pic: Team 5413 Stellar Robotics Offseason Drivetrain

[RoboticDaymon]

Originally Posted by Chris is me

Except the same four bolt pattern is present at the stationary, center wheel, implying a stationary block of some sort.

Well I cant speak for the team but if you look very closely at the outside blocks there appears to be slots cut in the metal around where the bolt go through. I would guess that this would make those blocks able to slide to tension the chain. But without the original designer posting about it I cant be sure. Just looks like that to me.