How exactly does this eccentric work?
 

I am building a Chuck's Bikes tandem that did not come with an eccentric. My cannondal wedge fit is too small to fit. The bottom of the frame has threaded holes for 2 large grub screws. Now on this bottom bracket:
http://www.universalcycles.com/image...edium/9789.jpg
How does one tighten it and rotate it? Grub screws perhaps? There are no holes on either side to facilitate roating the eccentric either.

What if you grabbed the bottom bracket lockring with a hook spanner? If the lockring was nice and tight and the grub screws loose, would that not rotate the eccentric?

Or could you not drill some appropriate-sized holes into both sides of the eccentric so that a pin wrench would engage them?

Once the retention system (e.g., grub screw, wedge/bolt, expander, pinch bolts) is loosened the eccentric should rotate freely by hand. Just grab it between your thumb and fore-finger from below the shell and rotate fore or aft.

Are you sure an eccentric wasn't shipped along with your tandem, perhaps stuffed in some wadded-up packing material? I only ask because I seem to recall someone else had the same problem with a Chuck's tandem frame and was searching for an eccentric, then discovered the one that came with the frame in shipping box during a subsequent check.

Double check your packing material. My eccentric was in the box a month before I realized it was there.