Here's an idea I happened to think of:
Use two vertical and sliding rails, the could be pivoted out at the same angle as the pyramid (either 68 degrees or 60 degrees). The ends of the rails would have a hook that was spring loaded and could collapse inward when pushed from the top, but hold rigid when pushed from below. Similar to rung lock mechanism on an extension ladder:
To start, one would drive to the pyramid, swing out the rails, and raise one rail so the hook would ratchet into the rail when it hit the rung, slide past, pop out, and grasp the rung. Then that rail would be retracted back, lifting the robot base. This process would be repeated for the second rail to reach the second rung, and then again with the first rail to reach the third rung.
A ratchet/anti-backdrive system would be in the drive for the rails, to reduce load on the motors and to keep the robot up when the match was over.
Just a thought I had. I haven't been on a robot design committee for a couple years but my mind still is in the "habit".
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Dean's List Semi-finalist 2010
1747 Harrison Boiler Robotics 2008-2010, 2783 Engineers of Tomorrow 2011, Event Volunteer 2012-current
DISCLAIMER: Any opinions/comments posted are solely my personal opinion and does not reflect the views/opinions of FIRST, IndianaFIRST, or any other organization.