Usually, when you put nine university seniors together from a mechanical engineering class in a room for a whole semester with no strict agenda, the last thing you expect to get is a useful product. But this team broke the mold and created a “human-powered spokeless bicycle”. Admittedly, only the back wheel is spokeless, but the Yale students had two very good reasons for that – time and money.
It ain’t pretty, but the students admit they just didn’t have time or the cash to spend on niceties like paint jobs, suspension, gears or even a second brake. All they wanted to do as part of their mechanical engineering class at Yale was prove that it was possible to build a human-powered spokeless bicycle - something they seem to have accomplished with this prototype.
As readers will notice, only the back wheel is spokeless. This was due to time and money constraints. The class only ran for a semester and manufacturing the rear wheel/rim was very expensive, so only one was machined to see if it would work.
One of the students, zhaolander, explained the reasoning behind the concept of the spokeless bicycle via reddit, “First, it looks cool. Second, we only had a semester so we wanted to pick something that was both feasible and challenging. Also, you can do a lot of things with the space that opens up where the spokes use to be. You can stick an electric motor in there. You can install some sort of gyro balanced storage basket. Finally, the fact that we couldn't find pictures of a real spokeless bicycle online really sealed the deal.”
The spokeless bike is a single speed unit that uses two cranks and two bottom brackets in the front to gear up the ratio. In bike parlance it goes from (IIRC) 53 to a 13, which is connected to the second crank and another 53 that connects to the rear hub. The rear hub is a ratcheting rear hub that is mated to the belt pulley.
The students admit that on this model the balance is a little off – it’s rather back-heavy – which does affect the performance of the bike when turning. However, if the front wheel was also spokeless it would help even things out. This is even though the the front wheel could be made a little lighter as some of the aluminum could be shaved off since there's no powertrain to connect to.
The 26-inch wheel/rim itself is made from T6061 aluminum, while the frame was water jet cut out of 1/8" thick aluminum alloy to keep the cost down. The team responsible for building the bike currently have no further plans to develop the bike, but zhaolander teases, "tons of improvements could be made in future (another class perhaps)".