Whatever the role is that leads to maximum inspiration. That's the role that the mentors and the students both need to play. It's also something that needs to be decided team by team and maybe even year by year within a team.
On a semi-related note, I asked the following question at a Kitbot build day for rookies (the mechanical and electrical groups were waiting on the programmers, for once):
What is the maximum amount of mentor involvement allowed in a robot build, by percentage?
After I heard the correct answer*, I explained to the rookies why that's the right answer, and that they would see teams that they might think were mentor-built. Not only was that not a problem, but that it might be beneficial to go and hang out with those teams for a bit, and learn from them. I think part of the role for the teams with a higher percentages of mentors is to share those mentors with teams that need help, trying to improve the inspiration on those teams, if those teams need the help.
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Past teams:
2003-2007: FRC0330 BeachBots
2008: FRC1135 Shmoebotics
2012: FRC4046 Schroedinger's Dragons
"Rockets are tricky..."--Elon Musk
