A couple Friday's ago it was my privilege to visit Minneapolis' Calhoun Cycle. They specialize in bikes for transportation—folding bikes, commuters and cargo bikes. While there, the owner Luke pointed out a custom display one of the mechanics had made:

This mini bike showcases how a dynamo front hub system works.

The cranks drive the front wheel of the display. At first I thought it was silly—all anyone had to do to power the lights was give the front wheel a spin. Luke explained that pedaling while turning the lights on and off gives tangible feedback about how much pedal-power the dynamo uses. Smart. 

When I took a closer look at the front wheel drive, I spotted a Problem Solvers Center-Lock Rotor Adapter.

Kind of hard to see what's going on here, but from left to right: the freewheel is mounted to a hub body that's been chopped off at the flange, which has been drilled to that it can be bolted to the Center-Lock adapter (complete with Presta valve nut spacers), which is mounted to the dynamo hub. Ingenious! 

Thanks to Luke for the good pictures (the poorly composed, out-of-focus picture is mine, of course), which he's also put into a brief slideshow on YouTube: