Really a turreted arm is overkill and your central bearing/bushing assembly will be prone to failure due to high loading (not to mention large expense). Trading the complexity of a rotating arm for a faster, simpler, better implemented fixed arm will usually result in a more competitive robot. The most common types of arms that were effective in 2011 were:
Telescopic arm with 1 rotating stage (2-bar):
610 2011/2007 - (
https://www.youtube.com/watch?v=yRrT9gEgT-Q, CAD on FRC designs)
233 2001/2007 - (
https://www.youtube.com/watch?v=YTs3b2w_GSw)
4 bar style arms:
148 2011/2007 - (
www.youtube.com/watch?v=XECmOwmYiu8, CAD on FRC-Designs)
2 rotating stage arms(2x 2-bar):
2056 2011 - (
https://www.youtube.com/watch?v=GJ1Op8XLsao)
Should you want to continue to pursue the rotating arm assembly you may want to ask 118 about their rotating elevator assembly (
https://www.youtube.com/watch?v=h3l6Xqts4to) though arms and elevators will induce different kinds of loads they may be able to help you with bearing selection. Best of luck!
__________________
Feroz Balsara
Team 1325 Inverse Paradox
FIRST Volunteer, College Mentor, Lead Design and Strategy Mentor!
2013 GTR West Semi-Finalists with 1241 and 2013!
2013 GTR East Champions with 1114 and 2056!
2011 GTR West Finalists with 610 and 1334!
Team1325.com