Defence on the High Goal?

['lil robo-girl]

The high goal is one of the most obvious ways to get more points. Assists, the truss, and other strategy aside, it would make sense to try to prevent the other team from reaching it. However, as you know, we are only given a 6-inch cylinder to work within.
I was wondering if any teams were actively pursuing that mechanism. We haven't totally ruled one out, if we can find an effective enough design, but that does seem unlikely.
So, what basic ideas have you come up with to block the high goal, if you've considered it at all? Even if your team has decided against that particular idea, maybe we could make it work.
Thanks!

[Whippet]

We've come to the conclusion that anything extendable that can reach that high within the rules will either be too brittle and break when hit with a ball, or too flexible and bend, violating the cylinder rule and getting a substantial penalty.

[blaze8902]

Can someone quote the rule that will clarify whether or not you will receive a penalty if your extension bends temporarily due to impact with the ball?

[EricH]

Originally Posted by blaze8902

Can someone quote the rule that will clarify whether or not you will receive a penalty if your extension bends temporarily due to impact with the ball?

It's a Q&A, actually. Q116.

[Gearheads1]

We're trying one and feel pretty good about it. Pneumatics and a 2X10; we'll see how it works!

[EricH]

Originally Posted by Gearheads1

We're trying one and feel pretty good about it. Pneumatics and a 2X10; we'll see how it works!

A 2x10? Isn't that going to be outside the 6" cylinder?

[Gearheads1]

Not if you rip it to closer to 2X6, which is what I really meant. Sorry, long day!

[JohnSchneider]

Originally Posted by Whippet

We've come to the conclusion that anything extendable that can reach that high within the rules will either be too brittle and break when hit with a ball, or too flexible and bend, violating the cylinder rule and getting a substantial penalty.

Unless it is taller than the top of the goal, so that when impacted, both ends of the "pole" are supported by the goal.

[MooreteP]

Originally Posted by animenerdjohn

Unless it is taller than the top of the goal, so that when impacted, both ends of the "pole" are supported by the goal.

But wouldn't that be interacting with the field elements?
Sounds like a Q&A to me.

[staplemonx]

We are using one of these. http://www.sportstop.com/2010-NCAA-HEAD-SPECIFICATIONS

[m1506m]

Originally Posted by staplemonx

We are using one of these. http://www.sportstop.com/2010-NCAA-HEAD-SPECIFICATIONS

At 6.5" this would not be within the 6" cylinder.

[Jimmy Nichols]

A concept we were pursuing before we decided to abandon the pole was actuated it outside of out machine so that it was then supported against the back wall to help prevent it from bending.

[Canon reeves]

Our team was going to defend the high goal, but we decided it would be easier for a shooter to move slightly and shoot rather than you move 12 feet, you could be fast enough to do it but if you are to top heavy it's just a fall over waiting to happen. it also can be easily counter defended because all it takes is one robot to come and get infont of you. A team that was able to play midfield and be flexible could be much more effective than a highgoal defender in our opinion.

[apm4242]

Canon reeves - exactly what we ended on, too. Originally we were thinking a double scissor lift mechanism but even with the best <6" diameter arm in the world, counter-defense could be achieved simply by placing another robot in the goalie zone. So, in the end, a strategy that could be completely nullified with something as simple as a large rock was deemed a poor use of time.

On the other hand, if you could vision-detect one of the balls or use another method to consistently block in autonomous, I think this could be very effective.

[JamesCH95]

Re OP: playing goalie was something we nixed early on as ineffective considering our overall strategy.

Considering the height of the 'goalie stick' you'll want to make it as light as possible. The Lacross head posted earlier is a good idea. A hockey stick shaft would work well too. Pultruded fiberglass or carbon fiber poles of sufficient size would also be good. Stiffness is important, so I would lean towards carbon fiber. Worst-case a quality broom handle would probably do the trick, we tested them as deflectors for another mechanism (cantilevered 2-3ft out being hit directly by a ball tossed 20+ft in the air).

Your real issue is deployment and maintaining a stiff mounting point. For the latter I suggest roller element bearings (cam followers are good) with adjustments to take any compliance out of the mechanism and a well-triangulated structure mounted to the chassis of your robot to mount any guides to. For the former I suggest looking at various telescoping mechanisms from various teams over the years, there are many. Also bear in mind that air cylinders can easily be purchased with 2-3ft of stroke, making a directly-actuated mechanism possible.

Originally Posted by Whippet

We've come to the conclusion that anything extendable that can reach that high within the rules will either be too brittle and break when hit with a ball, or too flexible and bend, violating the cylinder rule and getting a substantial penalty.

I believe that conclusion is erroneous.

A 2inx2inx0.125in square aluminum tubing would be wild overkill and won't bend or break. You could easily find a few dozen other OTS material solutions that would also suffice.