In the 2002 and 2003 seasons Wildstang (111) has used a crab steering system. Their drive system was powered by 2 Drill motors and 2 FP motors (one motor driving a different wheel), and their modules were rotated using 2 Globe motors. Check here for 2003 pictures
http://www2.wildstang.org/2003/inven...otographs.html
In 2003, The Sea Dawgs (258) used a similar system, but we used 2 Drill motors and 2 CIM motors to drive (1 per wheel), and 2 Globe motors to rotate each pair of modules.
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That link into Wildstang's Inventor Award submission is a really neat place to look at the intracacies of their robot. Their 2002 submission was great, as well.
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I'm going to find a few pictures of 258's 2003 system and link to them a little later.
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