unimpressive.. Now if you could open one side with a huge port, that would be a different ball game..

[Djur]

Originally Posted by tetravaal

I dont think that will work very well Daniel.. We tried something like that on the 1st day, and the output port limits the speed at which the cilinder will react.. Very unimpressive.. Now if you could open one side with a huge port, that would be a different ball game..

Check to see if quick release valves are legal in this game. We used one on a single cylinder in Breakaway and could shoot well over 30' if we had a good angle.

[nedrobotics]

In Breakaway, we scored from the far end of the field in autonomous and during the matches using a pre-pressurized, gate-latched pneumatic cylinder, and lots of surgical tubing to assist with kicking the soccer balls.

The cylinder re-tensioned the surgical tubing, was latched in the closed position, pressurized to 60psi (a force of ~180lbs), and another much smaller cylinder released the gate latch. Tremendous forces and speeds! That design helped our alliance win the 2010 Colorado Regional. With 120psi on the air cylinder our kick tests on soccer balls have gone about 55'.

If we wanted to kick a short shot, like if we were on offense, then we fire the solenoid to kick, and then immediately reverse it. We actually had good distance control, depending on how long of a delay we used between the extend and retract we had decent control of the stroke.

[WizenedEE]

Originally Posted by nedrobotics

In Breakaway, we scored from the far end of the field in autonomous and during the matches using a pre-pressurized, gate-latched pneumatic cylinder, and lots of surgical tubing to assist with kicking the soccer balls.

The cylinder re-tensioned the surgical tubing, was latched in the closed position, pressurized to 60psi (a force of ~180lbs), and another much smaller cylinder released the gate latch. Tremendous forces and speeds! That design helped our alliance win the 2010 Colorado Regional. With 120psi on the air cylinder our kick tests on soccer balls have gone about 55'. .

That's exactly what our team did (servo release instead of pneumatic). Except our balls would go about 10 feet. Probably just "rookie mistakes"

[JamesCH95]

In 2008 we had a 2-stage pneumatic launcher that would throw the ball clear over the bars through direct actuation (no mechanical advantage or spring assist), something we were told was impossible. The trick? Use multiple 1/2"-3/4" pistons, each with its own solenoid valve. Those pistons will respond VERY quickly.

[Brandon Zalinsky]

The design of the shooter is very important, but what I, personnally, think should be focused on more, is the quality of the build. Even if you have an amazing design, lousy build quality can cripple any team. However, if your design isn't so good, a well-build mechanism can make up for lost range with upsides, like consistency.

[samholladay]

What about using pneumatics for the ball lifter (that carries the balls into the shooter from a ball gatherer)? In 2006 it seems like a lot of the more successful teams used rollers and belts in a conveyer system to carry the balls. We were wondering if we could use pistons to literally push the balls up into the shooter. All I know is that our rookie year in 2006 we tried to use an auger and failed epically.

[IndySam]

Arghhh, so many mentions of "pistons" in one thread! Sorry guys but that's one of my pet peeves, the correct term is cylinders.

[Daniel_LaFleur]

Originally Posted by tetravaal

I dont think that will work very well Daniel.. We tried something like that on the 1st day, and the output port limits the speed at which the cilinder will react.. Very unimpressive.. Now if you could open one side with a huge port, that would be a different ball game..

Tell that to the pneumatic shooter we have in our lab

Originally Posted by IndySam

Arghhh, so many mentions of "pistons" in one thread! Sorry guys but that's one of my pet peeves, the correct term is cylinders.

IndySam is right (mostly) ... although I prefer the term 'Pneumatic Linear Actuator'

[DavisDad]

I'm toying with the idea of directly propelling the ball with compressed air: a cannon design. Think compressed air potato cannon. A quick calc for a cannon shooting the ball 25' would only require about 2 psi in the accumulator (air reservoir). This does not account for leakage around the ball and that may be a "show stopper". The calcs were based on a cannon only 8" long (same as ball diam) which would allow easy front loading.

[JamesCH95]

Take a look at the Cv of the solenoid valves we're allowed to use and determine if you have a prayer of flowing enough air through it. I have a feeling that might be your limiting factor.

[DavisDad]

Originally Posted by JamesCH95

Take a look at the Cv of the solenoid valves...

Thanks James for the heads-up. Compressed air limits are:

• Max supply pressure = 60 psig
• Solenoid Cv = 0.35
• Compressor capacity = 1.05 SCFM (says CFM in the rules ???)

My pressure required at the cannon will be less than 10 PSI = 50 PSIG dP. If I'm doing the air Cv calc right, I get between a bit over 10 SCFM.

I'm also looking at high pressure blower feasibility (~ 8 PSIG). Any thoughts on that legality?

[JamesCH95]

Originally Posted by DavisDad

Thanks James for the heads-up. Compressed air limits are:

• Max supply pressure = 60 psig
• Solenoid Cv = 0.35
• Compressor capacity = 1.05 SCFM (says CFM in the rules ???)

My pressure required at the cannon will be less than 10 PSI = 50 PSIG dP. If I'm doing the air Cv calc right, I get between a bit over 10 SCFM.

I'm also looking at high pressure blower feasibility (~ 8 PSIG). Any thoughts on that legality?

My math says that filling that volume chamber (8in diameter, 8in length, right cylinder) at 10CFM will result in an exit velocity of less than 0.5ft/s. No doubt this equation is simplistic, but it shows that the idea is two orders of magnitude off of what I consider a good exit velocity (50ft/s is what we're 'shooting' for) and I would abandon the idea as unfeasible, pneumatic component legality aside.

Hope this helps guide your design decision.

Using a fan or blower may work, and I don't *think* it would be illegal (I AM NOT THE GDC), but I don't think that it will efficiently transfer kinetic energy to the ball. I spent most of my junior year of college building and running turbo-machinery experiments, so this is a 'semi-expert' opinion, take it for what its worth. A decent, maximized, blower efficiency is usually around 80%, and I bet you won't be operating near this over a shot cycle given that the ball is accelerating away and therefore your flow rate is changing rapidly. I don't think the work of sizing motors, blower, housings, and a lunch tube to work optimally will be worth all of the inevitable efficiency sacrifices you'll be making.

[DavisDad]

Originally Posted by JamesCH95

My math says that filling that volume chamber (8in diameter, 8in length, right cylinder) at 10CFM will result in an exit velocity of less than 0.5ft/s...

The 10 CFM fills an accumulator (reservoir) until charged to about 2-3 PSI. The compressed air is released directly into the end of the cannon; like a potato cannon. The air is released very fast and the 2 psi acts against the 50 sq.in. surface of the ball = 100 lb force at initial release. My calcs say I need about 15 ft-lb energy to accelerate the ball to about 31 ft/sec. The size of the accumulator will determine the final exit pressure on the ball. Of course leakage around the ball is a big variable.

[Al Skierkiewicz]

The valve you would need to release that pressure still would need to be higher than 0.32cv (not 0.35) correct? Blowers are not illegal when driven by legal motors only.