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.
Quote:
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.
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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.