Posted on Reddit, they said only the rear wheel is bare in the middle because they ran out of time in the semester, but that a spokeless front wheel would actually be easier and lighter because they wouldn’t have to build in the drivetrain features.
Speaking of drivetrain, here’s the deal:
It’s a single speed setup. We used two cranks and two bottom brackets in the front to gear up the ratio. It goes from (IIRC) 53 to a 13, which is connected to the second crank and another 53 which connects to the rear hub. The rear hub is just a normal ratcheting rear hub that we mated to our belt pulley. Not sure if all these bike terms are right, but that’s the general idea.
The front wheel would be almost exactly the same as the rear wheel except that it could be a little lighter. Some of the aluminum can be shaved off since there’s no powertrain to connect to.
The wheel/rim itself is made from T6061 aluminum.
More pics after the break…
Thanks to everyone that tipped us off to this sweet contraption!